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Why don't airplane turbo piston engines have boost control? Why is it possible to over-boost piston aircraft engines? All turbo car engines have a wastegate that just vents pressure back to the intake, whereas in an airplane the pilot has to look at the manifold pressure gauge to protect the engine. <Q> The majority of piston airplane engines are based on very old technology, before computerization was available. <S> The vast majority of airplane piston engines are carbureted with manual mixture control, prop control and turbo control and the pilot has to manage all that plus carb heat manually. <S> New engine technology has been very slow to come into the piston market because certification costs are so high, and the market is so small. <S> It would cost engine manufacturers millions to develop and certify new turbo-normalizing systems for these old engines and as there are probably only a few thousand turbo-normalized avgas piston airplanes in the world they would never recoup the costs. <S> There are modernized engines on the market with electronic fuel injection, computerized engine management with turbo-control, and single-level operation. <S> These are slowly making inroads into the market <S> but it's going to take time. <A> Some of the early, basic, turbocharged aircraft did have a manual waste gate control. " <S> Turbo-normalizing" was designed to allow turbocharging at altitude and was not to be used a sea level. <S> If not used properly, it would be possible to over boost the engine at low altitude but a "blow off valve" was incorporated to prevent damage to the engine. <S> N93641, 1973 <S> Bellanca 17-31ATC Super Viking control panel showing manual waste gate control below throttle: <A> Now a dedicated turbocharged engine generally uses an sutomatic waste gate to control the flow of exhaust gases through the turbo, thereby regulating the manifold pressure available to the engine. <S> They're also a little more ruggedly built that a normally aspirated engine specifically for that purpose. <S> That being said, they do have their limits and smooth throttle inputs are suggested to minimize the risk of an overboost condition below the turbo's critical altitude. <S> A lot of normally aspirated engines were turbo-normalized, that is fitted with an aftermarket STC turbo kit ( <S> The Bellanca above looks to have been fitted with a Rayjay STC turbo kit). <S> Older STC kits for turbo normalizing used manual waste gate controls which had to be adjusted manually and we're not cleared for used below 3000-4000 feet to prevent overboost. <S> Here pilot negligence does present an opportunity for over boosting and damaging the engine through failure to regulate the waste gate and or engage/disengage the turbo at low altitude. <S> There are s number of aftermarket STC turbo kits such as those made by Tornado Alley which do have automatic waste gates to reduce pilot workload such as those found on the Cirrus SR-22 Turbo and Mooney M20TN. <A> Why it's possible to over-boost piston aircraft engines? <S> It's not. <S> Unless the system is malfunctioning or not set up properly. <S> while in the airplane pilot has to look at the manifold pressure gauge to protect the engine. <S> This is simply not true. <S> A pilot only has to look at the gauge to set the manifold pressure to whatever power setting he desires. <S> The turbo will never over boost. <S> All piston turbo aircraft have had over-boost protection since day one. <S> Most often by waste gate. <S> They are not controlled by computer. <S> They use pressure controllers that sense manifold pressure and divert oil pressure to supply muscle to open the waste gate.
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It is possible to overboost ANY turbocharged or turbo-normalized engine if handled improperly, aviation or otherwise.
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What are CAS and EAS used for? What are calibrated airspeed (CAS) and equivalent airspeed (EAS) used for? When would a pilot need to know these? <Q> The different airspeeds: <S> IAS is indicated airpseed CAS is calibrated airspeed <S> EAS is equivalent airspeed <S> TAS is true airspeed <S> CAS is IAS corrected for instrumentation and position errors. <S> The errors are most pronounced in slow and high angle-of-attack flight. <S> IAS figures in aircraft manuals are actually converted from CAS. <S> For ease of use. <S> How CAS is determined (Wikipedia link). <S> However, a modern plane with an air data computer (ADC) actually displays CAS, despite being labelled as IAS. <S> Below 200 knots and 10,000 feet, for all purposes, CAS equals EAS. <S> As the plane goes faster and higher and compresses the air, the air changes density, an effect known as compressibility that affects the CAS reading. <S> EAS is computed by the ADC on a modern fast plane, and together with the density altitude, the TAS is then known. <S> Ground speed and track (from GPS, navaids, and/or INS) together with the TAS allows the FMS to calculate and display the wind speed/direction. <S> Before ADC's, pilots used charts like those in the answer. <S> Summary: <S> In a modern plane, what the pilot actually uses is CAS, despite being labelled IAS. <S> And EAS is used in computing the TAS by the ADC. <S> Source used and a must read: Aerospaceweb.org—Types of Airspeed <A> Equivalent Airspeed is a measure of dynamic pressure, the quantity on which most aerodynamic properties of the aircraft depend. <S> It is almost always equivalent airspeed that the pilot wants to know. <S> However the device to measure dynamic pressure, pitot tube, is subject to various errors, so the pilot can't have equivalent airspeed. <S> The best they can get with simple fixed pitot tube is the Indicated Airspeed , which is affected by changes in angle of attack and side-slip angle (positional error) and also other instrument errors. <S> with pitot tube attached to an angle of attack vane to keep it aligned with the airflow, and with corrections applied for instrument error, the Calibrated Airspeed , which is the best approximation of EAS that can be provided. <S> Whatever the instruments provide is the best that can be obtained in given aircraft. <S> There is no way for the pilot to pull out a calculator or E6B and calculate something more precise, and they won't have time for that at the moments it matters anyway. <S> The best the pilot can do is know what magnitude of error can be expected in various flight regimes (which should have been determined in flight testing and listed in the POH/FCOM/QRH) and take it into account. <A> What pilots see in the cockpit of almost all modern aircraft is CAS. <S> Those without an air data computer display IAS. <S> These two will differ only minimally in the number they display in most circumstances. <S> Pilots use this indicator to try and stay above the minimum flight speed, and below the maximum flight speed specified in the Aircraft Flight Manual. <S> These speed limits are based on aerodynamics - exceed the lower limit and the aircraft will not be able to stay in level flight. <S> (This is an oversimplification!) <S> The SR-71 Blackbird is one of the very few aircraft that also had an EAS indicator. <S> At very high altitudes this is a more accurate indication than a CAS indicator of where the aircraft speed is in relation to the minimum limit.
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For engineers, TAS (actual velocity through the air) is used in lift equations, EAS is used in calculating dynamic pressures on the plane (TAS corrected for air density).
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Does "cleared into the Bravo at 3500" mean I must wait until I hit 3500 before entering it? Let's say I'm two miles away from entering the class B, heading straight for it at 1500 feet and climbing. Approach control gives me my clearance as "...cleared into the class Bravo at 3500 feet...". On one hand, they know my heading and altitude, so I assume that I should continue straight on, entering the Class B in my climb and level out at 3500 feet, which I have done often with no consequences. However, a very literal interpretation of the clearance would have me turn away and remain clear of the Class B until I had leveled at 3500, at which point I could turn back and enter it. If push ever came to shove, which interpretation is correct? <Q> On one hand, they know my heading and altitude, so I assume that I should continue straight on, entering the Class B in my climb and level out at 3500 feet, which I have done often with no consequences. <S> This is what the controller wants you to do. <S> It's slightly sloppy phraseology - "Cleared into Bravo, climb and maintain 3500" would be better. <S> But what she said is not really ambiguous in any practical way. <S> She would definitely not be expecting you to turn away, then climb, then turn back toward the B. <A> That's going to depend on your circumstances and previous clearances. <S> Most likely it means you are cleared to enter a shelf of the class bravo airspace when your aircraft is at or above 3500' ASL. <S> Check them before proceeding. <S> Another possibility is that the instruction is part of a procedure for a VFR transit route through the Class Bravo airspace which required the pilot, after establishing two way radio communications, to enter the Class Bravo airspace at a particular point, at a specific altitude then follow an established course through the class bravo under approach control. <S> See the supplements for the Terminal Area Charts fro VFR through specific Class Bravo airspace. <S> But, yes the controller's instructions here are pretty vague. <S> I've never heard <S> an approach controller say anything like that. <A> You could respond with "Cleared into the Bravo, climbing to 3,500, Nxxxxx" for your clearance read back to make your intentions clear. <S> For example, I was flying from west of Boston to the northeast, under the Bravo and skirting north of a Class D, and asked approach for flight following, with higher when able. <S> Approach asked if I wanted clearance into the Bravo at 5,500, I said yes. <S> Then he cleared into Bravo, climb to 5000 and direct to destination (being /G is nice for that). <S> Replied with 'cleared into Bravo, climb to 5,000, direct Pease (in this example), Nxxxxx'. <S> No problem. <S> I then continued to VFR at 5,500 after departing the Bravo and continuing northeast.
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Another interpretation is that you are cleared to enter a shelf of the class bravo with a floor at 3500', as listed on your charts.
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Does a runway have to be closed for not having markings due to resealing work? Is it required to close a runway if the paint has been removed for resealing the asphalt? <Q> Not Necessarily While some regulations or guidance material may call for some or most runways to be closed during maintenance or construction work, such as marking removal for asphalt reseal, this is certainly not always the case. <S> If markings are non-standard, faded, or removed, for any reason, the condition should be documented in a Notice to Airman (NOTAM) so that pilots and other interested parties will be aware of the condition and prepared for the non-standard situation. <S> An example of such a NOTAM includes this one from Randolph AFB (KRND), where some markings on runway 14L/32R are missing dues to removal and repaint during maintenance or construction work. <S> RWY 14L/32R SURFACE MARKINGS NON STD ; SOME MARKINGS MISSING DUE TO REMOVAL AND REPAINT. <S> Note that runway 14L/32R is not closed during this work. <S> However, the parallel runway, 14R/32L, is closed: RWY 14R/32L CLOSED <A> IT relies on being a Part 139 airport, mainly. <S> the Marking Standard, AC 150/5340-1L states the guidelines and standards for marking are the only method of compliance with airport certified under Title 14 CFR Part 139. <S> Part 139 is the certification and clasification of passenger airports. <S> Markings are also required for any airport receiving Federal grant money through the AIP Program. <S> At least, this is my understanding. <S> See the AC. <S> I should also point out the "Operational Safety on Airports During Construction has the same compliance requirement - AC 150/5370-2L - applying to Part 139 and AIP grant program airports. <S> This is why you may see non- standard markings or no markings (grass field) on private airports. <S> But there is a secondary consideration - State Funding Grants. <S> You may need to check with the State Aviation Responsibility if they are paying in part for the work as if you need to meet the FAA requirement. <S> Some states may be lenient due to cost. <S> State grants are applied on a matching basis, and it may cost a local GA only 1/10 the cost when receiving a State grant for the work. <S> Since even a simple seal and repaint project can cost $100K or much more, the decision to close a runway may rest with the State agency. <S> You see, most GA's no matter how small are eligible at times for FAA AIP or State matching grants, and this drives what they do, and why most non-commercial GA's still meet the FAA AC's for marking and construction safety. <S> Any corrections gladly welcomed. <A> Yes, of course you have to close it since it falls under the runway closure reason of "Obliterated or faded markings on active operational areas. <S> " From this document . <S> The "Obliterated markings" is what would cover the removal of the markings for any reason. <S> And with even simple common sense, why would a runway under construction be even open?
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Basically, if you are not a passenger airport with scheduled or non-scheduled service of aircraft with 30 or more passengers, or if your sealing project is not funded through a Federal AIP grant, you may leave temporary markings off as long as NOTAMS are issued to this effect to the pilots - that the runway is unmarked and they are on their own discretion whether to use or not.
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What is the meaning of "altimeter three-zero-one-one"? I've been listening to a lot of liveatc.net recently (mostly at CYVR). What does it mean when the ATC give an "altimeter" reading (usually around the 3000 area). Altimeter three-zero-one-one. I'm assuming it's like a QNH setting? But not in kPa? Addon Question: Is inches of mercury specific to the Americas? North America or other places as well? I've only flown in South Africa where we use kPA (SI). We'd get information from tower along the lines of QNH 1013 . <Q> That is a QNH altimeter setting in inches of mercury, with the decimal omitted. <S> So in the case given, that is a QNH of 30.11. <A> It is the barometric pressure at the airfield, in inches of mercury. <S> It is to two decimals, so you got 30.11 inches of mercury. <S> It is the same as QNH (which is the airfield pressure adjusted to sea level). <S> From flightsim.com ... <S> (it) is the barometric pressure, given in inches of mercury. <S> If you look on a standard wall barometer, you'll see that it equates to "fair". <S> In the UK, we adopted SI units (hectopascals/millibars) some years ago, and 29.92 inches is the same as 1013mb. <S> Anything above this value is regarded as "high" pressure, and anything below it as "low". <S> In the days before weather forecasts were dumbed down, you'd often see synoptic charts with pressure values on them. <S> In Europe, again, we don't say "altimeter", instead we use what are known as "Q codes", that go back to the early days of Radio Telephony and Morse Code. <S> So instead of hearing "altimeter 2992", in the UK you would hear "QNH 1013". <S> Effectively it means the same thing. <A> The reading given is what the atmospheric pressure would be on the field if it were at sea level in inches of Mercury (inHg). <S> This is most often used in adjusting a sensitive barometric altimeter in an aircraft so that it reads an altitude which is within +/- <S> 75ft of the actual value. <S> These sensitive barometric altimeters are required equipment on IFR flights and much more useful on VFR flights as well. <S> ATC often give an altimeter readout when handing aircraft over to another ARTCC or approach controller, generally as a courtesy to the pilot and, in the case of IFR flights, to ensure the flight crew is using the correct altimeter settings. <S> Other cases include at controllers at towered airports, in between the hourly ATIS broadcast update, when there has been a noticeable and fast change in the local barometric pressure at the field. <S> Off field and bush flying operations can make use of the same information in the form of portable weather stations such as Kestrel's series of handheld weather stations which provide barometric pressure readouts. <S> Pilots also will just set their altimeters to the established field elevation listed on charts in lieu of an altimeter readout as well. <S> The altimeter should then read to within +/-75 <S> ft of the correct altitude, provided the unit was serviced and inspected within 24 calendar months of the flight. <A> Altimeter settings are usually QNH (pressure at sea level), but they're occasionally QFE (pressure at field elevation). <S> The international standard for pressure is hectopascals (hPa), which is indicated by a Q in METARs. <S> The US and some other countries use inches of mercury (inHg), which is indicated by an A in METARs. <S> They're also in separate numerical ranges, e.g. Q1013 = <S> A2992 <S> , so you can easily deduce which is being used even without that hint. <S> Many aircraft (particularly ones expected to make transoceanic flights) will have altimeters that can be set using either unit; for those that don't, pilots will need to carry a conversion table when flying in areas that use units not matching their equipment.
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That refers to an altimeter adjustment to compensate for local atmospheric variations in pressure.
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How can you identify an Airbus or Boeing from the inside? How can you recognize a plane from the inside, when you are already sitting as passenger? In particular, is there a way to understand if you are inside a Boeing or an Airbus? <Q> Look at the safety card in the seat pocket in front of you: <S> As a side note, it will be beneficial to read the safety card as well. <A> There are many details to recognize, for example: The handle that locks the doors. <S> Image is a still from this video Image source <S> Another way is to read the safety card, <S> on them, you can read clearly if you are on a Boeing or Airbus, and on which type as well. <S> The first picture is a typical Boeing's door, and the second, an Airbus'.(source internet pictures from different types of handles)On Airbus A32F, when the landing gear extends, the exit lights will turn on. <S> The cabin interior differs from company to company, however the cockpit is unique, but nowadays, passengers are not allowed to visit the cockpit during the flights. <S> If you seat on the seats, from where you can identify the winglet, they could give you some tips, most of the Airbus A32F have shark winglet, but it is changing, however, scimitar winglets are typical from New generation Boeings 737. <A> When entering the plane have a look at the front door's frame. <S> I always check this sign just to know how old the plane is... <S> This placard is required by 14CFR45.11(g) <S> (g) <S> The identification plate described in paragraph (a) of this section may be secured to the aircraft at an accessible location near an entrance for— <S> (1) Aircraft produced for— (i) Operations under part 121 of this chapter, (ii) Commuter operations (as defined in §110.2 of this chapter), or (iii) Export. <S> (2) Aircraft operating under part 121 of this chapter and under an FAA-approved continuous airworthiness maintenance program; or <S> (3) Aircraft operating in commuter air carrier operations (as defined in §110.2 of this chapter) under an FAA-approved continuous airworthiness maintenance program.
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Airbuses have a sign showing when the door / plane was manufactured.
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Are the first solo flights by a student pilot more dangerous? The first solo flight is a nail-biting moment, not only for the student pilot, but also for the flight instructor who's sending him off. In theory not having a CFI reduces the margin of safety compared to flights with an instructor (at the same point in a student's training). I've also heard stories about mistakes and even crashes on first solo flights, and according to "Crashes of instructional flights" by Baker, Lamb, Li, and Dodd, solo flights account for about half of instructional flight crashes. Yet even though the biggest safety measure- a CFI- is gone, are these student solo flights really more dangerous? Are there any studies on accident rate among low time GA pilots vs (solo) students? Also, are incidents more common in the first solo flights than at other parts of a student's pilot training? <Q> There is no evidence to back the claim that the first solo ride of the student is more dangerous compared to the later ones. <S> US NIH conducted a study on the accidents with solo pilots, which doesn't indicate that first-time solo fliers are any more prone to accident than others. <S> Aircraft accidents with student pilots flying solo: <S> analysis of 390 cases by Sjir Uitdewilligen and Alexander Johan de Voogt analyzed NTSB probable cause reports of 390 crashes that occurred in the period 2001 – 2005, concluding that, Student pilots flying solo show fewer injuries and fatalities compared to general instructional flights while in our sample first-time solo student pilots did not feature any fatalities. <S> Note that this gives only the injuries and not the times the students got into accidents per se. <S> Out of a total of 3811 accidents involving student pilots, 390 occurred while they were flying solo and around 50 involved first-time student solo pilots. <S> From Comparative Analysis of Accident and Non-Accident Pilots by David C. Ison: <S> Most accidents (49.1%) were conducted with individuals holding a private pilot certificate. <S> Second in incidence were commercial pilots (28.2%), followed by Airline Transport Pilots (ATPs) (13.7%), and student pilots (5.7%) <S> Considering that 20% of pilots hold a student certificate, these individuals have a disproportionally low accident occurrence. <S> The report also gives some additional insight into the reason the first-time solo fliers have lesser injuries: ... <S> first-time solo pilots are commonly confined to the airport and practice their takeoff and landings. <S> Such operations may result in accidents, but they will occur near to the ground with a lower risk of a fatality <S> The report also gives some data about higher experienced student pilots sustaining more injuries, though nothing conclusive, noting that, ... in 25 cases, student pilots were reported to have more than 100 and up to 322 h of flight experience. <S> In the dataset, these pilots were significantly more often injured than students with less hours of flight experience. <S> It has to be noted that as the hours logged gets more, the students get into more demanding flights which may be reason for this increase in injuries. <A> I couldn't find any analysis of first solo flights, but based on NTSB accident reports <S> it looks like accidents are very rare. <S> There are only 60 reports of fatal part 91 (GA) accidents with the words "first solo" in the report, and 492 non-fatal accidents. <S> But many of those are false positives anyway, because they include reports with things like "with his first solo occurring about a month prior to the accident", so the real numbers are lower. <S> Training flights in general are very safe compared to other flights. <S> In 2015, student pilots accounted for only 6.5% of non-commercial fixed-wing GA accidents . <S> That's much lower than private (47.1%), commercial (26.6%) and even ATP (12.2%) certificate holders. <S> AOPA has a detailed report called Accidents During Flight Instruction that comments on student solo flight in general, but not on first solos specifically. <S> It says: Two-thirds of all fixed-wing training accidents come during primary instruction, and two-thirds of those are during the relatively few hours of solo flight by student pilots. <S> However, fatalities on student solos are extremely rare. <S> And it does give some information about your question on first solos vs. other phases of instruction: <S> Two-thirds of all fatal fixed-wing accidents occurred during advanced instruction, less than half of them while pursuing a specific certificate, rating, or endorsement. <S> Transition training, flight reviews, generic refresher training, and specialized instruction in areas such as mountain flying, aerobatics, and cropdusting collectively accounted for over 60 percent of all advanced dual accidents, including more than half the fatal accidents. <S> Other people have already commented on why student solo flights in general are relatively safe: the student is primed with plenty of recent training and instructor feedback, and the flight conditions are well controlled. <A> No. <S> Anytime you get on a car or airplane or any mode of transportation, it is dangerous. <S> Yet most of those journeys end without any incident. <S> First solo is a very short flight, mostly of a few circuits of the traffic pattern. <S> The instructor is watching and talking to the student. <S> The student is well trained at that point and literally know what they are doing. <S> I think Simon's comment is very important and needs to be remembered, most accidents can happen when confidence and ego can outweigh wisdom and learning . <S> You should also notice that most of student's flying occur in VMC or better conditions. <S> This includes both first solos and checkrides . <S> Being the pilot in command, you can cancel the flight if you think any condition is not suitable.
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Actually, student pilots themselves are prone to less accidents compared to others.
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When taking passengers, what should I do to prepare them? What kinds of stuff should I think about in terms of taking other passengers flying in a small airplane? Many potential passengers have never been in a small airplane. <Q> I go through the SAFETY checklist with all my passengers. <S> The FAA recommends this as well. <S> S eat Belts - This is where they are and how to use them. <S> A ir Vents <S> - Here are the air vents and how to use them F ire <S> - In case of a fire here is the location of the fire extinguisher and this is how you use it. <S> PASS method. <S> E xits, Emergencies and Equipment - Here are the exits on the airplane and here is how to open the door. <S> Know that you are in good hands and that I have been well trained to land safely under most situations. <S> If for some reason an emergency occurs in flight follow my directions. <S> Here is any safety equipment that you may want to use on this flight. <S> i.e. supplemental oxygen. <S> T raffic and talking - Please point out an traffic that you see and I will do the same. <S> Please no talking while I am on the radio. <S> Once we start taxiing to the runway please remain quiet til we are far enough away from the airport. <S> I will let you know when it is safe to talk again. <S> When we come in to land, I will ask that you remain quiet, unless an emergency situation occurs, till after the landing is complete and we are taxiing back to parking. <S> Y <S> our questions <S> - Do you have any questions? <S> Alright, lets go have some fun! <A> The essentials Seat belts—Operation of seat belts is the only FAA-required briefing item. <S> Airplane seat belts can be complicated, even for other pilots. <S> Doors—Car makers have generally figured out how to standardize door handles. <S> Not so with airplanes. <S> Demonstrate how to open and close the door, the location of all the exits, and how to kick out the windows if the doors won’t open after an accident. <S> Also, be sure to mention if one of your doors has a habit of opening in flight. <S> Fire suppression—Point out the fire extinguisher and explain how to use it. <S> Your rental airplane doesn’t have one? <S> Buy one and keep it in your flight bag. <S> The good-to-know Dress— <S> Airplanes are a foreign environment. <S> Give guidance on how to dress, both for the flight itself and in the event of an off-airport landing (boots, coats, hats, gloves, sunscreen, et cetera). <S> Signaling devices— <S> A tutorial on how to tune and transmit on 121.5 MHz is helpful, as is a discussion of how to use a personal locator beacon, the emergency locator transmitter, and any survival devices. <S> Creature comforts—Maybe not today, maybe not tomorrow, but someday one of your passengers will get sick. <S> Carry bags and point out where they are and how to use them. <S> Also explain the location of the vents, heat, and sunshades. <S> Talk time—A strict sterile cockpit may not be necessary at all times below 5,000 feet, but mentioning when it’s OK to talk and when it’s not is a good practice. <S> So is pointing out what a passenger can touch and what he or she absolutely should not (we’re looking at you, ejection handle). <S> — AOPA <S> I'd add to that list to not hold back when something needs pointing out, like another plane's lights. <S> And as Ron Beyer pointed out, to explain to the front seated passenger to keep their feet off the rudder pedals. <A> We were required to give what amounted to an "airline" briefing before each flight. <S> We were also required to have those stupid little briefing cards for each passenger (of which at least one was stolen on each flight). <S> Our Cessna 210, oddly enough, seemed to have the most popular cards! <S> We couldn't make enough of them. <S> Maybe people just think it's silly that a "little Cessna Piper Cub" has a briefing card just like a "real" plane. <S> I quit flying professionally in 2013 but continue to use 135.117 as my standard briefing. <S> •these are the seatbelts, this is how they work. <S> •these are the exits, this is how they work. <S> •these are oxygen masks, this is how they work. <S> •your seats recline but please leave your seatbacks in the upright position for takeoff and landing. <S> •the fire extinguisher is here, this is how it works. <S> •please don't smoke. <S> •there is a survival kit in the back of the plane...or in my flight bag...or both •(front seat passenger) <S> these are the controls, please keep from touching them. <S> •if you see another plane, let me know if the wings are on the top or the bottom and the number of engines you see (prevents passengers from reporting every single glint that may possibly be an airplane) <S> •if <S> you have any questions, PLEASE ASK! <S> If I things are busy and can't answer you immediately, I'll ignore you but circle back later.
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Make sure everyone knows how to fasten and unfasten, and when the lap and shoulder portions should be worn. If we need to land off the airport, I will ask you to pop open the door just before landing to ensure we can exit the airplane safely.
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What aircraft would have these tail numbers? Last night I was looking at a flight radar on my phone, and I saw two blips flying close to each other over Camden, NJ. They were heading northeast at around 250 knots, and the only information displayed was their registrations, listed as 1678c37 and 1678c38. A google search of these displayed no results. Are these military or other special aircraft? <Q> The following is not an answer , just what I know about flightradar data records and where to find data like yours. <S> The flightradar website on a computer updates its data by requesting this url, which contains coordinate bounds, filter settings and so on: https://data-live.flightradar24.com/zones/fcgi/feed.js?bounds=40.19,39.78,-76.26,-74.03&faa=1&mlat=1&flarm=1&adsb=1&gnd=1&air=1&vehicles=1&estimated=1&maxage=7200&gliders=1&stats=1 <S> I guess the mobile app is not different in this point. <S> The answer from the server is a JSON object like this: {" <S> full_count":14127,"version":4,"b2fd160":["AD3C6B",39.9674,-75.9941,230,34000,368,"1306","T-MLAT2","MD88","N952DL",1475422448,"BDL","ATL","DL2457",0,0,"DAL2457",0],"b2fe181":["A9FF54",39.9429,-75.9208,273,16860,378,"2347","T-MLAT2","B737","N743SW",1475422445,"PHL","PHX","WN601",0,1600,"SWA601",0],"b2fc0bf":["",40.0910,-75.8714,230,39999,368,"1361","T-MLAT2","GLID","",1475422448,"","","",0,0,"GLID",0],"b2fb3da":["A1A8DA",40.0949,-75.8623,98,8700,304,"3553","F-KPNE1","A320","N206FR",1475422446,"MKE","PHL","F91052",0,-896,"FFT1052",0]... <S> ,"stats":{"total":{"ads-":8655,"mlat":2916,"faa":1647,"flarm":346,"estimated":456},"visible":{"ads-b":6,"mlat":11,"faa":3,"flarm":0,"estimated":0}}} <S> There is one line per aircraft, starting with a 7-digit, lowercase hex number, followed by any information about the flight in square brackets. <S> (You can easily identify position, course, speed, registration, aircraft type and so on.)From the structure of the file and from the fact that you can observe many subsequent hex numbers when you collect lots of data, it seems the first number is a flightradar-internal identifier, acting as counter. <S> Whenever a new flight is detected, it gets the next number. <S> Within the square brackets, the first number seems to be the unique 6-digit hexadecimal (=24-bit) <S> aircraft ID @JScarry mentioned (and the third entry, a glider, doesn't have one). <S> But more interesting is that all data here is uppercase. <S> (And according to this site , text messages from the aircraft like flight ID doesn't have upper/lower case) <S> Now, you have two <S> subsequent , lowercase <S> 7-digit hex numbers. <S> This really looks like the flightradar-internal ID. <S> So, maybe flighradar had a glitch, or it had absolutely no further information about that flights, and displayed the internal ID instead. <S> What doesn't fit is the range, right now the numbers are about 164.000 (decimal) ahead. <S> (EDIT: <S> It can fit, they record 140.000-175.000 flights per day) <S> One can also retrieve data about flights with a certain internal ID from flightradar, but with your numbers, I get an empty record. <S> Yet, I think it was an internal ID, and you won't get the answer outside of flightradar. <A> Aircraft equipped with Mode S transponders transmit a unique 24 bit aircraft ID, in addition to a 4 digit transponder code (squawk). <S> There are two ways of displaying this unique ID, as an 8 digit xxdecimalxx octal number or as a hexadecimal value. <S> Your examples are are hexadecimal values and translate as xxx23563319xxx and xxx23563320xxx 131706067 and 131706070 in xxxdecimalxxx octal. <S> There is a tool at http://www.avionictools.com/icao.php to convert an aircraft registration to Mode S 24 bit ID for US and Canadian aircraft. <S> (I checked it with mine and it works.) <S> Different countries use different algorithms to create the ID's - some (such as Sweden) publish lists, others don't. <S> You can download the aircraft registration database for the USA at <S> http://www.faa.gov/licenses_certificates/aircraft_certification/aircraft_registry/releasable_aircraft_download/ <S> My aircraft Mode S transponder code shows up as registered to me, but neither of these show up in the list. <S> (Per the comment, it might be because the numbers you report are not Mode S transponder codes.) <S> Given that the numbers are sequential and they are flying close together at a high rate of speed, I suspect that you are right that they are military. <S> 2016-10-02 Edited to change decimal to octal. <S> Also, all aircraft in the FAA database have Mode S transponder codes—even if they don”t have a mode S transponder. <S> JS <A> The two aircraft in question were actually only one. <S> Apparently it was a glitch in the FR24 system. <S> It was an Embraer ERJ-190AR, registration number N949UW on flight AA1678 from ATL to LGA. <S> This also pretty much validates sweber's assertion that the numbers are internal FR24 codes, because the mode-S ID is AD306E.
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I'm convinced this numbers were fligtradar-internal identifiers, nothing concerning the flights themselves.
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How is a "fast jet" classified? In the book 'Pocket guide to military aircraft', they use the term 'Fast jet' for a certain range of aircraft. Is 'fast jet' a common and well defined term used within aviation? If so, how is it defined? In order to be classified as a 'fast jet', does an aircraft have to be able to reach a certain flight level, speed or other performance indicators? Does it need a certain engine type? Must it look in a certain way? <Q> In UK Air Traffic Control, the term has particular meaning as per CAP 413 (The CAA Radiotelephony Manual): <S> When receiving an ATS surveillance service, certain ex-military aircraft types have been granted a CAA exemption from the Air Navigation Order requirement to fly at an IAS less than 250 kt below Flight Level 100. <S> In order to alert the controller to this higher speed profile, pilots of exempted aircraft shall, on initial contact, prefix the aircraft callsign with ‘FASTJET’ or ‘FASTPROP’ (depending on propulsion type), e.g. “Kennington Radar, FASTJET G-ABCD request Deconfliction service”. <S> Use of this prefix shall be confined to initial contact with ATC agencies for periods of flight during which operations at airspeeds in excess of 250 kt are intended. <S> Once acknowledged, it will not normally be necessary for pilots to use the prefix in subsequent transmissions until making initial contact with other ATSUs. <S> In my experience, Fast Jet will generally be used to refer to pretty much any jet powered single or dual seat (i.e., non passenger carrying) aircraft <A> There is no accepted technical term called fast jet. <S> However, this seems to be used in media and other uses, especially in the case of British jets. <S> Most of them seem to refer high speed aircraft (BAE hawk, for example). <S> This conference to be held in London , for example repeatedly refers to fast jets: <S> BAE Systems provides cutting-edge electronic avionics systems .... <S> Its display systems offer fast-jet pilots a real-world view... <S> AMPA is used extensively across the RAF from fast jets and helicopters ... <S> (A) pilot following the Fast Jet training system will use AMPA at every stage of their training involving Tucano, Hawk T1 and Hawk T2 aircraft before moving on ... <S> The British seem to use it regularly, for example for the Hawk <S> advanced trainer : BAE Systems ... said, “... increase the Indian Air Force’s fast jet training capacity and establish a similar fast jet training solution for the Indian Navy. <S> The Hawk AJT fast jet training solution enables an Air Force or Navy... <S> My guess is that the usage of term is mostly found in UK (the book also appears to be from there). <S> There doesn't seem to be any consistency in usage. <S> While the examples above include the Hawk among others, another media report (UK again) refers to Dassault Rafale as a fast jet: <S> French Navy <S> Fast Jet <S> Duo set to thrill Air Day Crowds... <A> Based on this book— Flying Fast Jets: Human Factors and Performance Limitations —it seems to be a loose term that encompasses the performance and operating theater of the modern jet fighter . <S> The exact characteristics of fifth-generation jet fighters are controversial and vague. <S> — Wikipedia <S> From what I gather is, if the pilot is required to go through high-G training , then they'll be flying a fast jet.
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To reiterate, I'm not aware of any precise technical term called 'fast jet' and this seems to be (mostly) a British thing.
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Why isn't dumped fuel burned? Fuel dumping seems to have a lot of restrictions, like the need to do it above a certain altitude and over water. It also has to end up somewhere, even if it vaporizes, which is less than desirable. It seems like burning off fuel as it's dumped could solve these problems. Obviously there's the risk of rapid unplanned incineration, but what are the other factors? <Q> There's no benefit to burning dumped fuel, it actually introduces risk to the airplane which is dumping fuel and any other aircraft in the vicinity and possibly people on the ground depending on the altitude at which is done. <S> Building a system to burn it is not worth the time, effort and money given there's no good reason to do it. <S> Dumped fuel will vaporize and mix in with the air, and then break down over time from exposure to air, heat and UV light. <S> This is not ideal for sure, but burning it isn't environmentally friendly either as it produces CO2, CO and soot. <S> Evaporation of dumped fuel is a miniscule problem when looked at in context as it's such a rare occurrence. <S> Canada measured 58 million liters of gasoline and diesel lost to evaporation from retail outlets and pump in 2009, if you extrapolate that to the US <S> it's got to be over 100 million US gallons of fuel evaporating into the atmosphere every year. <S> An airbus A380 contains 320,000 liters of fuel, if you dumped all that at once it's not going to make a statistical difference. <A> Obviously there's the risk of rapid unplanned incineration, but what are the other factors? <S> "Rapid unplanned incineration", although appearing nowhere in the certification standards for any airplane, will be fairly high up on the list of thing aircraft designers try to avoid. <S> The linked F-111 dump-and-burn is very much an exception that is highly unlikely to occur in any civilian aircraft. <S> Dumping fuel from higher altitudes has not yet produced a problem for anyone, burning it as it leaves will require extensive (and expensive) testing that no one is interested in. <S> Save it for the air shows. <A> As GdD explained , while aircraft are supposed to be careful about where they dump fuel, the dumped fuel is not a significant hazard to health or the environment. <S> Large airliners departing for a long flight can be carrying enough fuel to fly for 6 to 10 hours, and must dump this fuel in less than a few hours. <S> All of the energy that would have gone into propelling the aircraft over a long period of time is released as heat in a much shorter amount of time. <S> This heat will be a problem. <S> Fuel dump nozzles are typically placed on the wings. <S> This allows the fuel to be dumped clear of the fuselage and engines, and is conveniently located right next to the fuel tanks in the wings. <S> If the fuel is burned directly from these nozzles, it will cause some issues. <S> The nozzles will have to be designed to withstand the heat. <S> The wings in this area also need to be designed for this heat, and prevent the fuel (vapors) inside from igniting. <S> The passengers would probably not be thrilled to see giant flames coming from the wings, and would definitely feel the heat. <S> The fuel dump nozzles could be moved but this adds complexity and risk. <S> The other logical place would be near the APU in the tail of the aircraft. <S> The tail would still be affected by the heat, and in some large aircraft there are still fuel tanks in the tail that must be dealt with. <S> All of these challenges, on top of controlling a massive fire outside of the aircraft, and burning the fuel provides relatively little benefit. <S> Simply dumping unused fuel is much safer for everyone involved.
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Burning the fuel represents much more risk than just "rapid unplanned incineration".
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How are aircraft transported to, and then placed, in an aircraft boneyard? I was looking at the boneyard at Davis Monthan Air Force Base and was wondering: How are aircraft brought there, and then how are they placed so tightly together? <Q> Most are just flown in to Davis-Monthan AFB and then towed over to the boneyard where they're 'pickled'. <S> There are a couple different levels of preservation depending on it's potential future (returnable to flight, parts, etc.). <S> More information is available at the AMARC web site. <A> Almost always a plane going to a boneyeard is flown to the general area. <S> Typically they are taxied, towed or dragged away from the airport itself. <S> CHEAP is the key word in any recycling / 2nd-hand operation. <S> Planes at the end of their economic lives, that cannot be flown because of damage or lack of maintenance, tend to be moved out of sight, valuable bits and hazardous materials removed, and the hulk reduced to scrap using normal construction/demolition equipment. <S> The scrappers near Mojave airport work the same way, in a bare dirt lot down the street from the storage adjacent to the airport. <S> I've been to AMARG <S> *, at Davis-Monthan, to Mojave Airport/Spaceport and a facility for smaller, general aviation, aircraft, Cessna 150s through commuter and business turboprops/jets. <S> The later had a large, grass, field, for last landings. <S> Other planes arrived by truck, in pieces. <S> Most airplane museums are near an airport, but exhibits are less likely to fly in. <S> But restoration isn't scrapping, the economics are different. <S> *AMARG, or the 309th Aerospace Maintenance and Regeneration Group (previously known as AMARC, the Aerospace Maintenance and Regeneration Center) <A> The aircraft can be placed very tightly together when they're being towed -- far closer than would be safe if they were being taxied, and at least somewhat closer than would be normal for parking if the expectation was they <S> they'd be towed/pushed back out in a day or three. <S> The desert there is big, but it isn't unlimited, so there's nothing to gain by wasting parking space with extra unnecessary feet of space between aircraft that probably will never move again. <S> And by the time that they're being towed to their final parking spot, they aren't in a condition to taxi under their own power anyway <S> -- engines have been purged of all fuel & oil (if not removed outright), etc.
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A plane headed for a museum or restoration shop, even as a donor, is often disassembled and sent by truck, train or ship.
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What is the descent rate in emergency situations? I fly a plane at 40000 feet. There is a sudden depressurization; what is the maximum vertical speed I can keep to come back at a proper altitude? Is this speed different for different emergency situations? (Engine stopping/fire/general emergency). Are there any numerical maximum values in different scenarios for, for example, a A320 or a B737? <Q> ( wikimedia.org ) <S> Part of a Boeing 747-400's autopilot control panel. <S> Maximum rate climbs and descents are achieved by using a speed climb/descent mode, where the pitch (nose up/down) controls a selected speed. <S> The button FLCH (flight level change) activates such mode (shown above). <S> Each manufacturer has its own name for it, but it's the same functionality. <S> On an Airbus it is activated by pulling the altitude selector knob (Airbus calls it open climb/descent). <S> In level change climb, the thrust levers are engaged at the maximum thrust for a climb, the autopilot then controls the plane's nose to hold the selected speed. <S> For maximum climb rate, a low speed (ideally Vy) achieves that, i.e., all of the climb thrust <S> minus what's needed for <S> the low speed is used for climbing. <S> For descents, the reverse is true -- fastest forward speed possible and idle thrust -- combined with the speed brakes. <S> The plane will nose-down to achieve that speed. <S> The rate of descent will be very steep initially, then it will ease off to hold the speed. <S> Speed brakes add drag, so to achieve the same speed the aircraft will nose down more, resulting in a faster descent rate. <S> As the plane descends into the thicker atmosphere, the descent rate will again start to decrease -- as the plane will be producing more lift and drag. <S> So we can't pinpoint an exact value, but 6,000-7,000 feet per minute is not uncommon. <S> Once a rate of descent is achieved, whether it's 1,000 fpm or 8,000 fpm, the g-force on the passengers will be 1 g, as there will be no acceleration in the vertical. <S> ( YouTube ) <S> A Boeing 777 flight crew demonstrating such procedure. <S> A lower altitude is selected FLCH is pressed <S> The thrust levers are idled -- by hand is quicker than the auto flight system (this does not disconnect the auto thrust) <S> The speed brakes lever is deployed A faster speed is selected -- the maximum allowable indicated airspeed increases as the plane descends into the warmer air where the local speed of sound is faster (thereby allowing a faster true airspeed, up to a limit). <S> The above applies for a rapid decompression, other scenarios would likely require a descent, but not that steeply. <A> In a rapid depressurization, you'd typically descend at MMO and transition to VMO until reaching your level-off altitude. <S> This is accomplished with the speedbrakes extended. <S> What vertical speed you'd get is unknown; essentially you take whatever rate this procedure gives you. <S> Initially, it might be 6000+ FPM, after transition to VMO, maybe a little less than that. <S> But, you set an airspeed , rather than a vertical speed. <S> Edit: <S> MMO <S> = maximum Mach Number (often, .82 or above, depending on aircraft type) <S> VMO <S> = maximum Indicated Airspeed (often around 340 knots) <A> I can't answer for to 40,000 feet (FL400—Flight Level 400—in pilot parlance), nor to an A320 or B737. <S> I can answer for a piston engine airplane with retractable landing gear at FL250, though. <S> As a private pilot, I frequently fly our Mooney 252 (M20K) at FL250. <S> I did an emergency descent drill, running through the procedures to initiate a maximum-rate safe descent, something I would do if I had a fire in the airplane or an oxygen emergency. <S> (The 252 is not pressurized: I have supplemental oxygen on board, delivered to my face using an oxygen mask.) <S> The procedure: power to idle, speed brakes deployed, landing gear extended ("down"), 160 KIAS (knots indicated airspeed), propeller control full forward (increases drag). <S> The 252's maximum speed with gear down is 165 KIAS, and I want that little bit of extra margin. <S> My vertical descent rate exceeded 5,000 feet per minute. <S> There are other scenarios, though, for "emergency descents": you might want to go as far along the ground as possible (engine failure, glide to a distant airport for landing), when you want to fly at the best glide speed (compensated for wind and for actual airplane weight, ideally); you might want to stay aloft as long as possible (engine failure right over an airport, and you want the time to attempt a restart or to prepare more thoroughly for the landing), so you'll fly at the best sink speed. <S> In my airplane, best glide is at about 85 KIAS, best sink is about 75 KIAS. <A> ( flightaware.com ) <S> In light of the comments above about MMO/VMO and lift/drag limiting descent rates, you can accelerate descents by banking the aircraft into a turn. <S> This allows you to increase angle of attack, thus increasing drag to keep speeds down, while rotating the lift vector away from the vertical so it's not working against you. <S> The combination allows for higher descent rates with the same MMO/VMO limits. <S> Some operators train for this, but my impression is not many, and it tends to scare the passengers.
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The Mesa E175 that had an emergency descent about a year ago peaked around 7000 fpm, in total taking 6 minutes to descend from FL340 to 10,000 ft.
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Why are airplanes parked at the gate with max rudder deflection? Quite often I see aircraft parked at the gate with rudder deflected to the max. I see this either with Boeing and Airbus aircraft so it must have been done on purpose. I know that there are dampers connected to the yaw, or are those not powerful enough to keep the rudder straight e.g. undeflected? <Q> The control surfaces of airliners are not connected to the pilots' control via cables; they are operated by a hydraulic pump. <S> When the engines are shut down, there is no hydraulic pressure in the pipes, and the control surface is free to move. <S> The rudder is moved from the center position by wind . <S> If you observe the gates, you should note that all airplanes have their rudder deflected to the same direction. <S> In a perfect no-wind scenario, the rudder would stay neutral. <S> There are no gust locks which the pilot must arm before leaving the cockpit on Boeing aircraft (and I presume Airbus too). <S> Gust locks are, however, common in general aviation aircraft. <S> They can also be found on some small business jets. <S> The reason being, control surfaces on small aircraft work "both ways" - if you move the elevator by hand, the yoke in the cockpit will move as well. <S> These are called " reversible flight control systems ". <S> Therefore, when the control surfaces are moved by wind, the entire system - yoke, cables, wheels, bearings etc. are all moved back and forth. <S> This brings a significant amount of wear and stress to the system. <S> The control surfaces on airliners are much heavier and much stronger. <S> Also, they are not "directly" connected to the cockpit's controls - <S> when there is no hydraulic power, pretty much every component is disconnected. <S> Unless you're facing gale force winds, it is safe to just let them swing free with wind and gravity. <A> I have no experience on Boeing or Airbus airplanes but the most likely cause would be gust locks installed on the aircraft. <S> Other airplanes have an externally mounted device locking the rudder in place. <S> http://www.weekendcfii.com/photos/c172preflt/C172_gust_lock.jpg <S> Other aircraft have a strap that goes around the flight controls andrudder. <S> The strap is tightened and the controls are locked in afully deflected state. <S> http://archive.da.aero/images/intelligence/content/learjet/200911-old_gust_lock.jpg <A> When the aircraft is parked there's no hydraulic pressure, which means that the rudder will be deflected by external forces, ie wind. <S> The ailerons and elevators might get deflected by the wind or their own weight as well.
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Some aircraft, like a C-172, have a pin that locks the aileron and elevator in place. Strong wind may also cause the surfaces to deflect past their designed maximum, causing damage.
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What is the power source of the clock in glass cockpits? I always get the impression that, once the shutdown & secure checklist is completed, there would be absolutely no electricity to any components in the cockpit or any aircraft systems. However, most flight management computers know the current time. The time is also needed for GPS positioning. How does the aircraft keep the time when the power is off? Is there a very small battery (similar to computer motherboards) which needs to be replaced once every few years, or is there a tiny electric current drawn from the batteries at all times? <Q> There are two ways this generally works: <S> The first is common in aircraft with hard-wired systems, while the second is the case for nearly every handheld-style GPS. <S> While GPS does not necessarily need to be powered all the time, it dramatically speeds up the satellite position lock if it is close to the correct time <S> and can produce the GPS 'almanac' (coarse orbit) from memory <S> can produce valid ephemeris (detailed orbit) data from memory has a valid last known position <S> The time, position, and almanac information give the GPS hints on which satellites to search for first. <S> Once the first satellite is locked on to it can acquire a time signal and the time is quite accurately synchronized to the GPS system. <S> The almanac is successively used to search for more satellites that should be in view, but will fail over to look for others if these are not found. <S> Once a satellite is found, if the ephemeris data has expired, it will listen for the ephemeris information which takes around 30 seconds to receive. <S> This is the main difference in the 'hot' 'warm' and 'cold' start time for a GPS receiver. <S> If no power is maintained in the GPS, at the very least the time will be lost, and more typically all of the almanac information is wiped out as well, resulting in a position acquisition time of a minute or more. <A> Interestingly enough, large aircraft are not actually powered down as often as you would think . <S> Much like your desktop computer there is most likely a small power source (often a small battery) that runs the clock(s) after it has been powered down (main shut down or main breaker shut off) <S> (im looking for some exact references for this as well). <S> There are lots of different avionics systems and combinations of equipment out there <S> so the answer will of course vary from plane to plane as well. <S> On a bit of a side not the current time is not needed to figure out your GPS position although time is the coordinating element that the GPS network uses its more about the difference in time received from the satellites than your apparent local time. <S> The Piper Archer I fly simply has the clock wired to the main bus before the main bus switch so it can continue to run when the main switch is off. <A> From Airbus FCOM <S> The clock has two electrical supplies, one of which is a direct connection to the aircraft battery hot bus <S> I cannot remember what the other supply was, but DC1 would be a good bet. <S> This seems to imply two things: a) clock is powered by normal power distribution when generators are working (DC1) and directly linked to main a/c battery when powered down (HOT BUS 1) b) at least on Airbus the clock itself does not have its own tiny battery
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A low-current hot buss that is always connected to the system battery A small rechargeable battery that powers low-power time and memory circuits
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When should a PPL student start learning navigation? A big part of the ground syllabus for PPL training is navigation and flight planning. The ground training feeds into practising navigation in-flight and of course eventually to the qualifying cross-country. What's the best time to start the classroom work on this subject, in the context of training that's spread out over a long period? What are the pros and cons of learning it at different times? If it makes a difference, I'm interested in the situation in the UK for an EASA PPL. <Q> As early as possible. <S> They say " aviate, navigate, communicate ", which puts navigation into a pretty high priority - just behind flying the plane. <S> It is more important than talking on radios. <S> I cannot see any downside for learning navigation too early beside the natural "memory decay" for acquiring any new material & knowledge. <S> Even basic navigation techniques will benefit your first day of flying (unless you're absolutely not interested in knowing where you are). <S> You can even discuss the route with your instructor during the pre-flight, even if flight planning is not the lesson today. <S> You will not get to know the details, but you will be introduced to aerial navigation. <S> That, of course, assume that you are learning at a comfortable pace and you are not struggling with the present material. <A> I would also say "As early as possible" with a different rationale and a few caveats: You need to learn about airspaces and charts so that while you're working with the maps, you understand what you are doing. <S> It would help also to understand a little bit about aircraft performance. <S> A lot of learning navigation is an iterative process -- you learn a little, go work a little, internalize a little, and build a broader base to learn on. <S> It doesn't hurt to try to build that base early, but keep in mind that if things don't make sense you may be missing some pieces. <S> It's difficult to get the full scope of what you need to know when you're just starting out, so be comfortable with the fact that it may not make sense all at once. <S> "Navigation" is a very comprehensive skill that gets better with study, practice, and time (ie retreading the knowledge and skills over a period). <A> I think what you are looking for is to understand the learning experience. <S> Much of what you learn in ground school only really makes sense in context, ie when you are in the left seat of the airplane. <S> Doing the classroom work makes the best sense when it is close to the time you will use it. <S> To get a license you can either go for an intensive course over a month or have lessons spaced out much more. <S> With intensive courses you go the ground school just before you start the actual flying, when it's spaced out the tendency is to do the book learning and written tests as you go along.
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Studying navigation way ahead of using it is unlikely to give you any real advantage as you will likely forget a lot by the time you do go flying and have to re-learn the topics.
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Is there anything wrong with this more symmetric aircraft design, and why isn't it used? I imagine a fixed wing airplane design that's a lot more symmetric than what I see today. This symmetric design has wings in the middle of the fuselage (neither high wing nor low wing), and the empennage is a symmetric cross. Two vertical fins, one on top and one on bottom, and two horizontal stabilizers. The tail fuselage would taper symmetrically too, instead of the underslope with flat top we usually see today. This would make the fuselage closer to a Sears–Haack body , which I believe is ideal. In other words, it would look a lot like the XB-42 Mixmaster : Ignore the weird engine. AFAIK, this design could use an engine anywhere. BTW, this is the only aircraft I know with the middle-wing and symmetric cross tail design—whether experimental or production aircraft.) The reason I imagine this is so the control surfaces are much more aligned with the center of mass. So the rudders, elevators, and ailerons will not produce any adverse torques when used. I think this will be more efficient , especially when using trims, and also is a simpler design as far as I can tell. To get around the problem of tail strikes, I imagine a single tail wheel attached underneath it. For small aircraft it might not need to retract. For larger aircraft, I don't know how or where it would retract to, but maybe instead some kind of aerodynamic shield can enclose/open around it, like a prolate or oblate spheroid shape. (An alternate symmetric design would be an X-shaped empennage—same shape, just rotated 45 degrees. I think for a given yaw, the combination of control surfaces would produce more drag though, but it's a way to increase ground clearance.) (A more exotic alternate might be to forget about takeoff rotation entirely, and just increase takeoff speed and the length required to literally lift off without pitching up the nose. This might not be feasible for large commercial aircraft though.) (But maybe best is to add canards with their own elevators, or all-moving canards, which will push up the nose and pivot at the wheel.) To me this symmetric design seems simpler and versatile. By versatile I mean it looks like it could be used for small and large aircraft, whether prop-engine or jet engine, military or civilian, and not really mattering where the engines are located either. Is there anything wrong with this design? Why is it not used more often? In fact I do not know of a single production aircraft with this design. If anyone knows of any aircraft in this configuration, whether experimental or production, please provide a link so I can read more about it and maybe discover some reasons for its success or failure. <Q> The biggest single problem with this is the location of the main spar - across the middle of the fuselage. <S> This might not be a problem for single seat military or sports aircraft but would be a major headache for almost any other design. <S> Imagine trying to load 100+ passengers with 50% of them having to clamber over or under a major obstruction in the cabin. <S> Yes, you can engineer around this but the resultant solution is likely to be heavier and more complex than simply moving the wing up or down and out of the way. <A> You are right, a symmetric layout would reduce flight mechanical complications like rudder movements causing a rolling moment on top of the intended yawing moment. <S> But would it be worth it? <S> Airplanes usually fly straight courses and keep manoeuvring down to a minimum. <S> The autopilot will deal with the cross couplings just fine, and aerodynamically the added control surface deflections are negligible. <S> But the new complications coming with the ventral fin are harder to ignore. <S> As you said, rotation at take-off will be limited and you need to take off B-52 style . <S> Note that the B-52 needs a high wing already to prevent its wingtips from scraping on the runway when there is too little lift to bend them up (beefing up the outrigger wheels would also be an option, but adds weight). <S> Now the aircraft will climb with a nose-down attitude which increases drag slightly . <S> Only the protection for the tail-mounted propeller afforded by the ventral tail justified its existence in the XB-42 (look at the <S> Do-335 <S> for another example). <S> When the XB-42 became the jet-powered XB-43 , the ventral fin was removed. <S> Or how should you load and unload large cargo if not with a rear ramp? <S> The ventral tail would make access to this ramp impossible. <S> Loading from the front needs a stronger and heavier nose wheel or additional struts like on the An-124. <S> Woe betide the crew who forgets to lower the strut before unloading the main battle tank through the front doors. <S> This complication never arises with a rear ramp. <S> Now for the fuselage shape: The symmetric tube is not as bad as the current upswept tail, but not ideal. <S> Look at gliders: Here the fuselage follows the upwash ahead and the downwash aft of the wing to create the least drag. <S> But again this will restrict the possible rotation angle at take-off. <S> Especially with wing sweep you are better off with an upswept rear fuselage and a shorter runway. <S> Just think of all the resistance in the population if you need to double the runway length at all major airports. <S> Or do you want to limit the utility of your new design by restricting it to Edwards AFB ? <S> Symmetry is only worth it if the aircraft is designed for aerobatics . <S> Even then, a symmetric wing airfoil is much more important than a symmetric vertical stabilizer. <A> You're right that there aren't any production aircraft with a 'symmetric' design. <S> But quite a few experimental aircraft have them, especially the tail sitter VTOL ones- <S> note that even they aren't perfectly symmetrical, showing the issues. <S> Convair XFV Pogo <S> By No information - US Navy, Public Domain, <S> Link <S> Lockheed XFV 1 <S> Public Domain, Link <S> Looking at these aircraft alone, we can see some of the issues we would face in these aircraft. <S> The main spar would have to pass through the fuselage, which will severely limit the uses of these aircraft- <S> it would be extremely difficult to use them in passenger and cargo carrying roles (Even if it is used, loading is going to be a problem unless you open the cockpit upward). <S> Having a lower fin would cause problems. <S> Unless you are going to take off vertically (which is rarely preferred), the landing gear size has to be increased as with severe limitation in the rotation angle during takeoff and attendant problems. <S> This will lead to weight issues and runway restrictions. <S> Then there are maintenance problems- <S> if you have to change the engines (which for symmetry, has to be inside the fuselage), the only way is to remove the bottom tail (kinda like the harrier, whose wing has to be removed). <S> Any aircraft has to be designed for production and operation. <S> These issues are too difficult to justify the use of symmetrical aircraft except for very specific purposes- <S> like <S> the XB-47 and Do-335 designed for speed and the XFV and XFV 1 <S> designed for vertical take off. <S> For any other aircraft, the required tradeoffs would be too costly to justify. <S> Why tinker with what's working for something that offers little practical benefits <S> (flight controls are doing fine without symmetry; even if there's a problem, modern autopilots can handle them fine) or just because it looks good on paper? <A> Just to add a very basic consideration to the already good answers here. <S> The 'ideal' Sears–Haack body is ideal only for drag, without considering the need for lift. <S> This makes the airflow non-symmetric in vertical plane, and thus the optimal body will not be symmetric (even from the purely aerodynamic standpoint, before we consider spars etc.). <S> A high wing, for example, is aerodynamically the most efficient in most cases. <S> It has positive interference with fuselage and will often have less drag than the equivalent middle wing. <S> Even on XB-42 <S> you may notice that the horizontal tail is placed high, above the wing. <S> This is usually done to reduce the effects of the downwash from the wing.
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While there may be minor advantages of having the vertical tail symmetry, there is no actual symmetry in the vertical plane for any airplane, simply because any airplane needs to produce lift - which is the biggest aerodynamic force.
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What is the weight that is used to balance an aircraft called? I remember I was reading about balancing an airplane a few days ago, and i came across a type of weight that is added to balance the airplane. But, I do not remember what it was called. Also could someone tell me the approved location of these weights on a Boeing 747-400? <Q> 747s in everyday operation typically use fuel for ballast when needed. <S> Ballast fuel is considered to be part of the zero fuel weight and you are not allowed to burn it, although obviously if you were about to run out of fuel, it's available. <S> Ballast fuel is carried in either the center tank or distributed evenly in the four main wing tanks. <S> Individual carriers have different ideas insofar as their preference for either center tank or wing tank ballast fuel. <S> Also, after the TWA 800 explosion back in the late 1990s, there were as I remember special rules for a time on carrying ballast fuel in the center tank. <S> Should you wish to explore the effects of ballast fuel on the CG of a 747-400, go to 747.terryliittschwager.com and select the first aircraft N402YY. <S> When the aircraft comes up, you'll notice that the BALLAST FUEL radio buttons at top center have the Center Tank selected. <S> If you put 100000 lbs of fuel in and then 1000 lbs of ballast, you'll see the zero fuel weight CG change from 30.6% MAC to 30.8% MAC. <S> Ballast fuel is more often necessary for 747s that were originally passenger airplanes and then converted to freighters than otherwise. <S> The problem is that the heavy structure added for the large cargo door aft of the wing brings the basic operating weight CG farther aft then before the cargo conversion. <S> 747s originally manufactured as freighters do not have this problem as they have additional structure for the nose cargo door in addition to the side cargo door structure. <A> I am pretty sure you are thinking of ballast . <S> These kinds of weights are used aircraft and in many other types of vehicles as well, particularly in ships, to maintain proper balance. <A> It is usually called as ballast. <S> From Wikipedia : <S> Ballast is removable or permanently installed weight in an aircraft used to bring the center of gravity into the allowable range. <A> terminology- or counterweight . <S> Placed where it produces the necessary torque for balance. <S> Usually in the nose or tail. <S> I don't have data specific to 747-400 <S> but here's a somewhat related article .
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It is called ballast - part of the inherited ship
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Which aircraft require that the vertical position of the centre of gravity is checked? We normally check the aircraft CG along the longitudinal axis and the lateral axis (sometimes referred to as the transverse axis) to ensure it is within limits. Until recently I was unaware of any aircraft that required a check and control of the CG along the vertical axis. None of the aircraft (B727, B747, DC-8, DC-9, L1011) that I have been involved in weight & balance detail for have required a vertical CG check. Recently, however, I have found that some B767 freighters do. My question is: Are there aircraft other than some 767s that require a vertical CG check? Edit in response to a comment: My purpose in asking the question was to learn how others might have handled a vertical CG check. You can see the method I used by going to http://terryliittschwager.com/WB/B767/load.html and searching the page for 'vertical'. Additional edit in response to additional comments: Some comments have expressed the opinion that there is little or nothing that can be done about the vertical CG. In practice, the vertical CG of cargo (and thus the airplane) is easily affected by specifying which ULDs (unit load devices—the so-called "igloos") will be used for loading. ULDs come in various standard heights. 96", 64", and 45" are oft used heights but there are others, and an array of custom heights. A usually safe assumption is that the mean vertical CG across ULDs is no higher than half their height. In the case of the 767, the published weight & balance documentation gives tables for average CG heights of 42" and 36". <Q> In many aircraft the vertical (Z axis) placement is of little impact on weight distribution. <S> However, in some aircraft it affects maneuverability. <S> So for an aircraft like a C-5 it is noticeable, yet a C-5 is not considered an aircraft where vertical CG would be a factor, as the nature of the operations are, well, cargo hauling. <S> In a helicopter, which tends to have a higher (Z-axis) CG with the top placement of the engine and transmission, the considerations are greater. <S> It doesn't impact loading in a normal sense, but there is a noticeable impact in handling particularly when roll moments are involved. <S> Stated perhaps more simply, static stability is normally bounded by longitudinal and to a lesser degree latitudinal forces. <S> However, a higher CG will impact dynamic stability where the consideration is not primarily limited to wing (rotor) and airfoil loading. <A> Since no one mention it I would propose Shuttle Carrier Aircraft <S> It is mentioned in page 4 of the Space Transportation System Cargo Abort and Recovery Operations: <S> (pdf) <S> This requires not only removal of the payload but removal of Orbiter main engines, tires, landing gear and other components as well. <S> In addition, the Orbiter Z axis (vertical) and X axis (longitudinal) center of gravity location must be within a limited envelope, as shown in Figure 1. <S> Related : https://aviation.stackexchange.com/a/23808/679 <A> As Mongo mentioned, it is generally more important in taller aircraft. <S> However, it must be noted that small aerobatic aircraft also have the operator check the vertical CG. <S> A good example of this is the Extra 300. <S> Look up a POH and check out the way CG is handled in this aircraft <S> - it's really interesting and different than any other I have seen.
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So the simplest answer is that it does make a difference, which is more than just measurable in some applications, but normally the difference is of small consequence and only a tertiary consideration.
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Is the induced drag independent of wing span? I am a new aviation student and I was reading about induced drag the other day. I know that it is produced as a result of the tip vortices and that the greater the aspect ratio of an airplane the less the induced drag force. But when it came to the equation of the force, it is equal to: $D_i = \frac{1}{2}\rho V^2 S \frac{C_L^2}{\pi AR \epsilon}$ If we substitute aspect ratio $AR$ with span/chord $\frac{b}{c}$ and plan area $S$ as $b\cdot c$, the span term will be cancelled and the induced drag will be affected by the chord length only. It kind of contradicts the effect of aspect ratio on the induced drag force, doesn't it? <Q> Aspect ratio $AR$ can be written as $\frac{b}{c}$ which is equal to $\frac{b^2}{S}$. Before we start substituting, note that $C_L$ also depends on the wing surface area $S$. <S> $L = <S> \frac{1}{2}\rho <S> V^2 C_L <S> S$ or $C_L = \frac{L }{\frac{1}{2} <S> \rho <S> V^2 S}$ <S> Substituting all this in the induced drag formula yields: <S> $D_i = <S> \frac{1}{2}\rho <S> V^2 S <S> \frac{C_L^2}{\pi AR \epsilon} = <S> \frac{L^2}{\frac{1}{2}\rho V^2 S <S> \pi AR \epsilon} = <S> \frac{L^2}{\frac{1}{2}\rho V^2 <S> \pi b^2 <S> \epsilon}$ <S> This shows that the induced drag is proportional to the inverse of the square of the wingspan. <A> Let's work this through... <S> $C_{di} = <S> \frac{C_L^2}{\pi <S> AR e}$ <S> NASA Page on induced drag coefficient <S> The overall coefficient of drag is the form/skin drag plus the induced. <S> $C_D = <S> C_{d0} + <S> C_{di}$ <S> NASA Page on drag formula <S> The actual force of drag assuming $C_{d0} = 0 <S> $ is $D = <S> \frac{1}{2}\rho <S> V^2 S <S> \frac{C_L^2}{\pi <S> AR e}$ Can be reduced to $D = <S> \frac{1}{2}\rho <S> V^2 c^2 <S> \frac{C_L^2}{\pi <S> e}$ <S> Where $c$ is the mean chord. <S> As DeltaLima pointed out in their answer, you could then substitute $C_L$ using the lift equation to show it is inversely proportional to the span squared. <S> Both equations are correct so what we can take away is: <S> As the chord is increased induced drag increases <S> As the span is increased induced drag decreases <S> In other words, the induced drag is inversely proportional to the aspect ratio. <A> As we know that induced drag is due to vortex generated due to pressure diffrence at chord. <S> So if the chord is longer more induced drag will be produced. <S> From mathematical equations we can say that coefficient of induced drag depend on A.R while total induced drag doesn't depend on A.R
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The coefficient of induced drag is inversely proportional to the aspect ratio.
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Are an aircraft's nuts and bolts generally either all Imperial or all Metric, or can they be mixed? This is a low-tech question, but I was wondering about the distribution of imperial vs metric hardware on aircraft. When current commercial aircraft land at major airports, a mechanic will know which set of wrenches to grab. Still, I wonder is everything metric, or are some commercial aircraft still imperial? Could an engine or some subsystem use one kind of hardware on a plane that mostly uses the other? What about at a more remote airport visited by a wider variety and vintage of aircraft? Would a mechanic need to go up and check before deciding which toolbox to use? Found in this comment under this answer <Q> Why not mixed? <S> If the airframe is manufactured in a "metric" country but the engine is from the US, you will find metric nuts and bolts behind the firewall (and on the engine mount) but Imperial on the engine. <S> If I remember correctly, the Robin DR-300 and DR-400 <S> that towed me many times had just that mixture. <S> Lycoming engine and French airframe. <A> The vast majority of civilian aircraft and powerplants flying worldwide are manufactured in the USA or Canada using almost exclusively Standard hardware, usually conforming to aircraft Mil Spec (MS) or AN specifications. <S> From that perspective, the answer to your question is that any given aircraft will most likely use all Standard hardware. <S> This is even true for some European built aircraft such as the Reims F172 manufactured in France, or the Italian SIAI Marchetti F260 . <S> These aircraft use standard hardware, such as AN bolts and washers. <S> As Peter Kämpf described, there certainly are aircraft with a combination of hardware types. <S> In any event, maintenance personnel will often have documentation detailing the exact type of hardware used on the airframe and engines. <S> Older aircraft may not have this documentation, for example for a Beech Staggerwing, but the vast majority of such aircraft will use Standard hardware. <S> Most aircraft mechanics do not have any metric tools in their aviation toolboxes. <S> There will be an exception, obviously, for those that do work on the minority of aircraft with metric hardware. <S> The metric box is typically reserved for use on automotive projects. <S> That does not mean there are no exceptions; there are. <A> We work with (Czech Made) <S> Aircraft Industries Aircraft <S> and they still use the Metric Systems.
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There are also a significant minority of aircraft that use exclusively metric hardware. Speaking from my experience of having worked at remote airports, on vintage aircraft, most toolboxes reflect the use of Standard hardware.
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Can large airliners such as a 747 maneuver without electricity? Small aircraft have the flight controls physically linked to control surfaces by some kind of cable and pulley system. For a large aircraft such as a 747, are the control systems mechanically aided and if so, can they be used without power? <Q> Flight controls are pretty hard to break For the 747 (at least through the -400) <S> specifically, the controls are entirely hydromechanical, <S> so yes , they will work without electrical power. <S> In general, all non-FBW airliners are this way. <S> FBW airliners vary, though. <S> All FBW Boeings and the first generation FBW Airbii <S> (A320 family, A330/340) have hydromechanical backups to the FBW system. <S> The second generation Airbus FBW system, found in the A380 and A350, has abandoned hydromechanical backup controls in favor of independently powered electrical backup systems. <S> In addition, the chances of total electrical failure are extremely remote -- a failed engine will likely be windmilling (spinning from airflow through it) and thus turning its generator to provide some power, the APU has a generator on it in case all the engines seize up, and there is also a generator that is directly or indirectly powered by the Ram Air Turbine on airliners that use one (all non-reversion twins have one, and so do the A380 and the 747-8 -- <S> earlier 747s don't, relying on windmilling engines for electrical and hydraulic power instead). <S> Finally, the aircraft has batteries that can provide a limited power reserve if all these other systems fail. <S> (FBW aircraft add to this with dedicated batteries for at least some parts of the FBW system.) <S> However, power loss is still a serious emergency <S> The main hazard posed by a severe electrical power failure, though, is trying to fly around in the clouds with one -- it can render you effectively "no-gyro", especially on older/smaller types that don't have a standby gyroscopic instrument with a dedicated power supply/internal batteries. <S> There have been cases where small airliners have gone down due to power failures -- while the flight controls were working fine, without power or a visible horizon, the pilots became spatially disoriented, and you can guess the rest. <A> It depends on the airliner. <S> In case of large airliners, the control surfaces are usually actuated by hydraulics, which in turn are controlled by (signals from) the Flight control Computer. <S> However, the present trend is to move away from mechanical backup systems- <S> so most modern aircraft are not controllable in case power supply fails. <S> The evolution of Airbus backup controls illustrates this point: <S> • <S> A320: full FBW controls, mechanical Back-up <S> (Pitch Trim & Rudder) <S> • <S> A340/A330: like A320, additional Yaw Damper to improve Dutch Roll damping even in Back-up mode (BYDU with hydraulic micro generator) <S> • <S> A340-600: <S> like A340 for pitch, Rudder becomes fully Electrical (BPS + BCM : Back-up Power Supply + Control Module) <S> • <S> A380: like A340-600 for Yaw control + BPS + BCM <S> also power <S> Electrical Pitch <S> Back-Up (elevators) linked to side-stick Electrical Roll <S> Back-Up (ailerons) linked to side-stick Pitch Trim <S> (Wheel is replaced by Switches). <S> You can see that while older aircraft designs had mechanical backup systems, newer ones tend to have electrical ones. <S> However, the probability of all the electrical supply failing at the same time is quite remote. <A> Specifically speaking, no they cannot. <S> However, most planes carry a generator that is powered off the wind, and thus the planes forward momentum. <S> This allows the plane to be flown without a functioning engine and power source. <S> This image shows the ram air turbine on F-105 <S> Thunderchief fighter-bomber: <S> See also https://en.wikipedia.org/wiki/Ram_air_turbine
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In case the electrical supply fails ( extremely low likelihood actually ), some aircraft have mechanical backup, while the others haven't got anything, apart from aircraft like 787, which have their controls actuated by electrical power and are dead once electrical supply fails.
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Can civilian aircraft fly through or land in restricted airspace in an emergency? This is a super hypothetical question of mine. I was wondering if civilian pilots who happened to be faced with a severe emergency could fly through or possibly request to land in restricted airspace? Mainly I am referring to Area 51? <Q> FAR 91.3 states that any pilot in command may deviate from any regulation or rules to the extent needed to deal with the emergency. <S> That includes entering restricted or prohibited airspace. <S> In the example that you suggested, yes you could do so and land at the Groom Lake flight test facility at KXTA, provided you could reach their controllers or contact Nellis Approach Control declaring an emergency. <S> I will say that if you do enter R-4808 N and land there, don't expect them to roll out the welcome mat. <S> You will be immediately met by USAF Military Police who will arrest you, most likely at gunpoint, and spend several hours, if not days, there or outside the compound being extensively questioned by Air Force Security personnel, the FBI and Homeland Security. <S> Your aircraft will be impounded and inspected, possible indefinitely, and search warrants issued for your property. <S> If they find out that you faked an emergency to enter that compound, you are in very serious trouble and face a variety of federal charges including trespass upon a classified installation and whatever else the DoJ can throw at you. <S> In addition, you would need a very, very good reason to even be anywhere near Area 51, as it is in the middle of a military reservation geographically the size of the nation of Switzerland in the middle of south central Nevada. <S> There are no published routes over the airspace and all commercial and civilian traffic is kept far, far away. <S> Details about the airfield are not published on government aeronautical charts or regional A/FDs. <S> See the VFR sectionals and enroute charts below. <S> The usual response from the authorities is to detain and question you to determine what happened and inspect the aircraft to verify your story. <S> If it's a legitimate emergency, no harm is done and they will release you and the aircraft; the NTSB will file and incident report and that's it. <A> Being an air traffic controller <S> I know this situation is not as simple as that. <S> Given emergency category pilot can decide to use restricted area or land a military runway. <S> But in the mean time pilot needs to inform ATCo's so they can coordinate with civil and military aviation authorities to keep flight from scramble jets, locked in air defense etc. <S> If pilot cannot communicate with ATCo <S> (so he/she will need to squawk 7700) <S> ATCo should guess what pilot is going to do and inform authorities. <S> Given situations above yes, an emergency plane can fly through restiricted areas etc. <S> But if there is any other way out pilot shouldn't choose to use restricted area like Area 51. <S> If it comes out he/she had other options but still used Area 51, that will be a big headache for the pilot. <S> (and ATCo needs to advice pilot that there might be other ways..) <A> It's a principle handed down to aviation from the traditional laws of the sea: <S> Any port in a storm. <S> In fact, if a pilot declares an emergency and asks for vectors to the nearest suitable landing environment, ATC might well direct him to an airfield that otherwise would be denied to him. <A> First, Groom Lake is a lousy example, because it's located roughly smack in the middle of the always-busy Nellis Range Complex, which keeps nonparticipating aircraft far, far away. <S> (The only emergency diverts it ever sees are Nellis Range participants who have to knock-it-off in a big hurry, I'm sure.) <S> A good example of this would be if you were puttering along the Western portion of the Eglin FAR 93 E/W corridor and something terrible happened -- making an emergency landing at Hurlburt Field would definitely be preferable to an off-airport landing or ditching. <S> Obviously, you'd be telling Eglin Approach about your predicament since you have an advisory service from them anyway, and the controller would simply tell the Eglin Range folks to broadcast a hold or knock-it-off to whoever's working in R-2915B until you're safely on the ground.
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OTOH, in a general sense of the question, the answer is "yes, if necessary for safety of flight, a civilian emergency can land at an airfield in restricted airspace." While Area 51 is a pretty extreme example, people have had emergencies and landed in military or other restricted facilities.
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Why don't we have helicopter airlines? Just a curious thought. Why isn't there any helicopter airline? Airlines that operate large helicopters that can transport 10 or 20 people a short distance? <Q> They do in fact exist, though they often use smaller helicopters. <S> A Google search on the term "heli taxi" yields thousands of results, and while a lot are probably irrelevant, the first few pages give hundreds of operators around the world, ranging from companies ferrying passengers between airports and major cities to companies servicing oil platforms at sea, islands too small to have airfields, etc. <A> Air Greenland is a good example of a company that uses helicopters in scheduled air traffic. <S> Unlike many of the other examples mentioned here, a large part of Air Greenland's helicopter operations take place as scheduled traffic, and not charter flights. <S> They operate the following: 2x Sikorsky S-61N with 19 seats 9x Eurocopter AS 350 with 5 seats 8x Bell 212 with 8 seats to and from multiple small cities and towns on the coast of Greenland. <A> The other answers demonstrate that there are several helicopter airlines, but I don't think that really answers the question. <S> Why aren't there more? <S> Simple economics. <S> Compared to other kinds of powered aircraft, helicopters are small, slow and expensive to run. <S> They do have the advantage that a helipad takes up much less space than a runway which means you could fly your helicopters right into the middle of the city, rather than to large airports in the suburbs or beyond. <S> However, helicopters are also very noisy, so that would be very unpopular with everybody else who used that part of the city. <S> This means that your heliport actually has to be out in the suburbs anyway, and you've just lost your only advantage. <S> All of this makes it very difficult to be a profitable helicopter airline. <S> All of the examples in the other answers are cases where special circumstances mean that helicopters can still work. <S> Taking people to oilrigs by air is much faster than by ship, but you can't land a fixed-wing plane on an oil rig. <S> Small, widely spaced communities might not be accessible by road and might not have the resources to maintain an airport, but might be willing to pay enough to support a helicopter service when it's their only option. <S> If you just want to transport "10–20 people a short distance", a bus is going to be almost as fast, much more comfortable and orders of magnitude cheaper in almost all non-special circumstances. <A> We do: Helijet International . <S> Helijet International is a helicopter airline and charter service based in Vancouver, British Columbia, Canada. <S> They operate regularly scheduled flights between: Vancouver Harbour Heliport and Victoria Harbour Heliport <S> Vancouver Harbour Heliport and Nanaimo Harbour Heliport <S> (Monday-Friday) Vancouver International Airport and Victoria Harbour <S> Heliport(Monday-Friday, limited flights) <S> I'm sure there must be other services where the geography and economy can support it. <A> There are helicopter airlines. <S> Definition: airline is a company that transports people by air and in so doing makes a profit (or tries to). <S> PHI , Bristow , and CHC are three of numerous companies who transport people to and from oil platforms as passengers, for a profit. <S> (At least, that's their aim). <A> Erickson Aviation operates a regular helicopter service from Nome, Alaska to Little Diomede Island, Alaska. <S> Little Diomede sometimes makes it onto lists of the most remote towns in the USA and is more or less a small rock in the middle of the Bering Strait with a fishing village on it. <A> New York Airways used to operate a helicopter taxi service until they closed in 1979. <S> They operated a number of helicopters, including the tandem rotor BV107-II. <S> If you ever watch the Clint Eastwood film Coogan's Bluff (1968), you'll see at least two of them operating off the Pan-Am building. <S> New York Airways <A> The helicopter option is popular with Hong Kong's high rollers, looking to hit the tables in Macau. <S> http://www.skyshuttlehk.com/ <A> BIH fly for offshore (e.g. North Sea oil) and defence industries. <S> They also offer training and sightseeing tours from London (Redhill) and Coventry. <S> BIH operated a regular Sikorsky S-61 service from Penzance Heliport to St Mary's Airport and Tresco Heliport on the Isles of Scilly from 1964 until 2012, when Penzance Heliport was sold to the supermarket Tesco. <S> There are plans to reinstate the service if a suitable new site can be found. <S> BIH jointly operated the Airlink shuttle service between Gatwick and Heathrow between 1978 and 1986. <S> The service ended because its licence was revoked after the M25 motorway had been completed.
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In the UK, British International Helicopters (formerly British Airways Helicopters ) is a helicopter airline, although they do not currently fly any regular public routes.
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Why doesn't a single engine airplane rotate along the longitudinal axis? As far as I know, the tail rotor in helicopters prevents the aircraft from turning in the opposite direction that the main blades turn (due to Newton's third law). On the other hand, torque in single-engine airplanes makes them drift away from the center of the runway during take-off (which must be compensated by using the rudder). Now, my question is: once in the air, why doesn't this torque make the whole aircraft spin along the longitudinal axe? Perhaps the engine's power isn't enough to exceed the resistance of the wings against the air? <Q> First, it's about torque, not power. <S> A helicopter rotor has a large amount of torque at a relatively low RPM. <S> A single engine airplane has much less torque at a higher RPM (Power = Torque X RPM). <S> On top of that, for a craft of similar size, the helicopter will have much more power (it has to lift the copter directly.) <S> So the helicopter has to deal with torque levels several multiples higher than that of a single engine aircraft. <S> If you look at some high power aircraft such as the P-51, it's a noticeable offset. <S> And that's set for cruise power. <S> Takeoff power requires additional rudder input. <S> It should also be noted that for smaller aircraft, P-factor is a bigger turning force during climb than engine torque. <A> Often times propellor driven aircraft have differential angles of incidence built into their wings such that they generate a counter torque to the engine. <S> Some turboprops also use differential exhaust stacks to make use of reactive thrust from engine exhaust to counter engine torque. <A> A Cessna 172 doesn't have enough torque to counteract the stabilizing effect of the wings and empennage. <S> The Grumman F8F Bearcat had a reputation for giving wild rides if power was applied too quickly at low airspeed. <S> My understanding is that you could torque roll an F8F ON THE GROUND without moving (much) - just jam the throttle forward from idle and watch how fast 2000 horsepower can pick an airplane up off the ground and flip it over.
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As to the solution, most single engine aircraft have the vertical stab offset by a small amount to generate a counter force to the torque.
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Is turning off engines before landing "Normal"? I was traveling by Airbus A380 recently and I was sitting near the wing.Throughout the flight, I could hear the airplane noise even with headphones on. Suddenly before landing, everything went silent. There was no noise at all. There was a strange silence throughout the aircraft. Everyone was scared and looking at each other, some even started praying. But we landed perfectly fine. It was like routine landing. So, I want to ask, whether it was normal? Or the pilot avoided telling us something went wrong? P.S. Before starting the landing process, the pilot informed about the weather being fine and said "there's a safety manual in your seat pocket." <Q> It's not entirely impossible for it to happen, but it definitely wouldn't be quietly ignored within the aviation community. <S> I promise you that you would've heard about it afterwards. <S> That said, the A380's engines are modern, quiet, and actually mounted quite a long way out on the wings, this makes them fairly quiet when idling, even when compared to other aircraft. <S> This is particularly noticeable after a long flight where they've been running at fairly high power for 8 or more hours, and is even more the case if you're not used to the A380, eg if you usually fly on common twins such as the A320, 737, 777 which are <S> much louder within the cabin. <S> I suspect, but can't be sure, that the engines were simply pulled back to idle (minimum power/thrust) and it sounded much quieter than you expected. <S> But no, the engines were almost certainly not simply turned off, that just doesn't happen. <S> The only thing I can think of that would cause that would be a flame-out, and you'd definitely notice that! <A> Two very good answers already. <S> I just wanted to mention that as far as I can tell there are just two instances where a modern passenger jet lost all four engines. <S> In both cases it was a B747 (in 1982 and in 1989), both due to volcanic ash, and they were both able to restart them eventually. <S> There is another report of a military aircraft (C17) that had a four-engine flameout in 2010 due to a lightning strike. <S> They were still able to restart two. <S> In summary, it seems as there is not a single record of a four-engine passenger jet landing without operational engines. <A> As mentioned above, what you probably experienced was the flight crew retarding the thrust levers on the engines to idle during the round out, typical of landing operations; the silence being the noticeable difference in sound as you had become used to cruise and/or descent thrust settings and the accompanying whine or noise the engines make when listened to from the cabin. <S> I am not aware of any procedures where a crew would knowingly shut down one or both engines of an revenue carrying airliner unless it was an emergency. <S> As a test of this, once the airplane touched down, did you hear a sound of the engines 'revving up' as the thrust reversers were deployed? <S> If so, the engines definitely were not shut down at round out. <A> Keep in mind that if something goes bad during the approach, the airplane must be able to do a go-around, i.e. full power and again airborne. <S> If you shut down the engines you would had no time (and speed) to restart them, and that would be against the flight safety. <S> Even if ALL the engines had stopped (it happened more than once, principally due to lack of fuel - you can search the history of the Gimli Glider), be sure you could notice it, because you would have landed in the nearest airport (and not your intended destination), and you would have lost the cabin illumination. <S> In that cases, the electric systems supply power to the most importants systems of the airplane, and at the cabin you should notice this effect. <S> You can at either case be sure the pilot would not put the flight into danger.
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There's virtually no chance of the pilot deliberately switching off all 4 engines, and even less chance of all 4 engines failing at the same time.
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Can we borrow Formula One's ground effect for airplanes? ( Source ) Inspired by the now banned late 70's F1 ground effect , I wondered if it can be adopted by airplanes. So, I came up with this: (Own work) The system A belly door that opens at slow speeds and leads to a narrowing cavity—inverted diffuser. In essence, the same as the F1 image above, but enclosed since there's no ground. And inverted since we need lift, not downforce. An F1 car's ground effect is the opposite of a plane's ground effect. The door is to stop its operation at high speed. Theory of operation The narrowing cavity will speed up the air, the air in the cavity thus will lose pressure (potential energy tuned into kinetic), the air outside the plane and underneath the cavity will be higher pressure, forcing the plane up. There's no mission, just an experimental racing Howard Hughes kind of thing. The engineering why is higher top speed, and low angle of attack slow flight. The way I see it at slow speed the center of lift will shift aft, thus lowering the required angle of attack, I'm not sure about the longitudinal control authority and stability though. Also, there'll be no need for high-lift devices and their associated systems, and possibly shorter wings, thus shedding weight and increasing top speed. Can it fly? Are the assumptions above correct? Engine location, nose gear location, etc., are not part of the question, just a pure aerodynamics question if we can make a cavity produce lift. <Q> The reduced pressure on the car not only exerts a downward force on the car, but an equal upward force on the ground. <S> Mythbusters did an episode where they drove an Indy car over a manhole to show that it does lift the manhole cover slightly. <S> The force on the ground is irrelevant because it doesn't move and is not attached to the car. <S> But in your drawing the same thing is happening. <S> The reduced pressure exerts an upward force on the bottom of the channel and an equal downward force on thing top of it. <S> They cancel each other. <A> The issue here is that ground effect requires there to be another body in which the airfoil is in close reference to (i.e. the ground). <S> The wiki article sums it up nicely <S> A substantial amount of downforce is available by understanding the ground to be part of the aerodynamic system in question <S> You cant have ground effect occur inside an airfoil and generate lift in reference to that airfoil. <S> In a more general answer, there have been "aircraft" of sorts (generally known as Ground Effect Vehicles) that have taken advantage of ground effect and the reduced drag benefits. <S> Generally speaking they were never terribly successful as they have a limited mission profile due to their operational requirements. <S> ( source ) <A> No, this doesn't work: it's directly analogous to trying to fly by grabbing your shoelaces and pulling upwards. <S> What your device would do is to increase the force between the top part of the channel and the bottom part of the channel, but those are both parts of the aircraft <S> so there is no net effect on the aircraft as a whole. <A> One of the reasons the lift is increased in the ground effect is the ram pressure, which produces an upward force on the wing/ aircraft when it is close to the ground- <S> this works only when the aircraft is moving relative to the ground. <S> The aircraft exerts an equal and opposite force on the ground. <S> Now, the same force is exerted on the lower part of the aircraft- <S> so in effect, the net lift produced is zero. <A> In short : The mechanism on F1 is a Venturi tube. <S> This tube and the principle of a wing have similarities between themselves, but the significant difference is the absence of downwash in the Venturi tube. <S> Due to this absence, lift is not created. <S> Details <S> The car wall and the ground create a Venturi tube . <S> In a Venturi tube air pressure is reduced where the section is constricted (according to Bernoulli principle ): <S> Source: <S> Wikipedia <S> This suction effect is the one also at work on a carburetor (where it can create icing due to temperature being lowered in the low pressure section) or an airbrush: <S> Source <S> It works in F1 because there is a tube created with the ground, the walls of the tube have a tendency to move closer, so the car is maintained close to the ground. <S> There is no lift per se, the vertical air motion (downwash) necessary to produce lift isn't created. <S> So your design principle... <S> A belly door that opens at slow speeds and leads to a narrowing cavity—inverted diffuser. <S> In essence, the same as the F1... ... won't create lift, because air mass, velocity and pressure are equal at inlet and outlet. <S> And, as soon as you adjust the Bernoulli/Newton effects so that there is an acceleration and a downwash, then you have created a wing: Source <S> In a wing, there is somehow a Venturi tube too: The upper wall is actually created by the viscosity and mass of the atmosphere above the wing, outside the boundary layer, and the lower wall is the wing upper surface: Source
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Ground effect works for the car because it increases the force between the car and the ground, over and above the car's weight.
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What is the reason of having an Angle of Incidence on an airplane? I know that the angle of incidence is the angle between the chord line of the wing and the longitudinal axis of the fuselage. I know that it doesn't change in flight because it is fixed. And usually, there is a positive angle of incidence on airplanes, which means that the wing kinda looks like this: credits: Naval Aviation Schools Command aerostudentguide(dot)pdf My question is, why is there a need to incline the wing like that? Why is there a need for Angle of Incidence? <Q> Strictly speaking, there is no need to set a particular angle of incidence- <S> the wing will decide that for itself depending on the conditions (speed, weight, altitude etc.). <S> What we are deciding is the The mounting angle, which is set for various reasons and is not variable in flight (except for some rare cases) including: <S> Mostly this is set so that the fuselage is (nearly) horizontal during cruise. <S> This is especially important for airliners- DC-10, especially flew at a pronounced nose high attitude requiring the cabin crew to walk uphill. <S> Setting the wing at an incidence helps improve the visibility- <S> this is important especially for carrier aircraft, where the pilot requires good visibility and also higher angle of attack (for keeping t/o and approach speeds low). <S> Having the wings at an angle and fuselage horizontal means that the drag is minimized, while the wing has the required angle of attack. <S> Though the angle of incidence is usually fixed, it can be varied in response to specific requirements. <S> A good example is the Vought <S> F-8 Crusader , which allowed the wings to be pivoted 7° out of the fuselage on takeoff and landing, resulting in a high angle of attack -- reducing the approach and take-off speed -- while keeping the fuselage level and giving the pilot a good forward field of view. <S> F-8 Crusader with the wing pivoted up during landing. <S> By USN - U.S. DefenseImagery photo VIRIN: DN-SC-88-06695, Public Domain, Link <S> Another example is the Martin XB-51 <S> which had a variable incidence wing to reduce the takeoff run. <A> The wing will pick the angle of attack that is appropriate for the given speed, air density and the needed lift. <S> If it is too high, the aircraft will accelerate upwards which will reduce the angle of attack, and vice versa. <S> The wing's angle of incidence will then define the angle at which the fuselage sits during flight. <S> What a proper angle is depends on the aircraft: <S> On transport airplanes, it makes sense to have a horizontal floor during cruise so the flight attendants don't have to push their carts uphill . <S> This will result in a slightly positive incidence angle. <S> On high performance airplanes the incidence is set to optimise the lift to drag ratio. <S> On aerobatic airplanes it is set to zero <S> so the aircraft can be inverted without elevator input . <S> On crop dusters, it might be important to give the pilot the best possible view <S> so he/she can fly safely while manoeuvring close to the ground. <S> The next important detail is the height of the tail surface relative to the wing's vortex sheet. <S> If the tail is too far above, it will sink into the wing's wake during stall and become less effective. <S> A deep stall stability condition might be the consequence. <S> Only by defining the angle of incidence can the airplane be built and operated as designed. <A> My understanding is this. <S> One of the design consideration of fuselage design is to avoid flow separation. <S> And another important thing is that usual looking fuselage is not very efficient at providing lift because both above cases produce huge amount of drag. <S> So it is important to avoid the fuselage from separating flow and non-lifting/less lifting in normal configuration in cruse condition. <S> To do so its important to keep the fuselage nearly horizontal Secondly to produce max L/D or nearly max <S> L/D wing has to operate in some positive AoA. <S> This can be achieved by introducing this incidence angle. <A> Let us denote $\delta_{wing}$ the incidence of the wing. <S> For moderate values of the angle of attack of the airplane $AoA$ the lift coefficient of the wing has a linear behavior :$$Cl_{wing}=\frac{dCl_{wing}}{dAoA}(AoA+\delta_{wing}-AoA_0)$$Where <S> $AoA_{0}$ is the value of $AoA+\delta_{wing}$ for which the lift coefficient is zero. <S> $AoA_0$ is a constant. <S> Basically the incidence of the wing increases the effective angle of attack of the overall wing. <A> You understand that lift is generated by the action of the wing pushing air molecules down as it moves forward, requiring an angle of attack to the air passing under the wing? <S> So if you don't tilt the wing with respect to the body of the aircraft, then to get the angle of attack required to generate lift, you would need to tilt the body as well, greatly increasing the (non-lift generating) surface area and so greatly increasing the drag. <A> Angle of incidence is required to generate lift if the roll axis is parallel to the airflow. <S> Otherwise the fuselage would also be required to present AoA in order to generate lift. <S> The wing's AoA = AoA of roll axis + angle of incidence and AoA <S> is the primary creator of lift, not the shape of the wing, contrary to popular belief. <S> Otherwise how could planes fly inverted?
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Setting the wing at an angle helps in keeping the drag low for the given lift.
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Why did WWII prop aircraft have colored prop tips? Why do propeller aircraft from World War II and similar planes sometimes have the tips of the props colored? I see it on single engine planes like the P-51 as well as bigger, multi-engine planes such as the B-17. <Q> The prop tips are painted for visibility, to show that the prop is turning. <S> This is especially important when the aircraft engine will be running in close proximity to people on the ground, but is also helpful in alerting the crew of other aircraft that the engine is running, and the aircraft might be moving soon. <S> For visibility, the tip color should be in high contrast to the blade, typically white on black. <S> Some operators paint the prop tips in an alternating pattern for a strobe effect for heightened visibility. <S> This is especially helpful when operating in areas where people on the ground may be unused to being around aircraft; the strobe effect is an attention-getter. <S> A three bladed prop painted in this way might use a pattern of one, two, and three stripes, or two, three, and four stripes. <S> Here is an example of what this pattern would look like on a 206: <S> Source: own work <S> This is what the pattern on a Quest Kodiak looks like in motion: <S> Source: excerpt from original photo by Dave Forney <A> That is not unique to WW2 planes, this is fairly common on most prop planes. <S> It is to increase the visibility of a running (spinning) propeller to help people on the ground from accidentally coming in contact with them. <S> The unpainted propellers on the large aircraft may be more related to wartime haste than anything else. <S> ( source ) From the Mccauley propellor guide 7. <S> Why are propellers painted? <S> The faces of the propeller blades toward the pilot are painted non-reflective black so the spinning propeller is not seen as a shiny, hypnotic disc. <A> Visibility. <S> Even on modern aircraft. <S> On the flight decks of carriers for example. <S> The E-2C and C-2A's prop tips are painted with a unique paint. <S> As the prop turns, the friction between the prop and the air cause the paint to glow making it easier to see. <S> The aerospace and automotive-grade paint is applied to the tips of aircraft propeller blades, helicopter main and tail rotors, and other rotating objects to allow personnel to avoid injury or death from coming into contact with them in low-light situations. <S> The paint was developed under a Naval Air Systems Command (NAVAIR) contract as part of the Navy’s Small Business Innovation Research (SBIR) program. <S> — Defense Holdings, Inc. Source — <S> The [above] un-retouched photos show how a propeller with its blade tips painted with DHi’s PL safety paint (seen as two green rings) compares to a prop painted with traditional red and white safety marking paint (which is nearly invisible). <A> As mentioned above, the bright paint is there to make it easier for ground personnel to spot the edges of the propeller arc in daylight operations. <S> The picture of the early B-17s looks late pre-war, when that was the style for the Air Corps. <S> Later example from the war do add this hi-viz paint to the tips of props. <S> I guess there were enough accidents associated with propellers that it became imperative to paint props this way for safety reasons. <S> It's not limited to WW II era airplanes. <S> Just about all propellers used today use this hi-viz paint on the tips, like the current production sample of an SR22.
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The tips on the opposite side are painted bright colors so the spinning propeller can be more easily seen to warn those on the ground about walking into it.
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Why isn't tungsten used in supersonic aircraft? Why isn't Tungsten used in supersonic jets or flights even though it has a High Melting and Boiling point? <Q> While tungsten does have a high melting point (I'm not sure what's the relevance of boiling point here), it has little else to offer for aircraft construction. <S> The main issue of course is weight. <S> One of the main goals of aircraft design is to reduce weight while achieving all the required performance parameters and tungsten <S> is among the heaviest elements around , even beating Uranium. <S> When you factor in its density, it appears less than <S> ordinary- <S> its specific strength is less than 100 KNm/kg , less than half of Aluminum. <S> Another thing is that tungsten is not exactly an easy material when it comes manufacturability. <S> Even its saving grace, the high melting point (over 3000$^{\circ}$ C) is not very relevant as far as supersonic aircraft are concerned. <S> The temperatures experienced in aircraft anywhere other than engines is well within that limit. <S> For example, the surface temperature of Concorde wouldn't even get to a tenth of it. <S> Concorde surface temperature; image from <S> erau.edu <S> Surprisingly, tungsten is indeed used in aerospace industry- <S> at exactly the other end of the speed spectrum. <S> it is used as a counterweight for controls in small aircraft and also as balancing masses in rotorcraft blades. <A> While having one of the highest melting points, Tungsten is very heavy (very dense). <S> Excess weight is detrimental in aircraft design. <S> Some of the parts that would need to be the most heat resistant, such as turbine blades are subjected to rotational forces that increase directly with the mass of the part. <S> Thus a high mass material such as tungsten would increase the forces the part would have to withstand. <S> These forces are already measured in tons per blade. <S> Tungsten is also brittle. <S> If a turbine blade failed, as does happen, it would be very difficult to contain. <S> Most other heat critical uses do not require high melting points, making other materials quite suitable. <S> Tungsten could have applications in ballast or balance weight applications, but lead usually works quite well here. <S> On heat sensitive supersonic aircraft, tungsten could possibly be a suitable choice for this application, as lead does have a very low melting point of 327.5°C. <S> On some of the fastest supersonic aircraft, skin temperatures could reach 200-500+°C, making lead unsuitable for these applications. <A> In extreme flight conditions (i.e., hypersonic flight), it is; the nosecap of the X-51A was tungsten (PDF). <S> Its density just isn't worth it at mere supersonic speeds. <A> Being at the extreme end of a scale (see: <S> melting point) isn't necessary to cross the threshold of being the most useful. <S> For example, the B-2s carbon-graphite frame is stronger than steel, less dense than aliminum, and has a melting point of 3,500 degrees C, whereas tungsten would melt at about 3,400 degrees <S> C. Both of these are far higher than necessary even if you account for gas-turbine compressor combustion, but reducing weight reduces work and increases speed.
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Tungsten is used in armor piercing projectiles; the results of a tungsten turbine blade failure would not be good.
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Why do jet engines smoke? ( YouTube video ) From the video linked above, I was wondering why the engines emit so much smoke? Has something gone wrong? Poor maintenance? Isn't it dangerous? <Q> Early jet engines used to create a lot of smoke due to these reasons (and due to lack of environmental regulations). <S> KC 135 engines creating smoke due to water injection By USAF Photographer - USAF photo, Public Domain, Link Water injection, while cooling the engine, quenches the flames to an extent, resulting in unburnt fuel, which comes out as smoke. <S> However, aircraft have moved away from water injection, reducing emissions. <S> Another reason for the smoke is inefficient combustion- <S> older jet engines (turbojets in first aircraft and low bypass turbofans) were not as efficient as engines today, which premix the fuel with air and pre-vaporise it before combustion, rather than using droplet combustion- basically mixing fuel more evenly with air. <S> Requirements of fuel efficiency along with stricter regulations mean that engines today have less emissions compared to their predecessors . <S> Smoke during Boeing 707 takeoff <S> ; image from nycaviation.com <S> In this case re-engining the aircraft with more efficient ones usually results in a reduction of smoke. <S> For example, the USAF re-engined the KC-135 s (from Pratt & Whitney <S> J-57-P-59W turbojet to the CFM International CFM56 turbofan ), which along with the elimination of water injection, reduced smoke. <S> On the top is KC-135s from an exercise in 1979; image from network54.com . <S> Below that is KC-135Rs from Singapore Airforce; image from reddit.com <A> Fundamentally, because jet engines do not burn a pre-mixed fuel/air mixture. <S> Fuel can burn in three ratios: lean, stoichiometrically and rich; respectively: an excess of air, exactly enough air, and an excess of fuel. <S> Ideally, one would always burn in a stoichiometric ratio; intuitively, one can feel that this means you don't waste fuel on heating an excess on air, and you're not left with any unburnt fuel. <S> This is how a typical spark ignition engine works: fuel is mixed in the carburetor, compressed and burnt. <S> The throttle varies how much fuel/air mixture enters the engine, but the mixture will always be (close to) stoichiometric. <S> A jet engine does not have the luxury of pre-mixing the air/fuel mixture before ignition. <S> Spraying Jet-A in the compressed, (hot!) <S> burning air will lead to ignition as soon as it comes into contact with oxygen, whether you like it or not. <S> The problem is that it will already ignite when the local mixture is still rich . <S> This will inevitably lead to soot formation, which is the smoke you see. <S> This is especially prevalant at high power settings (like during takeoff) - at a given RPM, the amount of air that is pumped through the engine is constant, and the amount of power is varied by injecting more or less fuel into the engine, thereby creating a less lean mixture at high power. <S> Note: <S> the engine RPM will react to the power setting in a jet engine; however, the amount of air will generally lag the amount of fuel at higher power settings <S> There are some methods to mitigate soot formation, which are all based on increasing the fuel-air 'mixedness' before ignition. <S> A lot of research is being done on this by improving the combustor . <S> The linked Wikipedia article has a very nice and thorough explanation on what exactly is being done for this, but in general (and extremely simplified), it comes down to spreading the fuel as much as possible and introducing as much air as possible (but remember that running too lean reduces efficiency), all without dousing the flames. <S> See the image below for the complex arrangments already made in the combuster on an older cannular design. <S> Source: wikimedia <A> Collin Krum has written a fairly in-depth article on the matter for Jalopnik. <S> It's also worth noting that not all of the engines in that video are jet engines. <S> From the article: Low bypass engines aren’t as efficient as high bypass engines, but water injection is the technology that is most responsible for the seemingly-eerie pictures of older airplanes riding black columns of smoke into the sky. <S> ... <S> Because the engine core is cooled by the injected water, the combustion chambers aren’t able to burn all of the fuel and water mixture, so some particles of the fuel and water are vented out the engine, which materializes in the form of the characteristic black smoke. <A> Some of the AGE <S> /GSE <S> I work with uses jet engines. <S> During startup and shutdown, surely expect the temperature not to be at its maximum. <S> That can be one cause of unburnt fuel. <S> Another cause could be a gradual buildup of fuel depending on the interval of the pneumatic thermometer's ability to help quench the bleed air.
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Smoke in jet engines is usually from unburnt or partially burnt fuel (or by water injection).
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Was the Boeing 747 designed to be supersonic? I heard a rumour that the Boeing 747 was originally designed for supersonic cruising. Is this correct? Are the airframe and wings able to cross the sound barrier without damage? <Q> No. <S> The Boeing 747 was not designed for supersonic flight, though during testing, it was pushed quite close to the sonic speed : Tom Cole, a spokesman at Boeing Commercial Airplane Co., said original flight tests of 747s conducted in 1969 and 1970 took 747-100 models to speeds of Mach 0.99. <S> However, the aircraft is not built for sustained supersonic speeds: ... <S> Boeing and the FAA said the 747 is not built for sustained flight at the speed of sound. <S> Its engines aren't powerful enough nor is it designed to deal with a destabilizing shock wave that develops around the speed of sound. <S> However, it is just possible that the airframe and wings can cope up with the supersonic flight, at least for a little while, though any sustained flight is not possible. <S> There have been cases where the 747 has gone quite near the speed of sound and lived to tell the tale. <S> China Airlines Flight 006 went into a dive and went near supersonic speeds before the captain could recover it. <S> As a result the horizontal stabilizers were ripped off and the wing bent permanently upwards. <S> Damage to China Airlines Flight 006 empennage. <S> By NTSB - China Airlines Boeing 747-SP Accident Report by NTSB, http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/ChinaAir/AAR8603.html , Public Domain, <S> Link <S> In 1991, a Boeing 747 of Evergreen airlines entered a steep right wing bank and approached sonic speed before recovery was completed. <S> NTSB notes : ... <S> the airplane was in a steep right-wing-down bank. <S> The flight lost approximately 10,000 feet of altitude, and the airplane approached supersonic speeds (0.98 Mach) before the recovery could be completed. <S> Later, the Israelis took it close to sonic speed . <S> In these cases, parts of the aircraft certainly experienced local supersonic flow; however, the airframe and wings are not designed for supersonic flow nor are the engines powerful enough. <S> In one case, the aircraft suffered extensive damage (though it was repaired and returned to service). <A> However, it was designed as an interim aircraft while the SST(SuperSonic Transport) was being developed. <S> As you probably know, the SST never panned out, and the 747 is now one of the most influential aircraft in the world. <S> As a book I read put it, the 747 was likened to a Mack truck of aircraft; it wasn't glamorous, and the SST was supposed to steal the show. <S> Some good reading on the 747 if you want more would be747: <S> Creating the world's first jumbo jet, by Joe SutterWide-Body: The triumph of the 747, by Clive Irving <S> It really is a fascinating story. <S> It was developed in a very short time, and the amazing part is that they got it right. <S> Anyhow, maybe you heard that it was supposed to be an interim aircraft and got it confused. <S> Hope this helped! <A> You can see from the design that it's not quite apt for supersonic flight. <S> This topic is best explained in aviation textbooks, but here's a simple explanation. <S> In subsonic flight there is a 'cushion' in the leading edges of the aircraft directing the airflow gently around the aircraft instead of having it hit the fuselage with full strength. <S> However, in supersonic flight the cushion cannot be sustained and the impact between air and fuselage is much stronger. <S> Taking this into effect it can be seen from studying supersonic aircraft designs such as SR-71 and concorde that the area where the oncoming air can impact the fuselage is smaller than in conventional airliners. <S> The bulge in 747's hull design wouldn't be optimal for supersonic flight.
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The Boeing 747 is NOT designed for supersonic flight...
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How does a jet's throttle actually work? How does a jet's throttle actually work? What does it do to the pressure chamber and the fire output controller? <Q> The throttle (or thrust lever) in a gas turbine engine adjusts the thrust produced by controlling the fuel flow to the combustion chamber. <S> Most of the modern engines are actually controlled by the Full Authority Digital Engine (or electronics) Control, FADEC (or Engine Control <S> unit)- <S> so the signals from the throttle are sent to the computer, which regulates the fuel flow based on various parameters (including engine safety) thereby adjusting thrust. <S> The computer handles the additional components of the engines like the thrust reversers and afterburners. <S> The image below shows the throttle controlling the fuel system through the engine control in the Pratt & Whitney F100 engine that powers F-15 and F-16. <S> Image from kaskus.co.id <A> I'd suggest that you review the topic of how a jet engine works , first, and then review how a jet engine fuel control unit works as it doesn't sound like you're very familiar with engine components; I've never heard of a 'pressure chamber' or 'fire output controller'. <S> Modern jet aircraft technically don't use throttles; rather they are equipped with thrust levers which are connected to a Fuel Control Unit (FCU). <S> This can come in the form of a mechanical computer in the case of earlier engines or a digital electronic computer called a Fully Authority Digital Engine Controller (FADEC), similar to the schematic in aeroalias's answer for the F100 fighter engine installation on the F-16 airplane. <S> This could be problematic to operate in flight as the fuel rate has to be changed as altitude - and consequently combustor inlet conditions - changes, making the engine vulnerable to flameouts from excessively rich fuel flow and compressor stalls from abrupt throttle changes. <S> FCUs were developed, specific to each engine to offer simplified control. <A> Jet engines run on the Brayton cycle which is isobaric (constant pressure) combustion from a thermodynamic perspective. <S> Assuming the engine is already in a steady state, when you open the throttle you introduce more fuel (regardless of how computerised or otherwise). <S> More fuel translates as more heat into the combustion chamber. <S> As we calculate this as constant pressure <S> this mean we increase the volume of the fluid flowing through. <S> In practice this is seen as a faster fluid flow rate exiting the chambersThis increased volume/flow rate impinges on the turbine as it expands adiabatically <S> it imparts more work into the turbine, spinning it quicker which spins the compressor quicker drawing in more airflow. <S> Once past the turbine the exiting gas flow has a higher velocity and higher momentum which through Newtons laws becomes greater thrust. <S> It's not finished there through. <S> The turbine/compressor will continue to speed up (adding more air to the system) until the system achieves a new steady state at a higher fuel flow, higher compressor/turbine rotation speed, higher turbine temperature and of course higher thrust. <S> We could keep adding higher and higher fuel flows but there are a number of limits to the system, which ultimately limits the maximum thrust.
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Early jet aircraft did use a throttle - literally a cockpit lever connected to a throttleable valve to precisely meter fuel into the combustion chamber(s) of the engine.
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How does the Aerobridge dock with an aircraft? What mechanism is employed by the Aerobridges to dock with the aircraft. I am not looking at how the plane docks but how the aerobridge manages to attach itself over the door of the aircraft? Is it some vaccum tech or what? From outside, one can only see the bellows/ flexible diaphragms. What I am looking for is actually - how two non-conformal surfaces can be "joined" in order to create a sealed "lock" (assuming its closed from all other ends). This came to my mind and now I am trying to understand this as the situation is almost the same. <Q> Rather they are just maneuvered up against them with a soft canvas hood which can be actuated around the fuselage allowing protection from the weather for passengers and crew. <S> The jetway is maneuvered to and away from an aircraft via a small control panel near the hood of the jetway which controls an electrically driven wheeled drive supporting the terminus end of the jetway as well as screw jacks in the support pillars for elevation control. <S> This allows a user to translate the length of the tunnel or rotate it about its connecting point to the terminal. <S> The tunnel can do this by means of telescoping sections. <S> The terminus of the jetway can be swiveled to match the curvature of the fuselage and the tunnel makes contact with the jet at the base of the terminus, usually with a neoprene bumper to prevent damaging the fuselage. <S> The hood can then be lowered for weather protection. <S> The jetway will reverse this process after the main cabin door has been closed and secured and before pushback to prevent contact and damage with the aircraft during pushback. <A> Well, the jet bridge does not actually join with the airplane. <S> If you look at the place where the jetbridge and the airplane meet, there is a rubber bumper and some accordion cover (that just comes down on top of the doorway) which are the only things which touch the airplane. <S> The two things never actually make a seal where they meet. <A> To answer the actual question, unless you can draw a vacuum seal it's not really possible without throwing straps around the object being captured and pulling them taut to hold it in place. <S> And even then you'd need some kind of compressive material to actually cause some sort of seal between the objects. <S> But that of course is out of the realm of aviation and thus off topic for this site. <S> Think the docking adapters on spacecraft, the in flight refueling systems on military aircraft.
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Well jetways don't exactly 'dock' with an aircraft; there is no hard coupling between the tunnel and the airplane like say that found with a spacecraft docking. Actual docking systems always involve specially designed parts that hook up to each other and lock in place, plus a sealing mechanism (for example a rubber sleeve).
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What is a Cessna 172's maximum altitude? What is the maximum altitude at which a Cessna 172 can fly? <Q> The absolute ceiling, or the maximum height an aircraft can fly to, is usually not published; manufacturers usually use service ceiling as the benchmark. <S> Depending on the model 172, this is between 13,000-15,000 feet ASL. <S> A Cessna 172SP has a published service ceiling of 14,000 feet ASL. <S> Again whether an airplane can attain these altitudes on any given day is dependent on the condition of the air. <S> The aircraft may be able to ascend higher than this on days when the air is very cold and there is a high local barometric pressure or lower on days when the air is warm and/or at a low barometric pressure in the region. <A> In September of 2007 in my 0-360 1959 172 <S> I attained 18,003 ft GPS above 19AZ. <S> I checked with Cessna customer service. <S> The fella called me back a couple of days later. <S> As far as he could find I did set a record. <S> The plane was still climbing slowly and rather wobbly. <S> I was happy to roll out and level off at 15 000 ft where I could catch my breath. <S> I took off with a little less than half gas. <A> According to this , the 172's absolute ceiling (the altitude above which it is impossible to fly under standard meteorological conditions) is 15,000 feet. <A> According to the C172M manual, the service ceiling is 13,100ft:
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Service ceiling is the maximum altitude which the aircraft can attain flying in air at Standard Temperature and Pressure (29.92" Hg and 15° C at MSL) and still be able to climb at a rate of at least 100 feet/min.
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Are aviation accident investigation reports always made public? How is the dissemination of aviation accident investigation reports regulated? Are the reports public by default, or can they be kept secret? Are there any known rules on this? If the reports are not public, do the people involved in the accident have a right to access the evidence and/or the reports? Can they find out what the verdict (if there is one) was? This surely depends very much on the country. Please indicate the regional scope of your answers. (My interest is specific but not limited to France.) <Q> Unless there is some risk of national security to releasing a public report of the accident, the reports are released. <S> You can search the public ones (almost all are public) at the BEA website . <S> The same applies for the other aviation accident and incident reports and you can find the available reports on the websites of the group that has jurisdiction over the accident/incident; <S> NTSB for the US, <S> AAIB for the UK, and many other ones. <A> This is a complicated answer, and yes, it is very dependent on country and even the type of accident. <S> First, be aware that there can also be a big difference in "incident" vs "accident", and they may be reported differently. <S> Next, each country has its own laws and regulations about the dissemination of materials generated by government entities. <S> I don't know French law or it's rules for releasing records, so I would have to defer to somebody familiar with it. <S> In the United States we have the Freedom of Information Act which regulates how documents are released, exemptions from release, and a request process. <S> Again, I'm not sure about the French, but in the U.S. we have something called Procedural Due Process which allows both sides of the proceedings equal access to evidence. <S> This comes from Due Process and by extension, the Magna Carta . <S> Really now we are getting into the rights and obligations under law and is a bit outside the scope of this site. <S> Point is, at least in the U.S. <S> a person in a civil or criminal lawsuit has the right to examine the evidence as equally as the prosecuting party. <S> Now, as far as current access to records... This is a digital age, everything is done on computers, fed to servers, and can easily be made available to the general public, usually if it is in the public interest. <S> 1989 was a different story. <S> The first "laptop's" weren't introduced until the 80's and ones that would run word processing software weren't readily available (or very affordable). <S> Most investigators at that time would take notes on paper then go back to an office and type them up (on a typewriter mind you). <S> These reports would then be given to others in the organization and filed. <S> The U.S. has done a pretty damn good job of digitizing old reports and it may be that the French have not have bothered to put the resources into digitizing these reports. <S> If your search for information is purely "on the web", you may need to actually visit a library (national) or make a request to the investigating agency. <A> USA <S> The public availability of information is regulated in <S> 49 CFR Part 801 : [TBD: insert here a summary of relevant parts of this regulation ] <S> European Union Dissemination of investigation reports is regulated through Regulation (EU) <S> No 996/2010 . <S> According to this document, the investigation reports are to be made public ("in shortest possible time and if possible within 12 months") <S> the following information shall not be made available (shortened - see Reg. <S> 996/2010 <S> Art 14 for complete text): <S> statements taken from persons records revealing the identity of persons information of particularly sensitive and personal nature <S> material subsequently produced during the course of the investigation information and evidence provided by other countries draft, preliminary, or interim reports or statements <S> cockpit voice and image recordings communications between persons involved in the operation of the aircraft recordings and transcripts from air traffic control covering letters and occurrence reports the regulation shall not apply for accidents and incidents which involve aircraft engaged in military, customs, police or similar services, except when the Member State concerned so determines. <S> (Art. 3.3) the question of guilt is not in the scope of the accident report. <S> Therefore the dissemination of a verdict is not covered by this regulation. <S> France BEA states on its website : " <S> In the context of an investigation that it conducts after an aviation disaster, the BEA: <S> Communicates through various means (internet site, press releases, and press conferences) at each major stage of its investigations (initiation of the investigation, information, interim report, and final report) to the media and the public. <S> Regularly sends mail to the families of victims providing updates on the progress of the investigation and gives them first access to reports to be published. "
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European Regulation European regulation n°996/2010 specifies that the BEA makes public information on the progress of its investigations and that it informs in advance the members of the families of victims.
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What kind of dihedral would be most stable? What kind of dihedral would be most stable? An airplane with wing span x ft and whose dihedral begins from the root(attachment point to the fuselage) of the wings and whose wing tips are y ft above ground level. An airplane with wing span x ft and its dihedral begins from the mid point of the wings from the wing root and its wing tips are y ft above ground level. An airplane with wing span x ft and its dihedral begins at a distance 2/3 of each wing from the wing root and its wing tips are y ft above ground level. Note: They are all low wing airplanes of equal size, power, weight, wing span, wing chord etc. Only the starting point of the dihedral and the angle of dihedral vary. I also believe a polyhedral wing will be most stable(everything being equal). Am I right? <Q> More dihedral doesn't necessarily make an airplane more stable. <S> With too much of it, oscillations like the Dutch roll are not damped any more. <S> A polyhedral wing can be chosen for different reasons than just stability: With the dihedral of the outer panels, any angle of attack change there is reduced by the cosine of the dihedral angle. <S> This means that the lift curve slope is flatter there and stall happens later. <S> This is a great way to combine an almost elliptical circulation distribution with pleasant stall characteristics, similar to a raked wingtip , but using dihedral instead of sweep! <S> For the stability derivatives of partial dihedral I recommend to turn to no other source than Sighard Hörner's Fluid Dynamic Lift . <S> In chapter XIV it shows a plot of a rectangular wing with an aspect ratio of 6 where the location of the onset of the dihedraled wing fraction is plotted over the X axis. <S> This data is taken from NACA's technical report 548 : <S> Figure 13 from Chapter XIV of Fluid Dynamic Lift by Sighard Hoerner. <S> Note that it plots the derivative of a derivative on the Y axis! <S> The $c_{l_{\beta}}$ curve can best be approximated by a sine curve. <S> Note that the Y axis shows the $c_{l_{\beta}}$ and $c_{n_{\beta}}$ derivatives over changes in the dihedral angle $\Gamma$. To arrive at your expression with constant tip elevation for different dihedral onset locations, the curves need to be modified by dividing them by the cosine of the partial span (assuming the root is 0 and the tip is $\frac{\pi}{2}$). <S> This would yield a constant value for $c_{l_{\beta}}$, so the dihedral onset is of secondary concern and the dihedral effect depends on the tip elevation. <S> Note: This is valid only for rectangular planforms - as soon as taper is involved, things get more complicated. <S> This PDF has more on effective dihedral of tapered wings. <S> NACA <S> TR 548 supports your opinion: <S> The tests also showed that with dihedral only the outer one-fourth of each semispan, the dihedral effect was maintained to a much higher angle of attack than when the complete wing had dihedral. <A> You'd right that the polyhedral wing would be most stable considering all other things being equal. <S> One way to compare the effectiveness of the dihedral angles between two wings is to determine the equivalent dihedral angle- which is the dihedral angle of a constant dihedral wing with equivalent roll moment. <S> The image below shows a curve relating the relative rolling moment of the wing as a function of the semi-span station. <S> Rolling moment as a function of semi-span station; image from <S> rc-soar.com <S> So, a dihedral starting from mid-span would have 65% effectiveness compared to the one starting from root- <S> i.e <S> if the dihedral angle at semi-span is twice compared to that starting from the root, it will be 30% more effective. <S> Let's plug in some numbers and check this. <S> Assuming that the 'y'- the height above root is 10 units for an equal semi span (quite unrealistic, I agree), the equivalent dihedral angle for various configurations can be given as below: conventional- starting from root - 1 starting from semi-span - 1.3 starting from 66% of semi span - 1.2 As you can see, the polyhedral wing is most stable, when only the wing dihedral is considered. <S> The best thing would be increasing the dihedral outwards. <S> However, there are other things to consider here- <S> like manufacturing isssues, locating engines, other things like wing sweep etc, which would make having a constant dihedral more cost-effective. <A> The good part is that it because of its width and mass, the wind will less likely be able to flip the wing and the plane over. <S> Hopes this helps:)
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I believe that the polyhedral wing is stable but not the best because the wings are wide and too easy turn.
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Has there ever been a sideways H-tail on an airplane? I've seen several aircraft with 2 vertical stabilizers and 2 rudders. This could be an H-tail like the B-25 Mitchell or the A-10 Warthog , or something more sleek like the Su-27 . However, I got to thinking, are there any airplanes that have 2 sets of horizontal stabilizers and thus 2 pairs of elevators? This would be a sideways H-tail. I guess it would be sort of like a bi-plane, but in the tail only. Do these exist somewhere? Why or why not? Experimental planes are okay. <Q> Most of the initial aircraft made by Wright brothers had the twin horizontal stabilizer setting. <S> However, the elevators in these cases were set in the front, rather than back, as is the norm now. <S> By Wright brothers - OhioLINK Digital Media Center, Public Domain, Link <S> Quite a few of the early aircraft had a 'box' like configuration, notably the Santos-Dumont 14-bis , which made the first public powered flight. <S> Again, though the pitch control was through the box like structure, it was more of a canard than a horizontal stabilizer. <S> Santos-Dumont 14-bis; image from Wikipedia One of the earliest aircraft with a 'proper' twin horizontal (as well as vertical) stabilizer was the aptly named Bristol Boxkite Bristol Boxkite; By Hpeterswald - Own work, CC BY-SA 3.0 , Link <S> Farman III; By C.C. Pierce & Co. - http://digitallibrary.usc.edu/cdm/ref/collection/p15799coll65/id/12574 , Public Domain, Link <S> You can see that most of these are early aircraft, which had structural limitations. <S> As the aircraft design matured, the 'conventional' layout became the norm as a single stabilizer assembly can be used to achieve the necessary pitch control. <A> The double decker horizontal tail was a popular choice for large biplanes, even into the 1930s. <S> Below is a picture of the Zeppelin Staaken R VI giant airplane and below it a Handley-Page H.P.42 passenger aircraft from 1931. <S> Zeppelin Staaken R VI over Leipzig <S> (picture source ) <S> Handley-Page HP42 passenger aircraft (picture source ) <S> As with the wing, a braced biplane tail makes for a stiff, lightweight structure. <S> An unbraced biplane tail was also chosen by Hermann Dorner for his light attack aircraft , not for weight reasons, but to reduce tail span in order to allow the tail gunner a larger firing arc. <S> The picture below shows a Hannover Cl II. <S> I guess this design comes closest to the requested "sideways H tail". <S> Hannover Cl II with raised tail, probably for compass calibration (picture source ) <S> I have yet to find a monoplane with a biplane tail. <S> Biplane tails vanished together with biplane wings. <A> There is quite a famous example of this! <S> but other than the Wright Flyer <S> , I don't know of any. <S> My layman conjecture as to why this is not more common is that the tail only needs to be large enough to counteract the moment that CG exerts relative to the center of pressure of the wing. <S> Large tail surfaces can balance large torque loads, but that is aerodynamically inefficient compared with maintaining a reasonable CG range. <S> Another aspect of that particular concern is that you can alternatively just make the tail boom longer to create a larger torque arm for the tail surface. <S> My answer to "why not" is that it's just not necessary. <S> There are too many other ways to address control and stability issues to justify increasing the complexity with a double-horizontal stab. <A> The only recent example I can think of (and it's still only in the design & prototyping stage so may not even count) is the Beriev BE-2500 super-heavy amphibious craft. <S> This has a couple of very unique features; first and foremost, it's designed to operate either as an aircraft or as a ground-effect craft , flying very close to the ground on a cushion of air. <S> This is why it has such an enormous wing area, and why the elevators have to be at the top of the rudders so as to not disturb the airflow around the wings. <S> Secondly, it's also amphibious - with two large pontoons providing buoyancy and balance in the water. <S> These are set as far apart as possible for balance, and are structurally connected to the rudders, giving a unique layout.
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Another good example is its predecessor, the Farman III , which had two horizontal stabilizers and a single vertical tail right in the middle, forming a perfect sideways 'H'.
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What is the benefit of a curved up flight deck? A Russian aircraft carrier Admiral Kuznetsov has an interesting aspect: the edge of the runway is raised, which “pushes” the plane in the air during the takeoff. Looking at takeoff videos, the curved edge seems very natural. All USA aircraft carriers I can think of have an absolutely flat deck, similarly to, for instance, USS Abraham Lincoln: The Admiral Kuznetsov's curved deck provides benefits , so why were most carriers not built the same way? <Q> Because the method of launching aircraft are completely different in these carriers. <S> Carriers with ski-jump, initially designed for RN Harriers (as @Simon already has explained), requires that the aircraft take-off under its own power. <S> On the other hand, large aircraft carriers having flat decks have their aircraft launched by catapults (with a notable exception) which basically throw the aircraft from the deck. <S> Though this system is heavy, expensive and complicated, it brings significant advantages to the table: <S> It allows aircraft with higher t/o weight to operate from the carriers. <S> USN operates F/A-18E/F Super Hornets, which weigh ~30 tons from its carriers (they even operated the heavier F-14 Tomcats). <S> The ski jumps, on the other hand restrict the aircraft t/o weight (which means less ordnance), as the Chinese are finding out. <S> Indian Navy operates <S> Mig-29Ks from its carrier, <S> but they are lighter (~25t). <S> The catapult allows for a significantly higher takeoff rate, which means a higher sortie generation. <S> As rusnavy.com notes : With its four catapults, a US carrier is capable to shoot one aircraft in every 15 seconds. <S> Kuznetsov has only three takeoff tracks. <S> Moreover, two bow tracks are not intended for fully-loaded aircrafts! <S> They can take off Kuznetsov only from one track which starts far behind the midship, i.e. an aircraft must run almost the whole flight deck! <S> Comparing to catapult, takeoff rate of ski-ramp is at least twice lower. <S> The catapult allows the launching of support aircraft (like AWACS), which have low thrust-weight ratio and would not be able to take off under their own power. <S> The ski jump takes up space in two ways- <S> physically, it occupies front deck space (on the other hand, aircraft can be parked over catapults when not in use), while the take off run required by the aircraft (greater with more gross weight) eats up more space, leading to limitations of the number of aircraft on the deck. <S> As for the exception, the USN operates carriers without ski-jumps, but these are not called as such- <S> they are called amphibious warfare ships an operate only VTOL aircraft like the F-35 Lightening II and V-22 Osprey. <A> The ramp design may be referred to as STOBAR (Short Take-Off But Arrested Recovery), and this is a fairly simple design to implement. <S> However, the complexity is pushed into the aircraft. <S> Since there is no catapult assistance, aircraft have a hard requirement to take off in the space available, given the ramp at the end. <S> This limits the types of aircraft that can be launched, typically to fighter aircraft that already have high thrust to weight ratios, or aircraft specifically designed for short takeoff capability. <S> Takeoff weight may be limited. <S> Aircraft still must be equipped with an arresting hook for landing. <S> A catapult system may be referred to as CATOBAR (Catapult Assisted Take-Off But Arrested Recovery), and this allows for launching a much wider range of aircraft. <S> For example, CATOBAR carriers can launch large aircraft like the C-2 or E-2. <S> These aircraft would not be able to take off from a carrier without catapult assistance, and provide carrier resupply or AWACS capability. <S> Even fighters that may be able to take off without assistance can be launched with much more payload. <S> However, this capability comes with a cost. <S> The aircraft will need to have strengthened landing gear to withstand catapult launches. <S> The carrier is also made more complex, placing an additional demand on a boiler or generator to provide the large amount of steam or electricity needed to launch aircraft. <S> Modern US carriers are nuclear powered, providing the energy needed for this system. <S> There are also practical considerations in aircraft carrier design. <S> The ramped deck may detract from available space on deck for parking aircraft. <S> You can find many pictures of CATOBAR carriers with aircraft parked on the bow area, which would be difficult on a STOBAR carrier. <S> The angled deck on modern carriers would still allow for launch and recovery of aircraft on a CATOBAR carrier with the bow area occupied. <S> The ramp also reduces forward visibility for maneuvering the carrier. <S> On a CATOBAR carrier, the flight deck must be designed to include the catapults, while on a STOBAR carrier, only the blast deflectors must be integrated into the deck. <A> Think of the ramp as free lift with no maximum lift coefficient so you can't stall while using it, and zero induced drag. <S> If you could make a catapult that curved upward...
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The catapult launch offers more options - it can operate in wider range of sea conditions compared to the ski-jump and can even launch aircraft even if one of the engines fail during the launch , a feat usually not possible for the aircraft in ski-jump.
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What are the disadvantages of a delta wing biplane design? The idea of a delta wing as I understand it is to reduce stress on the wing and drag on the leading edge. Now using two delta wings on separate planes, on one frame would presumably allow for a reduced wing size, and therefore less drag. I imagine it could also lead to a nice compromise with better control in slow flight than delta wing designs? However, clearly there are some major issues with this design, as a quick search uncovers no results for this design shape. therefore I pose the question: Why is it that designers have rejected this possibility; what are its major (dis)advantages? <Q> The main benefit of biplanes is that the lift can be distributed across both wings. <S> This provides more lift with less wingspan and places less load on each wing. <S> Less load means the materials can have lower strength. <S> This was very important in the early days of aviation, when engine power, materials, and weight were much more limited. <S> The major downside of a biplane is aerodynamics. <S> The wings interfere with each other, causing drag. <S> While structural bracing between the wings can reduce weight, it also adds more drag. <S> This means that a single wing will almost always perform better, and modern materials and designs should make that possible. <S> A biplane configuration does not make much sense for delta wings. <S> While delta wings have lower wave drag , they have higher viscous drag due to the large surface area. <S> A second delta wing will add more area, increasing both wave drag (from the cross section) and viscous drag (from the surface). <S> Configuration of the aircraft also becomes problematic. <S> Most aircraft with delta wings tend to be fairly flat, allowing lower area and therefore lower drag. <S> The closer the wings are, the more they will interfere. <S> The further apart they are, the more structure is needed, either in a larger fuselage or in structural braces, which increases weight and drag. <A> Lift is created by accelerating air downwards . <S> If you use two wings stacked on top of each other to accelerate basically the same amount of air, your efficiency goes down, not up. <S> The more air is involved in the creation of lift, the better for efficiency. <S> Reducing wingspan will drive up the lift-dependent part of drag, because the span loading (unit of mass per unit of wingspan to carry) goes up. <S> Biplanes make most sense if the requirement calls for high roll rates minimum structural mass and low airspeed, which was generally why early airplane designers chose this configuration to take to the air. <S> When engines became more powerful and the aircraft had to earn their money by transporting payloads, the monoplane won. <S> A delta wing makes most sense for trans- and supersonic speed. <S> Its capability for vortex lift allows low landing speeds even with thin airfoils without powerful flaps , and its high leading edge sweep enables a subsonic leading edge even at supersonic flight speed. <S> It might be interesting to mention one idea for a supersonic biplane here: This could be used to avoid shockwaves, but only at one particular Mach number when the shocks of the top and bottom wing cancel each other. <S> No airplane has ever used this concept, mostly because in order to work no lift must be created. <A> Besides allowing to be built of materials with less strength (which made biplanes widespread in the early days of aviation), the sole advantage of a biplane is better handling at very low speeds with a shorter wingspan. <S> There are still some biplanes in use today, but more in the "bush plane" category, as their shorter wingspans and low stall speeds allow them to land on rough and narrow fields. <S> The famous An-2 doesn't even has a stall speed, it lands almost like a parachute if you turn off the engine and pull back the stick. <S> So, the main reason one would chose a modern biplane is to be able to fly it at extremely low speeds or in rough environments. <S> Delta wings are designed for high speeds, the polar opposite of where biplanes are good at. <S> You can't optimize an aircraft for both very low and very high speeds, as it would perform worse in both categories.
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The main drawback of a biplane is drag, but drag increases with the square of velocity, and delta wings are best in high-speed flight.
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Is the Fortran language still being used in aviation? I am an aeronautical engineering student at Istanbul Technical University and our course plan includes Fortran as a programming language. I have some doubts about that because Fortran is an old language. Is Fortran still being used in aviation? <Q> FORTRAN is not used much that I'm aware of in aviation , but it is significantly used in aeronautical engineering . <S> I work with people that use Mark Drela's 'xfoil', 'xrotor' and 'aswing' programs on a daily basis for the design and analysis of airfoils, propellers and aerostructures. <S> And I've used the 'CHARM' model of rotorcraft dynamics. <S> All of these are written in FORTRAN and you often need to know the language to debug them or integrate them into other programs e.g. for global design optimization. <A> Fokker Services and DynamicSource AB have jointly developed an iOS Application to run <S> FORTRAN Take Off and Landing SCAP (Standard Computerised Airplane Performance) <S> modules on the Apple iPad®. <S> The app allows an operator to make the performance calculations shortly before take-off and therefore allows the opportunity to incorporate last minute changes with respect to aircraft loading and runway conditions. <S> OEM take-off and landing performance calculation modules are complying with the IATA SCAP interface specification. <S> They are written in Fortran. <S> Normally Fortran programs do not run on iPad® , but the software engineers from DynamicSource AB managed to make this possible. <S> The OEM-supplied SCAP module is combined with a calling program and an airport/obstacle database. <S> Via a user-friendly Graphical User Interface (GUI) <S> relevant data like aircraft-weight, wind, and runway condition are fed into the app. <S> Within seconds the take-off and landing data like V1, V2 and flap setting are presented on the screen of the iPad®. <S> Fortran at 59 Notes for "Fortran at 59 <A> FORTRAN is still in active use for AT LEAST the following reasons, not all of which I have seen spelled out here: <S> FORTRAN has a huge legacy base of code that just works and has stood the test of time. <S> Sure, you can pipe the source through a FORTRAN-to-C converter (which is how some modern FORTRAN compilers actually work behind the scenes), but then you largely ruin any self-documenting nature of the code -- which for many programs and algorithms is the only documentation that exists or is complete and reliable. <S> The syntax and control flow of FORTRAN is relatively simple compared to many modern languages and thus can be used as the "lingua franca" for distributing calculation algorithms that demonstrably work. <S> As a corollary to the immediately preceding point, the fact that FORTRAN is a relatively "dead" language that will not be revised can be seen as a good thing. <S> If you publish a scientific finding, and include the FORTRAN source of the algorithms used to extract the critical data and perform the analyses that support the finding, there is no question that in 50 or even 100 years, scientists and researchers will still be able to run your code somewhere. <S> Can the same claim really be made for something like MATLAB? <S> I think not. <S> You'd be crazy, of course, to try and write a GUI framework or really anything beyond pure number-crunching code in FORTRAN. <S> But what it does, it still does very well. <A> Yes, Fortran is still being used. <S> However, don't get too worried if you find your class less than exciting: <S> Most Aerospace engineers don't do much (if any) computer programming. <S> However, if you intend to go on to graduate school, pay attention in you <S> Fortran class!I think your first priority (regardless of your grad school plans) should be Matlab. <S> Everyone uses it today, especially if you publish. <S> The power of Matlab (and Mathematica) is in their ability to do algebraic equation simplification and producing pretty (publish ready) output. <S> Mathematica used to be the king of the hill in this area, but Matlab has pretty much pushed them out (although Mathematica is seeing resurgence due to the free Raspberry pi version). <S> These are both great tools, but if you need to crunch big data, the tools of choice in Aerospace are Fortran or c/c++.Fortran is preferable when dealing with complex numbers and has many built-in vector, matrix, and mathematical functions. <S> However, it falls short when trying to deal with pointers or interfacing with low level operating system functions (where c shines). <S> But, only a small percentage of Aerospace engineers write code in these languages. <S> Most of the Fortran at Boeing runs on their massively parallel machines performing electromagnetics and fluid dynamics calculations in research areas. <S> The c languages are primarily used in embedded systems ( <S> avionics).My recommendation: You should be proficient in Matlab but know you way around (be able to read and understand) both Fortran and c... <A> My current employer in the flight simulation industry still uses it on new work. <S> We are trying to move away from it, but its simply not possible (or sensible) to do 100% when we have a lot of fully-debugged reusable code written in it, and we still occasionally get flight models from vendors that employ it. <S> (That right there is your big huge clue that yes, the Aviation industry is still using it) <S> I believe most other major players in the flight simulation business are in the same boat. <S> Even when we do move away from it, its mostly to other non-VM procedural compiled languages like C++, which I suspect a lot of college students also consider "old languages" these days. <S> Even if we could get rid of Fortran in all our new jobs, we have a lot of delivered systems that use it, and those periodically need bug fixes or upgrades (obsolescent hardware replacement efforts, etc.). <S> So we would still have to support Fortran for another couple of decades. <A>
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I've been told directly by a director of UAV development for the U.S. that Fortran is still used in their UAVs.
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What are these aircraft at the Naval Air Weapons Station China Lake? What are these 12 aircraft at the co-ordinates 35.677323, -117.676903 ? I recognize the F-111 and C-130, but not the others. Source: google maps <Q> This answer is a Community Wiki .Community <S> edits are welcome. <S> The aircraft in the photo appear to be the following, or varients therof: <S> Douglas R4D-8 <S> (Super DC-3) source , photographer: <S> Brian Lockett North American T-39 <S> Sabreliner Boeing C-97 <S> Stratofreighter or KC-97 <S> tanker varient <S> McDonnell Douglas F-4 <S> Phantom II source , photographer: <S> Brian Lockett <S> Vought <S> F-8 Crusader North American T-39 <S> Sabreliner <S> North American <S> Brian Lockett Boeing B-29 Superfortress source , photographer: <S> Brian Lockett General Dynamics F-111B <S> tail number 152715 source , photographer: <S> Brian Lockett <S> Grumann A-6 Intruder <S> Douglas R4D-8 <S> (Super DC-3) Grumann A-6 Intruder No C-130 appears in the photo included in the question, though one may appear elsewhere near the coordinates linked. <S> Notes: 1 and <S> 11 are not C-47 Skytrain. <S> They are longer and have a square tail which is typically for the Super DC3 / R4D-8 <S> 3 is longer from the wing root to the nose than the same measurement on 8 , supporting that 3 is not a B-29.Moreover, in the photo of 7 , aircraft <S> 3 appears in the background which clearly shows engine nacelles like those of the B-50 or C-97 series. <S> The same photo shows a fuselage rising higher above the wing than a B-50, which is consistent with a C-97 variant. <S> 5 measures nearer the 54 ft in length of an F-8, versus the 46 ft in length of an F-7, supporting that it is an F-8 <A> 1,11- Douglas C-47 Skytrain 2,6- <S> North American Sabreliner <S> 3,8 - B-29 <S> Superfortress <S> 5- <S> Vought <S> A-7 Corsair II <S> 7- North American Vigilante <S> 9- <S> General Dynamics F111 Aardvark <S> 10,12- <S> Grumman A-6 Intruder <A> Douglas DC-3/C-47 <S> North American T-39 <S> SaberLiner <S> Boeing <S> KC-97 <S> McDonnell Douglas <S> SaberLiner <S> North American A-5/RA-5 <S> Vigilante <S> Either a Boeing B-29 or a B-50 Superfortress General Dynamics F-111 <S> Aardvark <S> Douglas <S> DC-3/C-47 <S> Either a Grumman A-6 or a KA-6 Intruder. <A> Confirm 7 is a North American A3J <S> - A-5 - RA5 Vigilante. <S> Looks a lot like a hot, 1960s fighter, a F-14, MiG-25, or F-15. <S> I've read that Soviet espionage delivered enough A3J information that TsAGI based the MiG-25 shape on it. <S> That's slightly odd, the A3J was a supersonic bomber with a deterrence role, like TSR-2. <S> But Navy requirements included max weight catapult launches from an ANCHORED aircraft carrier. <S> Deterrence means ready to go, 24/7. <S> This was when the USAF had nuclear-armed bombers airborne, 24/7.
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F-4 Vought F8U/RF8U Crusader North American T-39 RA-5C Vigilante tail number 156640 source , photographer: 4- McDonnel Douglas F-4 Phantom II Either a Grumman A-6 or a KA-6 Intruder.
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Can a pulse jet be used on a light GA aircraft? I have an idea for designing a light, cheap and fast 2-seated private airplane... I was thinking about using a pulse jet engine which is simple to design and build, and is cheap too. Noise is not an important concern in my region. The only things that I'm wondering about are efficiency, fuel consumption (range), vibrations and cooling. Is it feasible to use pulse jet instead of regular engines? Is the pulse jet functional and operational? <Q> In principle yes. <S> But some details will turn most potential operators off. <S> Noise is the obvious first one. <S> You might not mind, but cockpit noise and vibration in operation will certainly put an unacceptable stress on the pilot. <S> Just think how you will communicate with ATC or with a co-pilot. <S> Also, your choice of airports to operate from will be rather restricted. <S> Vibration also means that you need to ruggedise the airframe. <S> This will certainly eat up some of the mass benefits of the pulse jet, but is hard to quantify. <S> Now fuel consumption: The AS-014 would consume 350 g of fuel per hour for every Newton of thrust. <S> Compare this to the 60 g/Nh of a modern turbofan. <S> The additional fuel will eat up the remaining mass advantage once you desire to fly for more than just a few minutes. <S> Next will be take-off distance. <S> Unless you use a catapult , you will need a long runway. <S> The pulse jet has limited static thrust, so your initial acceleration will be poor. <S> At the high end of the speed envelope, though, thrust should be plentiful. <S> Cooling, however, is no problem. <S> Just expose the pulse jet to the elements and you are all set. <S> To summarise: Yes, a pulsejet is a possible power source for a GA airplane, but is a poor choice for a multitude of reasons. <S> It makes more sense in an unmanned, one-way application. <A> This question is pretty close. <S> And you should read here as well as here <S> These are key aspects of small GA planes. <S> The noise may not be an issue for you locally (in terms of noise abatements) but it may be an issue for the occupants of the aircraft. <S> In short it is possible (physically) but not really practical. <A> While the pulsejet powered Kawanishi Baika from the WW2 was really far from the GA, from the picture it looks like it was a relatively small plane of very comparable size, capable of taking up under own power, manned. <S> While none were eventually built, seems that the idea was accepted rather seriously at the time.
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Generally pulse jets are not great at low speeds (and can be hard to start when stationary).
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How do pilots identify the taxi path to the runway? When the aircraft is readying to taxi, the ATC asks them to proceed to some runway number, say runway 09. In big airports, how do the pilots identify the correct path to their runway? Does the ATC guide them? Or do they get a map of an airport chart? <Q> (Source: wikimedia.org ) Guiding is called progressive taxi and can be requested. <S> A follow-me car can also be used to guide the plane. <S> In some airports the follow-me car is mandatory , along with its fees. <S> In most cases the pilots use charts. <S> Either paper or electronic. <S> Some electronic charts offer a moving map feature, whereby the crew can see their position on the map. <S> Lastly, there's the new follow-the-greens ( video link ), in which the ATC programs the taxi route and the crew are then guided by smart green lights. <S> Follow-the-greens cockpit video / ATC audio in Singapore Changi can be seen here . <S> In all cases, except for follow-the-greens, the route is given. <S> It's worth mentioning that the taxiways are marked by signs as well. <S> Coming soon by 2020 is the taxi route display for pilots , in which the cockpit displays draw the taxi route via ATC datalink. <S> See possible interface here (Boeing). <A> Almost always pilots use a chart, ie a map which shows the airport from the air. <S> Runways are numbered according to their magnetic bearing (runway 22 is roughly aligned to 220 degrees magnetic for example) while taxiways are lettered. <S> As an example see the chart for La Guardia. <S> A pilot would be given a taxi clearance which gives an end destination and a set of taxiways to take in the order they should be taken. <S> For example, a pilot parked near the fire station might be given a taxi clearance like "US123 taxi to runway 31 via Foxtrot, Alpha, Lima, Bravo and Zulu. <S> " The pilot would look at the map and see the paths to take. <S> Some give directions, some indicate places where ATC have to clear a crossing. <S> Occasionally a pilot will need additional guidance in which case they can ask for a progressive taxi, where ATC will guide them through the airport, but this is rare as it is very labor intensive for ATC. <S> There are also vehicles with "Follow Me" signs and lights which can be sent as well (these vehicles need clearances too). <S> It is good practice for pilots to study the ground plan for any airport they plan to visit so they know what to expect when they get there, and have the plans available in the cockpit. <A> 'follow-me' cars, and progressive taxi can be used, but at a towered airport, ground control will give you that with your taxi clearance. <S> "United 2133, Laguardia Ground, taxi from the commercial ramp to runway four using taxiway alpha, echo, and bravo. <S> " <S> Using a taxiway diagram from the A/FD, you would locate your position on the plate, the taxiways in question and from there determine the route you will take. <S> In this case you'll turn left from the ramp heading northwest on taxiway A, then take a right on taxiway E, then take a left on taxiway B. <S> If you are unfamiliar with the airport, you can then request a progressive taxi." <S> "LaGuardia Ground, Beech <S> 2375 X-Ray, Unfamiliar with the airport layout. <S> Request progressive taxi." <S> NOTE: <S> This will annoy controllers at busy airports if you habitually do this as it is expected that you have this information ready at hand before you call ground requesting a taxi clearance. <S> The 'follow me' vehicles are usually used for quickly routing VIP or special use aircraft to a section of the ramp e.g. Trump's 757 to a section of the ramp cordoned off for a campaign rally, etc. <A> Very often, the instruction is in the form "Taxi to holding point RWY 24 via <S> H, L, cross RWY 13, K, B. <S> " The letters are the names of the taxiways. <S> The pilot then looks into the airport chart and follows exactly as instructed. <S> You must hold short before crossing runways, unless they are used as taxiways. <S> It is easier when the instruction is followed by "Follow the follow-me car. <S> " <S> , then you just follow the car. <A> They have the charts in the cockpit, either in electronic or in printed format. <S> As an example, see page 83 of this pdf , showing the charts for Amsterdam's airport (AMS/EHAM). <S> ATC will not only tell them to which runway to go, but also which taxiway(s) to use to go there. <A> In pilot training, it is taught to have a diagram of the airport and to study it before flight. <S> The tower is usually willing and able to help (as described in other answers: progressive taxi) but depending what airport you're at, you may have to act like the pilot in command and know what ATC is talking about. <S> You'd need to know where to taxi <S> and you'd need to do it fast. <S> Having the diagram of the airport is necessary but you also need to know it. <S> Sometimes taxi instructions change midway through taxiing. <S> You get the point. <S> The bottom line: pilot in command has to know where and when to taxi. <S> The rest of it is nice-to-haves.
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While taxiing there are signs on the ground which assist the pilot in navigating the taxiways.
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What is the name and purpose of this part on the flap at the DA40? There is a part on DA40's and also DA42's flap. I cannot find the technical document and I couldn't decide what is the purpose of that part. Is it a mass balance part or what? You may see the part at picture. (Note: First picture is not showing the part I meant to ask. The picture was wrong but I keep the picture not to make comments meaningless about it. Correct part is marked at second picture.) Edit: Sorry everybody, I drew wrong part before by mistake. The part marked at first picture is the aileron control rod. All previous answers and comments are correct for aileron. I add a new picture for the correct part and I found out it functions as a mass balance horn. We see housings from pictures but the related part is inside the housing.Edit time: 11th Nov, 2016 10:30 UTC <Q> It is an actuator fairing. <S> It covers the flap actuator so to minimize the drag created by it. <S> An actuator directly exposed to the airflow would create more drag, increasing fuel consumption and reducing the flight range. <A> The flaps on the DA-40 are slotted flaps, which are similar to plain and split flaps in that they typically pivot on hinges. <S> In the case of slotted flaps the pivot points are below the wing creating a gap, or slot, between the wing and the flap when extended. <S> These mechanisms are covered by a lightweight fairing which allows air to pass by cleanly, reducing drag. <S> You don't see these on airplanes with fowler flaps, where the flap is extended out the back of the wing rather than swung down on a hinge. <S> This is a more complex type of flap, but is typically more effective than other flap types. <A> Given the position on the wing, that appears to be the linkage for the aileron control rod which actuates the ailerons, not flaps. <S> The outboard flap hinge can be seen to the left of that. <S> With the new edit, yes, that points to the aerodynamic fairing for the outboard flap hinge.
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These are hinges, pivot points for the flaps, and some of them also probably contain the extension mechanism.
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Why do solar planes have many small propellers instead of fewer large ones? Many solar planes, like NASA's Helios (pictured above), NASA's Pathfinder , and to a lesser extent Facebook's Aquila employ the use of many small motor propeller sets instead of one or two engines like most planes. Why is this? Smaller motors tend to have slightly higher power density, but aren't the relative losses higher on the smaller airfoils of these propellers? <Q> Because they are very lightweight and fragile. <S> Therefore, thrust and propulsion mass must be distributed over span - a single, large propeller and motor would put too much force into the structure locally. <S> Also, it would require a higher landing gear to give the larger propeller the required clearance. <S> You are right about the higher losses. <S> However, these airplanes were built to reach record altitudes , and wing loading must be as small as possible to make that possible. <S> There the blade moves faster which will very effectively suppress flow separation. <A> Conventional commercial designs try to maximize kg-kms per dollar fuel cost or kg payload per dollar investment. <S> Or minimize operating & maintenance cost. <S> All these goals need an economy of scale that forces few large complex turbines. <S> On the other hand, most solar planes focus on raw, dollar-agnostic performance / endurance metrics like max height or max range etc. <S> This is an entirely different optimization problem. <S> Also, with higher payloads of conventional designs the structural weight of a sturdy airframe is already a sunk cost. <S> With solar planes your baseline airframe can be very slender so every strengthening is adding weight. <S> Another fundamental aspect is that in solar the generation is anyways distributed & not centralized. <S> Electrical distribution is relatively easier vs mechanical transmission. <S> In a conventional design it is difficult to get distributed generation (many tiny turbines & even if you did the fuel distribution system would offset any advantages) & no easy way to transmit mechanical power to multiple props unless you add a mechanical-to-electrical generation system. <S> PS. <S> A lot of this is speculation on my part based on your very interesting question. <S> I could be wrong. <A> Don't forget the electrical advantages of multiple motors. <S> No need to conduct all the current to a single place with long lengths of heavy wire, no need to control a large current. <S> Also, many small motors and propellers provide redundant depth/graceful degradation in case of a failure(s). <A> One long bus tying all the panels together and each motor connected to it allows all the power to flow to a subset of motors. <S> Once the sun comes back out, you turn all the motors back on and speed up. <S> This comes from living on a boat powered by solar panels and seeing just how powerful clouds are at turning 1KW panels in 200W panels. <S> Being able to pare back the drain on the batteries is the only way to survive the "brown out".
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In addition to the thrust distribution, a multi motor design also allows you to turn off some motors if you run into a cloudy situation that provides too little power. Also, boundary layer problems on propellers are less severe than on wings because the rotation will cause the slowed boundary layer to be moved outwards from centrifugal forces.
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Why does the MiG-15 have a cruciform tail? The horizontal stabilizers of the MiG-15 are halfway up the tail. This is called a cruciform tail. Why did they put them there? Why not a T-tail or the normal tail where the stabilizers are on the fuselage? <Q> The tail position is a compromise which is influenced by these factors: <S> Interference with the wing's wake: The tail should be outside of the boundary layer flow coming off the wing root at all normal angles of attack. <S> A high tail can cause a deep stall , something that was not known in 1947. <S> Today all similar designs try to get the tail surface below the wing's wake. <S> Lever arm: <S> A longer tailpipe means more mass and more internal drag and is best avoided. <S> Flutter: <S> The higher the horizontal tail is along the vertical, the higher the danger of flutter. <S> Here the longer lever arm (now in vertical direction) will lower the eigenfrequency of the bending mode of the vertical and the torsion mode of the rear fuselage. <S> I suspect that for that reason the full T-tail was not chosen. <S> Mounting the horizontal smack in the middle of the tailpipe would require a heavy spar there to carry the bending moment across the fuselage. <S> Mounting it on the vertical tail allows for a much lighter construction. <A> For a couple of reasons. <S> First the shaping of the aft fuselage does not offer the space to accommodate the structure for the tailplane and flight controls without adding on an additional blisters to provide space. <S> The routing of the jet pipe further uses up space as compared to an F-86. <S> See images below. <S> A low mounted tailplane would not have a clean airflow over it due to the MiG-15's middle mounted wing as opposed to the F-86's low wing design. <A> It’s a good question. <S> I remember that during lectures on aircraft structures, it was stated that the horizontal tail should be mounted either at the fuselage or at the top of the vertical tail. <S> Not in between, since that involves having to implement the downsides of both methods. <S> The case of the Bae 125 was mentioned: this was designed as a full T-tail, but during flight tests it turned out that additional vertical tail surface was required which was put on top of the existing structure. <S> Wikipedia mentions that the design of the MIG 15 was based on that of the Focke-Wulf TA 183 Huckebein , which was only built as a wind tunnel model implementing a serious T-tail, not a cruciform. <S> It seems probable that development of the MIG 15 vertical tail had a similar history to that of the Bae 125.
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By mounting the tail higher up on the swept vertical tail, its lever arm (in horizontal direction) can be increased without lengthening the tailpipe.
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What happens if the gust alleviation system on an A380 fails? In an answer , a user linked to this video of the gust alleviation system (GAS) on an A380. This seems like a complex system with many moving parts—all the ailerons move completely independently. What happens if the GAS fail, if for instance two ailerons get stuck in an extreme position? Or maybe even worse: imagine a sensor failure that produces two opposite extremes on each wing, such that e.g. the left wing have all its ailerons in the up position, and the right wing ailerons in the down position. Could this be fatal? Are there procedures for this in some checklist? This is a follow-up for my other question, What is a gust alleviation system? . This is not question Why do some aircraft have multiple ailerons per wing? as far as I can possibly see (though it was marked as such). <Q> You seem to overestimate the complexity and moving parts. <S> The GAS is a feedback system, it has sensors that provide information to the flight computers . <S> The flight computers can then use this to adjust the ailerons as a part of its normal flying. <S> GAS is not a completely separate, standalone system with its own control surfaces. <S> Gust Alleviation System (GAS) Failure Redundancy and good programming is key here. <S> By having multiple sensors, it reduces the effect of failure of one sensor and makes it easier to detect a failed sensor. <S> If you have 3 sensors saying you have an upwards gust and the 4th saying you have a side gust your software should be capable of detecting the outlier and act accordingly. <S> In addition to this, the amount of adjustment the system can make is also likely to be limited to a certain value and therefore it should be incapable of asking for full aileron lock. <S> All of this combined makes the chance of this system being capable of causing a fatal crash highly unlikely. <S> At best it could be a contributing factor. <S> System checks <S> As for checking the system, it is likely to be self checking. <S> The only components directly linked to the system are the sensors and computers. <S> If either fail the aircrafts maintenances logging system should detect it and log it or alert the pilot. <S> Aileron failure <S> This is a completely separate issue to the GAS failure. <A> You have a few questions here <S> so I will address them independently. <S> But first off in a more general sense you should understand that everything on an airplane is generally designed with a failure mode <S> this helps to ensure that if something fails it fails in a way to create the least adversity to flight. <S> However there are event scenarios where multiple units fail in such a way that an adverse condition can be encountered. <S> Generally (if you read accident reports) these can be avoided if an emergency landing is executed earlier on. <S> What happens if the GAS fail, if for instance two ailerons get stuck in an extreme position? <S> Or maybe even worse: imagine a sensor failure that produces two opposite extremes on each wing, such that e.g. the left wing have all its ailerons in the up position, and the right wing ailerons in the down position. <S> In this case the plane still, to an extent controllable . <S> I don't know for the Airbus, but generally speaking all systems like this have a manual override and can be disconnected. <S> So this is implying that the system is somehow stuck on and not responding. <S> It should be noted that in the Airbus this system does not independently actuate the flight control surfaces and most likely is bused as input to the fly by wire system. <S> On that note a sensor failure generally does not cause extreme inputs but instead causes no input. <S> Most things like this are <S> at least triple redundant <S> (so that you can figure out which sensor is bad) and if all are providing inputs that disagree the system usually disconnects and becomes inop. <S> So to create the case you ask about you would need to have 3 independent sensors provide the same erroneous input which is highly unlikely. <S> Could this be fatal? <S> Are there procedures for this in some checklist? <S> More than likely <S> but I don't have access to the official checklists so I cant say for sure. <A> Flying without the GAS switched on will increase the fatigue load on the wing such that it will accumulate more stress over time. <S> This is completely uncritical for the duration of a single flight and will only add up when the aircraft is permanently operated without the GAS working. <S> Basically, the GAS gives the wing a slightly longer service life. <S> If it fails, the safe life time of the wing's structure will be shortened. <S> A failed GAS means that the control surfaces behave like those on GAS-less aircraft, i.e. no more " valse des ailerons ", but no hard-over. <S> Now what happens when the aileron control fails is a much more severe failure case and consequently made much more unlikely by full redundancy. <S> Every actuator, every pushrod, every control computer and every control surface is doubled such that failure of any single component will not be critical. <S> Only a multiple failure could affect safety, but is proven to be highly unlikely .
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Its hard to say, but generally speaking no, the direct failure of a single system would not be fatal. Failure means that the GAS will not add its additional deflections to the control commands from the pilots or the autopilot.
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Can a wide body airliner land safely with a full fuel tank? Can a commercial double-aisle jet aircraft (e.g., 777, A330) land safely with a full fuel tank (minus the fuel spent on taxing and takeoff)? Has that ever happened? <Q> Can a wide body airliner land with a full fuel tank? <S> Yes! <S> But it is safer to land an aircraft below its published MLW. <S> Wikipedia has the relevant specifications for the B777 and the A330 Using the B777-200 as an example. <S> Maximum take off weight: <S> 545,000 lb / <S> 247,200 kg <S> Maximum landing weight: 445,000 lb / 201,840 kg <S> So this particular aircraft may have to drop roughly 46,000 Kg of weight if taking off at its maximum before it can land safely. <S> That's not to say it's impossible to land without doing so, but it's certainly not advisable. <S> When an emergency presents itself, what is "advisable" is getting on the ground as quickly as possible , and if that means landing overweight then so be it. <S> There have been plenty of times when an overweight landing has caused no damage - and even if the aircraft is damaged by an overweight emergency landing, that's still often a better outcome for the people on board than would be the case if the aircraft waited to get below its MLW before landing. <S> However, with that said, just because you are taking off with a full load of fuel it does not imply that you must be at MTOW. <S> You could be taking off with a full load of fuel but no cargo/passengers, in which case it is entirely possible that you may be below MLW. <S> And in which case the answer would be <S> yes, it's entirely possible to land with full fuel tanks. <A> They can land safely with full tanks but they will need the gear checked before they can take off again. <S> It's not unheard of, if you search for "overweight" on avherald <S> you can see a list of them <S> They will be marked as A38* or B77 <S> * . <S> For example this flight landed with a weight of 523t while the max landing weight of that aircraft is 394t. <S> If possible they will prefer to dump fuel or stay in the air to burn it off. <A> If there's a serious time-sensitive emergency, landing overweight is likely to be a far better plan than waiting around while burning off or jettisoning fuel. <S> As others have noted, an inspection, which involves time and money, is required after an overweight landing, as it stresses components, but aircraft are designed with structural tolerances to allow such a landing when necessary. <S> You might be interested in reading this Boeing AERO article (from 2007) on factors to consider when deciding whether to land overweight or to delay landing until below maximum landing weight: <S> Landing overweight and <S> fuel jettisoning are both considered safe procedures: There are no accidents on record attributed to either cause. <S> In the preamble to Amendment 25-18 to FAR Part 25, relative to fuel jettison, the FAA stated, “There has been no adverse service experience with airplanes certificated under Part 25 involved in overweight landings.” <S> Furthermore, service experience indicates that damage due to overweight landing is extremely rare. <S> Obviously, landing at weights above the maximum design landing weight reduces the normal performance margins. <S> An overweight landing with an engine inoperative or a system failure may be less desirable than landing below maximum landing weight. <S> Yet, delaying the landing with a malfunctioning system or engine failure in order to reduce weight or jettison fuel may expose the airplane to additional system deterioration that can make the situation worse. <S> The pilot in command is in the best position to assess all relevant factors and determine the best course of action. <S> Ultimately, it's a judgement call where the crew needs to assess the severity of the emergency, the likelihood of the situation to get worse, available runway length, and all other available information to decide whether an overweight landing is the best course of action. <A> Not a general answer, but in the book Flight Testing of the A380 by Claude Lelaie 1 , the main test pilot of that aircraft, he clearly states that during the test period, they landed the aircraft several times well over the MLW without any problems. <S> But, of course, these were test pilots... <S> The MLW is designed as a general limit that ensures that safe landing will be possible whatever the weather, runway length... and pilot performance! <S> I assume this must be the same for all contemporary airliners. <S> 1 <S> amazon.fr link (French), <S> amazon.com link (English). <A> There are many Boeing 767 and Airbus A300, A310, and A330 that no not have fuel dumping capability. <S> They just land overweight in case of an emergency and then do an overweight landing inspection. <A> I recall watching a documentary on the development of one of the newer larger jets - either B777 or A380 in which extreme braking tests were performed as part of the certification process. <S> The test was to evaluate gear/brake performance for either a rejected takeoff at MTOW or overweight landing, using brakes only (no thrust reversers). <S> Heat accumulated in the brakes transferred to the tires (not unexpectedly), either initiating fires or at least overheating them to the point that several burst. <S> Part of the test protocol was that firefighting had to stand by for several minutes before engaging the fires in order to represent a typical response time. <S> It demonstrated that although the aircraft could stop safely and the brakes had the capacity to do so, the amount of heat produced was almost certain to cause damage and posed a significant fire risk.
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Yes, you can safely land with full fuel.
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Why is there a pressure drop in the combustion section of a jet engine? This image, referenced in this question , shows in green the pressure value in a jet engine: The combustion section between compressor and turbine is where fuel is injected, mixed with air, and burnt. Why is there a pressure drop while combustion occurs and temperature suddenly increases by 1,500°C (to be compared with pressure increase after ignition in a reciprocating engine). <Q> The air moves¹ in direction of decreasing pressure except where forced by the compressor. <S> So the pressure must be decreasing to maintain desired flow. <S> If the pressure was increasing, the flow would stop and reverse and the engine would stop operating. <S> In fact, that's exactly what happens if fuel is added too fast: the energy quickly raises, but the still slow-spinning turbine provides too much resistance, so pressure will increase above what the compressor can provide and the compressor will stall, the engine will emit loud bang and some flames from both ends and likely flame out as it runs out of oxygen for a moment. <S> As already explained, in the normal flow the released energy increases the velocity of the flow instead of pressure. <S> ¹ <S> More precisely accelerates. <S> If the pressure was constant, it would keep moving. <S> But it must not raise. <S> It decreases slightly due to friction. <A> <A> In a reciprocating engine, the gases are trapped until the exhaust valve opens, unlike a jet engine where it's an open exhaust. <S> In a cylinder the gases are not accelerated. <S> So, v rise in a jet, p rise in an engine cylinder. <S> Temperature rise in both.
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The question you linked to contains the answer to your question: the small pressure drop in the combustor is caused by friction
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Has there ever been a tail-dragger with retractable tail-gear? This comes from a slightly related question about drag from landing gear . A tail-dragger is the old-school layout of aircraft, particularly WW2-era fighters. It's also known as Conventional Landing Gear . The first two landing gear is usually retractable, but the tail wheel is not. At least, I have never seen such a configuration with a retractable tail wheel. Has there ever been one? Note: question excludes now more common tri-cycles. <Q> Yes, there are. <S> The Boeing B-17 <S> Source: USAAF via Wikimedia , Public Domain (USGOV-PD) <S> Another example would be the Vought <S> F4U Corsair : <S> Source: <S> Wikimedia , cc-by-sa-2.0 Doubtless there are also other examples of aircraft similarly equipped with retractable tailwheels. <A> Concorde! <S> Actually a "bumper" <S> .Obviously <S> it was there to protect against over-rotation on takeoff, but the relevant item on the checklist was four greens, not three. <A> As others have mentioned, yes. <S> Later in World War 2, speed and range became more important than weight and mechanical complexity; an extended tail wheel may be mechanically simpler to build, but adds quite a large amount of drag, affecting range and speed. <S> There are too many examples to list with links/photos of them all, but a short list of examples include: Mitsubishi Zero. <S> P-51 Mustang. <S> P-40 Thunderbolt. <S> Later marks of the Supermarine Spitfire (around the MkVIII from memory; I spent 6 years working on a MkV restoration). <S> Some models of Messerschmitt BF.109. <S> The F models were 'cleaned up' aerodynamically with retracting tail wheels, while the subsequent G models had a fixed wheel due to a bigger tyre for better ground handling, which didn't retract as on the F models. <S> Later G and K models again used a retracting wheel to lessen the drag. <S> Notable for being an oddball in that it's a jet tail dragger and also equipped for aircraft carrier landings would be the Supermarine Attacker . <S> There's an in-flight photo with the wheels up here . <A> In addition to the military fighters listed above numerous civilian airplanes with conventional landing gear had retractable tailwheel, including the Beech Staggerwing, the Boeing 307, the Curtis C-46 and many others. <A> the friedrich models, earlier gustav models of the 109 and kurfurst had retractable gear <A> The Bf-109E-4's did not have retractable tailwheel, but the Friedrich which came after the E did have retractable tailwheel. <S> The G had a larger tailwheel to improve the on ground handling that was difficult because of the narrow track undercarriage. <S> This made the tailwheel unretractable. <S> The P-51s, many variants of spitfires, Fw-190, many P-47s, the P-36s, (which were not in service with the US but were with the French), most Yakolev fighters as mentioned above, the F4U, the Zero, the Ki-84 and many others. <S> The Stuka had no retractable landing gear but part of the reason was that the huge landing gear was used to reduce the airspeed in a dive. <S> In conclusion, most fighters and many aircraft of WWII had retractable tailwheels. <A> A few more examples are the Soviet Tu-2 <S> front line bomber (fully retractable) and the Il-10 attacker ( <S> partially retractable, i.e.: it folded into the fuselage but did not have a fairing). <S> Tu-2, note the tailwheel bay doors: Il-10, note the folded tailwheel:
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FLying Fortress is one example of an aircraft designed with a retractable tailwheel.
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What is the preferred way to slow down an airliner on a long runway? EDIT: Another way to phrase the question is, given an extra long runway, does it make sense to substitute mechanical braking (which is the primary way to slow down in a typical situation) partially or completely with something else, to reduce brake wear / roll down the runway faster? Consider an airliner landing on a very long runway (e.g. Boeing 737 landing on 12,000 feet+). The pilots are planning to vacate the runway near the end, so there is a lot of distance to spare. Ignore noise procedures, and assume there is no traffic behind to suggest an early exit. What would be the preferred way to slow down the aircraft in this scenario? Light application of reverse thrust only, no brakes? Light application of brakes only, no reverse thrust? Moderate braking until below a certain speed (e.g. 80 knots), then "coast" the airplane down the runway? ( This question addresses the primary means to slow down after a typical landing, while this question is about an idealistic case where there is plenty of braking capacity to spare.) <Q> There are several ways to slow down an airliner: <S> aerodynamic drag friction in the wheel bearings <S> reverse thrust <S> wheel brakes and a few even used a brake chute , but that went out of fashion a long time ago. <S> If the runway is inclined, landing uphill also will slow down the aircraft. <S> Friction and drag you get for free, so I would rely on those first. <S> Since they are highest when the speed is high, use them first until the aircraft is so far down the runway that it would overshoot without additional application of wheel brakes. <S> Use spoilers and leave the flaps down to maximise the deceleration. <S> Only at the end add wheel brakes so you have slowed down to taxi speed when the exit of the runway is reached. <S> So the best answer is none of the above <S> but: <S> Coast along with flaps and spoilers out until you need to brake more to avoid an overshoot. <S> Then apply wheel brakes. <S> The exact way how brakes should be applied depends on their type . <A> To make it efficiently its better to start with thrust reversers to reduce speed just after touchdown. <S> As speed reduces the effect of the reversers reduce. <S> To avoid FOD(foreign object damage) risks it is not recommended to use high revers thrust with low ground speed. <S> This what Airbus says and advises to the flight crews of A330s. <S> Three systems are involved in braking once the aircraft is on the ground: <S> • <S> The ground spoilers • <S> The thrust reversers • <S> The wheel brakes <S> THE GROUND SPOILERS <S> The ground spoilers contribute to aircraft deceleration by increasing aerodynamic drag at high speed . <S> Wheel braking efficiency is improved due to the increased load on the wheels. <S> REVERSE THRUST EFFICIENCY Thrust reversers are more efficient at high speeds. <S> Below 70 kt, thrust reversers efficiency rapidly decreases. <S> Below 60 kt with REV MAX selected,engine stall may occur. <S> Therefore, it is recommended to reduce the reverse thrust to REV IDLE at70 kt, and keep REV IDLE until taxi speed. <S> At taxi speed, and not above, stow the thrust reversers before leaving the runway, in order to avoid foreign object ingestion. <S> On very long runways, the use of pedal braking may be envisaged if the pilot anticipates thatbraking will not be needed. <S> To reduce brake wear, the number of brake application should be limited. <A> If you have a lot of runway at your disposal, I'd recommend the use of aerodynamic braking (hold a nose high attitude riding on the main gear), speed brakes and thrust reversers, followed by wheel braking starting at around 80 KIAS or so. <S> The reasons have to do with energy dissipation. <S> For an A380 landing at say 160 KIAS and following this procedure, the pilot has already dissipated 3/4 of his total kinetic energy which he started with at the time he applies the wheel brakes at 80kts, leaving only 1/4 of the original kinetic energy to be dissipated through the brakes in heat. <S> As drag forces are also directly proportional to the square of the velocity, it makes sense that aerodynamic braking and high drag devices will drain off a lot of energy very quickly while at high speed but their effectiveness is greatly diminished at lower speeds. <S> In addition, the wings are still producing a great deal of lift at touchdown, reducing the static coefficient of friction between the tires and the runway, making braking much less effective at higher speeds. <S> Thrust reversers are again going to be more effective at high speed as performance is boosted by ram air at the intakes and lower speed operation risks compressor stalls as well as damage from ingestion of FOD kicked up by the fan exhaust. <A> I experienced such a landing as a passenger and happened to film it: A319 landing in Stuttgart (EDDS) on runway 25 (10974ft, 3345m), exited on last high speed taxiway. <S> (Sorry for the poor video quality) Touch down at 3min 16 seconds <S> The pilots touched down at the normal touch down zone, used idle reverse and speedbrakes and low autobrake, then stowed the speedbrake (disables autobrake) and reverse, rolled with idle thrust and no braking down the runway at roughly 60 kts or so, then used light braking at the end of the runway to make the last high speed taxiway.
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WHEEL BRAKES Wheel brakes contribute the most to aircraft deceleration on the ground.
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Why are most runways made of asphalt and not concrete? From the little I know about vehicles in cities, nowadays concrete is preferred to asphalt for road construction as, while initially more expensive, concrete is supposed to be cheaper to maintain. From a recent reading I understand India also uses asphalt in most places. I have two questions: Why haven't airports switched to concrete? How can I check online the type of material used for passenger commercial airports around the world, especially transit hubs? <Q> Frankfurt Airport; a mosaic of concrete and asphalt <S> The runways at Frankfurt Airport are asphalt (old satellite imagery shows that they were concrete before), and the airport handles plenty of Superjumbos, the Airbus A380 <S> , so it's not a matter of handling heavy planes. <S> All runways in big airports, even those covered in asphalt, have reinforced concrete foundations that vary in depth. <S> They're deepest where the touchdown zones are located, shallower elsewhere. <S> That's why runway extensions usually just add extra takeoff distance, but the landing zones remain the same, creating a displaced threshold . <S> Displaced threshold; can exist for other reasons Zoom in <S> You'll see almost all the parking spots and holding areas for the runways are concrete, as well as the runway exits. <S> This is where a plane is expected to be stationary. <S> Concrete handles such stationary loads pretty well, while on a warm day the asphalt would deform. <S> Asphalt is called a flexible surface; concrete is called a rigid surface. <S> Pavement classification number <S> (PCN) is a standard used in combination with the aircraft classification number (ACN) to indicate the strength of a runway, taxiway, or apron (ramp). <S> Exposed concrete is notorious for cracking when exposed to extreme high and low temperatures. <S> It's also more expensive to install and repair. <S> But overall can be cheaper to install if you're already laying down concrete elsewhere, like most new airports, they just go for concrete everywhere, but it depends on where that new airport is located— Hot Dubai; asphalt almost everywhere except parking areas and hold short areas LAX; good climate and budget; concrete almost everywhere <S> a plane touches <S> The variables come down to climate, use, load, budget, job creation, maintenance, etc. <S> A single runway (like at PBG ) can also have both surfaces Airport diagram showing the PCN for all runways; F lexible and R igid <S> ( NASA ) <S> Another point in favor of an asphalt runway, is that it's more gentle on the tires during touchdown (since it's flexible). <S> You can find runway data at airnav.com for US airports, elsewhere you'll need to check the airport's AIP , like this one for Amsterdam; check the section 2.12 RUNWAY PHYSICAL CHARACTERISTICS. Or try searching for a nonofficial runway data repository, there could be one. <A> My first reaction to this question was that your assertion of "most" was untrue. <S> Nearly all major airports (airline traffic) use concrete runways. <S> However, according to the Asphalt Pavement Alliance , some 85%+ of general aviation airports use asphalt, and they claim some majors as well. <S> They claim that asphalt is more cost-effective and takes less time to lay down than concrete. <S> So for those airports, where long-term budgets might not be guaranteed, it likely makes sense. <A> nowadays concrete is preferred to asphalt for road construction as, while initially more expensive, concrete is supposed to be cheaper to maintain <S> You may find some disagreement from anyone who's actually driven on concrete roads... <S> Concrete as a surface is certainly more resilient to traffic in the short term. <S> However the resulting road surface is significantly less smooth. <S> This is very noticeable for European visitors to the US, where concrete is more widely used for road surfaces. <S> In the UK, some sections of motorway were built in concrete in the 1960s, and these are universally unpopular with drivers. <S> To my knowledge, roads in the UK at least are no longer built in concrete for this reason. <S> It perhaps is less of an issue in the US due to the very soft suspension which is standard on US vehicles. <S> Concrete is also very much harder to repair when it develops holes, and those holes tend to be deeper and sharper-edged. <S> Even after repairs, the resulting road surface will never be fully even. <S> This makes concrete less suitable for roads which experience freeze-thaw conditions, namely most of Europe and the northern US. <S> Concrete also has issues with thermal expansion, which makes it less suitable for places which experience high daytime temperatures (or at least this needs to be considered during construction). <S> As ymb1 says, you can put asphalt over concrete though, which gives you the best of both worlds. <A> In most cases, major aerodrome runway pavements are originally constructed using concrete (PCCP). <S> Improvements (resurfacing,strengthening, etc.) <S> on an operational runway are undertaken during off-peak hours (maybe nighttime) to avoid airport disruptions especially if an airport has a single runway configuration. <S> But because of the necessity of runway improvement, asphalt concrete are utilized. <S> Newly laid asphalt may be used immediately after the asphalt curing time. <S> Unlike concrete which cures in the first few days of paving, new asphalt may be allowed to aircraft operations as soon as it is compacted and cool. <A> Asphalt or concrete decisions on FAA sponsored projects are made on life-cycle cost analysis. <S> Sometimes one wins out over the other, but neither is inherently better.
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The runways you have observed may be originally constructed using concrete but resurfaced using asphalt.
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Why is water-contaminated fuel bad, but water-injection is not? A "wet" takeoff of a KC-135 with J57 engines—By USAF Photographer (USAF photo) [Public domain], via Wikimedia Commons Why is water-contaminated fuel bad, but water-injection is not? The way I understand it, water-injection lowers the combustion temperature, which is good and bad, good for cool yet increased power-output / mass flow, bad for wasting [unburnt] fuel. Why is then water dangerous when a trace amount of it is found in fuel? What's the worst that can happen apart from black exhaust and higher power? Water-injection in jet engines and piston engines is mixed with fuel before it enters the combustion chamber, so I'm thinking fuel already mixed with water should not be any different. Of course I'm wrong. But why? <Q> Because of the quantity of water in the fuel, as opposed to a careful introduction of water into the combustion process. <S> Typical water contamination is bad in fuel tanks as water is denser than aviation fuels and settles at the bottom of the tanks. <S> Aviation fuels are also hydrophobic (non-polar) and so do not readily mix with water. <S> Therefore water will settle unmixed at the bottom of the tanks, in the fuel sumps or feeder hoppers and when ingested into the engine will fuel starve it and cause it to shut down. <S> Water in fuel lines can also freeze there during cold weather, causing fuel starvation as well. <S> Fuel samples should always be taken of the gas when it is both in storage as well as prior to flying the aircraft, especially after <S> rainstorms or the aircraft has sat on the ground for long periods with low fuel in the tanks in a humid environment. <S> Fuel samples should also be taken approximately 30 minutes after refueling and the gas allowed to settle in the tanks. <S> A preflight sample of water contamination taken from the fuel tank sumps of a GA aircraft can be seen here. <S> Water injection, however carefully controls the amount of water going into the engine along with fuel at the point of combustion, allowing for continued engine operation. <A> Water-injection in jet engines and piston engines is mixed with fuel before it enters the combustion <S> This is actually somewhat wrong (or at least imprecise) <S> and I think it is adding to the misunderstanding. <S> The water and fuel are never "mixed" in the traditional sense as liquids. <S> An aerosol of fuel is injected... <S> Also, an aerosol of water is injected. <S> The intention is to have a typical fuel combustion which is also in the presence of water to cool the combustion. <S> This is a rather important distinction from a physics perspective. <A> Without some help, water doesn't usually mix around in the remaining fuel, but can combine to form larger droplets or even pools at the bottom of the tank. <S> If large quantities exist, it can be ingested by the engine and lead to loss of power or stalling. <S> Water not removed from the tank supports microbial growth. <S> Water in the system can freeze and cause problems for filters and other components. <S> I've heard of water in fuel causing erratic fuel quantity readings due to short circuiting the sensor (not sure how common that is). <A> That's why an antiicing additive is added to jet fuel - so that the water does not become ice. <A> Water in the fuel tanks can freeze, possibly causing blocked fuel lines or filters. <S> This can cause the engines to produce insufficient thrust, or even to flame out. <S> Even if the ice adheres to the inner surfaces of the fuel system in a thin layer during cruise and doesn't restrict fuel flow appreciably, it can be dislodged by a sudden increase in fuel flow ( for instance, during the landing sequence ), and create a blockage further downstream. <S> Water used for water injection does not cause this problem, as the only place where it and the fuel both are is in the engines themselves, which tend to be a bit on the warm side for ice formation. <S> Also, water has an extremely high heat capacity (meaning that it takes the addition or subtraction of a lot more heat to change the temperature of a given quantity of water by a given amount than it takes to change the temperature of the same quantity of pretty much any other liquid by the same amount), which causes it to cool down during flight much more slowly than the fuel does; the proportion of water in water-contaminated fuel isn't enough to change its heat capacity by much compared to pure fuel, but pure water is another matter altogether.
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Water in fuel will freeze, causing clogging of filters and nozzles, leading to the engine flaming out.
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Why would a helicopter hold a 'nose-up' in hover? (The Grand Tour; episode 2) SAS unit fast roping from a Blackhawk. Why is the helicopter pitched-up? Actual scene footage have it like that for a few seconds while holding steady over a building. How come it's not flying backward? <Q> This screen grab is from a few seconds before yours was taken. <S> No pitch is evident here. <S> Sketched above is rope angle and camera position (based on the staircase in both frames). <S> I think it's just the camera angle used that makes it look pitched combined with the rope's angle in the wind. <A> 1) <S> The 60 has a natural nose up, left wing down hover attitude. <S> I want to say 3, and 1.5 degrees, but I'm going off memory. <S> Given the angle of the shot, I would venture to say that it's more optical illusion of a excessive nose up angle than it actually is. <S> 2) <S> Given the nature of fastrope operations, and without opportunity to observe the video in entirety, it is possible the aircraft is still stabilizing its hover. <S> I would guess that SAS guys are only going to wait around just as long as they need to before they're out of the bird. <S> Or has already been suggested, gusting winds may be forcing the pilot to make adjustments since that building appears to be in a sort of valley which could make winds interesting. <S> MH-60S driver <A> When in forward flight, the rotor will be pitched down to convert some of the lift vector into forward motion. <S> This also results in the fuselage of the helicopter pitching down. <A> Just about every Helicopter has a forward tilt angle to the main rotor mast to allow for zero control force in forward cruise flight. <S> Faster ships have a greater angle.
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Therefore the fuselage is designed to be pitched up in a hover so that during forward flight it is level or close to level with the airstream for efficiency, and to maximimize pilot visibility to the front, and passenger comfort during the forward flight portion of a flight.
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How can you navigate "Writing" onto FlightRadar Plans? Sorry if the question title here is a bit misleading, the graphic here should explain all: I read a news story this morning about how a guy flying a Robin DR400 regularly creates inventive patterns in his flight tracks. Source The question is, how would the pilot be able to create this writing (and other creative patterns)? Autopilot instructions? Watching himself on FlightRadar? <Q> Most Robin 400s don't have autopilots, but some do. <S> Whether it has an autopilot or not it was almost certainly navigated using a pre-set course which was fed into a GPS. <S> One would use flight planning software to create a course using a series of waypoints which would then be uploaded to a built-in or handheld GPS, and then either flown by hand or followed by an autopilot. <S> You can see that the curves are mostly a series of small straight lines, I think that these straight lines are the space between waypoints, it could be the refresh between the FlightRadar <S> inputs causing the lines though. <A> During test flights to put time on the aircraft, the 787 flew some pretty cool designs like this as well, using much of the U.S. as their drawing canvas. <S> ( You can see this design and the filed route on FlightAware ) <S> Since they were at high altitude & on an IFR flight plan they did have to file their points with ATC. <S> (A total of 81 waypoints were used for the "drawing" portion of the flight, mostly latitude/longitude coordinates. <S> Bet they didn't file that over the phone!) <S> I think there was another that overflew every state in the lower 48, but I can't find it right now. <S> (Anybody, feel free to edit in the link if you find it.) <S> In the 787 case, the autopilot certainly was used... for the R222, maybe not so much! <A> Although I agree with the above answers I thought that the pilot may have flown the flight as he preflighted it. <S> How did you fly cross-country flights? <S> Pick your points and fly them.
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You would need a chart and the rest of your preflight planning kit; pilotage, 'I follow roads' and any of the other navigational aids mentioned in the other answers.
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What is a flat rated engine? I've heard that a "Flat Rated Engine" is an engine where the power is reduced to keep the internal temperature within certain limits when the ambient temperature is above a certain point. Is that correct? How does it work? <Q> Yes, a flat rated engine (my familiarity is with gas turbines, but the concept may apply to other engine types), is an engine for which the control system is designed to achieve the same level of thrust (hence the "flat" term), up to a certain OAT, then for higher ambient temperatures, the level of thrust decreases as a function of OAT, normally in a pretty linear fashion. <S> This control system operation gives identical performance over the flat portion of the OAT range even while the engine degrades (until it degrades to the point it hits the EGT limit), making the plane performance predictable. <S> But for higher OATs, it stops the EGT continuing to increase. <S> The temperature at which the thrust starts to decrease is typically 25 or 30 deg C, and can be found in the EASA or FAA engine type certificates (e.g. see section 6 of this EASA one for the CFM56-5 ). <S> See the graph from this CFM56 document below. <S> So, your understanding was correct. <A> This may be a good working definition <S> The Flat Rating Concept <S> The rating of a jet engine is the thrust performance that is guaranteed by the manufacturer for a new engine under specific operating conditions such as, take off, maximum continuous, climb, cruise. <S> Some <S> non Prat and Whitney (P&W) engines are rated to a constant compressor speed (RPM). <S> P&W rates there engines to a constant exhaust gas temperature (EGT). <S> This is referred to as the flat rating concept. <S> To get your head around this concept you must understand the following principle. <S> The temperature and density of the ambient air vary inversely. <S> Lower temperature = <S> > <S> Higher Density <S> Higher Temperature = <S> > <S> Lower Density <S> The amount of airflow (lbs/sec) through the engine is a function of compressor speed and air density. <S> It is greater when the compressor speed and density are high. <S> The compressor speed is a function of the energy available to the compressors turbine. <S> That energy comes from the combustion or air and fuel, so the turbine turns faster when the fuel flow rate is greater. <S> The compressor speed is also a function of the airflow through the compressor. <S> Higher rates of air flow reduce the speed of the compressor. <S> The compressors rotational speed and the amount of airflow through the compressor are independent, they affect each other though. <S> The turbine inlet temperature is proportional to the energy available to turn the turbine. <S> The exhaust temperature is proportional to the turbine inlet temperature. <S> So a higher EGT corresponds to a larger amount of energy to the turbine so it can turn the compressor faster. <S> When EGT is held constant, or lowered the result is a prolonged hot section life and at the same time provides the thrust to meet the certification requirements. <S> Or a bit more concise from wiki <S> The engine output in this case will always remain the same, but when atmospheric conditions such as high temperatures and high altitude (Hot and High) reduce the power output of the engine it has more headroom before it falls below the limited maximum output. <A> Flat rating is a concept by which an engine, as stated above is restricted, in terms of power or thrust output by the fuel control unit to produce a uniform power or thrust output as the aircraft climbs or descends until the ambient air conditions will not allow the engine to operate at or beyond the maximum thermodynamic output of the engine. <S> Like any other heat engine, the power or thrust produced by an aviation gas turbine (the gas core) depends on the available mass flow rate of working fluid (air in this case) as well as the operating temperature limits of the engine's hot section. <S> The maximum available power thrust a gas core can produce at sea level at STP is referred to as the core's thermodynamic rating. <S> As an example, the Pratt & Whitney Canada PT6-66D turboshaft engine has a thermodynamic rating of 1,850 horsepower, but the FCU flat rates this to a constant maximum power output from the driveshaft to 850SHP, which remains available all the way up to approx FL260, thereafter decreasing with an increase in altitude.
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When an engine is Flat rated it means that an engine of high Horsepower rating is constrained to a lower horsepower rating.
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Do pilots ever use the aircraft's ICAO 24-bit address when communicating with ATC? Do pilots know the unique ICAO 24-bit hexadecimal code for their aircraft? Do they ever give it directly to ATC? For example, to controllers who make the flight strips with destination, departure, type of aircraft etc. I know for a fact that some flight plans are sent out that include the unique hex code for the aircraft. <Q> The 24 bit address is intended for data protocol level of communications and is not used in voice communication. <S> Therefor there is no need for pilots to be aware of their ICAO 24-bit aircraft address. <S> They use the aircraft's registration if they need to identify the aircraft they are using for the flight. <A> I will agree that pilots generally do not know the ICAO 24 bit address for their aircraft. <S> However, with the advent of the ICAO format flight plan, operators who want to take advantage of ADS-B provided ATC services (such as where only ADS-B - no radar - is provided), <S> will have to include the hexadecimal equivalent of their aircraft's 24-bit ICAO address. <A> Do pilots know the unique ICAO 24-bit hexadecimal code for their aircraft? <S> Answer depends on the pilot really. <S> Mode S Address(24 bit ICAO address as you say) can be seen as IP of the planes. <S> It is included in some of the Mode S Mode S interrogations/replies as you pointed out. <S> For commercial airplanes, Mode S address is not changed during lifetime, generally but for some military scenarios, I have read that Mode S Address can be changed per flight for obvious reasons. <S> So you can say, some military pilots definitely know Mode S address of their aircraft. <S> In addition to that, some platforms may provide you with display and control of Mode S Address.
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Typically pilots do not know the 24-bit aircraft address of their aircraft. The 24-bit address is used by transponders for communication with Mode-S radars, ADS-B transmissions, by TCAS for tracking traffic and coordinating Resolution Advisories and by Data-Link communications.
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What happened to this airplane at Lombok Airport? Last month I was on holiday in Indonesia and I had to take a flight from Lombok International Airport (IATA: LOP ). While I was waiting for boarding I noticed an airplane (wreck) next to the runway that was somewhat burned down at the front (fire?). The abandoned plane at Lombok International Airport. (personal photo) I was intrigued by the way that it was just placed there, so close to the runway. I thought about an accident where this aircraft was involved in, could've have just happened a couple of days or weeks before. But I couldn't find any source in collaboration with this particular airport. I maybe thought that the airplane was used to train fire fighters, as I see that more often on other airports in the world. I tried to find more info about it on the web, but no luck. The airplane on the map I also headed out to Google Maps, Bing Maps and Apple Maps to see if the plane was there. Google Maps has the airplane on its map (see image below, top middle and slightly to the left), the data is from 2016, so says the footer. Google Maps location of airplane on Lombok International Airport, data consulted on 2 Dec 2016. Bing Maps isn't having the airplane on its map, but maybe that's because the map is outdated (?). Bing Maps location of Lombok International Airport, data consulted on 2 Dec 2016. Apple Maps shows an airplane in almost the same spot (it's just on the concrete I think), but is it the airplane? Apple Maps location of 'airplane' on Lombok International Airport, data consulted on 2 Dec 2016. Zoomed pictures of the plane The above picture is zoomed in on in the following pictures. Unfortunately, the aircraft registration is not visible. And now? I'm eager to know what happened to this plane. What type is it? Who is the owner? Can anyone tell me? Thanks in advance. <Q> ( Source ) <S> The aircraft's registration is PK-YVL . <S> It's a Boeing 737-300 that was operated by <S> Batavia Air before the airline ceased operations. <S> This plane is/was leased from Pacific AirFinance. <S> It has been withdrawn from use and stored at LOP since 31 Jan 2013. <S> After ceasing operation, some of the other 737-300's the airline had were delivered to Peruvian Airlines . <S> Due to its proximity to parked aircraft, it's not likely the plane has been converted to train firefighters. <S> The darkened area could just be storm blown mud. <S> ( Source ) <S> Same plane, previous operator. <A> It is entirely possible that it is there for firefighter training. <S> I believe that is the purpose of <S> this plane , at Seattle's Boeing Field. <A> Aircraftwas not there anymore last september. <S> Brobably scrapped. <S> Photo taken in 2017.
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It may be an old, decommissioned plane that they can start small fires in, and plan how to approach a plane, practice aiming their water cannons and putting the fires out.
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What's the difference between feathering, and flapping in a helicopter? Aren't both methods used to increase angle-of-attack (AoA)? Blade flapping will change the blades level, while feathering will change the pitch, but if both increase AoA why not just use one method? <Q> Feathering <S> The collective pitch control, or collective lever, is normally located on the left side of the pilot's seat with an adjustable friction control to prevent inadvertent movement. <S> The collective changes the pitch angle of all the main rotor blades collectively (i.e., all at the same time) and independent of their position. <S> That's what you referred to as feathering, notice it says " independent of their position ". <S> It's for collectively increasing or decreasing of the lift on all blades—the engine will keep the RPM constant. <S> Using the collective in level flight would cause a climb or descent, while with the helicopter pitched forward an increase in total lift would produce an acceleration together with a given amount of ascent. <S> — Wikipedia <S> Flapping <S> Flapping is position dependent as explained here . <S> Flapping is not pilot controlled. <S> It's to counter the dissymmetry of lift . <A> Flapping and feathering are both rotations about a hinge, with each movement having its own axis of rotation, as shown below in a figure from Raymond Prouty, Helicopter Performance, Stability, and Control. <S> It is a top view of a 2-bladed rotor with hinge offset. <S> The feathering axis allows the blade to be rotated lengthwise. <S> The pilot initiates this movement, via the cyclic and collective control stick, and the Swash Plate transfers this input so that the blades rotate about the Feathering Axis. <S> The Flapping Hinge allows the blade to rotate up/down. <S> They could point straight up - in normal operation the rotation of the blades produces centrifugal forces that are higher than the lift forces, and the blades point more or less horizontal. <S> The Flapping Hinges are there for counteracting lift dissymetry. <S> Flapping was discovered as a cure for rolling over when airspeed increased: a blade moving forward has more lift than a blade moving aft. <S> The flapping hinge allows the forward moving blade to move up, effectively reducing the Angle of Attack. <S> Likewise, the aft moving blade descends, increasing the AoA. <S> The effect was discovered by Juan de la Cierva when he constructed his autogyros in the early 20s. <A> Flapping, the vertical up/down movement of the blades, is not directly controlled. <S> What a pilot controls is the blade feathering or pitch angle. <S> Unless the rotor and blade are infinitely rigid, which would cause other problems, flapping will be a (often useful) side effect of feathering. <S> All else equal, higher feathering / pitch at a certain azimuth leads to higher flapping 90 degrees later in the azimuth. <S> This link explains the 90deg offset in technical details: <S> Helicopter Flap Dynamics
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Increasing feathering / pitch generally increases the aerodynamic forces on the blades, which changes the flapping.
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What is the correct phraseology for declaring a fuel emergency? If I am pilot, approaching my destination airport and realise that, after landing I will have less than 30 minutes of fuel remaining, how exactly should I express this when communicating with ATC? in ICAO rules in FAA rules in EASA rules For example, in a country where Spanish is an approved ATC language, would it be sufficient to say "ABC12345 FL210 en acercamiento y solicitamos prioridad para la aproximación. Al momento se nos ha presentado un problema de combustible" ("ABC12345 FL210 inbound and we request priority for the approach. Right now we have a fuel problem") <Q> (This is very closely related to this question , and see this one too.) <S> At least in the US, cutting into fuel reserves isn't an emergency by itself . <S> But assuming that things have gone beyond "minimum fuel" and you clearly need priority for landing then you should indeed declare an emergency. <S> The wording you mentioned seems 'weak' to me; if you do have to declare an emergency, there should be no possible doubt about it or about what you need. <S> Assuming that I was already in contact with ATC, I'd probably say something like this (see the AIM 6-3-2 ): <S> Mayday, mayday, mayday. <S> Louisville Approach, N12345 is declaring an emergency, low fuel. <S> We are now direct runway 35R for landing. <S> 3 on board, 15 minutes fuel remaining. <S> Note that if time is critical I'm not going to "request" anything, I'll just tell ATC what I'm doing and let them sort out the rest. <S> That phraseology and statement of intentions should be understood anywhere in the world. <A> ICAO <S> According to an IFALPA Briefing Leaflet of 2012 "Amendment 36 to ICAO Annex 6 Part <S> I" <S> The pilot-in-command shall advise ATC of a minimum fuel state by declaring MINIMUM FUEL when, having committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance to that aerodrome may result in landing with less than planned final reserve fuel. <S> Pilots should not expect any form of priority handling as a result of a “MINIMUM FUEL” declaration. <S> FUEL, when the calculated usable fuel predicted to be available upon landing at the nearest aerodrome where a safe landing can be made is less than the planned final reserve fuel. <S> EASA <S> The EASA guidance seems to be identical to ICAO guidance. <S> For example, the following text has been attributed to EHAM airport briefing (Jeppesen 10-1P10) Only when the pilot declares an emergency, radio call prefixed by MAYDAY (3x) for distress or PAN PAN (3x) for urgency, priority handling will be provided. <S> Calls such as “low on fuel” have no status in the Amsterdam FIR. <S> Related (see Pondlife's answer ) <S> Do I have to declare an emergency if I cut into fuel reserves? <S> When should the term "pan-pan" be used instead of "Mayday"? <S> How does ATC handle different kinds of emergencies? <S> Who has the higher authority, the pilot in command or ATC? <A> In Australia, from 8 November 2018, ... the fixed fuel reserve for day visualflight rules (VFR) for piston or turboprop small aeroplanesis 30 minutes. <S> and When conducting these checks, you may discover that you would be landing at your original planned destination without sufficient fuel, that is, your fixed fuel reserve remaining. <S> If this occurs, make an alternate plan to land safely with sufficient fuel at a different location than you had originally planned. <S> Your new safe landing location will depend on your aircraft capabilities and the conditions. <S> However, if a safe landing location is not an option and you are landing with less than your fixed fuel reserve [30 minutes of fuel], then you must declare Mayday Fuel . <S> Thus under your scenario, it would be MAYDAY MAYDAY MAYDAY FUEL ... https://www.casa.gov.au/publications-and-resources/standard-page/fuel-requirements-australian-aircraft
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The pilot-in-command shall declare a situation of fuel emergency by broadcasting MAYDAY, MAYDAY, MAYDAY,
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Could a turbofan have two adjacent fans? Is there any a point where it becomes possible/ideal to run two large front fans (side by side) powered from a 'single' core? Otherwise shoot this to pieces and explain the ways this is a bad idea. This inspiration for this question is from the design of some rocket motors which utilize a single turbine driving both pumps on a single shaft to feed multiple combustion chambers and nozzles. Example would be the RD-180 . <Q> Generally, it is more efficient to have one large than two small devices. <S> The twin fan solution not only needs a gearbox and driveshafts that a single fan solution does without, it also has more intake and nozzle surface area per cross section than the single fan. <S> This will cause more viscous losses and lower efficiency. <S> The only advantage would be if size limitations make a single fan impossible, but in that case it would be more straightforward to have each fan driven by its own core engine. <S> But the list is short. <S> The list of opposite designs where two engines would drive a single propeller or fan would probably be longer, and my favourite from this list is the LearFan . <S> @jwenting correctly reminds me that for completeness a single power plant driving two contra-rotating propellers should also be mentioned. <S> This is indeed the only way on airplanes of one engine driving two propellers, albeit not adjacent, that has seen wider adoption, from the RR Griffon on the Avro Shackleton to the <S> NK-12 of the AN-22, Tu-95 and Tu-114. <S> Of course, all single-engine helicopters also use this one engine to drive their two propellers … <A> From what I've read, bigger props (and fans) are more efficient, because they move more air. <S> However, at high subsonic speeds, the tips of props start to run into the sound barrier. <S> So, that seems to argue for more smaller props/fans, whose ends won't hit the sound barrier. <S> As others have mentioned, extra crankshafts and gears cost weight. <S> I think I've seen designs using superconducting generators and motors driving multiple fans. <S> However, I can't find it at the moment, and superconductors are probably not ready for prime time... <S> I don't know if you could bleed air from the edges of one fan, to drive, say, a fan on each side. <S> But if you could, that would move more air. <S> Although it might weigh a lot. <S> This is all assuming one turbine has enough oomph to drive multiple fans. <S> I don't know if that's the case, or will be any time soon. <S> Disclaimer: I'm guessing, from limited reading. <A> Actually, there's one example already: F35B STOVL . <S> It's not so impossible <S> I guess. <S> When the efficiency and weight penalty is offset by some other requirements, e.g. ground clearance (next gen 737-Max?), we may soon see a dual-fan-single-core layout in the future! <S> ( F135 engine + Rolls-Royce LiftSystem ) <A> Mechanically it is difficult, although moving more air with lower rpm props has the possibility of improving thrust efficiency per horsepower. <S> Keep in mind, while this approach certainly benefited the Wrights 30 to 50 mph craft, slower rpm props will more rapidly lose thrust efficiency as forward speed increases due to changes in their relative wind (Angle of Attack). <S> Especially for fixed props, smaller, with higher rpm, gave a greater effective thrusting speed range as aircraft design moved beyond the Wrights. <S> Variable pitch props partially solved this issue, enabling another leap forward to higher speeds, but now power output became more of an issue as 2x speed meant 4x drag leading to: Multiple engines turning multiple props, which also improved safety in case one engine failed. <S> Further improvements in power output lead to: more blades on props. <S> Still more power from jet turbines: many bladed fans. <S> Both with lower thrusting efficiency but much more thrust output and greater speed range than 2 blade props. <S> So, could a turbo fan have 2 adjacent fans? <S> One giant turbine running 2 fans? <S> Possible. <S> One giant turbine generating electricity for 4 fans? <S> Aha! <S> No mechanical linkages needed! <S> But, especially for large passenger aircraft, going with less than 2 power plants will be unlikely in the near future, unless it's a zeppelin.
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Increases in reliability and greater power producing efficiency certainly has started a trend towards fewer, larger jet engines with bigger fans. Famous examples of aircraft which used a single engine and two "fans" would start with the Wright Flyer models, all of which had a single engine drive two propellers via bicycle chains.
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What would non-potable water be used for on an airliner? Airliners have potable water tanks and distribution systems for galley functions and such; of course, this water is used for any non-potable functions as well as it's what's available on a modern airliner. However, this question makes me wonder if there are water uses on an airliner that could be served by a separate non-potable water system, or if all the water needed is potable. If there are non-potable water uses, what would they be? <Q> Aircraft travel in countries were pathogen bacteria or viruses are carried by insects which like to lay their eggs in stagnant water. <S> Aircraft water systems must be designed carefully to prevent spreading diseases. <S> On a typical airliner like the Boeing 737NG, you won't find any non-potable water source that would contain chemically untreated water. <S> Equipment is fed from the potable water tank. <S> Used water is either dumped overboard or stored. <S> From the aircraft familiarization manual , the water system: and the toilet waste system: Condensation water is a by-product of many systems cooling air (including by expanding it). <S> This water is collected and drained overboard. <S> Jet engines (including APU) are the main generators of water, as fuel combustion generates essentially water (in mass) and CO2. <S> It's worth noting that at cruise altitude, moisture in atmosphere can be insufficient for humans well-being. <S> The water extractors present in air-conditioning packs <S> then reincorporates a part of extracted water into conditioned air. <A> Non-potable water = undrinkable. <S> Lavatory facilities such as toilets and sinks, and showers such as in the Emirates A380s could be a use of non-potable water on aircraft. <S> That said, why complicate the matter by having two separate water systems? <S> Plus, dirty water would clog up pipes and build up deposits... <S> so why use it? <A> The water source needs to be checked. <S> When I worked in LH it was done twice a year. <S> It was a chore because we had to arrange an airport-pass for the lab guy as he need to get a sample from the spot where they got the water, as well as samples from two of the trucks. <S> Once the test has been passed we were good for another 6 months. <S> Actually the validity was for 12 months but the test was done every six to avoid any gaps, due to late lab reports, station overlooking etc. <S> A list of stations where water uplift was allowed was published on a page in our computer system. <S> If the airplane was inadvertently filled with water from an untested source FRA ops needed to be advised ASAP as the airplane water system would need to be cleaned/flushed before the next sector. <S> At one point we stopped pax flights and only flew freighters, at this time the requirement for water uplift stopped as freighters did not need so much water. <S> As such we stopped the water checks and KUL was taken off the approved water uplift list. <S> If I'm not mistaken the 74F took on around 400kgs, The MD11 around 250kgs. <S> One day we had an MD11F come in with almost zero water uplift and the Captain wanted water. <S> After some discussion we uplifted about two crates of large Evian bottles.
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Now if we're talking about aircraft that DO use non-potable water then look no further than fire fighting aircraft that pick up water from lakes and rivers and dump it on wildfires.
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Why do airlines retire the flight number after a crash? Perhaps it seems obvious, but I couldn't find a plausible reason why they do so other than that it evokes negative emotions among passengers and crew. Could there be other reasons to do so? For example, flight number MH370 was retired as a "mark of respect" for the passengers and crew. And out of interest, is there any case where an airline company reused a retired number for any reason or in certain circumstances? <Q> consider if you Google a flight number you can see the flight status, imagine if the number was from a past crash, you might for a moment think the one you're looking up had crashed <A> You don't want the flight number to conjure up images of crash while booking tickets, especially in when you type the flight number and google shows up the wreckage just below the flight data. <S> Also, it would be quite insensitive, with friends and relatives being reminded of their loved ones every time they hear about the flight. <S> However, it is not necessary that the airlines have to retire the flight numbers because of a crash. <S> A number of them are being used, a few examples being: Air Canada Flight 797 Delta Airlines Flight 723 <S> Air Asiana Flight 214 <A> You answered your own question, they retire numbers because of the emotional context. <S> Some people think that using such a number again shows a lack of sensitivity to the dead and their families, others might think that getting on a flight with the same number would be bad luck. <S> It's irrational, but many people would feel uncomfortable getting on a flight with the same number. <A> It's also done for calming passenger superstitions about such things as well. <S> Kind of the same reason that many skyscrapers do not have or list a 13th floor or nobody would board a flight listed as "United 666" or that left handed people are possessed by demons, etc. <S> You would like to believe modern people would not be influenced by such nonsense, yet how many people did you see reading horoscopes on the train on your way to work this morning? <A> I am a retired airline employee, the reason for retiring a flight number is for the respect of any fatalities. <S> No other secret reason. <S> (At least the “original” Airlines) it was ALL ABOUT RESPECT AND NOTHING ELSE.
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Retiring flight numbers after crash is mainly done to prevent the flight evoking negative emotions among future passengers.
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Do laser Christmas lights have the same dangers as laser pointers aimed at planes? With new laser Christmas decorations like this one, a laser appears to shine in patterns on a house for a decorative effect. If this is aimed so that some of the beams miss the house and go over it into the sky, could they cause problems to planes? Would the effect be similar to a laser pointer, and could the person with the decoration be prosecuted as shining a laser at a plane? <Q> A fine beam is needed do draw patterns. <S> A regular led would require a moving focusing mirror, something expensive. <S> There is a non-standard warning: " Laser aperture, Max output < 1 mW " near the leds: <S> As the leds are in the visible spectrum, this is equivalent in power to a Class 2 laser. <S> A Class 2 laser is considered to be safe because the blink reflex <S> (glare aversion response to bright lights) will limit the exposure to no more than 0.25 seconds. <S> ( Wikipedia ). <S> This image shows the effect of a 5 mW laser light. <S> You may use it for a 1 mW laser light by dividing the distances by 5: <S> Adapted from original on Wikipedia or from the original site : <S> A 0.99 mW Class 2 laser beam can temporarily flashblind a pilot or driver, causing afterimages, within 240 ft (73 m) of the laser. <S> It can cause glare, blocking a pilot or driver's vision, within 1050 ft (320 m) of the laser. <S> It can cause distraction, being brighter than surrounding lights, within 2 miles (3.2 km) of the laser. <S> The above distances are for a tightly focused beam, which is probably not the case of an inexpensive laser device. <S> The effects of a more diverged beam are weaker. <S> More info: <S> This hazard chart . <S> To sum up: <S> Most countries have regulations for dazzling a pilot, regardless of the mean and power used, it's the effect that is taken into account. <S> A class 2 laser led couldn't blind someone unless the person is at a few meters (15 m for temporary blindness and 3 m for eye damages, if the eye is forced to stay open). <S> As the class is not mentioned on the label, I would be careful when seeing this item. <S> There are actually 2 laser leds, a red and a green, is it 2x1 mW or 2x0.5 mW? <S> In practical the lasers probably can't illuminate the same eye, due to the divergence of their beams. <S> To draw a pattern a laser light must move, so the time of illumination of a point is reduced when the device is working correctly. <A> Yes, they do <S> The FAA will not tell you how to decorate your yard, it is not going around and regulating yard displays, however if your display is distracting pilots you will get an unwelcome knock on the door. <S> If you are pointing them up on purpose though, it's an $11,000 fine and possible jail time. <A> These types of lights are unlikely to affect an aircraft. <S> The lasers in Christmas projectors are 1 milliwatt lasers. <S> You can test this yourself by buying a 1mw laser pointer from Staples or other stationary store and having a friend shine it into your own car parked at the other end of a football field or wherever to see the affect. <S> Beyond a certain distance the light attenuates into invisibility. <S> Generally speaking the minimum power laser needed to affect an aircraft is a 5mw laser which can reach several thousand feet and affect aircraft which are landing. <S> Another thing to realize that the odds of a house light accidentally pointing at an object far away is pretty remote. <S> The typical divergence angle for a laser pointer is around 0.5 degrees, so assuming a hemisphere the random chance of an intersection would be 1 in 82,506. <S> Usually for a laser to present a distraction to an aircraft it has to be deliberately pointed and the person needs to be near the approach path of the runway. <A> A guy <S> I know who flies helicopters was momentarily blinded by a stray beam. <S> He confirmed the cause as laser christmas lights when he drove by the residence he was flying over.
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This power of laser is too weak to make a noticeable distraction beyond about 500 feet, so it would be unlikely to affect a plane.
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What software is used for aerodynamic wing shape optimization? I can see lots of research articles around aerodynamic shape optimization of airfoils and wings like this MDOlab program. But all stuff like that don't seem to be available for a simple customer. Personally I've not seen where I can buy or download it. The only programs for that purpose that I've managed to find are: Tosca Fluid (not adapted specifically for the airspace industry) ANSYS Adjoint Solver (probably OK, don't know yet) This Python code coupled with XFoil, but it's primitive and only for airfoils, not for wings. Somebody know some accessible software for shape optimization of airfoils and wings for an ordinary engineer , but not for scientists or programmers? <Q> If you follow the AIAA publication number (AIAA-2014-0567) given in the first frame of the linked video, you will find this article which explains in detail that the optimisation shown in the video was done on MACH: <S> These tools are components of the framework for multidisciplinary design optimization (MDO) of Aircraft Configurations with High fidelity (MACH). <S> MACH can perform the simultaneous optimization of aerodynamic shape and structural sizing variables considering aeroelastic deflections. <S> If you now google for MACH, you will find this article by Gaetan Kenway which explains in detail how the software works. <S> But this is not what you want, my impression is you need a simple to use software which can be downloaded and run within minutes. <S> My recommendation would be XFLR5 <S> which incorporates the XFOIL airfoil solver and adds modules for designing and calculating the whole aircraft. <S> YouTube has a variety of tutorials available. <S> Is that what you want? <S> However, a basic understanding of aerodynamics and the possibilities and limitations of the algorithms used will be very helpful - a good engineer should be able to think both like a scientist and a programmer. <A> I would recommend the use of Aeolus ASP for aerodynamic shape optimisation. <S> Edit: I am not associated with the software in any way. <S> I had found its shape optimisation features useful for an assignment at my university. <A> Specifically, most competition planes like F5D pylon racers and F3K hand launched gliders are almost all designed on XFLR5. <S> But XFLR5 is primarily for simulation. <S> Verifying your "hunches" are correct and testing your tweaks. <S> Design and optimization is still mostly done by gut feeling and educated guesses. <S> However, the RC community have come up with an XFoil based genetic algorithm optimizer. <S> Check out XoptFoil (google it). <S> You just need to give it a starting airfoil and the target characteristics you're after and let it evolve it until it gets as close as possible to your target. <S> Note <S> though that AI algorithms like the genetic algorithm can sometimes give nonsense results because it's the one that fits best to the desired target result. <S> It only means that the algorithm have managed to generate the best airfoil that has the characteristics you want in the simulated world of XFoil, not necessarily the real world. <S> You still need to build the wing and verify.
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I'd also recommend looking at XFLR5 because that's what I see most people in the homebuilt experimental and radio controlled communities use.
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Are there any known incidents of ejections by capsule? What are the survival chances? One hears of many stories of ejection seats but rarely of ejection by capsule. Probably because seats are so much more common. So are there any known incidents of ejections by capsule? F-111 was one such aircraft that had an ejection capsule I recall. <Q> While the F-111 had a custom build escape capsule integrated with the cockpit, escape capsule designs have been used in the past. <S> It was a special type of ejection seat which used a pressurized clamshell-type enclosure which could be deployed rapidly once the ejection process had been initiated. <S> It was designed specifically to protect a pilot against a supersonic, high altitude ejection which would have almost certainly been fatal using a conventional ejection seat. <S> The system was used on both the B-58 and XB-70 aircraft. <S> The system was pressurized allowing a flight crew to use standard life support equipment as opposed to a full body pressure suit for high altitude flight. <S> One notable ejection involving the Stanley capsules was the loss of XB-70 prototype No 2 on 8 June, 1966 near Barstow, CA. <S> During a formation flight of several other aircraft with the XB-70 for a General Electric photo shoot, an NF-104 collided with the starboard wing and tailfin of the XB-70 and disintegrated in flames, killing NASA test pilot Joe Walker in the process. <S> The Valkyrie continued on straight and level, then waltzed out of control and began tumbling toward the desert, spilling plumes of fuel vapor as it went. <S> Commander Al White initiated the ejection process using his Stanley capsule and egressed the aircraft but was seriously injured by failing to clear his arm from the clamshell enclosure during deployment. <S> The copilot, Carl Cross, failed to initiate ejection and rode the crippled Valkyrie to the desert floor, killing him in the process. <A> The F-111 capsule was great and I always felt glad to have it, especially at high speed. <S> However in my 8 years flying in it, I'm not sure that the ejections I knew about were much different statistically. <S> The fatal outcomes were late, upside down in a rapid roll or otherwise outside the parameters and the successful ones were mostly okay with a few non-grounding back injuries caused by the impact. <S> One case in Mountain Home, the Wing CC pilot broke his back after ejecting a few seconds after takeoff. <S> He was paralyzed but the WSO was not seriously hurt. <S> My impression is that these results are probably comparable to seat ejections. <A>
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One notable type was the Stanley Corp. Ejection Capsule . Yes, in the B-70 accident, one of the crew members escaped inside a capsule, but had part of one of his elbows shaved, as it was caught by the shell and cut on launching from airplane, and some backbone fractures on landing, as the parachute didn't work properly, speed when capsule hit ground was too high.
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Why does the F-111 have a capsule ejection system rather than a conventional system? Following on from the questions F-111 emergency landing with no wheel; what is done to reduce risks when loosing a wheel? and Are there any known incidents of ejections by capsule? What are the survival chances? I wondered, what is the reason for the ejection capsule on the F111? It doesn't fly particularly high or fast (compared to aircraft with conventional ejection seats). The only reason I can think of is that the pilots sit almost side-side and it would presumably be tricky to fire the first seat without seriously inconveniencing the remaining crew member. Are there any side-side aircraft with ejection seats? <Q> The reason the F-111 has an ejection capsule is pretty weird in itself- <S> its there because USN wanted it. <S> In 1960, USAF asked for an aircraft capable of supersonic flight for 400 miles, and capable of operating from short/unprepared fields and capable of crossing Atlantic unrefuelled through <S> Specific Operational Requirement (SOR) 183. <S> At the same time, USN was trying to develop a fleet defender for its carrier groups which had high loiter time (> 6hrs) and can detect/launch missiles at incoming bombers and sea skimming missiles at over 100 miles. <S> To this extent, the Douglas F6D Missileer was proposed, which got cancelled in 1961. <S> Unfortunately for USAF (and lot of others), US SecDef Robert McNamara decided that both these requirements could be met by the same aircraft- <S> actually, the only things they agreed about were that the aircraft would have swing-wing, have two seats and have two engines. <S> The USAF wanted tandem seating, while the USN wanted a side-by-side seating for improving crew co-ordination sharing the large radar display to launch missiles (like the A-6 Intruder, which had side by side seating, but conventional ejection seats). <S> The reason the ejection capsule was included was that USN believed that it would give better chances of survival in case of ejection over sea (where it was to function as a life raft) and in high speed ejection. <S> The USAF hated this as it increased the weight by over 500 lb, affecting performance. <S> In fact, the Boeing proposal included conventional ejections seats, which was required to be changed into a capsule (and was selected before McNamara intervened and selected the other one). <S> In the end, USN escaped from the project (ironically due to weight and performance issues), while the USAF and others got stuck with the ejection capsule, which they never wanted in the first place. <A> The United States invested in increasingly faster supersonic bombers in the 1950s and 60s in order to thwart conventional defences and interceptors operated by the east bloc, so the realities of Mach 2 or Mach 3 flight demanded these kind of enclosed and pressurized escape systems in the event of an inflight emergency or enemy attack. <S> But the realities of modern Warsaw Pact IADS using radar guided missiles made supersonic and easily detected bomber fleets an impractical investment for strategic nuclear delivery. <S> With the return to the subsonic flight envelope and lower operational altitudes made conventional ejection seats a much more mature and realistic option for an escape system. <S> A good example of this was the Rockwell B-1A, which was to have used an large four man escape capsule similar to the F-111's prior to its cancellation by the Carter Administration. <S> It's <S> successor, the B-1B which was optimized for slower and low level penetration abandoned the escape capsule for the mature and established McDonnell Douglas ACES II ejection seats at each crew station. <S> Additionally, escape capsules are large, heavy, complex pieces of equipment, not to mention expensive. <S> The F-111's escape capsule cost as much as a completed F-86 SaberJet. <S> Complexity increases the number of failure modes and risk of failure during emergency use exponentially, requiring more maintenance, etc. <S> Curiously one high altitude, high speed cruiser, the Lockheed A-12/SR-71, used conventional ejection seats throughout its career albeit requiring the crew to suit up in full pressure suits during the flight. <S> I do not believe that the seats were intended for use at supersonic speeds, leaving no means of escape for the crew during this regime of flight. <S> This was also true of the North American X-15, a Mach 6 research aircraft where an ejection at cruise altitude and speeds would have certainly proved fatal. <S> Are there any side-side aircraft with ejection seats? <S> Yes. <S> Multiple aircraft with this cockpit configuration used ejection seats including the B-1, B-52, B-2, A-6, OV-1, and T-37. <A> My response is that I was a design engineer on the F-111 project with responsibilities associated with the design and test of the module. <S> Traditional ejection seat concept provided no survivable protection for escape at the upper (higher) speeds and altitudes of the operational envelope of the F-111. <S> This is true for tandem or side-by-side seating configurations. <S> The only significant design constraint imposed by the Navy was to be able to separate up to 30 feet under water. <S> Interestingly, the control stick could be converted into a “bilge” pump handle in event of water landing. <S> The first use of the escape module was from a test aircraft having lost hydraulics in the flight control system. <S> This occurred over Bowie, Texas. <S> The pilot scratched his finger climbing through a barbed wire fence! <S> The only injury!
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It has to do with the realities of a supersonic ejection at high altitudes, which is usually fatal for unprotected aircrews, both from bodily trauma from exposure to a supersonic slipstream and the extreme low temperatures and pressures which would be encountered at typical cruise altitudes.
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Do (did) powered airplanes exist where pilots are not in a seated position? Well... all is said in the title. I mean "traditional" powered airplane, with a cockpit and long flight capable, not a paraglider. Upright pilot or prone pilot would qualify.Likely experimental or military. Source The concept was once studied with the XF-90, but didn't get to reality. <Q> In the first ones the pilot was rarely sitting. <S> Inspired by ships, some early aviators steered their craft by standing upright: <S> Almost all balloons were and still are flown standing upright. <S> Same goes for all Zeppelins, and they should qualify as powered aircraft. <S> All Lilienthal glider designs required the pilot to stick the forearm through a tube and grab a horizontal bar, so his weight would rest on the forearm. <S> Steering was done by swinging the legs left or right rsp. <S> back or forward. <S> The legs also doubled as the landing gear, much like in modern hang gliders. <S> Lilienthal experimented with carbon dioxide engines, so some of his gliders can be called powered. <S> Gustave Whitehead 's Number 21 design of 1901 was flown standing upright, but it is disputed that he actually flew it successfully. <S> The early Wright Flyer s were flown in a prone position. <S> Sitting came later . <S> The Santos-Dumont 14bis of 1906 was flown standing upright. <S> Similarly to the Wrights, Santos-Dumont 's later designs like the Demoisielle had a proper seat. <S> Santos-Dumont training to fly his 14bis <S> (picture source ) <S> The Horten IIId was a motor glider version using a 32hp Volkswagen engine, so this should count as powered, too. <S> Before anti-g suits were perfected, some designs used a prone pilot position to increase the possible g loads. <S> Here is an answer which covers this aspect. <S> René Leduc's ramjet-powered experimental aircraft used an almost lying position for the pilot to keep the cross section of the centerbody small. <S> Yvan Littolff in the cockpit of the Leduc 021 <S> (picture source ) <S> Most hang gliders use a prone or almost lying position for reducing the drag the pilot causes. <S> The powered ones should also qualify here. <S> Same goes for motor gliders derived from sailplanes, where the pilot position is almost lying, too. <A> Yes, but probably not what you have in mind. <S> Some weight-shift hang glider pilots are prone. <S> Hot air balloon pilots stand up. <A> I would also submit the Henschel <S> Hs-132 <S> Never flew, but four were built. <S> Based on the Volksjager WW2 had the most gorgeous aircraft..... <S> now everything is all angles and who can lock on and fire their missiles first.....
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The Hiller Pawnee had the pilot in a standing position. The Horten gliders were flown in a prone position so the pilot would present a lower cross section.
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Why are civilians not allowed to fly demilitarized US fighter jets? I have seen it is possible to fly demilitarized Russian fighter jets in the US. Why is it impossible to fly American demilitarized fighter jets? <Q> That's because US military is particularly concerned about chopping up its assets before civilians can lay their hands on them. <S> The procedures are covered in US DoD Manual 4160.28 Defense Demilitarization: Procedural Guidance . <S> The procedures for 'demilitarizing' military aircraft are particularly brutal: <S> Military Aircraft (a) Aircraft (Figure 29 and Figure 30) that are specifically designed for military purposes shall be demilitarized as follows: at a minimum, cut or break completely through at least one lobe of the fuselage trifurcated horizontal and vertical stabilizer spar attachment fittings, on both the right and the left hand sides of the stabilizer carry-through spar assemblies. <S> This demarcation of the prescribed DEMIL procedures is to ensure the aircraft is rendered unfit for flight . <S> (emphasis mine). <S> Demilitarization Procedure; image from Popular Mechanics <S> (b) Helicopters (Figure 31) specifically designed for military purposes shall be demilitarized by crushing, shredding, or smelting the entire airframe and fuselage, ensuring that the transmission mounts and supporting structural beams, engine deck in area of mounts, wing attaching mounts and support beam structure, and fuselage to tail boom attaching mounts and tail rotor gear ox mounts have been destroyed. <S> Of course, there are ways around this- <S> you can assemble the aircraft from parts or some aircraft will simply escape the procedure and is avialble : <S> In a letter to the chair of the House Armed Services Committee, AOPA President Phil Boyer ... stressed that certain aircraft (possibly aircraft not demilitarized) had been carefully maintained over the years and were now serving useful purposes. <S> but these are quite rare. <A> As the other have alluded, it is not impossible to fly demilitarized American military aircraft, it's just exceedingly difficult. <S> Many are just not available due to the government holding the aircraft in reserve, and older ones are often limited by the availability of parts. <S> The FAA provides guidance for obtaining airworthiness approval for former military aircraft in AC 21-54 which is the first step in being able to fly such an aircraft. <S> Also as pointed out, the FAA doesn't have type ratings available for the majority of these aircraft so that poses a problem in being able to fly it once it's airworthy. <S> The FAA addresses this using a Letter of Authorization or LOA. <S> the process to obtaining this is defined in the following FAA documentation . <A> There are plenty of ex-military planes from many nations in private hands. <S> I know of an F4 being restored to flying condition by a private individual. <S> He claims his will be the second in private hands. <S> A friend of mine owns an early MiG jet as well as a former Soviet trainer. <S> There have been several T-38s for sale from various online sources. <S> There are privately held T-33s out there. <S> At least one F-86.A <S> few MiG-21s. <S> At least one F-100.At least one F-104.At <S> least one MiG-29.At least one Harrier. <S> At least one F-8.A couple A-4s. <S> There is at least one Cobra flying around privately as well. <S> Saw it a few weeks ago. <S> The list goes on... <S> There was a proposal sometime back to convert obsolete A-10s to fire fighting tankers. <S> The outfit was, shall we say, "well connected" but it ended up not going anywhere. <S> It would have made a GREAT, albeit pricey, tanker platform if I do say so myself. <A> The Wikipedia article on the Lockheed F104 Starfighter mentions a privately owned example in the US.
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So basically, it boils down to the fact that the US military makes sure that the airframes won't fly again.
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How is it possible to perform a rapid climb / tight loop without stalling? I'm still trying to get my mind fully around "Angle of Attack". This makes sense to me in the most basic situations, but when I start throwing more dramatic situations at it, my understanding breaks down... which means I don't really understand it. Take this video for example (at 0:17 and 1:32): How is this possible? Is it due to the excess power of the aircraft allowing it to change its "flight path" constantly through the maneuver and thus keeping the flight path (relative wind) not far away from the Critical Angle of Attack? <Q> Short answer: <S> The maximum angle of attack is never reached in this video, thus the aircraft is not stalled. <S> Longer answer: <S> Stall is a problem mainly occurring during low speed flight. <S> Our angle of attack is always depending on our flight path. <S> Let's first assume, that are at cruising altitude in a level flight condition. <S> In this case the pitch angle of the airplane equals our angle of attack. <S> As generated lift is dependent on your airspeed and the lift coefficient (which is again dependent on your angle of attack), reducing airspeed in level flight while maintaining your altitude will force you to in increase the angle of attack. <S> At some point a further increase will result in a too high angle of attack and thus stall the aircraft. <S> Now, let's look at your problem: (source: aeroskytech.com ) <S> During climb, the trajectory of the plane is not equal the horizontal axis. <S> Therefore, also your angle of attack is not equal to your pitch angle (the angle between the longitudinal axis of the plane an the horizontal axis), but to the angle between the trajectory and the longitudinal axis. <S> During the loops showed in the video the airplane is not only changing its pitch angle but also its flight path, therefore it is not stalled. <S> An interesting example for maintaining your flight path while increasing are military aircraft in combat maneuvers, their pilots rapidly change their pitch angles while still flying in the same direction. <S> This works as a decent speedbrake, allowing them to intercept other aircraft. <A> The example of the GB-1 going vertical at 0:17 in the video will work just fine, so long as the pilot does not exceed the critical angle of attack on the wing. <S> It's being flown by a skilled aerobatic pilot who is familiar with the GB-1 flight envelope and is a pretty benign maneuver. <S> For an aircraft like that, I'd guess the maneuver begins around 160-170kts at a load factor of 4-6Gs; a decent pull on the stick but not enough to reach the critical angle of attack for those airspeeds. <S> In addition, the stall characteristics of those aerobatic aircraft are pretty benign; the onset just feels like buffeting and shuddering in the airframe and can be relieved simply by easing off stick pressure. <S> The example at 1:32 is a post stall maneuver where the plane is stalled and is simply hanging on the prop. <S> You can do this if you have enough power, and the maneuver begins at or near Vs. <A> Excess power, yes! <S> But also light weight and a robust, low aspect ratio wing. <S> Excess power helps maintain adequate airspeed at all attitudes, including straight up. <S> Prop wash also maintains airflow over the wings and particularly the empenneage control surfaces, but torque effects must be managed at low airspeeds. <S> Light weight is prized by aerobatic pilots because the aircraft can change directions easier and "follow" the pitch change, rather than continuing in the same direction while AOA increases. <S> This is a major problem with very heavy aircraft that have high wing loading such as airliners. <S> The other side of stalling due to excessive AOA is exceeding the G force (load) <S> limitsby pulling too hard on the elevator at excessive speed. <S> The wings break before you reach stall AOA. <S> Here the strength of the low aspect wing saves you, and the G forces serve as warning. <S> Finally, the low aspect wing stalls at a much higher AOA and lower airspeed than a high aspect wing. <S> Have a look at what most modern fighter planes have. <S> Add in a pilot properly trained and experienced in that type of aircraft, and you have one amazing video.
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The main difference is your speed, or so to say the excess power used for climbing.
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Why does an airliner fuselage have a constant section over its length rather than a tear drop shape? It is usually stated than a tear drop shape is a good shape for aerodynamic efficiency: Adapted from Nasa On the other hand, fuselage on an airliner has most of the time a long cylindrical section with round/tapered ends. I understand an aircraft has other constraints than just having the lowest possible drag. It comes to mind a cylindrical shape allows the same number of seats in most of the rows and also prevents to increase the section of the forward cabin. Without further explanation, it seems curious the fuselage has not a shape between a rounded cylinder and a tear drop shape which is often seen for gliders: Source Without going into deep details, what are the most important reasons preventing such design? <Q> On the other hand, fuselage on an airliner is most of time bullet shaped. <S> No, it is not. <S> A “bullet shape” has a flat end, which is where most of the drag is generated (at subsonic speeds). <S> But that shape is never used on flying vehicles except on rockets where the end is occupied by the rocket engines. <S> Instead, airliners always have a tapered “boat” tail, sloping gently enough to avoid separation (sometimes with help of strakes ). <S> The resulting shape is as if you split a droplet in the widest point and insert a piece of cylinder. <S> And the difference in drag coefficient between pure droplet and droplet with cylinder section inserted is very small. <S> Still, a continuously varying shape is slightly better than the cylindrical section. <S> And the early aircraft did have that. <S> Likely the last one of those was the Lockheed Constellation . <S> In contrast the tubular section is much easier to design, easier to make <S> and when they want to make a bigger version of the plane, they just insert a couple more frames and mount stronger engines to match the increased weight—between A318 to A321 or between all variants of B737-MAX, vast majority of parts is the same and there is just different number of frames and different engines. <S> And it's simple to load—seats are mounted on straight rails and containers simply slide in to the cargo bay. <S> And the difference in drag is small enough that the cheaper manufacturing and practicality will easily offset the increase in consumption. <A> A few things One of the main objectives for glider flight is making it as aerodynamically efficient as possible. <S> For airliners, it is to make it as economically efficient as possible. <S> This means that it has to carry as much as passengers (or cargo; sometimes, there is little difference) for the given fuselage volume. <S> Glider type designs in airliners will increase the possibility of tail strike significantly. <S> What is good for low speed flight is not exactly great for the high speed flight regime. <S> The loads associated are different. <S> The aerodynamic design of glider is based on one thing- <S> there is no engine. <S> This means that the drag has to be kept an absolute minimum for any meaningful flight time. <S> The airline designer, however, has the luxury of engines- <S> he/she can pay some penalty in the form of drag to improve other performance characteristics. <S> Any design is a tradeoff- <S> the structure at the rear of a glider eats into its carrying capacity. <S> It is tolerated because gains from reducing drag outweigh the added weight. <S> However, this is not the case in an airliner. <S> Aerodynamic efficiency is not everything- <S> there are aircraft which are blatantly inefficient aerodynamically, but fly anyway because they serve the purpose. <S> The wing carries the fuel in an airplane. <S> A teardrop shaped fuselage would require the wing to be well ahead of the cg (or you have to strengthen and increase size of the fuselage where the spar passes through). <S> This would increase the size of the horizontal stabilizer (or require lengthier fuselage), increasing weight. <S> There are practical issues <S> too- fuselage shaped like this would increase the boarding/deboarding time, reduce potential for further development (its difficult to plug fuselage sections in that case) among others. <S> One important point is that you're considering only recreational gliders. <S> If you consider gliders designed for transport, you can see that their shape resembles airliners- a good example would be the troop carrying gliders of WWII. <S> Airspeed Horsa ; Public Domain, Link <A> Airliners do actually have an elongated teardrop shape to them in a side profile. <S> In aerodynamics this is generally referred to as 'boat tailing' an object. <S> The glider has much more of a tear drop shape - and by that I take it you mean the tadpole like shape of the fuselage with a long slender tail - empty because there is no need for additional systems which are voluminous. <S> The pilot, avionics, controls, landing gear, etc. <S> all fit into the forward pod without a problem. <S> All the tailboom really needs to carry are the control linkages and structure. <S> Here it makes sense to have a long slender tail, just strong enough for structural purposes while minimizing skin friction drag. <S> Now most of the fuselage of an airliner is taken up by the passenger carrying pressure vessel which has to remain very large in order to do that job effectively. <S> It's also long enough that it will reach from nose to tail of the aircraft such that very little additional length is required to provide effective tailplane authority for weight and balance purposes. <S> A long slender tailboom is. <S> not necessary here.
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The shape was great aerodynamically, but it was expensive to build, it made it more difficult to ensure all elements have proper strength to withstand the pressurisation, every time they derived a larger version they had to redesign all frames and in operation it was not exactly convenient for loading either.
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Can a helicopter carry a large airplane? I saw on YouTube a helicopter carrying an airplane. Is this possible, I mean is the maximum load compatible with the mass of this aircraft? <Q> If you look more closely, this "airplane" is only the husk of a Tupolev Tu-134 , a rather small airliner, and the helicopter is a Mil-26 , the heaviest helicopter ever to go into production . <S> Not only are the empennage and the outer wings missing, but also the engines, which helps to reduce the load considerably. <S> Mil-26 lifting a Tu-134 carcass, seen from below ( source ) <S> The empty weight of a flightworthy Tu-134 is 28 tons, but the engines alone weigh 2.3 tons each. <S> Now remove the outer wing, empennage and cabin interior, and the remaining weight is within the 20 ton load limit of the Mil-26. <A> One of the purposes of the Sikorsky CH-54 was to transport aircraft. <S> Carrying a Chinook : <S> Lifting a Caribou : <A> http://www.angelfire.com/mo/242sdASHC/213th.html gives a first hand account of a crewman flying quite a few of these dangerous missions. <S> http://www.combatreform.org/CH53AliftsA1andA4.jpg shows an A-1 and an A-4 being lifted by CH-53s, but larger aircraft like F-4s and F-105s were similarly airlifted out of the jungle to prevent them from falling into enemy hands. <A> As said, the aircraft is tripped of heavy equipment. <S> The airframe itself is as light as possible to maximize cargo carrying capacity. <S> And on separate note the video title is a bit provocative. <S> The airliner is not big and even so it isn't in operational condition. <S> Not really #MindBlown as the title proclaims. <S> This is all within limits of the helicopter's capacity, but we don't see such deliveries quite often. <S> Think about carrying such cargo in strong winds. <S> Road/rail/sea transport of airframes is still preferable to helicopter transport when safety is a concern. <S> And when dismantling aircraft it's a good practice to use boneyards <S> where everything from storage to scrapping is done so that there is no need to transport airframes around.
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In Vietnam it was pretty common to remove crashed aircraft from the jungle using helicopters.
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How can I find the CG of a model aircraft based on its dimensions? Given the dimensions and gross weight of an RC model aircraft, how can I find the center of gravity? Can I calculate it, or perhaps there's some way to approximate it? <Q> You cannot. <S> Assuming that by 'dimensions' you mean the values for length, width and height <S> , there is no way to calculate CofG from it. <S> Two planes with exactly the same dimensions, but one with a thicker wings or tail, will have different C of G. <S> Even if you know the precise shape of the plane, the C of G cannot be calculated. <S> Replacing a wooden tail with a heavier metal one with the same shape would shift the C of G. So would replacing the engine with a heavier one. <S> You need either the plane itself, or exact plans showing all the components and their weights (and a lot of maths). <A> The question you have asked is competently answered by DJClayworth. <S> But I guess you want to ask something different, that is where the center of gravity must be in order to have a well-behaved aircraft. <S> The aerodynamicist's answer would be: Slightly ahead of the neutral point . <S> First, calculate the areas of both the wing and the horizontal tail. <S> Interpolate between the wing roots to include the section which is covered by the fuselage. <S> These areas are needed for scaling the influence of the wing and the tail. <S> Next, pick a reference point. <S> The nose of the wing root would be a good choice. <S> Then measure the distance between this reference point and the quarter chord point of both the wing and the horizontal tail. <S> For unswept wings, the quarter chord point of the wing root is sufficient; however, with swept wings you need to find the spanwise station where half of the wing area is inboard. <S> Use the sketch below for a graphical method: The grey area is the swept wing's planform. <S> First, add one tip chord length at each end of the root chord and vice versa with one root chord length at each end of the tip chord (blue lines). <S> Then connect the ends of the resulting lines (red lines). <S> The spanwise station where they cross is your mean chord (green line). <S> Use the quarter point of this chord (black circle) and carry it over to the root to measure the distance to your reference point. <S> Do the same for the horizontal tail. <S> If it is a V-tail , use the projected planform in the horizontal plane. <S> Now all that is left to do is to interpolate the two distances $x_{NP}$ with the respective areas $A$: <S> $$x_{NP} = <S> \frac{x_{NP_{wing}}\cdot A_{wing} + <S> x_{NP_{horiz. <S> tail}}\cdot A_{horiz. <S> tail}}{A_{wing} <S> + A_{horiz. <S> tail}}$$ <S> Now that you know the neutral point, place the center of gravity at 20% of the mean chord (remember the green line?) <S> ahead of this point. <S> In a normal RC aircraft with unswept wings this is approximately at one third of the chord length from the nose of the wing root chord. <A> If the model aircraft can actually fly you can narrow down where the center of mass is. <S> When the aircraft is sitting on the ground the CoG will be above the triangle described by the gear. <S> If it has a nose wheel then the CoG will be more towards the rear (so the aircraft can pitch up on takeoff). <S> If it is a tail dragger it'll be more towards the front. <S> Beyond that the center of mass will most likely be near or just in front of the wing root. <S> That way loss of control will let it remain stable instead.
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The center of mass will be along the centerline of the aircraft (usually by virtue of symmetry).
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Where does turbine vane and blade cooling air come from? Some large jet engines have a high combustion temperature to increase maximum thrust. First vanes and blades of the turbine must be cooled to prevent them from melting. One method is to circulate cold air from the compressor inside the element and/or create a coating of air on the element faces using channels and holes. Trent turbine HP blade with cooling channels, source How is air from the compressor channeled to the vanes and blades? How is cooling air prevented to escape to the space between rotor disks instead of going to the cooling channels, under turbine gases pressure? What approximate fraction of core power is used for such cooling? <Q> To build upon a few points in Peter's answer: <S> This diagram will probably help visualize it (I copied from this question <S> How is the central hub / shaft casing of a two-spool jet engine assembled? <S> ): <S> The seal between the disks is just a labyrinth seal. <S> Those chambers, however, are pressurized (by similar mechanisms as the cooling air was delivered to the blade). <S> So there is a tiny positive flow of air out of that chambers, which prevents the hot combustion gases from flowing in. <S> Refering to the diagram, the space in front of the 1st stage disk is pressurized from air coming from the stg 10 compressor through the series of passages colored in orange. <S> The space between HPT stage 1 and stage 2 is pressurized by air the comes along the inner diameter of the HP rotor, from an impeller between stage 7 & 8 compressor (in blue), and the space aft of the HPT stage 2 is pressurized from air the comes from the stage 4 compressor (by means of pipes on the outside of the engine, light blue color). <S> Pretty much every cavity/chamber inside the engine is pressurized somehow, to keep air from going in undesired directions. <S> I don't know exactly how much air is used for cooling. <S> It's on the order of 1% <S> (i.e. I know it's less than 10%, but certainly more than 0.1%) <A> Basically, the 'cooling' air is obtained from the diffuser and/or combustion liner (it will differ in different engines) and is routed both externally and internally (i.e through the casing and spindle) to the nozzle and rotors. <S> Though the details differ from engine to engine, the basics are similar, for example to the NASA Energy Efficient Engine . <S> From NASA CR- 167955 <S> High Pressure Turbine Test Hardware Detailed Design Report : <S> The vane leading-edge cavity is fed from the inner flowpath, and the aft cavity is fed from the outer flowpath ... <S> The Stage 1 rotor is cooled by air extracted at the diffuser mean line. <S> The image below shows the schematic of the airflow inside the engine used for cooling. <S> Engine cooling air supply; image from <S> NASA CR- 167955 <S> High Pressure Turbine Test Hardware Detailed Design Report <S> Latter stages are cooled with air derived from higher compressor stages. <S> For example, in this engine, The Stage I shroud is cooled with air supplied from the compressor dis- charge. <S> and The Stage 2 nozzle cooling air is extracted from the compressor at the exit of the seventh-stage stator. <S> As can be seen in the figure, the cooling air is prevented from escaping back using a number of seals. <S> Engine seals; image from <S> NASA CR- 167955 <S> High Pressure Turbine Test Hardware Detailed Design Report <A> Since the pressure of cooling air must be higher than the local pressure in the turbine, this air needs to come from the diffusor area, which is where the highest pressure in a gas turbine is found (see here for details). <S> Normally, it flows through the hollow high pressure spindle <S> so it arrives at the root of the turbine blades from where it finds its way to the surface of the blade. <S> Centrifugal forces help to push the air through the narrow holes, so in effect the turbine blades suck the air in at their root. <S> The seal between the disks is (to my knowledge - I am on shaky ground here) nothing better than a labyrinth seal .
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The Stage 1 nozzle is cooled by air extracted from the inner and outer combustion-liner cavities.
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What is the function of variable inlet guide vanes in terms of pressure change? Nowadays in the turbofan Variable Inlet Guide Vanes are more and more used. My question is: which is their function in terms of pressure change? The question is very specific: I know that they allow to give the most proper direction to the fluid, but do they act also to increase the pressure? So: what happen between the inlet and the outlet of each blade, talking in term of pressure? I need some reference, if possible. <Q> You need to be careful in understanding the significance of the variable guide vanes (VGVs) being variable . <S> You could think of them as a bit like venetian blinds - when they they are most open they present the least obstruction to the air flow, much as you get the most light through a set of blinds when they are at the right angle to the incoming light. <S> As you close them, you get less flow (light) through them, as they present a greater obstruction to the flow. <S> The VGVs are only variable to maintain stable flow in the compressor at conditions away from the design condition. <S> The design condition for jet engines is always high power during cruise (or at the top of the initial climb to be pedantic), so the VGVs only start to close at reduced powers. <S> At high power the vanes are at their most open to maximise flow through the engine, minimising pressure losses across them and maximising thrust. <S> As they are gradually closed when power is reduced, they present more of an obstruction to the flow (acting as effectively a variable area throttle valve in the path of the flow being closed down), so presenting an increased pressure ratio loss (or if you prefer reduced pressure recovery). <S> The increased use of VGVs really shows designers pushing at the limits of airflow stability in pursuit of better efficiency by maximising pressure ratio per stage at the design condition, at the cost of the increased weight of the mechanisms to drive the VGVs. <S> Not sure I expressed that very well, but first post on stack exchange. <A> Variable Nozzle Guide Vanes do the same job as non-variable ones, they are just optimised for a greater range of conditions so their characteristics will be the same. <S> From this article : They direct the airflow onto the turbine blades while at the same time converting pressure energy into kinetic energy. <S> There is also this blog , which is a very good and informative read about gas flow in a turbine. <A> VIGVs are similiar to IGVs with one major exception: VIGV's move either mechanically or hydro-mechanically to increase or decrease angle of small blades (located at front of compressor) to maximize airflow into the compressor. <S> Doing this allows airflow to not shock the 1st stage compressor blades which can minimize things such as compressor stall due to speed of aircraft. <S> The faster the air enters the compressor the more chance there will be to stall the compressor/engine. <S> Google Pegasus turbo fan engine (F402-RR-408) to see how the VIGV's help redirect the air on the dual shaft, counter-rotating compressor/fan. <S> This is an amazing engine that counter rotates to help with torque while the Harrier is in a picture perfect hover. <S> If the motor did not have this feature the entire fuselage would want to rotate in the direction of the spinning blades inside of the motor. <S> So the first section of the motor is the first of 3 stages of stators followed by a rotating stage of blades alternating by stator/fan/stator/fan blade which are clockwise spinning blades. <S> VIGV's redirect airflow counter-clockwise to enter the first of 8 stages of clockwise rotating blades. <S> To my knowledge, this is the only counter rotating motor.
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They will accelerate the flow and therefore reduce the pressure at the vane outlet.
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Is King Khalid International Airport in Riyadh actually very big? Apologies in advance if this is in the wrong place, there isn't a geography StackExchange so this was the next best option I could find. I've read multiple things about the huge size of King Khalid Internaional Airport (IATA: RUH, ICAO: OERK) in Riyadh, one source said it was bigger than Paris and others have said it's larger than the entire country of Bahrain. Judging from Google Maps, it really isn't particularly big. What's the deal with that? <Q> It depends how you define the airport. <S> I don't think your Google Maps method is sound, however; it depicts built-up areas, not the airport boundary. <S> You couldn't draw the same map around LAX , say. <S> The standard for measuring the area of an airport appears to be the total land owned by the airport. <S> And jet age airports, with their expansive noise buffers and office park reservations, tend to take as much as they can get. <S> DEN is reckoned the largest airport in the U.S., at 33,531 acres (~136 km²), though only a fraction of this is developed. <S> The numbers for total land are easy to find, the numbers for improved land less so, but I found an informative Globe and Mail article about Montreal-Mirabel. <S> When originally created, the land seized for the airport was larger than the city of Montreal itself— around 97,000 acres (~392.5 km²). <S> The article notes that the airport perimeter itself was only about 5,200 acres (~21 km²). <S> Still, it's the former number that is commonly bandied about, and the measure by which Mirabel was considered the largest airport in the world. <S> According to Kable , a London-based business information firm, King Khaled International Airport covered an area of 225 km² when it opened in 1983. <S> In 1999 it was surpassed by King Fahd International Airport , which occupies 776 km². <S> This is roughly the figure given by the 2013 Guinness Book of World Records . <A> It might help to have citations for the claims you mention - perhaps there's missing context. <S> That said, you're right. <S> The comparisons sound utterly false, based on Google Maps' measurement tool: Click to embiggen the images, but they're not remotely close: Bahrain's total area is around 700km²; OERK airport according to Google measures closer to 37km². <S> It's not even necessary to closely follow the Bahrain coastline to get a precise figure, the numbers are so far off. <S> That said, Wikipedia has an uncited claim <S> that: The airport occupies an area of 375 square kilometres (93,000 acres). <S> It seems likely but not guaranteed that this could be due an omitted decimal (37.5km², not 375km²) or to unscrupulous edits. <S> Even so: if it were 375km², it would only be larger than the administrative center of Paris (105km²) ; it would remain smaller than Bahrain. <S> EDIT: <S> that seems likely. <S> Back in 2013 an anonymous user added that its area was 300km² and the airport's size has, at least in print, steadily increased since then. <S> I imagine if you did some more forensics you'd find that this is all random IPs. <A> Not a complete answer, but possible airports limits, based on zoning data, may be these one: <S> Source <S> Other clues may be discovered in the same page. <S> The cadastral information is handled by MOMRA . <S> The company that surveyed this area may be Twozan . <S> This is a "community answer", so feel free to improve it. <A> The King Khalid International Airport (234 km^2) is larger than Paris proper (160.0 km^2). <S> The King Khalid International Airport is not larger than Bahrain (762.8 km^2). <S> To arrive at this answer I used some data from various sources. <S> Mostly non-official but dependable sources as I do not have the language skills to navigate Arabic websites. <S> I pulled street data from OpenStreetMap and using the very good find by the community wiki response georeferenced the future land use map with points using the polyline data. <S> Georeferencing is used to correctly orientate and scale raster images to geographical locations. <S> I then created a new feature using the rubbersheeted/georeferenced land use map to draw the rough outline of the land that could be used for airport activities; this is the land dedicated to airport use not necessarily the actual size of the facilities. <S> This should give us a rough idea of the size and shape of the airport. <S> 234 square kilometres. <S> Using data of the administrative districts for Paris, I summed the area of the 80 districts for Paris proper. <S> 160.0 square kilometres. <S> Using ESRI's shapefile for world nations, I found the area of Bahrain. <S> 762.8 square kilometres. <S> If you enjoy maps, come on over to the https://gis.stackexchange.com/ . <S> It is probably the closest to pure geography on SE yet. <A> It really depends on how you define 'big.' <S> In terms of size of the terminal and movement areas, it's not very big at all for an international airport. <S> Even medium-sized passenger airports in the U.S. are commonly larger than Riyadh's airport. <S> It has only 2 parallel runways and 24 boarding bridges. <S> By comparison, the medium-sized airport I usually fly out of in the U.S. has 36 boarding bridges, 3 parallel runways, and an additional crosswind runway. <S> The busiest airport - Atlanta International - has over 200 boarding bridges and 5 parallel runways in simultaneous use. <S> In terms of land area, especially land area <S> owned by the airport rather than just what it actually uses , it is indeed quite a bit of land, though that's not necessarily unusual, especially for newer airports built in places with a significant amount of available land. <S> Airports generally like to buy up as much land as feasible in order to have room for future expansion. <S> Many of today's large airports are now space-constrained as the cities they serve <S> have built up around them since the airport was originally built. <S> Airports that can try to buy up land that they might possibly need in the future in order to prevent running out of space to expand. <S> In 2015, Riyadh served 22.5 million passengers . <S> By comparison, Atlanta had 101.5 million. <S> The 50th-ranked airport was Minneapolis/St. <S> Paul International at 36.6 million. <S> So, by passenger traffic, Riyadh is probably somewhere around 100th worldwide, though exact rankings below 50th aren't made public by ACI .
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In terms of passengers per year, Riyadh's airport is relatively large, but nowhere close to the world's largest hub airports.
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What aircraft fly faster than 250 knots indicated airspeed under 10,000 feet for safety reasons? 14 CFR 91.117 limits aircraft to 250 knots indicated airspeed below 10,000 feet, but 91.117(d) allows aircraft to fly a higher speed if the minimum safe speed is higher. What aircraft and aircraft conditions might require an indicated airspeed higher than 250 knots? <Q> A 747 taking off at or near max gross weight will have a flaps up, minimum safe airspeed and climbout airspeed speed greater than 250 knots. <S> In such cases you didn't notify ATC as they expected it. <S> I tried to find what the exact numbers would be at 840,000 lbs, but I seem to have thrown out that manual. <S> I did, however, find a reference for a 747-200 with JT9D-7Q engines that gives the flaps up holding speed at 800,000 lbs as 259 kts at 5,000 feet. <S> Also, I do remember being on an arrival once, with the weight low enough that we could safely maintain well below 250, but that when we saw we were icing badly, we speeded up to somewhere around 300 to get the ram air temp above freezing. <S> In that case we notified ATC that we were doing so. <S> Also, ATC occasionally requests max speed. <S> For example, on Hajj flights into and out of Jakarta Halim airport in the late 1990s it was common practice for controllers to put you down low to get you under the traffic into Cengkareng airport. <S> They would then often request max speed. <A> FAA has letters of agreement with US DOD, which authorizes certain military aircraft to fly faster than 250 KIAS below 10,000 feet. <S> A good example of this would be the Northrop T-38 Talon , described in FAA JO 7610.4 Special Military Operations : <S> 12-10-11. <S> AUTHORIZATIONS <S> T-38/T-1 airspeeds in excess of 250 KIAS below 10,000 feet <S> MSL are authorized by competent military authority in accordance with FAA Order 7110.65 and the letter of authorization granted to DOD. <S> The reason for this waiver is discussed in NTSB report number FTW90FA151 : <S> THE T-38'S SPD WAS ABOUT 330 KTS; THE SPD LIMITATION OF 250 KTS HAD BEEN WAIVED FOR T-38 ACFT, DUE TO THE ACFT'S LACK OF CONTROLLABILITY AT THE LOWER SPD. <S> The relevant letter from forums.jetcareers.com : <S> Also, from AIR FORCE INSTRUCTION 13-201 : 14 CFR Part 91.117 covers aircraft speed. <S> The exemption has been claimed for other aircraft too- like F-15 Eagle, for example : ... <S> climb-out occurs at 350 KCAS for an air-to-air configured jet and 330 KCAS on one with air-to-ground ordnance. <S> ... <S> this is significantly higher than the 14 CFR speed restriction of 250 knots below 10,000 feet. <S> The F-15E, like most fighter aircraft, falls under the Letter of Agreement between the DoD and FAA allowing some military aircraft a waiver to that speed limit. <A> A number of military aircraft - one that I can cite off the top of my head is the T-38 - have speed restriction waivers from the FAA during operations for safety. <S> The T-38, for example, flies the traffic pattern at 270 KIAS in order to provide sufficient maneuvering capability without exceeding the AoA limitations of the aircraft and stalling it. <S> The F-104 probably has similar limitations in performance. <S> The SR-71 rotated at 230 KIAS and the pilot had to immediately retract the gear after liftoff to prevent structural damage from exceeding Vle of 300 KIAS. <S> As for commercial and civil aircraft, the speed restriction of 250 KIAS does not present much of an obstacle or impediment to safe operation, albeit <S> it’s a little slow for jets. <A> 777-200 stall speed at <S> max t.o. <S> weight is 192 kts. <S> 1.3 buffer brings that to 252 kts. <S> 777-300 stall speed at <S> max t.o. <S> weight is 207 kts. <S> 1.3 buffer brings that to 269 kts. <S> Because of the higher stall speeds, especially for the 777-300, ATC knows we'll exceed 250 kts on departure and frequently acknowledges it before we mention it. <S> On arrival, at lighter weights, it's not an issue. <S> On the 777-300 you don't have to have Flaps 1 out until approx 220 kts. <S> at max landing weight. <S> On the 777-200 it's slightly lower (approx. <S> 215 kts). <S> So the reduction in weight from max T.O. weight to max landing weight reduces the minimum clean speed by 35 kts (777-200) and 50 kts (777-300). <S> Most fighters, in normal ops with a clean wing, won't be close to stalling at 250 kts. <S> But they can pull more G's, thereby having more maneuverability, if they're flying faster. <A> In the EA-6B we had a waiver to climb out at 300KIAS. <S> Coming home <S> we were lighter and could easily make 250, but we were waivered to 300 if we were in formation to have extra margin for the wingman.
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Recognizing that some DoD aircraft performance requirements exceed 250 knots, the FAA issued an exemption to 14 CFR Part 91.117.
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Does oxygen become less available during night-time? The following excerpt is from the FAA's Pilot's Handbook of Aeronautical Knowledge (page 7-37): Some people flying above 10,000 feet during the day may experience disorientation due to the lack of adequate oxygen. At night, especially when fatigued, these effects may occur as low as 5,000 feet. Therefore, for optimum protection, pilots are encouraged to use supplemental oxygen above 10,000 feet cabin altitude during the day and above 5,000 feet at night. The book, in vague terms, suggests that the amount of oxygen (i.e. oxygen molecules) available at a certain altitude at night is less than in daytime. The regulations do not differentiate between day and night in regards to supplemental oxygen. What would be the scientific reasoning behind this? <Q> But no, the O2 molecules are the same night or day. <S> BTW, airline pilots in our 8000' cabins do not have different guidance for putting on the masks -- it's 10k, day & night both. <S> Air Force was, IIRC, the same 10k, with no difference in the rules day vs night. <A> Humans are diurnal. <S> At night, we get sleepy. <S> The effect is worse when we're extremely tired. <S> As a result, we are more susceptible to things that affect cognitive processing during those times. <S> Oxygen inadequacy or deprivation (meaning a reduction below the level we are physiologically accustomed to) is one of those things. <S> It's nothing to do with the actual amount of oxygen at a given altitude changing at night, just our ability to ignore the effect of the existing changes compared to ground level when it is night time. <A> The amount of oxygen in the air is the same day or night. <S> The big difference - which isn't really explained in the part of the PHAK you quoted - is that at night your eyes work differently. <S> Your eyes have two different types of photoreceptors: rods and cones . <S> Cones work best with high light levels and rods work best at low light levels. <S> So during the day, when there's plenty of light, you're seeing primarily with the cones. <S> At night, it's the opposite: your vision depends mostly on the rods. <S> But, rods are very sensitive to oxygen levels. <S> As the level decreases, they quickly stop working effectively. <S> During the day this doesn't matter because you're not using them anyway, but at night it does matter <S> and you can lose night vision at relatively low altitudes. <S> This is why the PHAK recommends supplemental oxygen at night: it's to make sure that the rods continue to work effectively. <S> The PHAK has a lot of information about "vision in flight", starting on page 17-19. <S> Page 17-24 explains the need for oxygen at night: <S> Unaided night vision depends on optimum function and sensitivity of the rods of the retina. <S> Lack of oxygen to the rods (hypoxia) significantly reduces their sensitivity. <S> Sharp clear vision (with the best being equal to 20–20 vision) requires significant oxygen especially at night. <S> Without supplemental oxygen, an individual’s night vision declines measurably at pressure altitudes above 4,000 feet. <S> As altitude increases, the available oxygen decreases, degrading night vision. <S> Compounding the problem is fatigue, which minimizes physiological well being. <S> Adding fatigue to high altitude exposure is a recipe for disaster. <S> In fact, if flying at night at an altitude of 12,000 feet, the pilot may actually see elements of his or her normal vision missing or not in focus
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Night vision is one of the first things affected by reduced oxygen levels, and that effect is masked in daylight, but can become consequential at night.
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Is there a convention for type of switch used and where? In most cockpits, you'll find the full gamut of switch types in use. Toggle, rocker, push-button and more. Each has their own "feel" and might be used for different situations. Is there any convention for what type of switch is used in a cockpit, and where/for what? Such as, is the Generator usually/always a toggle switch, and would it be "weird" or unexpected for it be a rocker switch instead? Everything could be a toggle switch, so why do manufacturers choose to use different types of switches for different things? The 737's overhead panel uses toggle, rocker, push-button, and rotary dial all together: These images are from a simulator, but the aircraft is modeled after the TBM 850. In it, you'll notice toggle, rocker and push-button switches: Same thing up top in the same aircraft: Here's a real image showing the same thing: <Q> I can't give you a 100% correct answer, but I'll try as best as I can, having some experience with much smaller aircraft (even than the TBM850): <S> You always have to keep in mind that aircraft manufacturers put most of their engineering efforts into designing aircraft concepts for a specific market and then casting their ideas into an actual airframe that fits all the systems that are needed to operate the aircraft. <S> Allmost everything else (engines, landing gear, avionics, A/C, lights, APU, steering, braking and anti-skid systems etc.) is developed and manufactured by external suppliers with the aircraft manufacturer responsible for adapting and orchestrating all the systems. <S> This might lead to the aircraft manufacturer simply using already available switch assemblies or <S> only slightly modifying the suppliers' reference designs for panels in the actual aircraft. <S> IMHO, this is easily recognizable when looking at the cockpits of (especially older) aircraft where there was no concept of the cockpit as a whole. <S> Whatever switch assembly was needed was just somehow installed into the panels. <S> As Boeing's 707 was a great success, its cockpit design (at least partly) found its way into the 707s successors/derivates/siblings 727 and 737. <S> This lead to the 707 setting the cockpit design paradigms for following (Boeing) aircraft. <S> Also, from a pilot's point of view, there are some semantic aspects about choosing a switch that 'feels right'. <S> For example: push-buttons to start an automated process korry-type switches for switching automatic systems on or off or for on-off switches that might be controlled automatically (And therefor show their status; Airbus uses these a lot due to their cockpit philosophy) <S> toggle switches for everything that needs an on-off type switch on low-level without other systems needing access to it (for critical switches with safety cap as seen in the 737 overhead panel) <S> rotary switches for mode selectors potentiometers for everything that is finely controlled by the pilot rockers maybe for mode selection between two modes where neither of both is just "off" are very intuitive to me. <S> This might be training or just experiences from everyday life, but I understand what they are doing even before having read the manuals thoroughly, which makes it easier to remember which switch does what. <A> Is there a convention for type of switch used and where? <S> Not in any strictly followed cross-industry way. <S> Brand X vs <S> Brand Y airliner <S> Even if two aircraft both use a similar toggle switch for something, they can disagree about which direction is on or off <S> Note also that brand Y has different toggle shapes for three-position switches but <S> brand X doesn't. <S> As jxe's answer says, within a single cockpit there is a lot more consistency. <A> Check document CS-25 <S> (and CS-23) for "certification specifications, including airworthiness codes and acceptable means of compliance, for large aeroplanes" . <S> It details all requirements for required indicators, switches and CRTs on large commercial aircraft (23 for not-so-large-aircraft), including the shape of the landing gear lever (must resemble a wheel) and flaps lever (must resemble a flaps),etc. <S> Goto 'Subpart F - Equipment' and 'Book 2 - Subpart F' . <S> Also check 'Book 2 - General AMCs' for more detailed requirments on the EFISs
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As far as I know, there are no strict conventions for this and this is why you see most aircraft types equipped with their own panels and cockpit design.
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Is there a commonly recognized placeholder airline name? I'm wondering if there is a common placeholder name for an airline , either implying a legally disclosed or fictional entity, which is frequently used? For instance, I've seen the terms containing 'widgets' used very often in an economics context. John Doe is often used in legal cases. *"Placeholder names are words that can refer to objects or people whose names are temporarily forgotten, irrelevant, or unknown in the context in which they are being discussed." -Wikipedia <Q> I think Oceanic Airlines is well known fictive airline. <S> It is used widely in Lost and also Alias, Castle, JAG, Category 6: Day of Destruction and in Executive Decision (the material from this movie was reused in a lot of low budget movies). <A> I would suggest Acme. <S> This includes Acme Airlines, Acme Red, Acme Giant, Acme Express, etc. <S> This convention is often used in the podcast world as a means of referring to one's employing company without directly naming the company but still differentiating between many of the real airlines. <S> However, these names may have outgrown their placeholder status in some cases and may now be synonymous with the names of the real airlines. <S> Artwork from the APG community <A> Why not use a variation on the "generic company names" from the aforementioned Wikipedia page ? <S> For example, Acme Airlines, Ace Airlines, XYZ Air. <S> If it's a small airline, Mom and Pop Air. <S> Note that in the example "XYZ Widget Company," the idea is to obscurenot only the identity of the company, but also to obscure what they do. <S> Since you have stated you want an airline, the "widget" part of thecompany name is redundant. <S> That's why I suggested simply replacing"Widget Company" with "Airlines" or "Air".
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At least within certain communities, Acme is a generally recognized placeholder name for airlines. If the generic airline is not associated with a particular market,an alternative is to use a placeholder geographical name:Utopia Airlines or Air Ruritania for a national-scale airline,Podunk Airlines for a local operation.
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How much of the landing runway is mine? If I am cleared to land a couple of miles on final, may I use the entire runway to the departure end, or do I have to comply with "taxi instructions" the tower controller might give me like "turn right at taxiway foxtrot," while I am still concentrating on safely completing the landing? If he gives such a clearance, and I don't acknowledge for safety reasons, do I still have to comply? If I do acknowledge and do not comply, have I committed a clearance deviation? It's great to "help the guy behind me on final" but is this type of clearance even supposed to be given? If I slide off into the grass trying to comply with a clearance that has no relation to my landing calculations, who goofed up? <Q> Everything in Dave's answer is entirely correct. <S> To add to it, AIM 4-3-20 says: <S> The following procedures must be followed after landing and reaching taxi speed. <S> Exit the runway without delay at the first available taxiway or on a taxiway as instructed by ATC. <S> (emphasis mine) <S> Controllers are not supposed to give pilots a turn off the runway until they've already reached taxi speed, but at busy airports, I've seen that rule stretched. <S> You don't have to comply with any ATC instruction that you deem unsafe, but if you do and you slide off into the grass, it's your fault. <A> If I am cleared to land a couple of miles on final, may I use the entire runway to the departure end, or do I have to comply with "taxi instructions <S> " the tower controller might give me like "turn right at taxiway foxtrot," while I am still concentrating on safely completing the landing? <S> You generally will not get a taxi instruction until the controller sees the aircraft is on the ground. <S> You have the whole runway available to you if you need it. <S> If he gives such a clearance, and I don't acknowledge for safety reasons, do I still have to comply? <S> As Ron mentions, you can always state unable. <S> It's great to "help the guy behind me on final" but is this type of clearance even supposed to be given? <S> If I slide off into the grass trying to comply with a clearance that has no relation to my landing calculations, who goofed up? <S> This is an interesting question and will for sure warrant an investigation. <S> As mentioned, you most likely won't be given a turn off until you are on the ground and the controller sees that. <S> If you make an unsafe turn, that's your fault as PIC. <S> I will provide an interesting anecdotal story somewhat related to this: When flying in a buddy's M20C, he knew that his hanger was at the far end of the 7000 ft. runway <S> we were in-bound on. <S> He, without informing the tower decided he would land long as he only needed a short distance. <S> This would avoid un-needed taxi time, so he came in a bit high. <S> The controller clearly assumed he was going to land short and would be off the runway sooner than we were, this in turn caused the controller to send the citation behind us on a go-around. <S> There was no fault given to us as we technically had the whole runway to land. <S> I assume the pilot of the citation was less than amused. <A> That doesn't mean you shouldn't clear it at the first available SAFE opportunity. <S> What happens when that rule is violated is shown time and again in runway incursion accidents, with the crash at Tenerife Sur between a KLM and a PanAm B747-200 being the tragic extreme (though that was a takeoff where another aircraft was still on the runway, unknown to the controllers and the aircraft taking off because of a breakdown in communications in dense fog). <A> Aviate, Navigate, Communicate. <S> In that order. <S> First, don't slide off into the grass. <S> You are still aviating, even on the pavement. <S> Second, safely get the plane to where it needs to be. <S> If that means that you take a later exit, so be it. <S> Third, and only third, communicate with the tower. <S> After you've ensured that you're not sliding off into the grass or missing exits. <A> I concur that 'Unable' is your best bet. <S> You are the Captain, not ATC. <S> If you flip the aircraft turning too quickly, s/he'll press the crash button and pour another coffee whilst you burn to death. <S> It's that simple. <S> Be aware that a 'safe' taxi speed is probably lower than you think it is. <S> It's hard to judge because the ASI is little use. <S> Any kind of 'fast' taxi may involve significant use of the flying controls, not just the brakes and steering. <S> It's only necessary for military, bush and floatplane pilots (I've done a bit of all 3), they get taught how to do it, and it requires a lot of focus, which means you won't be chatting to ATC at the same time. <S> Best advice is that if you feel any significant shift of balance, then there are probably aerodynamic forces still on the aircraft, and you should slow down until there aren't. <S> If you haven't used steering and/or brakes on the landing roll, then you should do a light test of them whilst still on the wide, straight flat thing, before trying to steer off onto the narrow, curved flat thing.
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The runway is yours and yours alone until you clear it one way or another.
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Is it legal to use handheld radios to listen to aviation frequencies in the USA? Is it legal to use handheld radios to listen to (general aviation) airport frequencies in the USA? Can I go to an airport with a handheld radio and listen to their frequencies? <Q> USC 47 301 in general is all about "transmission of energy", or broadcasting. <S> And it really is beyond the scope of government to say you can't stick a piece of metal in the air and process the signals it receives, provided you don't cause interference to anyone else. <S> Assuming your radio is receive-only, you really won't have a problem with that. <S> (short of a total malfunction!). <A> Sure you can. <S> I have an ICOM AC-24 Aviation VHF Transciever in my flight bag and will use it, often when walking around on the apron of untowered airports to be aware of, and communicate with, other aircraft on the ground and in the pattern using the CTAF. <S> Just be courteous with it and don't use the device to either interfere with ATC communications or for personal conversations with ATC or aircrews. <A> If you don't have the appropriate license and thus can't legally transmit, disable the transmitter. <S> The easy way to do this is to open the radio and remove the little plastic piece that protrudes through the case on the transmit switch. <S> Yes, you could push the switch with a pencil or other item, but disabling the transmit will show good faith that you are not breaking the law and have no intention of doing so in the future. <A> If they are broadcasting on frequencies that are public, then yes, you can listen in. <S> However, you can't interfere with the conversation (broadcasting from your radio, garbling their signal, etc.), because that's a violation of FCC regulation.
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Your receiver must comply with USC 47 302a , the law that says, "you can't interfere with other equipment".
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What will the pilot do if all the airspeed indicators fail? Are there any alternate instruments to indicate the airspeed in case of pitot tube failures? <Q> What you normally have is an unreliable airspeed procedure . <S> This generally says that you should, depending on phase of flight, maintain specific pitch, set specified thrust and then adjust for rate of climb/descent while keeping the pitch. <S> Since aircraft is trimmed for speed, generally the procedure calls for being light on controls and correct mainly with engines. <S> Exception is Airbus which keeps auto-trimming even with speed disagree warning on, so there side-stick controls climb and power controls pitch almost independently. <S> See also unreliable airspeed procedure for A330 . <A> Are there any alternate instruments to indicate the airspeed From SKYbrary : <S> Reliable Sources of Information <S> The following information sources, independent of the pitot static systems, can provide reliable information for situational awareness: rpm, and fuel flow, for engine thrust indication (not EPR, which may be unreliable); Pitch and bank display; FPV (Flight Path Vector) if available and derived from inertial and not barometric sources; Radio height when below 2500ft agl; EGPWS Stick Shaker - may not always be activated but if it is, it is independently reliable; Navigation systems can provide ground speed and position information (GPS can also provide altitude information); Radio navigation aids and RNAV. <S> ATC, in a radar or ADS-B environment, can provide aircraft ground speed. <S> If TAS can be determined, a rough approximation of IAS at altitude can be calculated by the fomula: IAS=TAS – (FL÷2) <S> eg <S> 400TAS FL300 = <S> 250IAS. <S> Note: Some aircraft systems are configured, as a safety measure, <S> such that stick shakers and pushers will not operate if there is disagreement between systems. <S> Thus, if the aircraft approaches and/or enters a stall, these safety features might not activate. <S> However, if the stick shaker does activate, it should, in the absence of clear contrary indications, be believed. <A> Depends of the type of aircraft - does it have a secondary pitot, inertial nav etc. <S> If it does - you're in luck. <S> Also - "Pitot failure" - that would mostly be clogged total pressure tube (insects . <S> . <S> . .), but could also be static, in which case pressure altitude & rate of climb may be unreliable too. <S> In other words - have to watch for overall funny behavior. <A> In the planes I trained in, no. <S> In my training both for small planes and for gliders <S> I did landings without instruments. <S> You get a feel for the speed and height with experience. <S> Of course a small GA plane or a glider are much simpler than a large airliner. <A> An alternative is getting ATC involved. <S> They could give an estimated speed of the aircraft. <S> Since speed is distance travelled over time, ATC should be able to take the time difference between the two blips on the radar. <S> Knowing the scale of the map in the radar, they can work out your speed. <S> For example: If the radar has a scale of 1km represent 1cm on the radar screen, and the blip refreshes every 4 seconds. <S> ATC could measure with a ruler (on the radar screen) <S> the distance between the previous blip to the new blip, say this is 1cm. <S> You know that 1 cm is actually 1 km in real life, and the the time between blips is 4 secs. <S> So the plane has travelled 1km in 4 seconds which is about 250m per second (1000m / 4seconds). <S> 250 m/s equals to about 900 kph.
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The ATC could give you updates on your speed. Some aircraft have angle of attack indicator, but most don't even though they have the sensor and use it for stall warning.
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Has a fixed-wing aircraft ever been built that featured multiple turbines powering a single propeller? Has a fixed-wing aircraft ever been conceived, prototyped or built that features multiple turbines powering a single propeller? The concept of a twin-engine aircraft with a single propeller is intriguing to me. Picturing something like a Pilatus PC-12 with two engines under the hood and a single prop might have some advantages. I come from a fixed-wing background and know little about helicopters, but if something exists I suspect it is a rotor wing. <Q> LearFan 2100 in flight (picture source ) <S> If you want to know why its official first flight date is December 32, 1980, read here . <S> LearFan 2100 engine arrangement (picture source ) <S> This engine arrangement was the LearFan's eventual undoing when the FAA denied it a proper certification because of concerns that the single gearbox constituted a single point of failure. <A> Well multi engine helicopters like the Bell 430 or the Westland EH101 do it all the time. <S> I don't recall any current production fixed wing aircraft using multiple engines to drive a single propeller, but the ill fated LearAvia LearFan used this propulsion arrangement, using two PT-6 engines to drive a gearbox connected to a pusher prop. <A> Yes, see Soloy's Dual-Pac concept. <S> Image courtesy of Soloy <S> The Soloy Pathfinder 21 is powered by the Dual Pac PT6D-114A. <S> It is essentially an extended and redesigned Cessna 208 with exactly what you describe: two PT6 engines geared to one prop hub. <S> I understand that the project has not progressed beyond the prototype built. <S> Image courtesy of Soloy <S> The Dual-Pac was also tested on a DeHaviland DHC3 Otter platform: Image courtesy of Soloy Quoting from the Dual-Pac page : <S> Soloy Dual Pac – Twin Engine reliability with single propeller symmetry. <S> The Dual-Pac was designed, patented and Certified by Soloy to safely combine the output of two independently operating Pratt Whitney PT6D-114A engines for a single propeller output. <S> The system was developed with extreme redundancy so that single engine operation is not only safe, but able to be done intentionally under certain conditions. <S> The Ayres LM200 Loadmaster was a similar design concept, though a clean sheet design using a different powerplant and also ultimately unsuccessful for economic reasons. <S> See also the rotorcraft applications of the P&WC PT6T Twin-Pac , such as those that Carlo Felicione mentions. <A> Well, there is the Armstrong Siddeley Double Mamba engine. <S> It powered the Fairey Gannet <S> It wasn't a true single prop, but rather a contra-rotating prop (which amaze me). <S> Found a few more, some being single contra-rotating, others...... <S> multi-multi-engine? <S> Aircraft powered by the Allison T40 <S> There is one example of the twin turbine to single shaft Allison T40 powering a single propeller aircraft... <S> the Republic XF-84H <S> The thing was apparently as loud as the Tu-95, due to having a prop that spun at supersonic speeds on its outer edges. <S> And the prop created a continuous visible shockwave.. <S> Personally, I am not sure if you would classify this as an aircraft, or more of a shock/awe weapon. <A> A similar concept was adopted on a bomber used by the German Luftwaffe in WWII. <S> The bomber, named Heinkel 177 "Greif" was a four engine but had just two propellers since a pair of engines was mechanically coupled in each of the two nacelles. <S> However coupling mechanically two engines on a single propeller revealed as a source of troubles (e.g. overheating occurred frequently on the rear engines) and the design proved to be unsuccessful. <S> This probably explains why it has not been used any more since then. <A> Depending on how strict you are about "single rotor" The AH-64 Apache has 2 engines and one main rotor. <S> From Wikipedia "American four-blade, twin-turboshaft attack helicopter" <A> Kamov Ka-26 (1969, 816 built) is powered by two 325 hp (239 kW) <S> Vedeneyev M-14V-26 radial piston engines mounted in off-board nacelles, connected by a transverse shaft which drives the co-axial rotors. <S> According to Wikipedia , the reciprocating engines, although more responsive than modern turboshafts, are relatively maintenance intensive. <S> The Ka-26 is underpowered with its two radial engines, especially when used in cropdusting role, where excess payload is common. <S> No other helicopter exists in the world that runs at constant 95% engine power for most of its flight regime. <S> This leaves the pilot with little power reserve for emergencies. <S> Due to frequent overloads, the interconnect shaft which joins the two engines is prone to breakage and requires frequent inspection. <S> NOTE <S> An edit to the question makes this answer nonresponsive. <A> In level flight it was essentially an autogyro, driven by twin turboprops on short wings, deriving a fraction of its lift from these and the rest from the undriven rotor. <S> To achieve vertical takeoff and landing, the rotors were spun by tip jets, fed from bleed air from the turboprops, augmented by fuel burnt in the tip jets. <S> Although it seems to have been technically successful both in lifting capability and speed records for rotorcraft, the tip jets made it unacceptably noisy at takeoff and low altitude, precisely where noise was most objectionable. <S> I wonder if bleed air alone could work nowadays (given higher pressure ratio turbines) to reduce the tip jet noise. <A> The CH-53 uses 2 jet engines to power one rotating wing.
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The LearAvia LearFan 2100 used two separate PT-6B to drive a single pusher propeller through a common gearbox. The Fairey Rotodyne probably counts, depending on your definition of "single rotor".
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At what point is a turbine powered ducted propeller considered a turbofan? Turboprop Propellers can be ducted for extra thrust. What are the criteria for determining that the engine is no longer a ducted propeller design, but a turbofan? Does there have to be a type of blade design, a fully separate nacelle/pod, number of blades? Or are all turbofans technically shrouded propellers with some augmented thrust from the turbine exhaust ? <Q> tl;dr <S> They're pretty much all considered turbofans with a few exceptions from the '70s such as this experimental Britten-Norman Islander . <S> They key difference is a prop can be considered a separate entity (add-on) to the turbine for a turboprop, but a fan is an integrated component for a turbofan. <S> Slightly longer answer After a fair bit of thought and research <S> I hope I've managed to come up with a satisfactory answer, though to start with a disclaimer. <S> The aviation industry is far too fond of merging and creating new words to describe new engine architecture. <S> Take Open Rotor vs. PropFan for example. <S> To get technical about it, you could look at the similar/reverse argument about the difference between an open rotor turbofan and a turboprop, as addressed by the EASA . <S> If you look at Appendix 1: Open Rotor Definition (Page 86) of that document they outlined the following key differences Open rotor module that cannot be distinguished as a separate entity <S> However the following was the agreed definition, which is still rather ambiguous. <S> A Turbine Engine featuring contra-rotating fan stages not enclosed within a casing <S> I think the first one is more key, the prop can be considered as a separate entity, attached to the front of a turbine and powered by a gearbox. <S> A fan is an integral part of the engine and cannot really be considered a separate entity, as it actually forms part of the low pressure shaft and is considered the first stage of the low pressure compressor. <A> In general (there are often exceptions to any rule), a turboprop unit is likely to have a gearbox between the turbine and the propeller. <S> The propeller is likely to be capable of varying its pitch. <S> Also, the propeller may be a set of two contra-rotating propellers in the case of a high power turboprop. <S> A turbofan engine is unlikely to have these features, although PW does have a GTF geared turbofan. <A> A propeller has relatively few blades, which are relatively long and slender. <S> A fan has many blades, with a relatively large chord. <S> Like a household fan . <S> A parameter to catch blade count and chord relative to blade length, is the disk solidity $\sigma$ . <S> Area of all blades summed together, divided by the area of the circle defined by the blade tip length: <S> $$\sigma = \frac{\text{blade area}}{\text{disk area}} <S> = \frac{A_b}{A} = <S> \frac{N_b <S> c R}{\pi R^2} = <S> \frac{N_b <S> c}{\pi <S> R}$$ with $N_b$ = number of blades, c = blade chord, R = blade radius. <S> Image source <S> There does not seem to be a defined transition point of $\sigma$ , above which we're talking about a fan. <S> The 8-bladed propeller of the A400M with a blade radius of 2.6m has a solidity ration of about 0.3 which is amongst the highest in the world. <S> We instantly recognise it as being a propeller. <S> Author 1 <S> The fan of a geared turbofan like the PW 1000G is instantly recognisable as a fan, with its 20 relatively fat blades and a $\sigma$ close to 1. <S> Note that both are driven by a gearbox for obtaining a beneficial tip speed. <S> Or are all turbofans technically shrouded propellers with some augmented thrust from the turbine exhaust ? <S> Indeed, technically a fan is a type of propeller. <S> Turboprops also have thrust directly from the turbine exhaust. <S> 1 <S> By Rafael Luiz Canossa - IMG_9975, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=55662586
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The difference between a ducted propeller and a turbofan is mainly determined by the difference between a propeller and a fan.
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What priority if any is given to Emergency Services in flight clearance? When requesting takeoff/landing and route clearance is any priority given to Emergency Services IE air ambulances, firefighting rigs, S&R etc. I'm assuming even though these services rise to the level of life or death, they are not treated with the same urgency as an air emergency but I don't know that for fact. <Q> I work as a fixed-wing pilot for a hospital-based Air Ambulance program. <S> Let me add my experience to the ATC orders accurately cited by Pondlife's answer: <S> the MEDEVAC call sign (the old "Lifeguard" <S> is still used when filing the flight plan) indicates a need for priority handling. <S> ATC is often helpful in providing us with priority routing. <S> This includes giving us direct clearances, moving us up in the landing que, allowing us an unrestricted approach speed, and otherwise expediting our flight. <S> However, ATC does not always provide priority handling, and I have often experienced ground delays of 5-10+ minutes as ATC apparently prioritizes other traffic, including air cargo and the like. <S> This is rarely a big problem as patients are typically stable, but it can be frustrating when priority handling is expected. <S> However, if medical staff determine that a patient is in critical condition, we will announce this to ATC—typically accompanied by a request for a specific clearance or change to a previous clearance. <S> This announcement re-iterates our need for priority handling and indicates the urgency of the situation. <S> In this way we can work with ATC to best care for the patient. <S> We will often make such an announcement when checking on with approach control for their information with no specific accompanying request. <S> Occasionally, however, we will need to request such priority handling because ATC has issued us speed restrictions or delaying vectors to put us behind other traffic. <S> ATC is very good at working with us when we do need the priority handling. <S> In other words, ATC usually automatically gives us priority handling, but when they don't— <S> and we need it—we ask for it and they are very good at working with us to provide the priority handling. <A> In my experience, yes they will hold for emergency related vehicles. <S> I fly out of KPNE often, where a lot of the Philly Police and Emergency choppers are kept. <S> I have been held for their takeoff before. <S> I don't know if this is regulation or simple courtesy <S> but I can assure you it happens. <S> On a similar note, I once spoke to the designer of the Philly Bravo airspace about this very issue. <S> He explained that when the airspace was redesigned (a few decades ago now) the shelves were deliberately placed so that all of the hospital helipads were accessible without entering the bravo. <S> Basically the emergency choppers can come and go with out clogging ATC for clearance in and out of the Bravo. <S> In uncontrolled airspace this is not really an issue and emergency helicopters will rarely go into class A. <S> So this leaves you with Class B, C and D departures and arrivals. <S> In the case of Philly the helicopters are stored at a less busy airport outside of the bravo for operations commonly under the shelf. <S> This most likely varies heavily from place to place and their may be arranged understandings in different Bravo's. <A> (I'm assuming you're asking about the US, based on your profile.) <S> Provide air traffic control service to aircraft on a “first come, first served” basis as circumstances permit, except the following: [...] <S> a. <S> An aircraft in distress has the right of way over all other air traffic <S> [...] b. Provide priority to civilian air ambulance flights <S> (call sign “MEDEVAC”). <S> Use of the MEDEVAC call sign indicates that operational priority is requested. <S> When verbally requested, provide priority to AIR EVAC, HOSP, and scheduled air carrier/air taxi flights. <S> Assist the pilots of MEDEVAC, AIR EVAC, and HOSP aircraft to avoid areas of significant weather and turbulent conditions. <S> When requested by a pilot, provide notifications to expedite ground handling of patients, vital organs, or urgently needed medical materials. <S> Other flights that get priority are presidential ones, search and rescue etc.
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The FAA's ATC orders section 2-1-4 has a list of aircraft operations that should be given priority, including emergency service flights, but an aircraft in distress always has the highest priority:
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Why are the top speeds for jet engines higher than for propellers? I realize turbines are more efficient than piston engines, but if that were true, then why don't turbo-props reach jet speeds? <Q> The thrust of a propeller is proportional to the inverse of airspeed, while the thrust of a pure turbojet is roughly constant over airspeed in the subsonic region. <S> This means that two airplanes with the same static thrust, one propeller-powered and the other jet-powered, will reach very different top speeds. <S> And, no , piston engines are more efficient . <S> A piston engine produces a constant torque $\tau$, independent of speed. <S> This torque drives the propeller which produces work $W$ per unit of time on the air passing through it. <S> This work per unit of time is power $P$ and proportional to the product of torque and propeller speed $\omega$, which is again constant over airspeed $v$. <S> The power to propel the aircraft is the product of thrust and airspeed and equals engine power times propeller efficiency $\eta_{Prop}$. <S> When airspeed goes up, thrust must go down proportionally for power to stay <S> constant.$$P = <S> \tau\cdot\omega = <S> T\cdot <S> v\cdot\eta_{Prop}$$$$\Rightarrow T <S> \varpropto <S> \frac{1}{v}$$ Turbojets, on the other hand, profit from flight speed because the intake pre-compresses the air when it slows down ahead of and in the intake. <S> This pre-compression lifts the pressure level of the whole engine, so it sees an increased mass flow with increasing speed, producing higher thrust. <S> This effect by itself would increase thrust in proportion with the square of flight speed, but the same effect which reduces the thrust of a propeller acts on a turbojet as well. <S> This effect, however, is less pronounced because the jet accelerates less air to a higher speed , and both cancel each other, roughly. <S> Turboprops are even closer to piston-powered propellers, so their thrust drops even more with increasing speed. <S> This means that the speed at which drag equals thrust drops when you move from turbojets to turbofans, and further to turboprops and is lowest for piston-powered propeller aircraft. <A> I'd like to visually illustrate why propellers aren't suited for high speed flight. <S> First, let's consider a variable-pitch propeller mounted on a capable engine. <S> If you study the two sketches I drew above, you'll notice as the horizontal speed increases (right image), the thrust direction moves away from the forward, despite the increased airflow and local lift on the blade. <S> This is what many textbooks erroneously call "taking a bigger bite", but as you can see, it's the same bite (angle of attack). <S> Figure 11-8, FAA Pilot’s Handbook of Aeronautical Knowledge <S> So the faster you fly a propeller, the lower forward thrust you get, making you unable to go any faster. <S> Above graph shows T A (Thrust Available) for a propeller decreasing the faster the plane flies. <S> Another factor is when you fly as fast as the propeller's tip speed—say Mach 0.75 (a Boeing 737 Classic in cruise)—the airfoil of each blade will be flying much faster than your forward speed (compare the hypotenuse to the vertical/horizontal sides in the topmost image). <S> The airflow around the airfoil will be supersonic. <S> Straight wings (and blades) don't do well in supersonic speeds (too much nasty drag). <S> For a fixed-pitch propeller, let's say we dropped a plane with a fixed-pitch propeller from a mothership at high speed, the airflow will hit the top surface of the propeller disk, creating backward thrust—effectively propelling the plane backwards. <S> It's best when the plane's forward speed keeps the propeller disk from approaching the sound barrier, and doesn't result in the thrust being directed too much away from the forward. <A> For a turbo prop the limiting factor to some extent is the efficiency of the propeller, not the engine. <S> There have been a bunch of attempts at very fast turbo props over the years with the fastest most likely going to the XF-84H <S> Thunderscreach <S> but in all of the cases the propeller becomes the limiting factor. <S> First off, to get going in the speed range you mention with a usable size propeller <S> your tips will go supersonic which presents problems into its self. <S> The XF-84H suffered from this and you can read up on why that was a noise issue. <S> On top of the noise issue it simply becomes more efficient to use a jet at those speeds so in practice its the power plant of choice. <S> Many of today's top preforming turboprops easily encroach on the speed of light jets.
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Turbofans are more similar to propeller engines, so here the thrust goes down over airspeed, and more so for higher bypass ratios .
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What is the fuel consumption of an aircraft in a holding pattern? I am doing a research about fuel cost when an aircraft is about to land. they may be asked to be hold due to the traffic congestion at the runway. consequently they consume extra fuel. My question is how I can estimate the cost per minute or second being late of their *target time. Where can I get more details on this? *target time: As I noticed each aircraft has a target time to land which is the most economical time and speed for them. My research is about aircraft landing scheduling during rush hours where there are several objective functions such as maximizing the runway utilization, minimizing total delay and fuel consumption to be considered. these objective functions are subject to some constraints like aircraft's time window (earliest landing time,latest possible landing time), minimum time separation, Constraint position shifting...In the literature that I have read so far they considered a fix fuel cost as a function of delay. as an instance: "Vj denotes the cost per unit time of the extra fuel associated with lateness relative to ULTj , then the overall extra fuel cost is : summation of Vj * (Landing times - ULTj) " (Aircraft Runway optimization, Mesgarpour, 2012) Since it is more mathematically issue no body really pay attention to the details of that fuel cost or any other cost caused by the delay. <Q> The fuel rate while holding depends on elements such as weight, altitude, speed and aircraft configuration. <S> Airbus uses the concept of green dot which is the speed with minimum fuel consumption per time unit in clean configuration. <S> This table shows fuel needs for a A330/A340 at 170 tons and 1,500 ft: <S> Fuel flow vs. speed. <S> Source <S> While the green dot speed is the one offering the best fuel rate while holding, it assumes no flap and no slat. <S> This speed may not be practical for certain airports where slats or flaps are advisable due to the rate of turn in the holding pattern. <S> To provide the necessary flexibility, Airbus publishes the fuel rate for three other combinations of speed/configuration (S speed is the minimum speed for flaps retraction): <S> Fuel flow vs. weight for 4 configurations. <S> Source Altitude is also a factor preventing an optimal fuel flow. <S> Example for the green dot speed: Percentage added when departing from the optimal altitude. <S> Source <S> The total fuel required to hold can be somehow minimized by not flying at cruise speed when it is known that a hold will be required at some point. <S> Savings can be done by flying at green dot speed to the holding point: <S> Source <S> That means determining the fuel flow depends on airline operating procedures and holding pattern design (e.g. altitude), but a maximum can be roughly predicted by looking at the manufacturer published documentation. <A> Every aircraft should have a published fuel-burn rate, typically measured in GPH (Gallons per Hour) or Pounds per Hour. <S> This rate does change a bit depending on ambient conditions (temperature & pressure), throttle, and weight. <S> But its a pretty good planning rate. <S> There are other costs, beyond fuel costs, associated with delayed landings, such as crew costs and running the airplane and engines closer to their next inspections and service times. <A> I'd have to look at the data again to remember how much more, but I recall it was fairly significant: <S> at least compared to cruise. <S> This analysis was done as part of a study the airline was using to calculate the cost of capacity constraints in the terminal area.
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To answer based on some data I had correlating aircraft in confirmed holding patterns (not speed-restricted en-route delays) vs. high altitude cruise, the short answer was: they use more - mostly because they were in low-speed manouevring, with flaps set.
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From which ATC station is push-back clearance requested? When parked at the gate that requires a push-back onto the taxiway, from which ATC station is the push-back clearance requested? Is this the ground or apron station, or is that still departure clearance delivery station (as they better know the slot times, etc.)? <Q> At controlled aerodromes, the aerodrome control tower is responsible for separating aircraft on the maneuvering area (from other aircraft, and from obstacles, vehicles etc.). <S> At large aerodromes, there are different tower working positions, operating on different frequencies and with different callsigns. <S> So the "which exact ATC station" question really varies from airport to airport. <S> You might talk to "xx tower", "xx ground" or something else entirely. <S> Note that at many airports, the gate area (apron) is NOT a part of the maneuvering area. <S> Technically speaking, ATC is not responsible for separating aircraft outside of the maneuvering area. <S> Instead, pilots, tug drivers, vehicles and other persons on the apron follow different priority rules when a pushback is required (traffic laws normally state that vehicles shall yield to aircraft; the rules of the air have rules regarding aircraft right-of-way). <S> However, some major airports have designated positions for coordinating this effort, which - from the pilot perspective - looks just like ATC. <S> They operate on a VHF frequency, and typical callsigns are "xx apron" or "xx ramp". <S> Note, however, that such stations do NOT provide air traffic control - technically, they provide advisory service, and they are not responsible if a collision occurs, because ATC separation is not provided outside the maneuvering area. <S> Persons staffing such positions generally do not have to be fully qualified air traffic controllers (this will vary from country to country), and are sometimes employed directly by the airport, instead of an air navigation service provider. <S> In summary: if the pushback occurs on the maneuvering area, the aerodrome control tower has to approve it. <S> If not, no ATC approval is required, but there might still be other stations coordinating pushback. <A> It depends on the airport. <S> I don't have a statistics, but from what I've seen, usually it is the ground station, as they coordinate the movement of airplanes on the ground, and they have an idea if the runway lineup queue is long, or another plane is taxing behind. <S> In non-busy airports (the ones which only get a few flights per day) the same guy might be the clearance delivery, ground and tower at the same time. <S> So the pilots are basically talking to the same person. <S> KJFK is one exception where push back is coordinated by "ramp", as you can hear for yourself in this ATC recording with Air France 011 <S> Heavy who was apparently was not very familiar with that airport's operations. <A> Most likely either ground control or <S> if there is a designated frequency for a secure apron movement, that would be used. <S> Check the A/FD entry for the airport or ATIS for further information.
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If a pushback is done onto a taxiway which is a part of the maneuvering area, the aerodrome control tower must approve this first.
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It is possible for an airplane to get infested by animals? Is it possible for an airplane to become infested by animals like mice or rats? Is it possible for them to survive? Do airliners do anything to prevent a scenario like this? Has it ever happened before? <Q> Yes, I have personally worked on multiple aircraft that were infested by animals. <S> All of these aircraft were small planes, single engine Cessnas for example. <S> A typical example would be one or two small mouse nests in the wings. <S> I also found at least one wasp nest in an aircraft wing. <S> The worst I ever saw was a Mooney that had extensive mouse nests throughout the airframe. <S> That aircraft had been unairworthy for at least a year by the time I saw it. <S> That Mooney ended up being parted out and scrapped, largely because of extensive corrosion in the wings which was either caused by, or aggravated by, the mouse nests. <S> Urea can induce corrosion in aluminum, and finding a mouse nest or other evidence of rodent activity should prompt closer inspection. <S> All the other instances of mouse nests that I have found in airframes were in aircraft that flew several hundred hours a year and these did not suffer any major damage. <S> There is also the classic warning to check the pitot tube in case a mud wasp has clogged the intake with a nest. <S> I have never witnessed any of these occurrences myself. <S> The mud dauber wasp is notorious and is suspected of being a contributing factor in at least one fatal airline accident that I am familiar with: Birgenair Flight 301 . <S> Photo source , courtesy of the FAA <S> Many means of prevention are available, including typical pest prevention methods such as traps and poisons—in my experience all reserved for use in the storage hanger. <S> The most aviation specific forms are the various covers used to protect pitot tubes , engine inlets , etc. <S> Photo source , courtesy of the FAA <S> As far as the possibility of animals surviving, I suppose the odds are low. <S> I have never encountered a live animal in an airplane (pets excepted). <S> Some flights, particularly international ones, apparently make a practice of spraying some form of pesticide in the cabin to kill mosquitoes and other unwanted creatures. <A> Yes! <S> As Jonathan Walters stated in his excellent response, this is entirely possible. <S> I can't say which airline I work for, but last summer we had a rash of aircraft (I think 5 in one week) that had rejected takeoffs or air turn backs for erratic airspeed indications. <S> As it turns out, those nasty little dirt daubers (mud wasps?) loved the height of the pitot probe on this particular type of aircraft, and the diameter of the entry hole. <S> They were quick too as standard procedure was to pull the covers off 1 hour prior to flight. <S> I've heard of mouse and rat infestations, but have been fortunate enough to never have had to work on an airplane with such a problem. <S> Again, as Jonathan Walters pointed out, they will chew through wiring like it's their favorite food, from what I'm told. <S> As an aside, the standard operating procedure for animal infestations (inside the pressure vessel) is to close the aircraft up entirely and fill it with an inert gas (nitrogen, I think) - depriving any animal in the aircraft of oxygen. <S> As I recall, the process isn't quick, but it is very effective. <S> Finally, sharing a funny story... About two years ago, a plane came in with, I kid you not, a writeup for "Snakes on the plane." <S> Somehow, I'm not quite sure how, two baby pythons managed to get into the aircraft. <S> This, of course, cascaded into every possible Samuel L. Jackson quip and quote you could possibly imagine about snakes being on an airplane. <S> I'm not entirely certain how the flight crew discovered it, but I must admit, if there was a cockpit camera, we would have surely reviewed the tape on that one! <A> It is not only possible to survive, it makes their life more comfortable. <S> I know of several gliders which were taken over by mice. <S> One I cleaned out myself, a Grob 103 Twin Astir . <S> The mice went up through the opening of the tailwheel, climbed up the whole length of the vertical tail and made the inside of the horizontal tail their living room. <S> The small compartment at the nose of the tailplane, which is separated from the main volume by a web, became their restroom. <S> But they did not sleep on the bare glassfiber. <S> They went up into the cockpit and gnawed on the seatbelts to extract fibers for their nests. <S> I had to replace the seatbelts, but I doubt I got all of the nesting material removed from the hard-to-access inside of the tail. <S> At least the "restroom" was easy to clean ... <S> The mice moved in in late fall, after we had parked all gliders in a hangar for the winter break. <S> I discovered the infestation only in spring, when I checked the airplane for flightworthyness.
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I have also heard stories from many pilots and mechanics of finding birds nests—for example in engine intakes or the empennage—and of rodents chewing into or through electrical wiring. For any animal stowing away on a pressurized aircraft operating at high altitude I should think the low oxygen partial pressure and temperature would both discourage survival outside the pressure vessel.
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How does the V-22 Osprey share engine power between its rotors? I learned through a comment on this question about multiple engines powering a single propeller that the V-22 Osprey can power both rotors from a single engine, or use both engines to power a single rotor. What are the mechanical systems that make this possible? <Q> It is possible to drive the two rotors of the V-22 Osprey from a single engine using a segmented driveshaft connecting both engine shafts via gearboxes: <S> The drive shaft is depicted in blue in the left wing. <S> Source <S> If one fails the same rotation speed is maintained, but each rotor receives now half the power of the remaining engine. <S> A similar mechanism is also used on the CH-47 Chinook family: <S> Source <S> This is a CH-47 Chinook green drive shaft: <S> Source <S> On aircraft with two distant rotors, it is vital to have both rotating, as if one slows or stops the aircraft is unbalanced to the extend it crashes. <A> Tilt rotors and virtually every other VTOL aircraft with more than one lift rotor (Chinook, K-Max) or proprotor (AW609) must employ a shaft between these lift units, so when one engine is out the other keep the units turning will half power (which doesn't mean half rotations per minute, but half maximum torque). <S> That's why available power reserve on the engines of these aircraft is important; choosing engines that are 'just enough' for the normal job may deny their certification for obvious safety reasons. <S> A failure or a simply deceleration of one rotor/proprotor would cause disastrous asymmetry of lift along the aircraft center of mass. <S> Also, many of these aircraft require the rotors to be permanently synchronized (and, therefore, connected) to simply avoid collision between their counter rotating blades. <S> In tilt rotors, rotor sync is also beneficial when talking about vibrations, acoustics and symmetry of aerodynamic flow through the airframe. <S> Finally, connected proprotors are also a solution towards simplicity regarding yaw: the AW609, for example, doesn't have a rudder, since it can yaw by simply changing the blades pitch of one proprotor (or changing both in opposite angle values). <S> That's why every aircraft with connected rotors/props and two or more power plants slowly spins all the blades even when only one engine is starting. <S> Since the first transmission of output inside the engine is done through air without a mechanic shaft connection (using the free turbine solution), the engine doesn't suffer that much from overload. <S> Over pressure in the combustion chamber may be an issue, but is easily addressed with bleeding valves and/or FADEC protections. <S> The details of those connection shafts are not very new, resembling the shafts that connects main and tail rotors on heavy helicopters of traditional design, but far more robust and having no reduction gears. <S> They are basically assembled with the less amount of segments possible. <S> The connections between them must be as precise as possible, withstanding some difference of torque between the segments in order to avoid over twist efforts that could lead to failure. <S> Also, they can't absorb differences of angular momentum (like the springs on a manual car transmission clutch does) since this can easily evolve to a resonance between the rotors. <A> The cross shaft of the V-22 is normally unloaded. <S> It only takes up the load <S> if an engine fails, at which point everything continues as normal albeit with reduced power. <S> Alternatively, if the shaft is damaged, but you've still got two good engines, the aircraft flies as normal because the shaft isn't being used anyway. <S> On the CH-47, though, the shaft is always under load because that's how the front rotor is powered by the engines in the rear. <S> If that shaft is damaged, it will result in an immediate loss of the aircraft, even with two good engines.
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Each engine drives its own rotor and the connecting shaft.
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Why do ATC instructions to change level include the words "climb" or "descend"? ATC instructions to change level include the words "climb" or "descend" depending on the direction of the vertical maneuver. For example, "Descend to 2500 feet" or "Climb to FL70". For comparison, instructions to turn to a specific heading often, but not always , include the words "right" or "left". We can say "Turn right heading 120" or "Turn left heading 360", but in some situations we may simply say "Fly heading 180". When using "Fly heading", it is implied that the turn should made in the direction that requires the smallest change of direction. A pilot heading east instructed to "Fly heading 360" will always perform a left turn, even if the word "left" was not included in the original instruction. Similarly, for speed control, we have phrases such as "Reduce speed to 220 knots" and "Increase speed to 280 knots", while we can also simply use "Maintain 240 knots", in which case the pilot will then speed up or slow down as appropriate. Radio phraseology is designed to be as short as possible, and radio calls should include no excessive words. This makes me wonder, why do we always include "Climb" or "Descend" in level instructions? If a flight is at FL320 and we need to instruct it to get up to FL340, it is self-evident that the pilot must climb, not descend. Using this logic, a phrase such as "Maintain FL340" or even just "FL340" (Example: "[callsign], FL340") should suffice. I can think of reasons who we do use climb and descend. It most likely improves situational awareness for both controllers and pilots (including other flights on the frequency). It could also enable pilots to identify situations where they mishear a level instruction (Example: for a flight on FL320, instructed to "Maintain FL240", the crew might mishear this and think they are cleared to FL340. If the phrase " Descend to FL240" is used, this is less likely to happen). Finally, "Climb to" and "Descend to" is not much longer than "Maintain". However, this leaves the question of why we have such "neutral" phrases for heading and speed restrictions. Wouldn't enforcing the use of "Right", "Left", "Increase" and "Reduce" introduce the same benefits we get from using "Climb" and "Descend"? Is there a historical reason the phraseology concerning level changes is designed the way it is - perhaps an incident or accident where another phraseology was used? Or is it a coincidence that level instructions are different compared to heading or speed restrictions? I can come up with "qualified guesses" myself, so I am hoping someone with actual knowledge on the topic can provide a factual answer. <Q> Adding the instruction "climb/descend" to the flight level is an example of linguistic redundancy offering a very rudimentary form of error detection for voice communication (which is inherently "unreliable", as it can be misheard by the receiver – on top of the sometimes poor ATC radio channel quality ): <S> In […] telecommunication, error detection [is a] technique that enables reliable delivery of […] data over unreliable communication channels. <S> Many communication channels are subject to channel noise, and thus errors may be introduced during transmission from the source to a receiver. <S> Error detection techniques allow detecting such errors. <S> ( source ) <S> "climb to FL420" instead of "climb do FL400" ). <S> Therefore ATC instructions are repeated on the receiving end by the pilot . <S> (For a non-aviation analogy, the same technique is applied when dates are agreed upon on the phone as "Friday, 4 January 2019" , although the day of the week is already implied by the date itself.) <S> In essence, your question "Why do ATC instructions to change level include the words 'climb' or 'descend'? <S> " can be best answered by the (limited) added information transmission security these instructions provide. <S> Therefore for me the real question is why instructions concerning speed and heading don't obligatorily require this sort of disambiguating instruction – especially so as this unspecificity can demonstrably lead to confusion . <S> I hope someone else will be able to answer this part of your question, as I don't have specific knowledge about this aspect of it. <A> There are a lot more ways to let an aircraft climb or descend than giving just a simple descend or climb instruction and all these additional instructions base off the basic instruction to climb, e.g. R: DLH123, descend FL120R: <S> DLH123, descend FL120, cross ABCDE at or below FL150R: <S> DLH123, descend via ENTRY1A arrivalR: <S> DLH123, when ready descend FL120 to reach at ABCDE Please note that the phraseology to descend or climb does not include the word to , so it doesn't make it any longer than maintain. <S> Additionally, just saying R: <S> DLH123, FL120 is too ambiguous and could lead to misunderstandings, as any level or altitude transmission over the frequency without an instructing word is interpreted as a statement. <S> Reading the above would be interpreted as DLH123 giving their current flight level, rather than an action item. <A> Communicating the supplementary word left <S> /right wrongly still describes a possible action that may not end up well. <S> Communicating climb/descent incorrectly does not, and may help to detect that the altitude inside the message has been misunderstood.
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Therefore adding the instruction "climb/descend" offers an additional layer of security, because the pilot would never descend when instructed to climb (and vice versa) and the pilot is able to detect an instruction mismatching the flight level, i.e. "climb to FL240" when already at FL320 (taking the example in your question) ... but not perfect security (because the pilot at FL320 would not detect an error if ATC mistakenly instructs him to
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What are the pros and cons of having a side-stick versus a centered control stick in a fighter aircraft? The Eurofighter Typhoon features a centered control stick: While for example in the F-16 the stick is on the right side panel: I find the latter configuration much more natural/ergonomical. Especially since the concept of HOTAS ( Hands On Throttle-And-Stick ) implies that the pilot has his hands on the same control element most of the time. I've heard of one reasone for having a center stick is to allow for ambidextrous operation (operations with both hands, alternatively).But this seems to be counter-intuitive with HOTAS, especially since the throttle controls are still on the left side only. I find it difficult to image an ergonomical position for the pilot while holding a center-stick and a left hand throttle control. So what are the reasons for a center stick in the Typhoon?Any experiences of pilots having flown both types of configurations? <Q> It’s also useful in an emergency, say if your right arm was injured by shrapnel, etc and cannot actuate the stick effectively, requiring you to fly with your left hand. <S> Side sticks do have the advantage of less cockpit clutter. <S> The stick is mounted off to the right and doesn't directly block critical instruments from the pilot's view or have its range of motion restricted by flight gear, kneeboards, etc. <S> In a/c with conventional control systems the center stock was a necessity as it acted as a lever arm allowing the pilot to overcome aerodynamic forces on the control surfaces with muscle power alone and one could force a maneuver using both hands. <S> In the age of hydraulic flight controls and fly-by-wire, this is irrelevant. <S> As to ergonomics, it's fairly comfortable to fly a center stick as your wrists will naturally rest on your thighs when seated and your hands naturally float to that position. <S> Side sticks are also comfortable but require an armrest to operate effectively, particularly when pulling Gs. <A> For fighter aircraft some will argue that under high g loads it is easier to use a side stick then a traditional centre stick. <S> Sure might be true for some, but in my opinion when you sit down your hands rest in your lap natually and also <S> in case your right hand gets injured during combat you can always fly a centre stick left hand in emergency situations. <S> Centre stick in fighter aircraft is an absolute must have in my opinion. <S> A fighter pilot in combat should use both hands on a centre stick for high g maneuvers- allowing flexing, tensing the muscles throughout the aggressive maneuvers. <S> It is a fight up there after all <S> and you want your blood pumping <S> , you have to be able to get aggresive physically in the cockpit to help the heart pump blood better to your brain. <S> This is not good for your wrist health at all over long periods of time. <S> Operating centre stick uses your shoulder and entire arm muscles more then just your wrist flexors. <S> Leading to prolonged limb health over all. <S> The side stick is a must ban on military aircraft in my opinion. <S> It should only be used on civil smaller private aircraft for nothing more then relaxing flights for sight seeing. <A> Besides the issues already covered, it appears to me that older fighters would prefer a center stick so the pilot can switch hands if he needs to see behind the cockpit in either direction. <S> The newer USA F22 & F35 use a helmet with virtual vision and supposedly the pilots don't need to twist their heads to see behind them - though some pilots have challenged the safety and effectiveness of this feature. <S> source picture updated source <S> This is a side stick F16. <S> Note the ability of the pilot to brace with his free hand looking to his right but unable to do the same looking left because his right hand must stay on the side stick. <S> A center stick would have allowed a free hand in either direction.
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Center mounted sticks are useful for maintaining positive control of the aircraft while operation some cockpit system on the right consoles and flying with your left hand. With a side stick only thing that is getting aggressive is your wrist flexors! As far as size and weight are concerned, both center mounted and side sticks are pretty much the same in a fly-by-wire aircraft - just a 4-way transducer LRU with a handgrip attached to it.
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Can an experienced airplane spotter identify planes only by sound? I come from a background in railroad watching, and often times one can identify the maker of a railroad locomotive purely by sound. Maybe not the exact model of locomotive, but at least what type of diesel engine is in the locomotive. Although there is a similar question here: What could cause GE and Rolls-Royce turbofan engines to sound different? , my question is whether an experienced airplane spotter could be near the end of a runway at a busy commercial airport and be successful in identifying the model of commercial jet aircraft landing and taking off only by the sound the spotter is hearing from the aircraft as it flies overhead? To me as an inexperienced airplane spotter, they all sound similar. But to airplane spotters, all railroad locomotives may sound the same too. :-) <Q> I can also tell a Rolls Royce engine from others because Rolls Royce engines make a quite "harmonic" and "warm" sound as it powers up. <S> Now here is the fun part: I correlate the sound with the type of the plane by comparing the Doppler effect as the plane passes by. <S> It tells you how fast the angular velocity is in relation between you and the plane. <S> The variation in loudness gives you the approximate distance to the plane - if the plane is far away, its loudness would change slowly. <S> Combine that with the geographic location of yourself and the flight paths of planes, it gives you the speed of the plane. <S> The speed of the plane is important because it tells you the size of the plane. <S> If I hear a loud multi-prop engine moving slowly, I'd bet a transport plane, something like a C130. <S> If it is moving quickly, I'd bet an aerobatic aircraft. <S> The location where I live is directly under one of the SIDs of a major airport. <S> Planes are usually ~3,000 feet when they pass above me. <S> One thing I notice is that long route planes like Boeing 777 or Airbus A340 makes a noticeably louder noise. <S> This is because these planes carry a lot of fuel on takeoff, and their climb performance is restrained compared to short haul airplanes, meaning they pass above me at a lower altitude, hence the louder noise. <S> I cannot distinguish from sound if it is a B777, B747, A330 or A340, but I know it is not a B737 or A320 unless the pilots fly slow and low. <S> I confess <S> I have an unusually good hearing ability. <S> I often hear faint sound or noises which others cannot notice. <S> I am also a musician. <A> Yes it is possible, although it is kind of hard to prove it over the internet. <S> 1 <S> When a teenager I lived under the approach path of Westover AFB. <S> My friends and I had no difficulty at all distinguishing among these types by sound alone: <S> Douglas DC-3 <S> Douglas DC-7 <S> Boeing 707 Douglas DC-8 <S> Lockheed <S> L-188 <S> Electra Lockheed L-1049 Super Constellation Convair <S> B-36 <S> Boeing B-47 <S> Stratojet Boeing B-52 <S> Stratofortress <S> Convair F-102 <S> Delta Dagger (singly or flights of two or four) <S> Lockheed F-104 <S> Starfighter (singly or flights of two or four) <S> North American F-100 <S> Super Sabre (singly or flights of two or four) <S> We only looked up when some other type flew over. <S> 1. <S> This line is an homage to kevin who said it first. <A> A few years ago I was camping at Download Festival with a friend who is a 747 pilot. <S> When we weren't watching bands we spent a fair bit of time in our tent playing the "identify the engine" game as aircraft took off from East Midlands airport right over our campsite. <S> She was pretty successful, pointing out the differences between jet engines, discussing the difference between a Graunch and a Whine, such that I can now easily distinguish between a Rolls Royce and a GE engine, between 2 and 4 engines, likely airframe (based on launch noise and volume) etc. <S> So generally, yes, you can distinguish between many types of aircraft by noise profile. <S> One stumped her, though - and I identified it as <S> a C-130 (from my years in the Falklands this was a familiar sound) <S> so we watched it go by and then got back in the tent. <S> The next noise we heard was something neither of us could identify. <S> So we climbed out of the tent - as did everyone else around us. <S> The loud, earth-shattering roar that increased in volume was the Antonov <S> AN-225 Mriya taking off almost directly overhead. <S> Never going to forget that one. <A> Of course. <S> I live right at the beginning of the runway 30ILS intercept area of KOAK. <S> I hear a lot of planes, and you can usually identify an a320 variant (like a321) by its higher pitched noise compared to the 737. <S> The 737 sounds like a hollow whooshing <S> sound(like one you would make with your mouth). <S> The MD-11 and DC-10 sound like the 737 but louder. <S> 777 has its distinct GE90 sounds. <S> Not very many 747/787's come by though. <S> There aren't enough 757/767 for me to actually remember and recognize their sound. <S> Keep in mind, these planes are all probably on idle as they are getting ready for final. <S> Also a short story: <S> Once I was just sitting by my computer <S> and I heard what sounded like a huge jet outside. <S> It sounded so loud, definitely worth of 4 engines. <S> I didn't recognize the sound <S> so I opened FR24, and guess what? <S> it was a British Airways A380. <S> So basically after a while of matching the sound with the plane you get used to it <S> and you just 'know' what sound they make. <S> Just like someone calls your name <S> and you think "hey, that guys talking to me". <A> Yes and no. <S> The heard sound depends on aircraft's speed, altitude, surface positions (flaps, AoA), gear, weather (especially wind direction), other external noise (e.g. nearby busy roads) and of course engines (big proportion). <S> So a "resident planespotter" like @kevin can clearly identify aircrafts very well just by sound. <S> At a different airport with different environment conditions (especially different approach procedures), it is much more difficult. <S> By the way, the aircraft dependent noise (engines, gear, flaps) is studied and optimized during design of an airplane.
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Yes it is possible, although it is kind of hard to prove it over the internet. Generally the type of engine (propeller / turbo-fan / turbo-prop etc.) is quite easy to distinguish as they make very different sound.
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What are the costs of 1 hour flight in modern low-cost airlines? Thinking about "low cost" airlines that often tickets of about 40 Euros for 2 flight hours, I was wondering how these companies can cover their costs. Considering for example EasyJet that fly with Airbus A319 (150 seats), with a unique cost of about 90 million dollars, on a typical 2 hours flight (common average European route) every flight could gain about 6000 Euros in tickets. I can't understand where is the "gain" considering fuel, crew costs, maintenance etc... Can you give some references? <Q> According to the calculations, each passenger on board an Airbus A320, which has a capacity of 154, costs the airline $68.50 (£47.06) for the 260-mile journey. <S> The one-hour flight costs the airline an estimated $2.50 per passenger [for fuel]. <S> The total cost equals \$10,549 per hour "with profits as low as \$10 [per passenger] on some flights". <S> Also from the article— <S> If you want to be a millionaire, start with a billion dollars and launch a new airline. <S> — <S> Sir Richard Branson <A> This article presents the full breakdown of the operating costs of an A320. <S> TL;DR : <S> about 15kUSD/hour, including market-based depreciation. <S> The scenario is based on a private-jet scenario, with much fewer hours per year than your typical EasyJet aircraft, so this number should be considered as the upper limit of the actual operating costs of a low-cost airline. <A> There are a lot of factors that account for this. <S> This answer covers the bulk purchase aspect of the deal. <S> Basically EasyJet and the like see cost benefits by only flying a singly type of plane and thus only need mechanics and pilots trained on that air-frame and spare parts are interchangeable etc. <S> They also see discounts, as mentioned in the comments by not offering things like meals, free luggage etc. <S> Since they make short haul hops between nations often they may be able to work out deals for hauling cargo as well as people to undercut the cost of your ticket. <S> I cant find the article but it has been noted that in many cases by buying 100 planes at a time significantly reduces the cost of each air frame. <S> They then in turn sell them in a shorter period of time and don't fly them to the end of their life. <S> In many cases an air frame thats only a few years old will hold good value considering the sever discount <S> it was original purchased at. <S> You can find some info on the cost of operation for a long haul flight here . <S> Things like fuel consumption rates etc and the like will carry over to short haul flights.
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For the low-cost model there's an article called The true cost of flying revealed , which uses a 154-passenger A320 for its figures.
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When is the descent clearance requested from ATC? Is there a rule / Standard Operating Procedure as to when request the descent clearance during cruise flight? Something like one minute before reaching the Top of Descent point? <Q> Whether there are any formal policies for when to request descent will depend on the airline. <S> However, I doubt formal procedures are established, since it should be pretty obvious to pilots when to request descent. <S> Controllers are able to estimate when you are going to request descent, based on experience, known level restrictions and typical aircraft performance. <S> Controllers who have been working the same sector for a few years will be able to tell pretty much exactly when a certain flight is going to request descend, based on the current wind, runway in use, airline and aircraft type. <S> What this means to you, as a pilot, is that you can expect the controller to be ready for your request; You can normally expect to receive a clearance for descent immediately after requesting it - <S> so there is no reason to request it several minutes in advance. <S> Very few pilots will request descent several minutes before ToD. If they do, I can - if traffic flow permits - use the phrase "When ready descent to FL160". <S> You are then free to start your descent when passing the ToD. Honestly though, if you call me up and say "Request descent in 5 minutes", I will most likely just reply with "Roger, call me back when ready for descent". <S> The traffic situation can change significantly in 5 minutes, so I don't want to issue a clearance that may not fit into the future traffic picture. <S> In the end, the early request just costs time on the frequency, which can be a scarce resource in a busy sector. <S> Moral of the story: as a controller, I know my airspace very well, and I have a pretty good idea of when you are going to be ready for descent. <S> Because of this, there is no reason to request descent before you are ready for it. <S> If you do, it will not matter at best, and be slightly annoying at worst. <S> ATC can of course also descend you before your ToD for various reasons, but that is another discussion. <A> The pilots have the better picture performance wise. <S> ATC has the better picture traffic wise. <S> Aircraft with modern avionics get wind-data via ACARS , SATCOM, FIS-B , etc., which is fed into the vertical performance calculations, together with the company's cost index , the top-of-descent (T/D, ToD) varies. <S> There isn't one fixed scenario. <S> If ATC requests a descent before reaching the T/D for traffic management, pilots must comply. <S> Alternatively, ATC can remind the crew and leave it up to them— Flight123, when able, descend FL240. <S> Flight123, at your discretion, descend FL240. <S> The crew would then descend at the T/D and report leaving their current flight level. <S> Equally, ATC can force a flight to miss its T/D for traffic management. <S> Another example is if the tail-wind is strong it will shift the T/D farther from the destination. <S> If ATC didn't realize it from the high ground-speed, the pilots can remind the ATC— ATC Center, Flight123 is ready for descent. <S> ATC Center, request descent at time four five, Flight123. <S> Time four-five means :45 of the current UTC hour. <S> Variations above depend on locale (US, EU, etc.) <S> , thanks to Jonathan Walters and J. Hougaard for supplying variations. <A> I agree with everything said above, adding that it might depend on the PF(pilot flying the leg) in our aircraft, our vertical path is displayed which takes in to account headwind or tailwind and in preparing the flight on the ground when loading the flight plan on the FMS we can select our descend profile i.e a standard 3° path or higher. <S> Some colleagues prefer steeper descend so they can stay higher for longer therefore reducing fuel consumption. <S> Therefore it also depends on personnal preference really. <S> Having said that, certainly in Europe, controllers will ask you to descend before you request it and the London area will even ask you to be level by a certain distance....
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From a controller point of view, I will expect you to request descent when you are ready for it - so a minute or so before reaching your top of descent point.
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What is flight inspection, as provided by Cobham Aviation Services? At about midnight, I saw a small plane (a Diamond Twin Star ) take off from Heathrow, on flightradar24. It then proceeded to fly in irregular loops around North London, at low altitude, 1700ft. The plane had registration G-COBS, and seems to be owned by " Cobham Flight Services ", which provides "flight inspection services". Their web page advertises how good they are, without explaining what they do. It seemed unusual, as such small planes don't normally use Heathrow, and flying low over a city at night also seems unusual. What was the purpose of a flight like this? <Q> From their website, Cobham conducts commissioning, return-to-service, engineering and periodic flight inspections in addition to trials work on a range of systems including, CAT I/II/III ILS, MLS, PAR, DVOR, NDB, U/VDF, TACAN, DME, AGL and PAPI and PSR/SSR. <S> The specialist capabilities include procedure validation, ADS-B and MLAT-systems, <S> ship borne navaids, FI programme management, technical investigations, communication tests and trials, windfarm trials, flight inspection advice, and training. <S> Cobham has formal approvals from UK CAA Safety Regulation Group (CAP 670), UK MoD, INAC (Portugal), ENAV (Italy), British Standards Institute (BS EN ISO 9001:2008), Germany BAF, and Air Safety Support International OTAR for UK Overseas Territories. <S> It looks like they test airport/en-route equipment such as approach systems and ADS-B systems etc. <S> This can presumably be done in any aircraft equipped to fly/test those approaches and systems. <A> Flight inspections are flights performed to measure the performance of the communication, navigation and surveillance (CNS) infrastructure of air traffic control. <S> Flight tests are required to examine the signals-in-space as received at the aircraft after being influenced by external factors such as site conditions, ground conductivity, terrain irregularities, metallic structures, propagation effects, etc. <S> source: <S> ICAO <S> DOC8071 <S> In this case the inspection flight seemed to be performed to inspect the performance of the Instrument Landing System at RAF Northolt . <S> The aircraft did numerous approaches on runway 25 and flew across the localizer twice at approximately 11 km (6NM) from the runway threshold. <S> This is a normal procedure for ILS testing. <S> For those interested in the details of the ILS testing procedure seen on FR24, it is described in section 4-10 of ICAO Document 8071, Manual on Testing of Radio Navigation Aids, Volume I (Testing of ground-based navigation systems). <A> I live nearby Frankfurt airport and every few months or so the DFS (German ATC) issues a press release about inspections flights. <S> Sample from their homepage <S> : Flugvermessung am Flughafen Frankfurt <S> (Flight inspection at Frankfurt Airport) <S> Noise disturbance to be expected during the day and at night 14.11.2016.- <S> In the period from 17 to 20 November 2016, calibration flights will be conducted at Frankfurt Airport. <S> The accuracy of the instrument landing systems of the southern runway and the centre runway will be inspected for landing direction 25 (westerly weather patterns) of the southern runway and 07 (easterly weather patterns) of the centre runway. <S> The calibration aircraft being used is a twin-turboprop Beechcraft Super King Air 350. <S> During this time, noise disturbance is to be expected during daytime and nighttime hours. <S> Despite the night curfew at Frankfurt Airport, technical flight checks such as calibration flights may also be conducted at night as they would have a great impact on regular air traffic during the day. <S> The calibration of technical facilities is indispensable for the safety of air traffic. <S> DFS would like to apologise for any inconvenience caused by such flights. <S> This one was for RWYs 25L and 07C <S> but three months earlier they did similar flights for RWY northwest (07L/25R).It's interesting (and attracting) <S> that flightradar24 shows the flight around LHR from your question. <S> Next time I hear about inspection flights in my area <S> I'll have a look at flightradar24 too. <S> Update: <S> A few days ago DFS announced further calibration flights from 16 to 19 February 2017 around FRA/EDDF to inspect ILS accuracy for RWY northwest (07L/25R). <S> I figured out they use (at least) two aircraft, D-CFMB and D-CFMD . <S> This time it was the latter. <S> They flew on Feb 16 (left) and Feb 17 (right): <S> But the funniest one must have been on Feb 15 from DRS (Dresden) to Berlin (SXF), rendering kinda crop circles: <S> All pictures from FR24. <A> From the Flight Inspection Wikipedia entry : Flight inspection refers to the periodic evaluation of navigational aids used in aviation, such as flight procedures and electronic signals, to ensure they are safe and accurate. <S> Unlike flight tests, which analyze the aerodynamic design and safety of the aircraft itself, flight inspection comprises reviewing flight procedures ( <S> such as routes, approaches and departures) to ensure navigational support <S> is sufficient <S> , there are no obstacles and the procedure is reliable.
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It may seem unusual, but it is actually a very common procedure, done regularly as part of national and/or international aviation standards, and every time there is a significant change to ground infrastructure which may affect Nav Aids signals.
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How long does it take for an FAA licence to be delivered? Would anyone have an idea how how long it takes for a licence to be posted out. The airmen search tells me my ATP processing was completed at some point last week. So the licence has been finalised. Do they post the licences straight away and do they use Fedex or DHL, normal or priority? I live in Australia. And need to present this licence at an interview in a weeks time which is why i ask. Are there means of expediting or tracking the licence in the mail? Between the flight school and the fsdo losing my paperwork and forgeting signatures and corrections being sent to the wrong FSDO offices, its taken me about 5 months to get this licence processed. Ive missed out on some job offers already because the companies would not accept temporary licences. Id rather not miss out on this one. If anyone has a clue, it would be most appreciated. I know fedex says its about 5 working days economy mail and UPS says 7 working days economy mail. But i have never delt with either. Thank you kindly <Q> The FAA has, at least in the recent past, been backlogged with some forms and certificate issuance has been one of those items. <S> My private pilot certificate took nearly 3 months to arrive (hence, my temporary certificate almost expired). <S> I had to make several calls to my DPE (Designated Pilot Examiner), who then reached out to the FAA in Oklahoma City to see what was wrong. <S> It turned out a computer glitch had erased my knowledge test report. <S> After several times around, this was fixed and my certificate showed up within several weeks. <S> In the USA they always send it via First Class Mail (uncertified, no tracking number). <S> Last August (2016) <S> my new certificate showing my instrument rating showed up just a month or so after the checkride, so much faster. <S> If you have a question, don't hesitate to reach out to your DPE - they are very helpful and can get things moving again if they're stuck. <S> Also, make sure you keep all test reports and other documents until you receive your certificate in case they somehow get lost in the system. <S> And when you get your new certificate - don't forget to sign the back or it is not legally valid! <S> Regarding your interview - your temporary airman certificate is valid for all purposes until the expiration date. <S> You can bring this to an interview as it is as valid as the plastic card. <S> I don't know if a company is allowed to reject you because you only have a temporary certificate while your plastic one is being prepared <S> - I'd look into this and maybe ask an attorney as that doesn't seem like it would be legal to me since the certificate is valid. <S> Cheers! <A> In recent times, it’s taken about 45-60 days from issuance of the temporary airman certificate. <S> Again, as mentioned, your temporary airmen certificate is valid for all practical and legal purposes until the permanent one arrives. <A> The temp certificate is useful only in the USA, for those of us needing validations it's useless. <S> The FAA use the cheapest mail they can find therefore sending a license by mail can require up to 60 days which is about how long it took in the 1920s. <S> One would have thought by now they could have taken an online payment to use FEDEX which would reduce this to just 3 days.
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The FAA does list what license applications are being processed on their website under airmen Certification so you can get a general idea of when you will receive your license in the mail.
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Is there a definition of light/medium/heavy aircraft? I'm surprised this hasn't been asked before but I couldn't find it by searching. For separating arriving aircraft, ICAO PANS-ATM-Doc 4444 Air Traffic Management refers to aircraft as "LIGHT", "MEDIUM" or "HEAVY" but I cannot find any definition of what makes an aircraft fall into any particulate category. I would of expected a limit on MTOW for each category, does such a definition exist or is it more of an informal definition? 5.8.2 · Arriving aircraft 5.8.2.1 Except as provided for in 5.8.l.l a) and b), the following separation minima shall be applied. 5.8.2.l.l The following minima shall be applied to aircraft landing behind a HEAVY or a MEDIUM aircraft: a) MEDIUM aircraft behind HEAVY aircraft- 2 minutes; b) LIGHT aircraft behind a HEAVY or MEDIUM aircraft- 3 minutes. <Q> Section 4.9.1.1 of ICAO <S> PANS-ATM-Doc 4444 Air Traffic Management defines LIGHT, MEDIUM & HEAVY aircraft for the purpose of wake separation: 4.9.1 Wake turbulence categories of aircraft <S> 4.9.1.1 Wake turbulence separation minima shall be based on a grouping of aircraft types into three categories according to the maximum certified take-off mass as follows: a) <S> HEAVY (H) — <S> all aircraft types of 136,000kg or more; b) <S> MEDIUM (M) — <S> all aircraft types less than 136,000kg but more than 7,000kg; and c) <S> 4.9.1.2 Helicopters should be kept well clear of light aircraft when hovering or while air taxiing. <S> Note <S> 1. <S> — Helicopters produce vortices when in flight <S> and there is some evidence that, per kilogram of gross mass, their vortices are more intense than those of fixed-wing aircraft. <S> Note 2. <S> — <S> The provisions governing wake turbulence minima are set forth in Chapter 5, Section 5.8, and Chapter 8, Section 8.7.3. <A> Let me add the proposed Super category. <S> According to Wiki and this article : ICAO mandates separation minima based upon wake turbulence categories (WTC) that are, in turn, based upon the Maximum Take Off Mass (MTOW|MTOM) of the aircraft. <S> These minima are typically categorised as follows: <S> Light (L)– MTOW of 7,000 kilograms (15,000 lb) or less; Medium (M)– MTOW of greater than 7,000 kilograms, but less than 136,000 kilograms (300,000 lb); Heavy (H)– MTOW of 136,000 kilograms (300,000 lb) or greater. <S> A fourth category is currently being taken into consideration by ICAO: <S> ¹ Super (J)– Refers only to the Airbus A380 <S> Even though the resolution to add the "Super" category is still under consideration, both the FAA (see below) and EUROCONTROL have already implemented guidelines concerning the Airbus A380. <S> (emphasis mine) <A> The FAA answers this question here: <S> Weight Class <S> Weight Class Weight class is based are assigned by APO130 based on the TFMS observed aircraft codes. <S> There are 6 categories -- (A) Heavy, (B) B757, (C) <S> Large Jet, (D) <S> Large Commuter, (E) Medium, (F) Small. <S> (A) <S> Heavy: <S> Any aircraft weighing more than 255,000 lb such as the Boeing 747 or the Airbus A340; <S> (B) B757: <S> Boeing 757 all series; (C) <S> Large Jet: <S> Large jet aircraft weighing more than 41,000 and up to 255,000 lbs such as the Boeing 737 or the Airbus A320; (D) <S> Large Commuter: <S> Large non-jet aircraft (such as the Aerospatiale/Alenia ATR-42 and the Saab SF 340), and small regional jets (such as the Bombardier Canadair Regional Jet), weighing more than 41,000 and up to 255,000 lbs; <S> (E) Medium: Small commuter aircraft including business jets weighing more than 12,500 up to 41,000 lbs such as the Embraer 120 or the Learjet 35; and (F) Small: <S> Small, single, or twin engine aircraft weighing 12,500 lbs or less such as the Beech 90 or the Cessna Caravan. <S> Unknown; refers to unspecified equipment. <S> "Light" Aircraft follows the same definition as "Small" in the above text. <S> Wake turbulence is no joke - you can feel it if you come in behind a larger aircraft even several minutes after it lands, and often even if you stay above its glide path and land beyond its touchdown point, as you should. <S> There was a Grumman Tiger landing at my local airport that didn't pay attention, ignored the tower's "caution wake turbulence" warning, and got flipped inverted and subsequently crashed as a result of wake turbulence from a UH-60 military helicopter that had departed several minutes prior. <S> The pilot, very fortunately, walked away but the aircraft was ruined. <S> Note that even though helicopters are not mentioned in your post - any helicopter leaves persistent rotor wash and you should be extremely cautious and wait several minutes before attempting to takeoff or land anywhere a helicopter has been.
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LIGHT (L) — aircraft types of 7,000kg or less.
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