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Why aren't contra-rotors used on the V-22 Osprey? The Osprey has 38 ft (11.6 m) rotors in a rotating nacelle on each wing. The rotors are powered via a gearbox as in usual turbo-pro fashion. Is any reason that is obvious that smaller contra-rotating rotors wasn't adopted. It is noted on Wikipedia that the rotor diameter is currently 5 ft (1.2 m) below ideal, wouldn't a contra format be more compact on this front. Due to the requirement for folding rotors, their 38-foot diameter is 5 feet less than optimal for vertical takeoff, resulting in high disk loading. <Q> Instead of having a set of contra-rotating proprotors on each side, if you're after decreasing the disk loading, a span increase would also do the trick, allowing wider proprotors. <S> However the Wikipedia paragraph starts by saying: Due to the requirement for folding rotors... <S> The main contributor to its less-than-ideal size is the folding requirement to save parking space aboard ships, since the primary operators are the US Navy and the USMC. <S> Adding another set of rotors or increasing the span won't help: ( Source ) <A> Aircraft design is always the art of finding the right compromise. <S> Even if a feature might promise to increase efficiency in some way, this may come at a great price. <S> If your suggestion were to be implemented, the aircraft would go from having two rotors (which is already a high number) to four. <S> I am not familiar with the specific design, however these are in my opinion some of the drawbacks that would arise: Increased complexity: increases the effort of design, operation and maintenance. <S> Rotor systems represent a significant portion of the overall aircraft production costs, hence this solution would surely bring about a significant increase in unit cost. <S> Also consider you would have at least 8 blades to maintain instead of 6. <S> Increased structural mass. <S> Possibly increased noise emission (though I am not so sure about this point). <S> Most aircraft designs would surely have more unconventional features if the only thing that mattered were increased performance or efficiency. <S> However other aspects are often just as important, if not more. <A> Is any reason that is obvious that smaller contra-rotating rotors wasn't adopted. <S> Smaller contra-rotating rotors would not have higher efficiency! <S> The efficiency of lift/thrust generation by propeller increases with the amount of air it affects. <S> But when you put one rotor above another, they both affect the same air, so efficiency is not increased. <S> Contra-rotating rotos are only slightly more efficient, compared to single rotor of the same diameter , because the second rotor counters the rotation of the slip-stream behind the first one that otherwise also carries away some energy. <S> But typical saving due to this is around 6%, which is by far not enough to warrant the hugely increased complexity, especially in the most critical component of a rotorcraft, the gearbox. <A> Picture source Co-axial rotors are insanely complicated. <S> The V-22 had to overcome many first time problems and is very complicated. <S> Combine the two, and you'll have a bunch of weeping engineers and no product. <S> On a co-axial rotor: <S> Both the rotors need to have their individual swash plates being able to generate collective and cyclic inputs. <S> But one swashplate is above the other. <S> if the rotor heads are fully articulated, there needs to be enough distance between the two to allow for differences in flapping dynamics. <S> But a rotor high above the helicopter creates a bit of a construction problem. <S> The rotors turn in opposite directions, requiring two different sets of gearing & drive train, all sharing the same axis centre line. <S> the same mass of air is accelerated to a higher velocity. <S> The obviously less complicated solution of a greater diameter rotor, accelerating more air, runs into its limits when the blade tips approach supersonic speeds. <S> The Osprey tilts its rotors to be able to fly faster than a horizontal rotor helicopter, the limiting factor again being blade tip speed, but now in the propeller way. <S> The Tu-95 does use contra-rotating propellers, to be able to fly faster than with single propellers with the same thrust. <S> Picture source <S> So yes, aerodynamically two sets of co-axial rotors would have benefits for the Osprey. <S> Have two sets of co-axial rotors and tilt them ? <S> No way.
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Aerodynamically, co-axial rotors can deliver a higher end thrust than a single rotor of the same diameter, at the expense of less efficiency: But it would be an impossible engineering challenge, the Osprey is pretty complex and had plenty challenges to solve as is.
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Can you identify this airplane? Im thinking the window sequence and the shadow (possible a prop?) Might be your best help. My dad bought this photo and him nor I can figure it out. I work at a dang airport, too! TIA. <Q> It was a strategic bomber used by the US in the Pacific theater of World War II. <S> The lower row of four windows and then another further aft matches pictures of the B-29. <S> The "U.S. AIR FORCE" markings are a post-WWII style. <S> Source <S> It's also possible that it's a B-50 Superfortress . <S> This was an upgraded version of the B-29 with new engines and other changes that are hard to see in the picture. <S> Only 370 were built. <S> Although it's not clear when the picture was taken, and only 5 examples of the B-50 still exist. <S> The B-29, on the other hand, has way more. <A> Boeing typically has the tight airforce markings near the nose. <S> The photo bears heavy resemblance to the kb-50 as its lower nose portion fit the look when you zoom in on the OPs image <S> you can see the window matching more then the kb-97, was just so big.. <S> KB-97 <S> KB-50 <S> Either way they are both variants of the previous answer. <S> turret and no turret comparison images below. <A> http://s10.photobucket.com/user/deattilio/media/Arizona%2008/Pima%20Air%20Museum/IMG_3206.jpg.html <S> https://www.flickr.com/photos/golftwo/4510556800
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It's most likely a Boeing B-29 Superfortress . If I were to guess I'd say the picture is of the B-50 at the Pima Air Museum.
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Is it unusual for an aircraft to flash its landing lights in sequence? Walking this evening I looked up and saw a plane which I assumed was on approach to Liverpool John Lennon. When I looked carefully I could see that as well as the anti-collision strobes it was flashing two lights in sequence. I assumed they were the landing lights as they were very bright and positioned towards the wing tips. However , they were clearly flashing one at a time, left then right. I've never seen this before, is it normal and does it signify anything? <Q> The flashing lights help to make the airplane more noticeable. <S> They have also been suggested to reduce the risk of bird strikes . <S> This is offered as an option or add-on for many types of aircraft. <S> The FAA requires landing lights to be on for commercial flights under 10,000 feet, and encourages pilots to turn them on at least when near an airport or in low visibility. <S> Flashing the lights makes them less likely to be confused for something like a star at night. <A> It is certainly a standard feature on the Dassault Falcon, we have a "pulse"position where it flashes as you describe which we switch below 10 000 ft, and then the "ON" position which we use on we are clear to land. <S> The latest being purely a company SOP. <A> I thinking what you saw were the landing lights. <S> Airplanes do tend to have taxi lights and landing lights in order to make it easier for pilots during night time.
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In addition to helping the pilots to see ahead of them when on the ground in dark conditions, landing lights help to make planes more visible to others.
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Can a missile be fired when a fighter jet is inverted? Is there an attitude limit for firing a missile from a fighter jet? Can the pilots fire them when they're pulling Gs, or inverted? <Q> The combat advantage of fighters (as opposed to heavier-payload bombers) is their maneuverability, therefore a missile delivery restriction such as g-limit (think Sidewinder heat-seeker in a dogfight) or attitude would unnecessarily restrict their efficacy. <S> As a Vietnam-era fighter and attack pilot I fired both unguided (aim and shoot rockets) and guided (target lock-on and shoot) missiles, and neither had associated attitude limits. <S> Missiles that fall clear of the weapon station before rocket-motor ignition (such as the TV-guided Walleye or the optically-pilot-guided Bullpup) are obviously restricted from negative g to ensure safe separation from the airplane, i.e., negative g release from an under-wing weapon station would all but guarantee impact with the airplane. <A> Yes. <S> Specific weapons can be employed within specific limits and load factors of the flight envelope, some of which includes inverted flight for air to air missiles, as this F-22 test pilot demonstrates during the Raptor's flight test. <A> Yes, Modern air to air missiles can be fired while manoeuvring but it can reduce kill probability. <S> So missiles can be fired when aircraft is inverted but within certain g-limits.
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Firing a missile while manoeuvring also depends on altitude of aircraft, type of missile and effectiveness of seeker.
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How can I create a map of all paths of flights incoming to an airport in a given day? Is there any where I could find a map overlaid with the paths of all flights that came into a given airport on a given day? I've found a lot of maps that show the current location of all flights, or the path of a single flight, but I haven't been able to find any that have the paths of many flights at once. I don't really want to scan through every flight manually, but if I could see all of their paths I could pick out the ones that have interesting tangents for further study. Background: I recently moved in to an apartment near an airport. I enjoy watching the flights come in, but one of my new roommates is less thrilled. He remarks that some of the flights seem to be pointed directly at our building until their final turn, so if the pilots were somehow incapacitated, we'd be in trouble. I think that's geometrically incorrect, but would like to prove it. <Q> Well you didn't state which airport you are interested in <S> but obviously you only want data for a single airport. <S> You might want to look into a noise abatement reporting system. <S> For instance, London Heathrow maintains the great website Webtrak ( https://webtrak52.bksv.com/lhr4 ) to communicate with the pubic about changing SIDs, STARs and noise levels. <S> (They already have much of the TMA over the heavily populated area, and they want to add another runway) <A> One option you have is to ask the airport for the data. <S> They can deliver it to you in a shp-file that you can open with QGIS that is free software. <S> With QGIS you can create maps and filter the radar tracks. <S> All major airports often have a track monitoring system that saves data från the ATC-radar not from the ADS-B transponder. <S> Usually the airport environmental department and the airport acoustics team/consultants have access to the historical flight track data. <S> Here are some examples of track monitoring systems that airports use ANOMS <S> CASPER <S> TOPSONIC <S> FlightRadar24/ <S> FlightAwere etc. <S> mostly consist of ADSB crowd input and is not fully reliable. <S> Some airliners also send out the wrong position from their ADS-B transponder. <S> That is called spoofing. <S> To my knowledge FlightRadar24 only lets you export one path at a time. <S> You can also setup your own gear and record ADSB data with dump1090, that requires som skills, money and time. <A> I would start with the approach charts for that airport, see if the flight paths are indeed over your housing, and at what altidude. <S> There are also sites like this one that show "live" (likely delayed some number of minutes) tracks of aircraft currently airborne. <S> You can zoom in and see if any tracks are over your housing. <S> This is the Boston, MA area for instance: <S> https://www.flightradar24.com/42.36,-71.01/7 And this one shows where they departed from and where they are landing https://www.radarbox24.com/@42.47000,-71.26623,z14 <A> You mention the arrival path before the final turn to the runway, known as the base leg on a visual approach. <S> When cleared for a visual approach the pilot flies the base leg as near or far from the runway as he or she sees fit based on altitude, distance, obstructions, traffic to be followed.
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The gov't published approach charts are here https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/dtpp/
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Is "Tally-Ho" used in ATC radio communication, specifically in the UK? This question Are "Tally-ho" and "no joy" acceptable ATC terms for civil operations? concerns the use of the phrase "Tally Ho" to mean "target in sight" in civilian air-traffic-control communication. It was largely answered (and somewhat asked) in relation to the US/FAA, where it is not acceptable but sometime heard. However "Tally Ho" is/was a British phrase, and my question asks the same specifically of British/NATS/CAA communication. Again, I'm interested as to whether it is actually heard, and whether or not it's generally considered acceptable. I am aware that some efforts are made to keep English usage international, though most feeds/transcript I've heard from the US have an awful lot of regional idioms and phrasing in them, so I'm not sure the extent to which it is adhered to. (For people outside the UK, "Tally Ho" is generally considered archaic and comically mannered in general life these days, even within the UK, which is why I'm particularly interested as to whether its usage survives here in aviation). <Q> It used to be used in military comms in combat. <S> Its usage arose during WW1 when the Royal Flying Corps (and later the Royal Air Force) drew its crews mostly from the "officer classes" who, in general, were also fox hunters or supporters of the same. <S> "Tally ho" is the cry shouted out by a huntsman when the fox is spotted and the hunt is on. <S> I served in the RAF from 1976 to 1986. <S> Then as a civilian in the military until 1993 and in that time never heard the phrase. <S> I suspect that it has died out since it is not standard phraseology and perpetuates stereotypes which have no place in modern, professional organisations. <S> A non-standard, but common phrase is a simple "visual", but the correct phrase in both civilian and military use is "traffic in sight". <A> No, Tally-Ho is not accepted phraseology in UK civil aviation, and in 14 years of flying in the UK I've never heard anyone use it. <S> At non-ATC airfields you occasionally hear some non-standard phrases, often with a bit of humor, but I've never heard that one. <S> If a controller asks if you have visual contact with an aircraft you would just say "affirmative" or "negative", or you can say something like "G-BT is visual the traffic". <S> If you are in the circuit (pattern) and you can see there's another airplane in front of you you can report "contact one ahead". <S> Tally-Ho is anachronistic, and you'd never use it conversationally except in irony. <A> No, "tally-ho" is not acceptable. <S> CAP 413 , the UK Radiotelephony Manual, defines a correct response to traffic information like this: G-CD, traffic is a Cherokee upwind and a Tomahawk late downwind Roger, G-CD ... <S> Traffic in sight, G-CD <S> The phrase "tally-ho" is not mentioned anywhere in CAP 413. <A> The short answer is no. <S> It is never used by either controllers or pilots. <S> " <S> In sight" would be the term used by civilians. <S> It's true, that I have never conducted a survey. <S> It was mentioned earlier that CAP 413 (which is the reference) doesn't mention it: <S> that leaves us, I guess, with either the training we've received, if that was in the UK, or the little experience we have. <S> I humbly have both. <S> I completed my training years ago there <S> and I fly, day in day out in UK airspace, from Heathrow to Bigin hill, London city, or even RAF Northolt, and have been doing so, for a good 17 years and counting. <S> Again, in that timeframe I have never ever heard it. <S> On a side note, most if not all my British colleagues come from the RAF, and even with them I have never heard "tally-ho" or maybe as a joke amongst us.
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I have never heard "tally ho" used in civilian aviation and it not a recognised phrase so should not be used. A civilian ATCO would not think positively about anyone using that phrase.
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Are there any ILS approaches in Class E airspace? When descending on an ILS you can descend to 100' above the TDZE if you have the approach lighting system in sight. Cody Johnson wrote an article explaining how one pilot mis-interpreted what the rules allowed him to do, descended below 100' when there were obstructions in the way and crashed into a hill. ( https://iflyamerica.org/misunderstanging_part91.asp ) Section 91.129(e)(3), Operations in Class D Airspace, is also extremely applicable in this accident. It says, 'An airplane approaching to land on a runway served by a visual approach slope indicator shall maintain an altitude at or above the glide slope until a lower altitude is necessary for safe landing.' Class C and B incorporate Section 91.129(e)(3) by reference, so the rule applies in that airspace as well. It doesn’t specifically apply to operations at airports in Class E airspace. My question is are there any ILS approaches in Class E airspace? Is there a a rule that prohibits them, or conversely, only allows them when there is a tower? <Q> There are plenty of ILS approaches in Class E surface area (e.g. KCLM, KHQM, KPWT). <S> In fact the presence of an ILS will usually require that some kind of controlled airspace extends to the surface. <S> For an untowered airport this means a Class E surface area. <A> <A> KPNE has an ILS for their 24 runway <S> they are class D airspace between 1100-0400Z and class E all other times. <S> The approach, as far as I know, remains on while the airport is class E. <A> Around airports, instrument approaches are what class E is all about. <S> That's what results in the "keyhole" shape of class E 700ft and surface area extensions. <S> Class E surface area surrounding an airport is usually used for airports that do not have a tower or at times when the tower is not operating. <S> From AIM 3-2-6 <S> §e.1. <S> Surface area designated for an airport where a control tower is not in operation. <S> Class E surface areas extend upward from the surface to a designated altitude, or to the adjacent or overlying controlled airspace. <S> The airspace will be configured to contain all instrument procedures. <S> (a) <S> To qualify for a Class E surface area, the airport must have weather observation and reporting capability, and communications capability must exist with aircraft down to the runway surface. <S> 1 <S> (b) <S> A Class E surface area may also be designated to accommodate part-time operations at a Class C or Class D airspace location (for example, those periods when the control tower is not in operation). <S> But Class E extensions are also used to protect approaches to towered airports in B,C, or D areas. <S> AIM 3-2-6 §e.2. <S> Extension to a surface area. <S> Class E airspace may be designated as extensions to Class B, Class C, Class D, and Class E surface areas. <S> Class E airspace extensions begin at the surface and extend up to the overlying controlled airspace. <S> The extensions provide controlled airspace to contain standard instrument approach procedures without imposing a communications requirement on pilots operating under VFR. <S> Surface area arrival extensions become part of the surface area and are in effect during the same times as the surface area. <S> 1 <S> Anywhere there are instrument approaches not protected by class B, C, or D airspace you can expect a class E extension. <S> Anywhere aircraft on approach are expected to go below 1000 feet <S> there will usually be a class E surface extension. <S> 2 <S> 1 FAA Aeronautical Information Manual [PDF] 2 Russ Roslewski, How are Class E surface area extensions determined?
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Visalia, CA (KVIS) is an uncontrolled airport with a Class E surface area and an ILS with 200' minimums.
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Why does a clean configuration lead to the generation of greater wingtip vortices? "Slow, heavy, clean" are the three major conditions generating stronger wing vortices. It's very clear how "slow and heavy" aircraft create stronger vortices, but why a "clean" configuration generates stronger wake turbulence is less clear. I did some digging on this, and found some people saying "use of the flaps reduces the AoA and thus leads to weaker wake turbulence" and others claiming "use of flaps moves the center of lift toward the root of the wing and that leads to less lift around the tip of the wings and thus less wingtip turbulence. Which explanation is correct? Edit) I checked the answer given here What is the relationship between angle of attack and wake turbulence? , but I'm not really sure "not really" is the right answer to this. The AIM (Aeronautical Informational Manual) is very clear about this, designating "clear" (along with "heavy," and "slow") as one of the three factors that increase wake turbulence. <Q> I would actually assume the opposite to be true. <S> Let us assume the vortex intensity and the induced drag are directly correlated. <S> The induced drag coefficient can be expressed as: $c_{Di}=\frac{c_L^2}{\pi\cdot AR \cdot <S> e}$ <S> $c_L$: <S> Lift coefficient $AR$: <S> Wing aspect ratio <S> $e$: <S> The so-called Oswald factor , a number which equals one for elliptic lift distributions. <S> It decreases for distributions that deviate from the elliptic one. <S> Most wing designs aim to achieve an elliptic-like lift distribution in order to minimise induced drag in clean configuration . <S> As flaps, spoilers, air-breaks and so on are deployed the lift distribution will deviate substantially from the elliptic one (see diagram), hence reducing the $e$ factor and increasing the induced drag. <S> If the first assumption still holds, an increase in induced drag will have been caused by an increase in vortex intensity. <S> Additionally, significantly higher lift coefficients can be achieved with deployed high-lift devices, which also contribute to increase vortex intensity. <A> What causes wing vortices? <S> When the wing produces lift, there is higher air pressure underneath it, and lower air pressure on top of it. <S> At the wing tip the high pressure air flips over to the low pressure air, and this creates the rotational element of the vortex, as described in this article. <S> The more lift is generated at the wing tip, the stronger the vortex will be. <S> Aerodynamic lift is a product of lift coefficient, air density, air speed, and wing area. <S> For subsonic speeds: L = $C_L$ * <S> ½ <S> * ϼ * $V^2 <S> $ * A. <S> Only the factor ½ in this equation is a true constant! <S> We have one equation with five variables, so lets have a look at what varies when. <S> Contrary to our first instinct, wing area is not a constant. <S> Modern aircraft have Fowler flaps at the trailing edge, <S> which are extended outwards and increase the wing area, as well as changing the curve of the wing which increases lift coefficient at a given AoA. <S> So there is the first part of our answer: <S> with deflected flaps we have more wing area to produce a given amount of lift, therefore lower required air pressures, therefore less air flippings at the wing tip :). <S> The second part of our answer also has to do with flaps. <S> Elliptical lift distribution is only possible when the wing tip has zero AoA, a situation designed to occur in cruise. <S> This same clean wing is very ill suited to produce the same amount of lift at the lowest possible landing speed. <S> CL is a function of angle of attack and of wing shape. <S> The answer with the graph of CL shows CL at constant alpha as a function of flap deflection. <S> A graph of CL at constant flap deflection as a function of alpha would show relatively more lift generated near the wing tip, and that is where the wing vortices are generated. <S> Flaps are located more inboard, meaning that when deflected, a greater portion of the lifting force is generated away from the wing tip. <A> I've seen both of those reasons used to explain this, and probably they both contribute to it, but in my CPL training I was taught the reason <S> is that a non-clean aircraft (and remember that this includes landing gear, spoilers, slats, etc.) causes airflow to be disturbed which reduces vortex generation. <S> The statement is always made referring to 'clean', not 'flaps retracted'. <S> The question came up also on Quora , and two answers came back, one with the reasoning I gave, and another using the increased AoA concept. <A> I am not sure that everything is so simple and obvious regarding flaps and gear. <S> Actually with flaps we have at least four points for vortices generation: on wing tips and on flaps outer edges, and they can mix with each other. <S> FAA/EASA answer seems based upon the following NASA research , and takes into account combining wing tips vortices with flaps/gear vortices, and faster weakening of total vortex strength. <S> I suppose that it really makes sense: aircraft in clean configuration generates "traditional" rather well-studied vortices, while aircraft in landing configuration generates much more complicated interfered turbulent flows. <S> It is very hard to say which one is stronger and more dangerous. <S> Very interesting thread about the subject can be found on PPRuNe , with nice pictures of totally confused situations when vortex from the left wing is dissipating, while the right one remains stable and narrow. <S> And here is one more research about wake turbulence with interesting results.
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A clean wing configuration is designed for the cruise condition, where there is lots of airspeed to generate lift and we want to keep induced drag to a minimum.
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Can a contra-rotating helicopter simply tilt its entire rotor set instead of using a cyclic? I was reading this interesting question and, per answer #1, a normal helicopter cannot do it because gyro effects would probably mean the body of the heli would tilt more than the rotor. So now I think about contra-rotating helicopters, like the Ka-50 . They don't need tail rotors, because the contra-spin cancels out reaction torque (except when they want to yaw, for which they extend little things at the blade tips of one rotor, producing more torque there and therefore opposite yaw). Anyway, can't a contra-rotator just tilt its whole hub instead of using traditional cyclic (swash plate, scissors link, which in fact are a lot more complex for a contra-rotating helicopter). <Q> Juan de la Cierva, inventor of the autogyro, on the C.30 went to a tilting rotor. <S> Most autogyros tilt the entire rotor for cyclic control. <S> Some autogyros apply engine torque to the main rotor to assist in achieving short takeoffs. <S> Now for this brief time, the autogyro is functioning like a helicopter, and the main rotor is driven by the engine prior to takeoff. <S> There is now a torque from the engine acting on the airframe, that requires more pilot hand force to control the rotor while the engine is driving the rotor. <S> Counter-rotating rotors on a helicopter would neutralize the reaction torque into the airframe. <S> If one is going to use a swashplate for collective control, it is easier to just control cyclic conventionally. <S> Here is one example of a helicopter that tilted the rotor for the cyclic: http://www.aviastar.org/helicopters_eng/bensen_zipster.php <A> I don't understand your idea of "tilting the shaft", how would you do that? <S> With the cyclic control it is very easy to tile the aerodynamic force but not the whole helicopter, why would you use a more complex mechanism of tilting the shaft (and the engine), and how would you do it? <S> Moreover, since you are referring to another question that already has an answer, do you think it is easier to tilt a single shaft or the double coaxial shaft of the Ka-50? <S> The cyclic system gives a direct response to input and it is a very simple system. <S> To prove it, try to Google AW609, that is a convertiplane working with the principle you talk about. <S> See how complex, risky and expensive a convertiplane is and you will realise it in few seconds! <S> The V-22 Osprey (Like the AW609) tilts the whole engine, and it is a hell of a system, very complex, expensive, risky and not competitive. <S> The advantage there is to have something that can be VTOL but can flight faster than an helicopter. <S> A pure helicopter that tilts the rotor would have no advantage and only disadvantages! <A> The cyclic does not "tilt" the disc. <S> It cyclically alters the blade pitch to vary the angle of attack which causes an increase or decrease in the lift produced cyclically around the blade orbit. <S> The blade "flies" into position with the blade reaching a maximum where the swashplate is at <S> it's maximum and a minimum 180 degrees later. <S> For complete accuracy, due to precession, the cyclic input is made 90 degrees in advance of the desired lift change. <S> The disc is titled by aerodynamic forces and therefore from the power input from the engine. <S> It is not moved by the forces applied by the cyclic control and links. <S> The cyclic on a light helicopter is generally connected directly to the swashplate with mechanical links. <S> The disc tilt can be controlled with the lightest of touches. <S> In a hover in no wind, you can move by applying pressure to the cyclic with the cyclic barely moving. <S> A tiny force on the swashplate results in a large force on the disc. <S> If you used links to mechanically move the entire disc, rather than causing the large aerodynamic changes, it would have to oppose them. <A> It's the twin-rotor that can't do it! <S> To control the attitude you have to create a torque. <S> You do that by offsetting the aerodynamic force (lift) from the centre of mass, and whether you do it by changing the lift distribution or shifting the centre of mass does not matter too much. <S> Except you can achieve larger change by changing the lift distribution (via cyclic control). <S> Now however helicopter rotor is a gyroscope and that does complicate things quite a bit. <S> The gyroscopic effect means that applying sideways torque makes the craft pitch and forward and aft torque makes it bank—the force must be applied 90° ahead of the direction you want to bank in the direction of the rotor rotation. <S> For cyclic, the links actually ride the swashplate ahead of the blades, so when you tilt the swashplate forward, the advancing blade pitches down, which makes it start to descend and reach the lowest point in front and everything pitches down nicely. <S> But when using weight-shift to get the same effect, with counter-clockwise-rotating rotor you'd tilt the rotor right ( <S> shift weight right, effectively). <S> It would be rather weird, but with the controls properly rigged probably possible. <S> However on twin rotor, shifting weight to the right will make one rotor want to pitch forward, but the other one want to pitch aft. <S> And they'll just twist and stress the shaft, but not do anything! <S> The cyclic easily solves this, because is decreases the lift at different place on each rotor so they both want to tilt the same way, but weight shift can't do that. <S> So you could do it on a single-rotor craft. <S> It would not really be simpler (tilting driven, spinning axles is not easy) and allow less manoeuvrability, but it would work. <S> With counter-rotating rotors you can tilt each differently to get the desired effect (the tiltrotors do that). <S> But with contra-rotating rotors you can't tilt each differently as they are on the same axis, so you can't do it this way at all and cyclic with a swash-plates and scissor-links <S> is the only option.
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So yes for a very small helicopter, it should be possible to tilt the main rotor for cyclic control, without hydraulic power assist. The gyroscopic effect will work against you and I have in mind no way to move a so big part of the Mass of the helicopter.
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How can hang gliders and paraglider pilots prevent stall? Aircraft and gliders usually have instruments to measure air speed and angle of attack, which should be monitored to prevent stalling the aircraft. However, it seems that most paragliders and hang-gliders lack such kind of tools. How do the pilots avoid stalling without these kinds of instruments? <Q> Paraglider pilots learn " active flying ", whereby you use feedback from the wing to determine what's going on. <S> You monitor the tension in both controls (the "brakes"), and the wing's attitude (if the wing pitches forwards then you feel like you are swinging backwards). <S> In bumpy air (such as on the edges of thermals, or in wave) <S> active flying is used to keep the wing more or less above your head. <S> If the wing surges forwards then you risk a collapse; if the wing falls back then you risk a stall. <S> In smooth air a stall is only likely if you are pulling the brakes down too far. <S> This can happen accidentally, especially in nil-wind landings if you mistake your ground speed for airspeed. <A> Paraglider Pilots can induce a stall by holding the brakes at seat or waist height until the wing retards. <S> The wing does not want to do this and will resist but a full stall will eventually be induced this way. <S> Pilots will feel and hear the reduction in forward airspeed. <S> To come out of a stall, the pilot may smoothly move the position of the brakes upwards anticipating a surge where the wing recovers and may dive or surge in front of the pilot. <S> Performing a 360 in light wind conditions, the side of the wing on the inside of the turn may stall. <S> Typically, smoothly and promptly coming out of the turn using the brakes, will cause the wing to recover, failure to recover may result in a flat spin. <S> Flying near full speed with minimum brake also risks a deflation of the wing on the left centre or right sides. <S> This might be exacerbated if the pilots all-up weight is at the upper or lower weight limit of the glider; typically gliders come in xs s <S> m l xl sizes. <S> Prompt appropriate use of the brakes is pretty much all a paraglider pilot has to recover normal flight in all the scenarios above. <S> If in doubt pilots should follow the instructions in the gliders manual and ensure they have enough recent flying hours in the conditions they wish to fly that they can do so safely, ie not freeze, recognise the symptoms of a stall for their glider, and react appropriately. <S> Like all aircraft it won't be possible to recover from a stall below a certain height, so a pilot should have enough skill not put themselves at risk whilst still having fun! <S> I'm guessing their priority will also be to get air flowing over the wing by pulling in on the control bar - but I'm only guessing as I was a PG pilot not an HG pilot. <A> Well in case of hang gliders there is notable amount of force on speedbar (control handle) which always tries (in case of properly designed glider) to move speedbar back to trim speed position which is near stall + 10kph. <S> Also, due to combination of swept wing and washout (root has higher AoA than wing tips) <S> stall starts from the root of the wing and causes slight nose drop. <S> If pilot won't resist to it wing will restore its speed and full stall will be prevented. <S> Full stall usually requires pilots intended actions and is performed only during landing flare. <S> In rare cases full stall may happen in-flight as well, but it is result of poor decisions or aerobatics which is prohibited on HG. <S> In most cases full stall is ended up with tumble and throwing of reserve chute -
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I imagine hang glider pilots will feel and hear the wind, and be aware of the pressure on the control bar.
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How does an aircraft recharge its batteries? I assume aircraft have batteries that power up all electronic devices on board. But how are these batteries recharged? When the aircraft is on the ground, it can be connected and recharged in the airport, but mid flight? Is there a way to charge the batteries in the air ? Next question, bit trickier: how many devices must be plugged by the passengers (via USB) and how long it takes to drain all energy on board of a 787 ? <Q> The engines turn generators which supply the electrical power to the aircraft, including a battery charger that keeps the battery at 100%. <S> (Normally, power coming "from the battery" on the diagrams, is actually coming from the battery charger or another component like a Transformer-Rectifier converting AC to DC current. <S> The battery is very rarely actually being drained in flight.) <S> If you had an aircraft battery & went to deplete it with USB devices, it would take a lot of them & a really long time. <S> Aircraft batteries store power way beyond what our normal cell phones & iPads do, and can power all the emergency systems on the jet for an hour or more (radios, INS, flight instruments, minimal lights, GPS, flight management system, etc). <S> Of course, if you're down to just the battery, in-flight entertainment is NOT one of the systems being powered! <A> The better way to think of it is this: the electrical system of an aircraft is not battery powered at all. <S> It is powered by engine driven generators or alternators. <S> These devices provide all the electrical power used while the aircraft is operating in the air or on the ground. <S> However, when the engine(s) isn't/aren't running, electrical power is needed to operate some systems and (for many aircraft), start the engines. <S> Once the engines are running, excess generating capacity is used to recharge the battery(ies). <S> If the engine(s) or generator(s) fail in flight, the battery(ies) take over to power essential aircraft systems. <S> Many aircraft also have APUs (auxiliary power units). <S> These devices are engines which drive generators, air compressors, and perhaps also hydraulic pumps, but produce no thrust. <S> Their job is to provide auxiliary power for an aircraft when its main engines (the ones that provide thrust) aren't running. <S> Most larger multi-engine aircraft have them, as do all large airliners. <S> Typically, when an airliner is parked at the gate, its main engines are shut down, and its on-board electrical needs, air conditioning, etc., are being supplied by the APU. <S> The APU is kept running until the main engines have been started (usually when it is pushed back from the gate). <S> At the end of a flight, before the main engines are shut down, the APU is started again. <S> In this case, the only role for the batteries is as a backup source of electrical energy. <A> Every now and then I get to fly two DH82a Tiger Moth that are retro fitted with batteries and alternators to provide power for the radio and transponder as this type originally was not fitted with any electronic systems -- along a few other things e.g. brakes, tailwheel, flaps, a reasonably-sized windscreen, adjustable seats, some useful avionics and of course cabin heater or air conditioning. <S> The alternator is basically a small windmill turbine located under the belly of the aeroplane and between the undercarriage. <S> I believe the alternate doesn't start properly recharging the batteries until you have a good healthy airspeed, although it windmills after the engine starts. <S> You can see it actually in this photo of one of our two Tiger Moth: <S> Also these aeroplanes don't have any USB outlets, so we usually recommend the pilot and passenger to fully charge their mobile devices before each flight, specially if it is a long-haul flight.
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The aeroplane's electronics are driven by the battery which usually gives us 5-6 hours of operation time I guess, however, with the installed alternator -- given they are not broken, the batteries get recharged mid-flight and once in a while on the ground using battery chargers too -- batteries should be detached in order to be charged on the ground.
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Would a gimbaled, always horizontal cockpit be beneficial to fighter jets? Would it be possible to have a spherical cockpit that was gimbaled in jets such as fighters so the pilot was always upright. With all controls in the cockpit wirelessly communicating with the rest of the jet? Wouldn't this be an advantage as it would be easier to aim and the pilot wouldn't get disorientated and could see anywhere by maneouvering? <Q> With enough engineering (read, money), all sorts of things would be possible, but if you picture the aircraft in a hard, level turn, the g-forces would be pressing "down" relative to a conventional cockpit, but "sideways" for a cockpit that was gimbaled so the pilot was sitting upright relative to the horizon. <S> And that would probably be a lot harder to take than the usual "down" G-forces. <S> Resisting 9 G's pulling your hand and forearm straight down can be done with a support for your arm (side-stick controller) or a bit of a ledge at the bottom of the handgrip (side-stick or center stick), but keeping precise control of the aircraft with 9 G's pulling your hand sideways might be a lot harder. <S> Beyond that, the sideways G force would be pushing your head to the side, which probably ends up banging your helmet -- pretty hard sometimes -- against whatever restraint or canopy it meets. <S> Something that achieves some of the goals you mention is the "Virtual Reality" helmet of the F-35, where the pilot can essentially look through the airframe and "see" aircraft, targets, and whatnot even in places that he wouldn't have an actual line-of sight. <S> That allows him to look in any direction, reacting to threats, tracking his target, and so forth. <S> And without having to gimbal the cockpit. <S> Although for what the F-35's cost, that might actually be cheaper! <A> How would this be 'easier'? <S> The pilot would have no direct reference to the orientation of the aircraft. <S> The upright pilot pulling back on the stick would expect the aircraft to pitch up. <S> With the aircraft in practically any orientation the actual effect could be anything, including pitch down. <S> How would you map the control inputs to the actions of the aircraft in a way that would make any sense to the pilot? <A> The actual biggest issue with this is that in many maneuvers the pilot does NOT want to be upright, precisely because of the G forces involved. <S> In a fighter jet, a sudden nose down maneuver from level flight produces negative G forces - it causes the blood to rush to the head, producing a "red out", which is very painful and potentially lethal. <S> To counteract that, fighter pilots roll the aircraft so that its inverted (belly up to the sky, cockpit down to the ground) and then pull back on the stick to "climb" downwards. <S> This produces positive G forces on the pilot, forcing blood to rush into their lower limbs, triggering a "black out" - but the pilot can control this by use of their g-suit and various exercises to force blood back up the body. <A> When maneuvers are executed, usually you want the resultant force to be exerted along the axis head-foot, like weight is exerted, because you already know how to fight weight / gravity, and this about all that you are able to do easily and safely. <S> Source . <S> In an aircraft, the aerodynamic force is (more or less) normal to the wings, even in a turn properly executed. <S> So it's more natural to continue to have the body normal to the aircraft floor than having it gimbaled and having a transverse force to fight against, poorly.
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So, no, you don't want the pilot to be level and upright all the time, often the pilot will deliberately make themselves not upright because its safer and more pleasant.
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What are the differences between the SR 71 variants? I read that all SR 71 blackbirds were different, what was different with each one and is one regarded as superior to the rest? Why? <Q> Like every military aircraft built over the years, the aircraft evolve. <S> So to address the aircraft's history and all variants, let's refer to it as the Blackbird. <S> The Blackbird started out as the A-12 procured for the CIA. <S> Fifteen of these were built with one being a 2-seat trainer. <S> Two of the 15 were modified into M-21 aircraft prior to delivery. <S> The M-21 was designed to launch the D-21 drones. <S> The SR-71 at the Intrepid museum (60-6925) in New York was built as an A-12. <S> One of the M-21's is at the Museum of Flight in Seattle with a D-21B drone. <S> Three high-speed interceptor prototypes were built and designated as the YF-12A and were capable of carrying 3 air-to-air missiles. <S> Two crashed and the third is at the National Museum of the AF . <S> The interceptor was cancelled and the RS-71 program, renamed SR-71 after LBJ's misstatement at the press conference, went forward for the AF. <S> Twenty-nine SR-71A's were built along with 2 SR-71B trainers. <S> When one of the trainers was lost in 1968, the surviving aft part of one of the crashed YF-12A's was mated to the front part the SR-71 static test aircraft to create the sole SR-71C. <S> There's a huge Blackbird community online. <S> Detail specs and history are available at blackbirds.net and at <S> SR-71 Blackbirds . <S> The question of which is superior is an opinion, but one can assume that the SR-71's were "better" than the A-12's as they came later building on what was learned from both the A-12 and YF-12A. <A> You may be referring to the fact that pilots felt that all Blackbirds seemed to have a distinct personality e.g. 962 was a hangar queen - a real lemon - whereas 972 never let you down. <S> Blackbirds were virtually a hand built airplane <S> but as to whether each one was different may have just been a matter of opinion. <A> There are a few variants of <S> the SR-71 but there is only 1 that was ever used in an active military role. <S> The YF-12 was the SR-71's initial test airframe . <S> Of the three airframes build tests were carried out by the Air Force and NASA. <S> Notice the nose is slightly different than the eventual production version. <S> ( source ) <S> A twin cockpit instructional SR-71 (SR-71B Serial Number 17956) airframe was built to train the pilots. <S> ( source ) <S> As far as I know the SR-71 only had one airframe variant, the SR-71... <S> ( source ) <S> The airframe was however capable of carrying a wide variety of payloads as dictated by the mission. <S> You can find a nice overview of them here . <A> If you measure them in stealth, max altitude or speed. <S> A-12 comes out on top. <S> (not that stealth ended up mattering as Russians started to hook up computers to their radars and would then be able to spot the A-12s, they were never flown over Russia for that reason.) <S> If you measure in armament YF-12 would come out on top. <S> ( image from cia.gov article OXCART vs Blackbird: <S> Do You Know the Difference? )
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If you measure them in surveillance equipment or range, SR-71 would come out on top.
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Is it normal for instantaneous GLOC to occur at 5 G's? Is it normal for a trainee to have an instantaneous G-force induced loss of consciousness (GLOC) at 4-5 G's in a light military trainer aircraft like Socata TB 30 Epsilon, after doing a manoeuvre sequence? <Q> That sounds really unlikely to be a G-LOC. <S> That usually happens at much higher loadings after 3-4 seconds of straining. <S> The counscious and cognitive centers of the brain take a few seconds to shut down once the systolic and diastolic pressures hit zero in the brain. <S> It may be an indication of another underlying medical issue. <A> I agree that doesn't sound normal. <S> I didn't strain unless I was pulling in excess of 4 and never experienced any ill effects. <S> I also never had a student GLOC and we would pull north of 6g's pretty routinely. <S> They should definitely be checked out medically. <S> I will caveat this because you used the word instantaneous. <S> It would not be unusual in my opinion for your student to go to sleep if they were pulling a sustained 5g's and were not correctly using their g-strain. <S> Every person's resting g-tolerance is different, and can be higher or lower on any given day based on a lot of factors. <A> Normally, there should be signs of oxygen deprival before full loss of consciousness. <S> In my experience, first the field of sight narrows down as if someone drew a curtain in the eyes (tunnel vision), and then you go totally blind. <S> This would happen to me at maybe 1 g less than usual when preceded by inverted flying, but still only above 4 g. Hearing and reasoning are not yet affected - for this it needs more gs. <S> How many depends on how long the load factor lasts and on general health. <S> Training also helps, as do breathing techniques like the anti-g straining maneuver . <S> From an FAA brochure on this topic: This is a physical technique where the aviator pushes air out of the lungs against a closed glottis, while simultaneously contracting the muscles in the calves, thighs, and shoulders. <S> is resistance inhibits the blood from owing away from the brain, and it simultaneously increases the pressure in the carotid arteries. <S> Instantaneous G-LOC is only possible with very rapid rates of g increase to a level above 6 to 8. <S> At 4-5 gs this should not happen to a healthy person.
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I would recommend to see a physician about this.
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Could the V-22 Osprey be used as a close air support platform? I saw the US was looking for a new close air support plane. Why do they not use the V-22 Osprey ? It is able to travel slowly and could carry more weapons than an A-10 , for example. <Q> Can it be? <S> Sure. <S> Let's take a look at what it would be replacing. <S> The A-10 was designed from the ground up to be a platform for moving the GAU-8 into range of the target. <S> It has good low speed flight characteristics. <S> The engines are mounted high and to the rear to protect them from FOD (both debris kicked up by the GAU-8 and hostile weapons fire). <S> The cockpit is within a 540Kg titanium armored tub to protect the pilot and critical flight systems. <S> It has wing hard-points for carrying additional munitions should the GAU-8 not be sufficient for the current mission. <S> Why won't the Osprey be adapted for CAS? <S> Because it travels slowly, it's susceptible not only to MANPADS and other traditional AA systems, but simple small arms fire becomes a threat. <S> For example, the Douglas A-1 Skyraider (which the A-10 replaced) - a "propeller-driven design was also relatively slow and vulnerable to ground fire. <S> The U.S. Air Force and Marine Corps lost 266 A-1s in action in Vietnam, largely from small arms fire ." <S> ( Source , emphasis mine) <S> Those huge props (38' diameter, which is smaller than the optimal 43' ( Source ) ) are a very vulnerable target - damage to them may make the aircraft unflyable. <S> Hits to the engine rotation system that may not cripple <S> the aircraft may cause it to have to land with the props in the vertical plane instead of horizontal. <S> They're designed for this without destroying the rest of the aircraft, but that means thorough inspections and expensive prop replacement prior to its next flight. <S> It could have an armored cockpit surround retrofitted, but it's not designed for it. <S> It could have hard-points mounted, but they would need to be integrated with this swing-wing mechanism which would significantly increase the design/build cost and complexity <S> The swing-wing (used for stowing the plane on a carrier) could be eliminated, but that would defeat one of the main uses of the aircraft. <S> It's highly likely that the replacement for the A-10 (current thought trends toward the F-35, but that's contentious) will be more similar to the A-10 itself. <S> That kind of role has some unique requirements that can be fulfilled by a more multipurpose aircraft, but not as well. <A> The V-22 is not without its strong points as a support aircraft. <S> However, CAS is a specialized role for which it will never truly be ideal. <S> That's not to say it wouldn't be feasible to deliver weapons with one, once modified appropriately. <S> The good news is that you could likely bring it up to roughly attack-helicopter levels of armament. <S> I estimate you'd get roughly AH-1 levels of firepower, but with a transport capability and over significantly longer ranges. <S> Essentially, you'd end up with a sort of modern, squishier version of the Mi-24. <S> The squishiness is a significant concern though. <S> Compared to virtually any rotary wing platform, the V-22 is large and loud. <S> It's easier to acquire by sensor, by sight and by ear. <S> It's also not particularly resistant to ground fire. <S> In that sense, it bears some of the some limitations of UH/CH platforms or "C" class fixed wing A/C. <S> In that sense, a weaponized Osprey is actually competing to be a newer-bigger MH-60L Direct Action Penetrator. <S> You could also view it as an update to AC-47D (Puff the Magic Dragon). <S> There is certainly a niche there, but as a general purpose, high performance, ground attack <S> A/C it falls short. <S> As noted above, external stores would degrade performance and there would be limitations imposed by the airframe concerning capacity. <S> When you start taking weapons off the table, you start limiting capability. <S> My verdict: - Viable long range, rotary-wing, general purpose support/strike platform- <S> Not a true/ideal replacement for fixed-wing CAS capability <A> CAS, no. <S> Mini-gunship, firing standoff weapons in coordination with marines on the ground, quite likely will happen. <S> The V22 should be able to substitute, albeit with less effectiveness, any role the C130 performs for the marines(cargo, tanker, gunship, ISR). <S> There will be scenarios where C130s can't get to the airspace but V22s are embedded with the MAGTF and will always be there. <A> The V22 will be contributing as a CAS platform for the USMC along with KC130s until the service finds a suitable platform to replace the A10. <S> Marines are actually running out of fighter jets. <S> At this point, only about 87 of its 276 F18's are serviceable at any time. <S> For any flying arm, roughly 30% availability is really bad! <S> And the A10 cost \$20,000/hr flight time and is increasing constantly because of the aging of the airframe. <S> The services gambled with the F35 and lost, so until the F35 is combat worthy or is scrapped and a suitable replacement is found for CAS role, the under-funded marine corps is making due with what they got. <S> The Harvest Hawk modification kit for all the services KC130s, adds an electronic jammer, a Target Acquisition and Designation System, and hard-points. <S> Load-outs have featured as many as four AGM-114 Hellfire and ten AGM-176 Griffin missiles. <S> They’re hardly as sophisticated and capable as AC-130U/W/J gunships, but the modular kits cost far less(\$10 million vs. \$200 million). <S> The Osprey’s weapons kit is less defined. <S> With hard-points for targeting equipment and laser-guided missiles—APKWS or Viper Strike. <S> And they will be capable of such functions, though just as DanS said, "albeit with less effectiveness".
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The speed, altitude and maneuverability of the platform will never be ideal for integrating into fixed-wing A/C formations, nor will they confer the ability to out run or out fight even the most outdated of adversary fixed-wing A/C in an unescorted role (an A-10, for example, is more than an match for a V-22 air to air).
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Are tower simulators used in civil ATC training? Pilots use cockpit simulators, what about training of air traffic controllers working in control towers? Control tower of Québec / Jean Lesage airport (CYQB). Source . How do they train? Are there full visual simulators with runways, taxiways, radio traffic, etc? The question is valid for a country with large aerodromes. <Q> Absolutely (and not just civil ATC training - military as well). <S> A large part of modern ATC training is simulator training. <S> This is true for all types of ATC - area control, approach and aerodrome (tower). <S> For area and approach, the simulator is fairly simple, since the essential bit is a radar screen and a screen with flight information. <S> For tower, there is the visual aspect as well, which makes tower simulators quite large and complex. <S> Some tower sims are relatively simple - 4 big TV-screens with a 3D model of the airport, and a couple of computer screens with radar and other equipment. <S> There are also full size, 360 degree sims, where the "windows" are created by an array of projectors or large screens. <S> After working traffic in one of those for a few minutes, you start to forget that you're not in a real tower. <S> During simulator training, students can run scenarios in the simulator that are either based on generic airports or real airports. <S> The traffic levels and situations can be tailored to match the expected learning curve of ATC students. <S> This makes simulator training a great tool for both initial and recurrent training of air traffic controllers. <S> Much like pilots, after getting our license, we have to go back to the sim once a year to practise unusual situations, emergencies and so on. <S> For every controller position in the simulator, there are 2-3 connected "blip driver" positions, from where the aircraft movements are controlled. <S> The controller in the simulator will talk to the blip drivers via "radio", and the blip drivers will respond as pilots and provide the necessary input to make the planes move around accordingly. <A> In fact: yes! <S> Here in Germany the controller training starts off with much classroom lessons to learn the theoretical basics and only some sessions in the tower- or center simulator. <S> During the training the amount of theoretical lessons decreases and the simulator sessions increase. <S> The last few month consist of simulator sessions only, so it's a huge and important part of the training. <S> A video about the so called "towsim 3D" can be found here . <S> And here are some pictures taken by me (click each for higher resolution). <A> For civilian control towers and the assorted radar positions <S> For the tower: <S> ( Image source + more info ) Click image for high-res. <S> The simulator consists of two modules: Radar control simulator to simulate air situation in area of any complexity level, size and intensity of air traffic; controller’s workstation interface is completely equal to real ATC system interface produced by NITA, and Tower simulator which includes 3D projection system for airfield and landscape image representation (solution based on high resolution wide-screen panels is an option). <S> There are about 100 models of airplanes and helicopters of various types, colored as aircraft of world and domestic airlines companies, as well as the models of ground vehicles, people, and animals. <S> In order to simulate real environment for Tower controller the seasons, daytime, precipitation, smog, light storm, and various clouds are simulated. <S> On job training from an actual tower is also very common. <S> Tower simulators are also available for the military . <A> An example video of a professional ATC simulator can be seen here . <S> It shows that not only tower control training is supported, but also ground control (executed from the tower cabin), approach, and area control. <S> The student can be at various skill levels (to become a controller, to refresh current controller license, to transfer to a different working site). <S> It is also used for AFISO training (for Flight Information Service training). <S> Training can be targeted for any purpose: Military operations, VFR traffic, de-icing conditions, emergencies like bird strike, fire situations, and so on and so on. <S> More in-depth descriptions can also be found at this blog , mainly about the simulator and how it works, but also other areas where an ATC simulator can be used: New airspace design, airport construction work, and more.
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The answer is yes, tower simulators are indeed used in civil ATC training. the answer is yes they're available.
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How are aircraft shipped to their customers? This is sort of the inverse of this question . I was looking at the Boeing facility in Renton, WA in Google maps, and I realized, the airport is across the (Cedar) river from what I assume to be the construction facility. The Boeing facility in Everett, WA is also across Highway 526 from the airport. That prompted this question: How is an airplane that just finished getting built (in any facility) delivered to the airline that bought it? This question is targeted at large passenger aircraft being delivered to airlines. <Q> As for the Boeing factory its self, the Everett Factory users Paine Field as their runway. <S> If you look closely there is a bridge that crosses the highway and connects the plant to the main ramp of the airport. <S> This appears to be painted for car traffic but is also used for aircraft. <S> The Renton Factory lies adjacent to Renton Municipal which it uses to fly the aircraft in and out there <S> is also a small bridge connecting them over the river . <S> Similarly the main airbus factory is located next to Toulouse–Blagnac Airport . <S> Bombardier lies next to Montréal–Pierre Elliott Trudeau International Airport . <A> Final assembly usually takes place at a location with its own runways or collocated with an airport, so once airframe assembly is complete, the aircraft undergoes its final inspections, test and acceptance flight and is then simply flown to a location specified by the customer, typically a hub or maintenance base. <S> To use the Everett facility as an example, it is adjacent to Paine Field (KPAE) and the assembly facilities have direct access to the airport environment. <A> In general the customer sends their own pilots out to take delivery of the airplane. <S> Usually they are immediately pressed into service. <S> When I was out at the Everett facility in summer 2000, we had customers who would pick up a 777 at KPAE, then make the short flight south to Sea Tac Intl <S> right to the gate and immediately fuel and load it for a intercontinental flight. <S> Most aircraft factories are located at public airports for exactly that reason. <S> See the VFR sectional for the Wichita KS area. <A> Boeing does not ship airplanes to customers! <S> Getting the wings put on happens at Boeing, because they have the equipment & expertise to perform this crucial step correctly; that's not something you want being done after delivery. " <S> Some assembly required" works fine for many things, but not for airliners! <S> When the airplane leave the factory, it is flown to the purchasing airline -- typically by that airline's own pilots, as discussed in this question .
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They are flown to their customers by either Boeing or pilots from the given airline.
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Is a compressor blade slowing down the airflow or accelerating it? When a jet aircraft flies at maximum speed, are compressor blades actually a barrier to the air flow, or is the airflow accelerated by the compressor? <Q> are compressor blades actually a barrier to the air flow, or is the airflow accelerated by the compressor <S> These are not exhaustive alternatives. <S> Keep in mind that subsonic fluid flow when constricted accelerates and pressure decreases ( Bernoulli's principle ). <S> What the compressor does is increase the pressure. <S> The speed decreases slightly. <S> are compressor blades actually a barrier to the air flow <S> Actually it's complicated. <S> In a sense they are. <S> The compressor always takes the air at around M0.5 irrespective of flight speed. <S> That means at slower speed the engine needs to suck air from wider stream while at higher speeds some air is spilled over the intake lips. <S> So in a sense, the compressor is a barrier. <S> But then, the compressor must increase the energy of the stream, otherwise the engine could not produce any thrust. <S> Just the energy goes in pressure, not velocity. <S> So in this sense it is definitely not a barrier. <S> In fact, the thrust acts mainly on the compressor, because that is the most significant aft-facing surface on which the pressure in the combustion chamber can act. <S> At supersonic speed it works differently. <S> Now pressure changes can't affect the flow upstream, so the air can't be spilled over the intake lips anymore. <S> Instead now the intake must decelerate it by shock waves and then expansion in a diffusor. <S> This is needed, because turbomachinery only works well in subsonic flow¹. Since pressure increases as the flow speed decreases, this also increases the overall pressure ratio of the engine and thus its efficiency. <S> Note that the air also heats up, via adiabatic heating , as it slows down and compresses. <S> Somewhere around M5–6, the air becomes so hot from the compression that adding more heat to it by burning fuel <S> is no longer practical, so above that speed, the combustion must occur in supersonic flow. <S> This is the scramjet engine. <S> It does not have any compressor or turbine, because it gets all the compression from constricting the flow and it turbomachinery wouldn't work at that speed anyway. <A> Jet engine axial type compressors rotor blades do accelerate airflow. <S> It is important to note that the net speed change in velocity is usually negative, that is, airflow through the compressor section taken as a whole is usually slowed. <S> Additionally, the engine intake generally slows airflow as well while increasing pressure. <S> This occurs within the airflow prior to direct contact with the compressor. <S> Jet engine axial compressors are comprised of multiple pressure stages with the primary design of increasing pressure, not velocity. <S> Each pressure stage is comprised of pairs of rotors and stators. <S> The rotors consist of rows of compressor blades arranged radially on a rotating spindle. <S> The stators consist of fixed rows of vanes arranged radially and placed after and between the rotors. <S> Subsequently, the stator vanes and the decreasing geometry of the compressor design slow the speed and change the airflow direction (which is also an acceleration). <S> Each pressure stage raises the pressure, typically with a small net decrease in speed. <S> See the following figure and text excerpt from the Jeppesen A&P Technician Powerplant Handbook: <S> The task of an axial compressor is to raise air pressure rather than air velocity. <S> Therefore, each compressor stage raises the pressure of the incoming air while the air's velocity is alternately increased then decreased as airflow proceeds through the compressor. <S> The rotor blades slightly accelerate the airflow, then the stator vanes diffuse the air, slowing it and increasing the pressure. <S> The overall result is increased air pressure and relatively constant air velocity from compressor inlet to outlet. <S> Figure 3-29 <A> Well some basic math might reveal the answer. <S> If a turbojet has a compression ratio of say 20:1, gas flow entering the combustion chamber will be at a 20 times higher pressure than the gas flow entering the engine inlet. <S> If we assume the overall cross sectional area of the gas passage through the stators and rotors in the compressor does not change (this is usually not the case) then the gas flow would have to slow. <S> Since Mdot <S> = rho <S> * Vdot <S> = rho <S> * A <S> * vdot and by IGL for simplicity, P = rho <S> * R <S> * T <S> this gives Mdot = <S> (P/RT) <S> * A <S> * vdot <S> Since Mdot and A remain constant and P increases, vdot must decrease to compensate. <S> While temperature does increase, it is not enough to compensate for the change in pressure, which can be shown with a sensitivity analysis. <S> Ideally you want to decelerate the gas flow as little as possible as the decrease in momentum creates a drag impulse upon the engine. <S> Both centrifugal and axial ompressors narrow in volume as gas flows through the core to reduce this.
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The compressor blades of the rotors accelerate the airflow and impart a momentary velocity increase.
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Where does the difference between calculated and actual groundspeed come from? I'm a paragliding pilot. At school we learn that the trim speed of a paraglider is about 38km/h airspeed, the accelerated airspeed is about 45km/h and the minimum airspeed is 22km/h - being inside the weight range of the wing. If I fly with a headwind of 25km/h, my groundspeed should be: 38-25=13km/h. Well, from my flying experience (1200 flights in total) with that kind of headwind I never went forward +13km/h groundspeed but much less, near the minimum relative speed (22km/h). Why there's a difference between the calculated groundspeed 13km/h and the actual groundspeed? <Q> I have a little paragliding experience. <S> While only a tiny fraction of yours, I think I can answer your question, which boils down to: data accuracy. <S> The trim speed of a fixed-wing aircraft would depend on its weight. <S> Without accurately measuring the pilot's weight (FYI the measurement in small aircrafts is precise to pounds / kilograms) and plotting that against a chart, the speed you were told in school is only an approximation. <S> I (like others in the comments also) question the accuracy of your speed data. <S> To accurately measure forward airspeed, you'd need a pitot tube pointing in the right direction . <S> Or you can use a wind measuring device which measures speed and direction To measure your ground speed accurately you'd need a GPS. <S> To combine the two (wind speed + ground speed), you'd need some sort of computer to do the computation, either in real time or with recorded data. <S> The ground station only measure wind speed at ground level. <S> When you're up in the air (albeit relatively low compared to aircraft), the wind can be different. <A> It also depends on doing your winds aloft calculations correctly and accounting for both the wind speed AND angle relative to the direction of flight. <S> Take the winds at a 60° angle, our headwind component is only going to be half the total wind speed, etc. <S> Then there are installation and calibration errors. <S> I don't know what a paraglider has on it in order to sense airspeed but a primitive pitot static system of some sort would be a reasonable guess. <S> I don't know what kind of error may be associated with that as well. <A> Actual groundspeed is not in itself a useful (or deterministic) number while flying. <S> It's useful as a concept. <S> You get your measured ground speed from your instruments / sensors. <S> They'll give you a reading that's as accurate as you can get. <S> This isn't enough for most flights however. <S> Even in 2017, our data is still faulty. <S> In engineering, the difference between actual and measured anything is called the error . <S> In this case, groundspeed has an error while using instruments. <S> Errors usually come in ranges. <S> For example, in paragliding, you may see a measured groundspeed of 12mph, with an error of +/-1, meaning that the actual ground speed can be between 11 and 13 mph. <S> Error can also have two parameters as it's range. <S> For example, you may be going along at 12 mph, and have an error of +2/-0, meaning that actual speed is between 12 and 14 mph. <S> usually one of the parameters in a two-parameter error will be zero. <S> If they're both non-zero, non-equal values, you're going into probability distributions, and other mathematics of the sort.
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It depends on the difference between the predicted wind speed for the winds aloft vs what was actually up at that altitude at a given time.
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Is the old paint removed before applying a new one? I've heard that paint on large airplanes weigh 250+ kg. When an aircraft gets a new owner, do they remove the paint that was previously on or simply paint over it? If it is removed, how is it removed? What is the correct procedure for painting/repainting an aircraft? <Q> Yes, paint imposes a significant weight penalty on larger aircraft. <S> On commercial airliners, that weight translates to a reduction in cargo, passenger and fuel carrying capacity, and that means less money to be made on every flight. <S> That is why some airlines have chosen to remove most of the paint and opt for the bare-metal look. <S> However, there are tradeoffs to be considered, such as the fact that bare metal is much more susceptible to corrosion. <S> These days removing paint from an aircraft is a relatively straightforward proposition if you know what you are doing. <S> There are a number of environmentally-friendly paint stripping chemicals available that when applied to the aircraft surface, cause the paint to bubble and lift off the underlying airframe. <S> Other products are then used to clean remaining residue, treat the metal for corrosion protection, prime and paint. <S> This explanation is intentionally simplistic, but it covers the basics to answer your question. <S> If you want to see the process in action, you might check the many YouTube videos that show time-lapse recordings of aircraft being painted. <S> Personally. <S> I think they are fun to watch. :) <A> Adding to Juan's answer: <S> It depends on the new operator (I intentionally didn't say owner). <S> If the new operator is leasing the plane for a short time, they usually just use easily removable decals (which may look ugly after some flying). <S> Even if the operator doesn't change, the plane is repainted usually once every 5 to 8 years as this KLM blog explains . <S> In this case the old layer is indeed removed. <S> Sanding and stripping <S> An aircraft can be disrobed of its old paint coat in a number of ways. <S> A Fokker is sanded by hand with a sander. <S> A Boeing or Airbus is partially sanded, partially stripped. <S> Stripping is carried out using a liquid which, at 25°C, can strip an aircraft of all its paint in 24 hours. <S> Once all the old paint has been removed, the primer is sprayed onto the aircraft. <S> It takes around six hours for each layer to dry. <A> If you're referring to airliners, the paint indeed has a significant effect on the aircraft weight and more importantly center of gravity. <S> Airliners are mostly sold on plain white, with all but mandatory markings removed. <S> Aircraft must also be weighed regularly every 3-5 years, even if no painting or other modifications are made.
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When a new paint-over is done, the aircraft must be weighed to determine the new weight and CoG. Small partial paintings can be made without the need to weigh the aircraft, but unfortunately I don't know what are the limitations. The paint can then be scraped off with plastic tools or removed with a pressure washer, and the stripping chemical is washed off.
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Is there a standard format to exchange airspace information in electronic form? I am looking for information about airspace definitions. On maps they look great and a pilot has no problem reading maps and NOTAMs, but what about autopilots? Do they use some kind of standardized interface/database? If it exists, where is it defined? I am not specifying a country because hopefully there only one standard (or an extremely limited set). Should this not be true, I would like to focus on Europe and North America. <Q> The actual database each uses is typically encrypted and compressed using proprietary algorithms. <S> The source data for all of these databases normally start out in ARINC 424 format. <S> Unfortunately, A424 is not available free of charge. <S> The ARINC 424 specifications are not a database, but a "standard for the preparation and transmission of data for assembly of airborne navigation system data bases". <S> The databases are compiled by companies such as Jeppesen . <S> Jeppesen collects the data from the controlling agencies around the world, checks it, and merges it into a world-wide database that they then sell (typically via subscription). <S> Some information for US airspace is available directly from the FAA . <S> It is not in a format that can be directly loaded onto aircraft, but may be of use offline. <A> Aerodrome/Heliport including movement areas, services, facilities, etc. <S> Airspace structures Organisations and units, including services Points and Navaids Procedures <S> Routes <S> Flying restrictions <S> The Forum on the AIXM site is pretty responsive but relatively quiet. <S> The data available through AIXM seems to be mostly European based but the system was not designed to be restricted to EU. <A> There's also a "new" kid on the block: <S> The open source initiative <S> Open Flightmaps <S> offers curated eAIP for many countries free of charge. <S> The custom format OFMX is a fork of AIXM 4.5 which adds and will add new features and modify very few existing features in order to accommodate things like proper obstacle groups, plate packages etc. <S> It should be fairly easy to adapt an existing AIXM 4.5 parser to consume OFMX by following the migration guide .
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The majority of GPS navigators and FMS have a dataloadable navigation database. ARINC 424 is an international standard file format for aircraft navigation data maintained by Airlines Electronic Engineering Committee and published by Aeronautical Radio, Inc.. The Aeronautical Information eXchange Model (AIXM) was designed to provide a standard model of data exchange for things like:
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Is this a famous aviator / airplane? This may be a little off topic but I could not find a better community or website. I have two photo postcards with a man in front of a plane. Pretty sure it's Charles Lindbergh but an exhaustive Google search for anything related visually has only turned up another picture of CL with a similar jacket on. So is this who I think it is? Can anyone come up with a "verifiable" narrative to accompany these photos? Perhaps the type of plane in the background? <Q> Thanks to the research of the other two answers, I finally found the context for these two photos. <S> The following page describes the events leading up to the photos, although the original is in German: https://www.boeblingen.de/,Lde/start/WirtschaftEntwicklung/Chamberlin.html Long story short, he was attempting to beat Charles Lindbergh on the transatlantic record, but Lindbergh won due to numerous delays. <S> Chamberlin decided to go a little further, to Berlin, and beat the distance record instead. <S> There were numerous technical problems with his plane, however (the Miss Columbia ), and he ended up having to land in Eisleben, about 90 miles west of his goal on June 6, 1927. <S> After a day spent repairing the plane, he then proceeded to Berlin. <S> The event seen in the photos is a parade/celebration thrown in his honor as he leaves on the 15th. <S> By comparison, here's a photo from the same event showing Chamberlin in the same clothes: <S> I was unable to identify the specific plane behind him in the photos, but it was NOT the Miss Columbia . <S> Due to the many technical problems experienced during the race, Chamberlin elected to return by sea. <S> What we see in the photos is him about to board a passenger plane that will take him to the ship. <S> As far as I can tell, the Miss Columbia was shipped back separately, although his co-pilot (and the plane's owner) <S> Charles Levine wanted to fly it back despite the problems. <S> What About the Plane Type? <S> The plane that Chamberlin is boarding in the photos looks to be a Dornier Mercury , which was a common passenger plane in Germany at the time. <S> The door size/shape and top of the plane (what we can see, at least) match up quite nicely. <S> Here's a shot of one from a similar angle: <S> Thanks to @TomMcW for finding that. <A> The pictures are of Clarence Chamberlin, after he landed near Boeblingen in 1927. <S> Thanks to Omegacron for pointing out this website, which also has the exact same picture as the 2nd one you have. <S> https://www.boeblingen.de/,Lde/start/WirtschaftEntwicklung/Chamberlin.html Notice the similar bouquet of flowers, <S> postcards in his front left jacket pocket, and how his jacket is buttoned. <S> ( gettyimages ) <A> ( wikimedia ) <S> I may be wrong, but it looks very like Clarence Chamberlin ; the Wikipedia picture is quite small, but if you look at some other pictures you can see a very strong resemblance. <S> According to Wikipedia he carried the first transatlantic passenger, flew an aircraft off a ship, and was a famous barnstormer. <S> So there are plenty of reasons why he could have ended up on postcards. <S> I don't know what the aircraft is. <S> Wikipedia says that Chamberlin's most well-known aircraft was Miss Columbia , a Wright-Bellanca WB-2 . <S> But the pictures of it show it has a square door under the wing, whereas your pictures show a rounded door rear of the wing. <S> He was also associated with the "Curtiss Condor CO" (a Curtiss T-32 Condor II ?) <S> but again, it doesn't seem to match visually.
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They are indeed of Clarence Chamberlin (a contemporary of Lindbergh) and were taken on June 15, 1927 at the Stuttgart-Boeblingen Airfield in Germany.
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Why do buses at some airports differ from conventional ones? Why do buses at airports differ from conventional ones? Why do they have such wheels or cover wheels at all? Source . <Q> Apron buses are dedicated to transportation in the airport area, the one your show is located near the air museum at Salzburg airport / LOWS ) in Austria. <S> Similar buses are very commonly seen at airports: Apron bus. <S> Source . <S> The bus is traveling on short distances, it's maximum speed is 40 km/h, the price is lowered in proportion of the simplified design (more technical data ). <S> Regarding the hidden wheels, considering the speed and the apron flat surface, this is possible for aesthetic reasons (many additional advantages come for free, e.g. fuel savings, protection against debris and stowaway). <S> More importantly, the bus is a kneeling type type designed to accelerate passenger transfer. <S> The floor can be lowered to: To board and leave the bus more rapidly (no or small step). <S> To be accessible to everybody with no help, including when seated in a wheelchair (no lift required). <S> This may be of some particular interest in a region subject to important snow falls, like in Austria. <S> Wheel access is provided by a panel: Aero ABus <S> But this type of buses also exist with some or all apparent wheels: Source . <S> Airport buses may be wider than regular road buses, they are not subject to public road regulation: Source . <S> The model shown in the question can carry 100+ passengers in standing position (5 seats). <S> Source . <S> Apron buses can also have a bridge included (see also mobile lounges ): Source . <S> Unrelated comment: Salzburg, in addition of being the birthplace of Mozart and a famous ski resort, got an airport well known for its difficult approach during winter snowstorms , with the aircraft flying close to the mountain sides . <A> Washington DC Dulles (IAD) airport had, at least up until a few years ago, giant buses that looked like some 1970's vision of the buses of a moon colony. <S> Source: Wikipedia <S> The reason for this was that the buses articulated up several feet to reach and dock with the terminal buildings and sometimes with aircraft themselves. <S> I remember that they were slow and felt rather weird to ride - almost entirely unlike riding a downtown city bus. <A> Here are some reasons: <S> These buses have different transportation requirements. <S> Mainly, they don't need to drive at high rates of speed, but rather carry large number of passengers over short distances. <S> The reasons the wheels are covered is to reduce the possibility of FOD (Foreign Object Debris) to get inside the wheels and force a repair on the tarmac; note that this not the standard design - many of these busses have exposed wheels. <S> The large windows, lower ingress/egress and limited number of seats are all designed for quick loading / unloading of passengers.
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Protecting the wheels also keeps clear the space needed to lower the bus, and prevent accidents.
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Why has the range of movement of the control surfaces changed over the past year? During the annual inspection on our glider, we discovered that the maximum downwards extension of the right aileron (i.e. full left stick) was outside the manufacturer's tolerance. The measured value was 32mm and the manufacturer allows 40mm ± 5mm. What are the possible causes of a change in the geometry of the system such that the ailerons no longer move in the range they did last year? For reference, the glider is a 1983 Schleicher ASW19b, with standard l'hotelier control connections and aluminium push rods over bell cranks in the fuselage and wings. <Q> We found the problem. <S> The control stops are under the seat and are made of plywood. <S> It looks like at some point in the past someone had added a small layer of plywood to reduce the control deflections but that over time the glue had deteriorated or the wood had swollen, so that there was now too much stop. <S> Removing the extra ply and sanding the glue back to the wood fixed the problem. <A> Or a cable that's become too long (stretched...) causing full deflection to no longer move the surface through its full range of motion. <S> My guess if the aircraft is regularly cleaned and inspected in between flights is the latter, as it's something that's creep in slowly and gets worse over time. <A> Coming to this question late, but a recent experience I had might suggest a reason. <S> While assembling our club's Open Cirrus last weekend with another pilot, we noticed the gap tape on the elevator was missing. <S> My compatriot applied new tape while I attended to other assembly items. <S> After we completed the rigging, we did a positive control check, and, to our surprise <S> we were not getting full deflection on the elevator . <S> After some examination I discovered the issue... <S> the tape was applied in manner that prevented the elevator from moving completely. <S> When you apply tape to an elevator (or aileron) you have to apply the top tape with the control surface down and the bottom tape with the control surface up , thus allowing full movement. <S> Is this your issue? <A> It's very hard to say exactly what is wrong in this case, but much if it is worrying. <S> As it is only one of the ailerons which is not deflecting that does narrow the possibilities. <S> It could be that there is an obstruction which is preventing full deflection, this could be something as simple as foreign object debris working its way into somewhere, or something has come loose. <S> A bell crank could be loose and shifting rather than transferring all of the movement. <S> The wing could have flexed somehow, changing the length of rod needed to deflect the aileron fully. <S> Try having someone hold the stick still while you wiggle the aileron, if you get play in it then it's likely a loose bit somewhere. <S> In any case I would get some professional help on this if you haven't already.
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One of the linkages in the pushrod system could be loose. Possibly an obstruction somewhere, causing it to not move through its full range because it gets blocked by something.
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Which 'pusher' propeller aircraft have been used in active military service? The only 'pusher' aircraft I know of that has been used in active military service is the SAAB 21. There are several prototypes out there, but I can't see that any others were used. Which, if any, other aircraft are there? Maybe the Japanese 'shinden' but if memory serves me that is only a prototype. <Q> If you also count drones, the General Atomics MQ-9 Reaper Drone is a pusher propeller aircraft in active service. <S> Here are some others: <S> Convair <S> B-36 <S> Peacemaker <S> Vickers F.B.5 "Gun Bus" Airco DH.2 <S> Curtis Model E Royal Aircraft Factory F.E.2 Royal Aircraft Factory F.E.8 Voisin III Bomber <S> Boeing <S> GA-1 <S> You may notice that a lot of these aircraft are very old designs. <S> The problem is in 1914 <S> the US Army (there was no US Air Force yet) banned pusher type aircraft after a number of pilots died in them. <S> This mentality carried over on the other side "of the pond" and very few pusher type aircraft entered service after 1916. <S> The SAAB 21 was responsible for the development of ejection seats because a major problem with bailing out was hitting the propeller. <S> Because the prop was behind the pilot, bailing out meant getting pushed through the wood chipper... <S> The B-36 is a good example of this configuration in its limits. <S> It is a massive aircraft with a 19 foot propeller (second largest propellers in use). <S> Engine fires were common due to mounting the engines backwards and not getting sufficient heat over the carburetors. <S> The aircraft was later modified as the XB-60 with swept wings and 8 jet engines but was inferior to the Boeing XB-52 (later becoming the B-52) and was abandoned. <S> The other problem is that a pusher type design contributes a lot to the drag of the aircraft and is relatively inefficient compared to tractor designs. <S> By the time swept wings were in fashion (mostly because jet engines pushed speeds higher and higher), the need for propeller driven military aircraft dropped dramatically in the jet age. <A> The German Do335 'Pfeil' was a twin-engined fighter of the forties. <S> One engine driving a tractor prop at the front, and the other driving a pusher prop at the tail, with a long transmission shaft. <A> The Cessna O-2 (337) quickly comes to mind. <S> Then there are various UAVs, the MQ-1 and MQ-9 are the most prominent. <S> And the Convair B-36 is another good one. <S> The Dornier Do. <S> 335 heavy fighter. <S> The Kyushu J7W1. <A> Here are some more pusher types to add to the list. <S> I tried to ensure that all had some kind of active service record, not including evaluation prototypes or designs not built. <S> With a couple of exceptions noted below, all of these served in the First World War. <S> Fighters and bombers with single pusher propellers: Farman MF.7 and MF.11 ; Breguet Bre.4 and Bre.5 <S> AGO <S> C.II reconnaissance aircraft, single pusher propeller. <S> .(The <S> last two were operational in the Second World War.) <S> Grigorovich M-16 reconnaissance floatplane, single pusher propeller. <S> There were also a number of aircraft that had both tractor and pusher propellers, such as the Caproni Ca.4 bomber (two tractor propellers and one pusher propeller) and the Zeppelin-Staaken R.VI bomber (two tractor propellers and two pusher propellers).
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Flying boats with single pusher propeller: AD Flying Boat ; Aeromarine 40 ; Curtiss Model F ; Hansa-Brandenburg CC and W.18 ; Lohner L ; Macchi M.3 and M.5 ; Grigorovich M-5 and M-9 ; Beriev MBR-2 ; and Supermarine Walrus Various German bombers, each with two pusher propellers: Friedrichshafen G.II and G.III ; Gotha G.II , G.III , G.IV , and G.V ; Rumpler G.I, G.II and G.III ;and Albatross G.III .
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What's the meaning of "straight and level"? Indeed a very strange question. My understanding of straight and level is: The aircraft is flying at a constant heading and constant altitude, and maybe at a constant speed, and this has nothing to do with the aircraft attitude. However I was reading this in " Big Red Today ": "If you just keep it straight and level, the chances of surviving are better," Ms. [...] said. "But as soon as you start to turn, you put yourself at risk of a stall-spin. Here this is clearly about maintaining the aircraft neutral attitude while landing, so losing altitude, and probably speed. Is this use of "straight and level" correct? What is the definition of straight and level, if any, regarding heading, attitude, speed, altitude? Note: Please explain for all parameters mentioned above to remove all ambiguities. <Q> Is this use of "straight and level" correct? <S> What is the definition of straight and level, if any, regarding heading, attitude, speed, altitude? <S> My understanding and the instruction I have received has always lead me to understand that Straight-and-Level is independent of Attitude and Speed. <S> However to maintain straight and level flight at a given speed you will have to put the aircraft in a given attitude . <S> Generally speaking at lower speeds aircrafts have a higher nose up attitude to maintain level flight and a more nose down attitude at high speeds to maintain level flight but this can vary by design and wing mounting. <S> In this case I would say it was used a bit improperly. <S> The statement should have been more along the lines of "the pilot should have maintained his heading and conducted a straight ahead emergency landing. <S> You can read more on why that is here . <S> You can refer to the full NTSB report of the accident here for all the details. <A> I'll quote from Rod Machado 's first ground school lesson: <S> Straight flight means the airplane's nose remains pointed in one direction and the wings are parallel to the earth's horizon . <S> Level flight means the airplane doesn't gain or lose altitude . <S> (my emphasis) <S> Therefore, there are three constraints for "straight and level" flight: <S> Constant heading (i.e. yawing the plane while keeping wings level doesn't count) <S> Wings level Constant altitude (i.e. vertical speed indicator reads zero) <S> It does not constrain: Speed Pitch <S> I believe the author of the article unintentionally used the term wrong. <S> I bet what he meant is "straight and <S> [wings] level", not "level" in "level flight", which means constant altitude. <S> The point in the article is that one should not be making turns while in close proximity with the ground, as keeping the wings level will provide you maximum lift against gravity, thereby reducing your chances of hitting the ground, or even if it does, reduce your impact energy by lowering the velocity change in the vertical direction, or let the landing gear absorb the impact before it hits the fuselage. <A> Straight and level is a kind of the broader steady flight . <S> Steady flight is "a special case in flight dynamics where the aircraft's linear and angular velocity are constant in a body-fixed reference frame." <S> As constant velocity means no acceleration, <S> straight and level is maintaining altitude, heading, and speed. <S> A plane on approach would qualify as a steady longitudinal descent. <S> The omaha.com article's use of <S> straight and level is technically incorrect, but colloquially can be forgiven. <S> The Wikipedia article is largely based on McClamroch, N. Harris (2011). <S> Steady Aircraft Flight and Performance. <S> Princeton, NJ: <S> Princeton University Press. <S> ISBN 9780691147192. <A> Like many phrases, the meaning of "straight and level" depends on the context. <S> Unlike acronyms, or specialized phrases like "surface area of controlled airspace", it's not a phrase that should be considered to be "owned" by the FAA. <S> In aviation, the vast majority of the time, we use this phrase to mean that we are flying in a straight line at constant altitude, with the wings level, without specifying the exact pitch attitude of the aircraft. <S> But in the context of a crash landing, it's logical to assume it might something else. <S> The article would arguably be a little more clear if it said a "straight and level attitude ", or said something like that, but the statement as written need not be viewed as erroneous.
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In the airplane flying handbook the FAA defines straight and level flight as Straight-and-level flight is flight in which heading and altitude are constantly maintained.
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What procedures are followed for a planned landing in a field? If an aircraft was making a planned landing in a field/sports ground/other large flat area what landing procedures would be followed? My thoughts are that it would be very similar to a non-towered airport, with self announcing and flying a bit of a pattern to check the landing area is clear. Obviously this is more likely to apply to helicopter but it could potentially be a plane. <Q> Not just helicopters. <S> It happens all the time in my neck of the woods (Alaska) in small planes with big bouncy tires. <S> We probably have more "field landings" (called bush landings, or "off airport operations") than landings at actual airports. <S> OK, well <S> maybe not quite <S> that many - but enough that my local aviation college has an entire semester course dedicated to it for it's professional piloting program. <S> If there are other aircraft in the area, which sometimes happens at popular hunting/fishing/floating drop-off locations or glacier tours, then self-announcing on frequency is done like at a non-towered airport. <S> But, it's usually remote enough that it's not done. <S> Quite frequently, it's two planes for one party's charter - one to carry the people, and one to carry their gear. <S> In that case, they're usually talking to each other the whole way, and know each other's intentions anyway. <A> One thing to keep in mind when landing on any non-airport grass field: there's a fair chance that you won't notice the small rut in the grass until your nose wheel hits it. <S> That's another reason why it's a good idea to do a low and slow pass over your intended landing area. <S> Another thing to remember is that it's a lot easier to get in than it is to get out. <S> You'd hate to make an awesomely successful landing in a field only to find out that you'll hit the trees at the far end on your way out. <A> First of all, I look for power or telephone lines. <S> The wires are almost invisible against the ground, but poles and towers are more or less conspicuous. <S> Second, the wind has to be right, and third, the surface should be OK. <S> Grass may seem nice, but it can disguise important irregularities, like irrigation ditches. <S> The best is naked dirt, easy to examine by making a low pass...
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The first act is usually a low pass to inspect the conditions and determine the best landing direction (if there is more than one option), assuming that the winds will allow it.
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Why does this regional jet have its air brakes wide open before touchdown? I was looking at a detailed picture of a plane while following its path on Flightradar24.com. Here is the Avro RJ45 I am talking about: I wonder why its aerobrakes at the empennage seems wide opened before touchdown. What I remember from all the planes I took is flaps are at maximum before touchdown and aerobrakes (sometimes automatically) opens when landing gears touch the runway. Is it due to special constraints for this particular aircraft? <Q> ( Source ) <S> F-15 landing with airbrake extended. <S> ( Source ) Airbrakes on the Fokker 70. <S> 1. <S> It allows steeper approaches From Wikipedia : <S> The engines [on the Avro] lack thrust reversers due to their perceived reduced effectiveness in anticipated conditions. <S> Instead, the plane features large airbrake with two petals below the tail rudder at the rear of the fuselage, which has the advantage of being usable during flight and allowing for steep descent rates if required. <S> ... <S> also... <S> Airbrakes on the Fokker 70 's tail section – similar to that found on the BAe 146 / Avro – allows it to conform with the 5.5° glide slope at London City Airport. <S> 2. <S> Some aircraft are overpowered with high power-to-weight ratio. <S> The thrust lever range alone won't be enough to hold the approach speed. <S> The thrust-to-weight ratio for the RJ100 is 0.28:1, compared to 0.16:1 for the comparable Boeing 717. <S> It's even higher for the smaller RJ's. <S> Low power and the plane loses speed, some power and the plane gains speed. <S> So, more power is used in conjunction with airbrakes, such as the F-15 shown above. <S> Once on the ground, they help slow down the plane, same as spoilers. <S> ( Source ) Spoilers. <S> Spoilers have the added benefit of spoiling the lift–transferring more weight to the tires for increased braking capability. <S> Related: <S> Why do some aircraft (e.g. Avro RJ85) have rear-mounted air brakes? <A> Primary reason is speed control. <S> The thrust output of a jet engine does not have a linear relationship to the gas core or fan speed and the most effective thrust range <S> is somewhere between 75-100% N1. <S> This puts the aircraft at considerable risk at lower altitudes or on short final where a large thrust increase may be needed to correct for a gust factor, wind shear or rapid descent. <S> Unfortunately it takes a period of time for the gas core and fan of a jet to 'spool up' and start providing the needed thrust. <S> This slow response time of early jet engines in critical power situations has produced horrifying results, as was the case here on July, 1955 with a fatal rampstrike of an F7U-3 Cutlass coming aboard USS Hancock (CV-17). <S> See at 5:43 into the video. <S> It can also happen even with the most modern engines as this F-18 rampstrike proves. <S> To compensate for the thrust response problems, pilots will fly the pattern and approach at a high thrust lever setting, then maintain speed and descent control using application of speed brakes. <S> This gives good energy management and control but allows the pilot to quickly get thrust if he needs it to return to glideslope, climb or go around altogether. <A> The Fokker F-28/F70/F100 and the BAe 146 <S> /Avro RJ are the only two airliners with rear mounted air brakes because they were the only two airliners not designed with thrust reversers. <S> It is Standard Procedure to use the rear mounted air brakes on every landing because they add drag and reduce the landing distance. <S> Other airliners don't have this type of air brake simply because they don't need them. <S> These two types also employ wing spoilers for use on touchdown just like other large aircraft. <S> Wing spoilers are only used after touchdown, or at higher altitudes, and are not used during the final approach and flare.
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Commercial jets and military fighters tend to be quite 'slippery' and require drastic throttle reductions to slow down without the use of speedbrakes. It allows better speed control
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I overboosted an engine in a Mooney 231 - do I need to do an inspection? I have an intercooler, but no wastegate. Manifold pressure was not controlled on takeoff and went to 50. The max is 37! If overboosting doesn't really exist because the relief valve opens, then how did the gauge even get to 50? It was at that level for 20-30 secs. The engine appears to run great afterwards. Is there anything that should be inspected or done? <Q> This most likely warrants a call to Don Maxwell the veritable Mooney expert <S> but I would for sure have the engine checked by a Mooney expert or someone that knows their way around the TSIO-360-GB. <S> At the minimum a compression test and possible borescope check is in order . <S> If you have the early 231 in its original config you have a fixed waste gate that can be over boosted on takeoff . <S> The engine also had a fixed wastegate in the exhaust system, meaning careful pilot technique was required to keep from over boosting the engine on takeoff. <S> If the pilot inadvertently added full throttle for takeoff or a go-around, the engine would over boost, with only a mechanical pop-off valve in the induction system to save the engine from literally coming apart on the runway . <S> Fixed wastegates also mean high turbocharger speeds (RPM) at altitude, which reduces turbocharger life <S> I don't know much about the gauge itself <S> but it may warrant checking it to make sure it is operating properly. <S> You can also reach out to continental and ask them what the over boost limit is. <S> There is a chance they have some data on it or can let you know of a good course of action. <A> It's advisable to have that engine inspected as that kind of overboost can cause severe detonation and damage the engine. <S> This may mean a complete tear down of the engine. <S> I'm not an A&P by any means <S> but I think that's want they're going to advise. <S> Or you could simply have a bad manifold pressure gauge; have that inspected first; it could save you a lot of money. <S> Did you encounter additional symptoms i.e. Engine really running at a high pitch, possibly with knocking accompanying it? <A> WHAT? <S> 50" for 20 seconds??? <S> That's nuts! <S> The first call should be to CMI. <S> The engine user manual directs a user to see Continental Service Bulletin M67-12 after operation in a sustained overboost condition. <S> I would say this event qualifies! <S> Read the SB, call CMI, and <S> then call an engine shop. <A> I had a P337 skymaster with two of those TSIO-360s, though mine had automatic manifold pressure control <S> so overboosting was less common. <S> The manual said an inspection was necessary for even a short overboost of 4 inches if I remember correctly.
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I would say that you should definitely have the engine inspected. The relief valve may have failed.
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In which phases of flight should the carb heat be turned on? I have about 200 flight hours in a fuel-injected C172. I have just jointly bought a C152 with a carburetor and I am getting used to using the carb heat. I am scared whenever I hear stories about engine failures due to carb icing. What I know is to turn CH on when: RPM lower than 2000 When visible moisture is in the air and when it's raining But should I leave CH on when taking off in the rain? Can you give me some ideas about other phases and conditions of the flight when I should turn on the carb heat? <Q> Carburettor icing is rare at high RPMs, as there will not be much of a venturi effect. <S> To have carburettor icing in such a scenario, it would have to be very cold and very humid <S> /wet, in which case you would probably also encounter airframe icing, and might want to reconsider your flight. <S> Applying carby heat has two downsides: <S> The air will be unfiltered, meaning dirt or other contaminants can be sucked into the engine; More importantly, the warm air means you won't be able to reach your usual maximum RPM. <S> These are two undesirable traits for takeoff. <S> The POH in a Cessna 172 <S> I fly says to have carburettor heat off for takeoff and landing, but only really says it should be on when you suspect icing. <S> I was taught to be much more conservative - prevention is better than cure. <S> I apply carby heat whenever the RPM is below the 'green range', unless it is especially hot and dry outside. <S> However, I remove it when I'm about 30 seconds from landing, <S> in case I need that extra power for a go-around. <S> You also shouldn't apply it 'half way'. <S> Either it's all in or all out. <S> Boldmethod has a good article on why it's important, and you should pay attention to the conditions where it is most likely to occur. <A> You should refer to your POH for the official word but according to this copy of the 152 POH , For a rough engine <S> A gradual loss of RPM and eventual engine roughness may result from the formation of carburetor ice. <S> To clear the ice, apply full throttle and pull the carburetor heat knob full out until the engine runs smoothly ; then remove carburetor heat and readjust the throttle. <S> If conditions require the continued use of carburetor heat in cruise flight, use the minimum amount of heat necessary to prevent ice from forming and lean the mixture slightly for smoothest engine operation <S> Similar notes are made in the cruise section Carburetor ice, as evidenced by an unexplained drop in RPM, can be removed by application of full carburetor heat . <S> Upon regaining the original RPM (with heat off), use the minimum amount of heat (by trial and error) to prevent ice from forming . <S> Since the heated air causes a richer mixture, readjust the mixture setting when carburetor heat is to be used continuously in cruise flight. <S> And also The use of full carburetor heat is recommended during flight in very heavy rain to avoid the possibility of engine stoppage due to excessive water ingestion . <S> The mixture setting should be readjusted for smoothest operation. <S> for a cold start without preheat, The procedure for starting without preheat is the same as with preheat except the engine should be primed an additional three strokes just prior to pulling the propeller through by hand. <S> Carburetor heat should be applied after the engine starts. <S> Generally you should run carb heat any time you SUSPECT <S> carb icing. <S> You can take a look at this AOPA brief on carb ice . <S> You can also check out this brief from the NTSB . <A> When I was taught to fly in an Aeronica Champ in 1966 <S> my instructor would always tell me to apply carb heat just before reducing the power for landing. <S> Leave the carb heat on until you are going to reply the power for a go around. <S> As others have stated if roughness was detected ad carb heat. <S> My instructor taught Sully how to fly in 1967. :-)
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Leave the carburetor heat on until the engine run smoothly.
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Is it dangerous to do a skidding turn to lose altitude without increasing airspeed? I was taking some lessons in a light sport aircraft in South Africa a few years back, my instructor taught me something which I had never seen or heard of before or since. We went through an emergency scenario in which we had to make an emergency landing in a field (not really landing but just going through the motions, of course). I found a place to land and started my descent, but had to loop back around after I passed it. The instructor then told me to give full right rudder with left aileron to quickly descend without gaining airspeed. Wouldn't this qualify as a recipe for creating a spin and possibly killing myself? Should I actually implement that skidding turn in an emergency to land if need be? <Q> As Ron Beyer pointed out in a comment, your instructor was showing you a forward slip - a pretty standard maneuver for light aircraft. <S> A spin would involve full rudder and a stalled wing, which usually means pulling the yoke or stick back a lot. <S> That's why overshooting the base-to-final turn can be dangerous - you likely already have a lot of rudder in <S> and it's tempting to pull back on the yoke to try to tighten up the turn. <S> An unexpected spin at low altitude is not recommended as recovery tends to be both abrupt and fatal. <S> As long as you're keeping the yoke more or less centered forward and back and your airspeed up, there should be nothing to worry about. <A> I just want to go back to the OP's concern that rudder one way and aileron the other way is related to a spin - it's my understanding that this is a cross-controlled situation, and that is something that can't be ignored, so <S> (again, I'm saying this from an armchair not-even-a-pilot standpoint) <S> it will influence what you have to think about doing at the same time - i.e. not getting slow or finding another way to approach stall regime. <S> See also the link KJP gave in a comment for the difference between a slip and a skid: " What is a skidding turn (vs slipping turn)? <S> " - this link includes information about the opposite spin-resistance vs. not-spin-resistance of those two maneuvers. <S> While slipping on final straight-in may not be an easy or likely way to enter a spin, it's not a completely risk-free proposition (like many aspects of flight aren't) for various reasons and while I wouldn't personally avoid it, I'd learn more about it, talk to my instructor about my concerns, practice it with her up high, and of course read answers to similar questions to get a sense for the widespread Internet commentator feelings on the matter." <S> Googling "can forward slip lead to spin" yields (among others) results (which I lack reputation to post more of): http://www.askacfi.com/5189/forward-slip-and-classic-countercontrol-stallspin.htm <S> Answers and components of answers seem to run a range of things like: <S> "slips like this are perfectly OK" "slips like this are probably perfectly OK, depending on aircraft and weather details <S> " "don't cause a stall and you won't spin" "even stalling in a slip condition won't/shouldn't <S> cause a spin <S> because you're not yawing" <S> "slips like this are OK but from this condition you can enter certain other conditions which aren't OK <S> " "try it way up high and see" <S> And the FAA " airplane flying handbook " has this (and more) to say: ( https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/airplane_handbook/ chapter 8, section "Intentional Slips", pages 11 and 12, which I identified from one of the comments in the above google results): <S> "Unlike skids, however, if an airplane in a slip is made to stall, it displays very little of the yawing tendency that causes a skidding stall to develop into a spin. <S> The airplane in a slip may do little more than tend to roll into a wings level attitude. <S> In fact, in some airplanes stall characteristics may even be improved." <A> Slipping an aircraft is mostly perfectly safe. <S> I say mostly because there are exceptions: <S> Some aircraft operator's manuals explicitly forbid slipping. <S> This might be because of the general handling or aerodynamic characteristics of the aircraft. <S> There are other reasons outside of handling why slipping is dangerous to some types of aircraft. <S> For example aircraft with jet engines, especially fuselage-mounted ones are prone to engine stall when airflow to the engine is disturbed. <S> Other reason could be unexpected results on ie. <S> fuel feeding with sideways acceleration. <S> Also slipping disturbs the airflow to the pitot-static system, so speed, altitude and vertical speed indications are unreliable while slipping. <A> "Is it dangerous to do a skidding turn to lose altitude without increasing airspeed" <S> This is a great question as it underscores the importance of approaching at around 1.3 times stall speed. <S> Also, of critical importance, is your instructor did NOT request a skidding turn <S> , what was requested was a forward slip, although I admit this may have taken me by surprise too. <S> Anything like this should be learned from an expert and practiced at altitude in a plane that allows for it. <S> In a Cessna 172, approaching at 65 knots, with 20 degrees of flaps, they are a joy to do. <S> 50 knots would be much more dangerous. <S> This is the killer. <S> However, in a forward slip, The airplane maintains its heading (straight), creates drag with the rudder push, and controls lateral movement along the heading line with aileron. <S> In a straight wing GA aircraft, after the rudder push, there is no difference in the wing tip speeds,just make sure you keep an eye on the airspeed. <S> The change in glide slope can be fairly dramatic, making this a very useful tool. <S> Just roll out and straighten out before pulling elevator to "round out" your short final. <S> Your instructor did not steer you wrong.
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That said, as a maneuver (on an aircraft that slipping is allowed with) it is safe and normal use of flight controls. A skidding TURN is dangerous as it creates a much greater speed differential between the wings, prompting a poor soul to "hold the inside wing up" with aileron.
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How can dynamic and static pressure be explained? How exactly do you explain dynamic pressure? If someone asked me what the ASI reads, I would say it reads the dynamic pressure, which is the ram air pressure (total pressure) - static pressure = dynamic pressure But would explaining dynamic pressure as "the pressure the pitot tube experiences through the air ? As for static pressure, how would you explain that? Would you say static pressure is the pressure the aircraft feels whether it is in motion or not? <Q> You are very close. <S> Your explanation of static pressure is correct, but not your dynamic pressure. <S> Ram air pressure is what the pitot tube measures, in other words the total pressure experienced. <S> It is your airspeed gauge which measures dynamic pressure by mechanically (in the case of a traditional pitot-static system) subtracting static pressure from ram air pressure. <S> If I was explaining this to a layman I would say that ram air pressure is equivalent to sticking your hand out the window of a moving car, while static pressure is the pressure inside the car. <S> That's a bit of an over-simplification as the pressure inside the car will be lower than outside due to the movement through the air, but it gets the point across. <A> Use an energy analogy: <S> Dynamic pressure equals kinetic energy, Static pressure equals potential energy. <S> Total energy = total pressure. <S> For the more math inclined: <S> In the gravity field of earth, potential energy is mass times gravity acceleration times height: $E_{pot} = m\cdot <S> g\cdot h$. Kinetic energy is mass times speed squared, divided by 2: $E_{kin} = <S> m\cdot\frac{v^2}{2}$. Dynamic pressure $q$ is similarly density times speed squared, divided by 2: $q = \rho\cdot\frac{v^2}{2}$, which makes it a volume-specific kinetic energy. <S> In other words, the weight of this column of the atmosphere compresses the air lower down so this pressure can support all the air resting on top of it. <A> Short answer: It's the dynamic pressure which is at work in a sea anchor: <S> Source <S> Let's see how we can separate effects of static and dynamic pressures. <S> Use the water similarity: <S> Blow up a balloon and submerge it in water. <S> As you go deeper, the balloon volume shrinks as the static (ambient) pressure increases. <S> Move the balloon at some speed through the water, its shape changes because the dynamic pressure created by the displacement is not equally distributed over its surface. <S> Dynamic pressure is comparable to static pressure unevenly distributed. <S> It's dynamic pressure that slows down a parachute. <S> If there was no static pressure, the effect would not change. <S> To observe the effect of dynamic pressure alone, you can replace air by water in the parachute, this is what is at work in a sea anchor . <S> (You can also demonstrate this in air, but this would requires to inject air under a parachute in vacuum, not simple...) <S> To be complete: In this experience the balloon also receives a buoyancy force because air and water densities are not equal. <S> A the weight is added to stabilize the balloon. <S> When the balloon contains water, this buoyancy force disappears and the weight is not required any longer. <A> If you remember that the air is really a swarm of molecules moving in all directions at very high speed, and that pressure -static or dynamic- is caused by the impact of those molecules, then everything is very clear...
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Static pressure is the weight force of the mass of a column of the atmosphere all the way to space resting on the base area of this column.
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What is profile drag? I know about induced drag, parasite drag, form drag, skin drag, wave drag, and interference drag. But I don't encounter the term profile drag often, and I can't find a good definition of it. Is profile drag the same thing as form drag? If not what is it? <Q> The composition of total Drag as it is shown below: Thanks to DRAGBUSTERS... <S> This document can solve this question, and analyses the drag in detail. <S> Profile Drag Definition: <S> Profile Drag is the drag incurred from frictional resistance of the blades passing through the air. <S> It does not change significantly with angle of attack of the airfoil section, but increases moderately as airspeed increases. <S> Taken from here . <S> Definitions of profile drag as they are in dictionaries: <S> The portion of the wing drag that is due to friction and turbulence in the fluid and that would be absent if it were nonviscous <S> The part of the drag on an aerofoil or aircraft which arises directly from its profile and from skin friction (i.e. the part not attributable to lift). <S> By reading this ...(in fifth par.) <S> Form Drag Definition: Drag which depends on the shape of the aircraft, is called form drag . <S> The following definition has been taken from here . <S> Profile Drag or, sometimes called form drag, is the drag caused by the separation of the boundary layer from a surface and the wake created by that separation. <S> It is primarily dependent upon the shape of the object. <S> Form or pressure drag is caused by the air that is flowing over the aircraft or airfoil. <S> And finally, the most commonly types of drag encountered are, Parasitic Drag, composed of Form Drag , which is the result of the aerodynamic resistance to motion due to the shape of the aircraft, Skin Friction Drag , which is due to the smoothness or roughness of the surfaces of the aircraft, and Interference Drag, which may occur where surfaces with different characteristics meet (e.g. wing and fuselage) <S> Induced Drag, which is a secondary effect of the production of lift,and Wave Drag which comes into play when shock waves are developed close to the surface of the aircraft in transonic and supersonic flight. <S> Taken by this Skybrary Article which describes very nicely the types of drag. <A> I have seen this term wrongly used. <S> The right definition refers to the drag of an aerodynamic 2D profile. <S> Essentially, friction drag and form drag, ignoring the induced drag being a 3D phenomena. <S> However, in some papers I have seen the use of this term as equivalent to the form drag itself, not being restricted to a 2D phenomena. <A> I share your confusion about those many sources of drag. <S> In the end, many of them describe similar things. <S> When doing a performance calculation, it is extremely important to add all drag sources and to do this for every one only once. <S> Drag estimation requires meticulous bookkeeping . <S> Therefore, I would distinguish only two types of drag: <S> Viscous drag, where the flow is slowed down by friction. <S> The result is a force parallel to the local surface, and viscous drag is its component parallel to the flow direction at infinity. <S> Pressure drag, where the local lift vector is tilted away from the vertical (in reference to the flow direction at infinity). <S> Profile drag is a muddle because it adds both types, but only part of them. <S> This makes proper bookkeeping harder. <S> As Trebia Project writes, profile drag is the drag in 2D flow and neglects both interference and lift-related components. <S> But when designing an aircraft, profile drag is easy to get at - just look it up or run a calculation . <S> Profile drag includes the full friction component of the unswept wing without engine and real-world effects (so no drag from flap gaps, pylons, flap track fairings, rivet heads ...), the pressure drag from incomplete pressure recovery and wave drag in supersonic flow. <S> It excludes the lift-related drag (induced drag) in subsonic flow, the pressure drag stemming from interference and the drag increase in the slipstream of a propeller. <S> All these drag sources need to be added and be kept free of drag that was already considered in the profile drag data. <A> The total drag acting on an aircraft in flight is the sum of: Profile drag Induced drag Interference drag Profile drag can be further separated into: Form drag Skin friction drag <S> Form drag is produced whenever the streamline airflow passing over an aircraft separates from the surface and becomes turbulent. <S> An example of extreme form drag is the effect of a flat plate placed at right angles to the airflow: <S> Skin friction drag is a function of the layer of air closest to the surface. <S> As air flows over a wing, the roughness of the surface and the viscous property of the air itself slow it down. <S> Much like other fluids, the more viscous the air, the greater its retardation. <S> At the surface, the air particles adhereto it and their relative velocity is reduced to zero: <A> Principles of Flight | ATPL - Lesson 6 <S> Part 2 - 7:34
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Profile drag is the combination of form drag and skin friction as it results from the cross-sectional area, or profile, of the aircraft, presented to the relative airflow.
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Why don't drones use ducted fans? If efficiency of converting battery power to lift or thrust is paramount, why don't drones use shrouded or ducted fans, instead of unshrouded propellers? This is the only image I could find to clarify what I mean by " ducted fan ": Image source (public domain) My thoughts: An extremely light weight duct could be made, so weight is probably not a factor Increased suceptibility to winds could be a big negative Maybe it doesn't make much difference at the low thrust levels of drones <Q> Ducted fans are great for fast forward flight but not for static lift. <S> Explanation: <S> Yes, the 'duct' reduces losses at the blade tips, However, adds significant losses at the intake lip and exit where the adjacent air is pulled into the flow. <S> For ducted fans installed in aircraft, These losses are reduced at high forward velocities and increased at low forward velocity. <S> For drones, there is situation with perpendicular intake flow, when drone is travelling sideways and fan pointing up, there is even greater losses at front intake lip. <S> The most efficient blade design for static lift is to have the blade as long as possible (like a helicopter) and travelling as slow as possible. <S> Least efficient to have short blades travelling at high velocity. <S> It is easier to imagine what is going on if you increase the viscosity and imagine the fluid is water instead of air. <S> Very large blades would move water only a small about, but over a large area. <S> however, very tiny blades would be require to move vast amounts of water through a small area to produce the same thrust. <S> moving that much water increases drag as the blades have to suck in water at the intake and the exiting water would be slowed very quickly by the surrounding water at the exit. <A> They are used - have been for almost 2 decades. <S> Check out Avid Aersospaces T-hawk. <S> AVID, in subcontract with Honeywell, assisted in the design of T-Hawk,a ducted-fan micro air vehicle (MAV) as part of an accelerated DARPAproject. <S> T-Hawk is an unmanned micro air vehicle that providesreal-time situational awareness in critical situations with over30,000 hours total flight hours. <S> (At the link) <A> The Ducted Fan has a narrow field of speeds where its efficiency is higher than an open propeller, or a turbine, see image, as elements in DF design, <S> as distance of blade tip to duct and others, it was discussed in Aviation Stack Exchange, may change results, this is better tested experimentally, according to the desired use for machine. <A> Cons Using ducts, weight will increase than advantage of getting smooth airflow to blades. <S> Using only propellers there will be more maneuverability for sudden change in direction. <S> Pros Using ducted fans, undisturbed airflow during windy or gust situations <A> The efficiency of the ducted fan can be increased by the shape of the duct. <S> If the airflow is compressed, i.e. the outer airflow section is thinner of the inner section, the fluid is compressed (more compression means more speed in the airflow) and that's what gives most of the trust in normal propellers even if not ducted, if you note in small propellers airplanes, typically twin engines, there's a small porthole and another smaller one in the back of the engines, that's where the compressed airflow comes out, more or less similar design happens in jet engines <S> I mean bigger airliners, not rockets. <S> I was looking into building a ducted fan drone, but none of the commercially available ducted fans seems to follow this design.
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The reason not many drones use ducted fans is efficiency.
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What is the typical angle of attack aircraft fly at and at what angle of attack do they stall? At what angles of attack do aircraft typically fly at? How much of a margin is there before aircraft stall due to an increase of an angle attack due to factors such as gusts or rotation of the wing section due to deformation? <Q> It depends basically on the wing section. <S> Some of them stall at a higher angle of attack than others... <S> To quote typical values (for wing + body, since not only the wing gives lift...) <S> a given plane may achieve the flattest glide (best range, L/D = 12, at 155 knots) with an angle of attack of 4º. <S> If you wish to fly slower, you can do it at 115 knots, with L/D = 8, and a steeper AoA (13º) or you can choose to fly faster, at 210 knots, always with L/D = 8, but with an AoA of 1.5º. <S> Thus, and except for the best L/D, there are always two angles of attack for the same L/D, one of them steep (slower flight) or flat (fast flight)... <S> The stall, for the example I'm quoting (book 'Mechanics of Flight, by A.C. Kermode)' takes place at 15º... <A> It depends. <S> These factors influence the flight angle of attack: Altitude. <S> Higher up the air is thinner, so the flight angle of attack tends to be higher. <S> Aircraft speed. <S> Fast airplanes sometimes need to limit lift by flying at a slightly negative angle of attack. <S> Wing camber and incidence. <S> High camber means high lift already at zero angle of attack. <S> Extreme cases like the <S> B-52 <S> need to fly with a visible nose-down attitude when flying low and fast or when the high lift devices are deployed. <S> Aircraft weight. <S> This is both influenced by aircraft mass and the load factor flown. <S> Wing sweep. <S> Higher sweep means lower lift curve slope, so a higher angle of attack is needed. <S> Thankfully, stalling is also delayed, in extreme cases (delta wing) above 30°. <S> Aspect ratio. <S> A lower aspect ratio works in similar ways to sweep: Stall is delayed to higher angles. <S> Gliders, on the other hand, stall already at 10° - 15° angle of attack (depending on flap settings). <S> Mach number: At transsonic speeds the developing shocks on the wing can stall the aircraft at much lower angles than those usual at low speed. <S> Rate of angle of attack change. <S> In dynamic manoeuvers the stall lift coefficient could be pushed up by 50% . <S> Directional stability: The F-4 Phantom II is limited to 23° angle of attack simply because the vertical tail will be insufficient at higher angles. <S> Here the aircraft does not stall but is artificially limited . <S> Normally, the designer tries to set the wing incidence such that the fuselage is level at the design speed and altitude. <S> The wing angle of attack is then also near zero or at low, single-digit degrees. <S> The stall angle of attack, however, is all over the place, from high single-digit values (high-speed stall) up to more than 30° (highly swept, low aspect ratio configuration with vortex lift ). <A> An aircraft typically flies at angles of attack range about 2-5 degrees, depending of the flight altitude, speed and g-load of maneuver. <S> It's much more (about 10-12 degrees) <S> when flight speed is near to take-off and landing speed. <S> So the safety margin is about 10 degrees, but the margin drastically decreases in take-off and landing. <S> Therefore it's dangerous when an aircraft, say, is in approach to landing while undergoes a vertical gust that may lead the aircraft into stall.
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The critical angle of attack when an aircraft goes to stall usually is about 15 degrees, mainly depending of the wing plane form, flight Mach number, the wing section profile and flaps position.
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What would be the airspace class when no vignette is visible on a US VFR sectional chart? If a airport doesn't have a pink vignette nor blue vignette on a VFR sectional chart, but the airports around this particular airport has pink vignettes, would this airport's Class E start at 1200 AGL or would this airport be Class G up to 14,500 MSL? For example, Grayson County (M20) - circled here in red - has no pink vignette but other airports near it do: <Q> The vast majority of US airspace where no more restrictive airspace exists has class E starting at 1200ft AGL with class G below. <S> You can see an area of class G up to 14,500 MSL just north of the TCS VORTAC near to Truth or Consequences, NM which is south-southwest of KABQ. <S> There are several other areas in the 48 states as well. <S> If it's inside the pink vignette, G extends up to 700 AGL. <S> Of course, if it lies within a pink dashed line indicating class E to the ground at such a nearby airport, then the airport you mentioned does not have any class G above it either. <S> One other helper I use - if you see any federal airways nearby and there is no blue vignette indicating the presence of class G up to 14,500 MSL then you can usually safely assume it is class E above 1200 AGL if no other more restrictive airspace overlies the area. <S> Federal airways are 4 nm wide on each side or the course centerline and always exist within controlled airspace (class E or better). <S> These are labeled on a VFR chart as the light blue lines with V-number labels - also called Victor airways. <S> As such, V 49 west of the M20 airport you mentioned would be an example and is pronounced "Victor forty-nine". <S> At M20 - the airport you ask about - the airspace up to 1200 ft AGL is class G <S> , then class E up to but not including 18,000 ft MSL, then class A at 18,000 MSL up to FL600, then class E to space. <A> You are correct. <S> M20 is in Class G airspace up to 1200 ft AGL, then Class E airspace from 1200 ft AGL to 17,999 ft MSL, then Class A airspace from FL180 to FL600, then Class E airspace from FL600 and above. <S> As noted earlier more and more Class G airspace from surface to 14,500 ft MSL are being converted to Class E airspace due to increased traffic congestion in the CONUS. <S> Examples can still be found in the southwest. <S> Large swathes of Class G still exist in Alaska due to vast remote sections of territory there. <A> Another way to check the airspace around an airport is to look it up in the Chart Supplement. <S> M20 <S> You will notice that there is no airspace line in the airport data. <S> That usually means it is <S> Class G. All of the other airspace types (E,D,C,B) are listed e.g. KOWBAIRSPACE: <S> CLASS D svc <S> 1200–0400Z‡ other times CLASS G. KBWGAIRSPACE: <S> CLASS E <S> If you see clearance delivery, ground, and tower frequencies then, at least for most of the day, the airspace is not Class G.
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As long as the airport you are talking about "near airports with pink vignettes" is not under the pink vignette, then G extends to 1200 AGL.
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Would an Aero L-159 Alca air frame be able to withstand a supersonic engine? Aero L-159 uses a Honeywell F124-GA-100 turbofan engine. First question is, can it be fitted with any modern supersonic jet engine? If YES, why isn't Aerovodocody doing that? If NO, why? <Q> By 'supersonic jet engine', I presume you mean an engine which would make an L-159 capable of supersonic flight. <S> Could you mount such an engine on this aircraft? <S> Possibly, but why would you want to? <S> An L-159 isn't exactly engineered to be a top of the line high performance fighter; its design and intended use is as an advanced subsonic trainer aircraft based upon the earlier L-39 and L-59 airframes. <S> Its job is to prepare student pilots for more advanced tactical aircraft and has handling qualities similar to fighters while retaining forgiving flight characteristics for new students so they can more easily build time and experience in high performance jets. <S> In addition, the aircraft is designed to be affordable and easy to maintain for third world air forces. <S> Supersonic flight never was considered as a requirement for the role by Aero Vodochody. <S> Therefore a much more expensive and exotic engine is not needed here. <A> First question is, can it be fitted with any modern supersonic jet engine? <S> Fitted? <S> Why not. <S> It wouldn't have any advantage though. <S> If YES, why isn't Aerovodocody doing that? <S> Because it wouldn't make the plane fly supersonic anyway. <S> Just look at it. <S> Straight, relatively thick wing, small small elevator with fixed stabilizer. <S> If you try to push such design above around M0.7, the drag will start to increase like crazy and the nose-down change in trim will really test the limits of elevator authority. <S> For supersonic flight you need either swept (for low supersonic) or thin wings and an all flying horizontal stabilizer. <S> That is, a completely different design. <A> The Albatross family of jets will only have the third world market as it stands. <S> 1st and 2nd world markets are beginning to be dominated by supersonic trainers, so the question isn't without merit. <S> You don't build trainer jets just for aerobatics. <S> As others mentioned, the wing is too straight, and the stabilizer isn't all-moving. <S> You need both, or it will just dive and crash. <S> Good looks isn't enough. <S> As a supersonic trainer, it doesn't need to be very fast or go past Mach 1.5, just enough to provide supersonic training. <S> Assuming so, the intakes should be fine. <S> The engine change should also be minimal, as there is a version of the F-124 <S> that now produces 48kN dry. <S> That's almost double, so <S> I doubt it's not enough thrust. <S> Yes, all this would only make sense if the jet is able to supercruise, or it would, as others point out, have stubs for legs. <S> The L-39NG is now out and that plane with its 16kN engine shows that Aero is focused on an economic trainer more than a high performing one. <S> The Albatross simply needs major surgery for the latter. <S> If anything, the G-4 Super Galeb is better suited for the job with its Tomcat style swept-wing and all-moving tail. <A> Assuming you can find a modern supersonic engine that physically fits, then yes it can in principle be fitted. <S> But if you mean could it then go supersonic, no <S> it could not. <S> Drag would build sharply at transonic speeds, due primarily to the straight, unswept wing and tailplane. <S> If the engine were powerful enough to overcome that, then the aerodynamic forces unleashed by the transonic shock waves would rip the plane to pieces. <S> Supersonic jets have to be a lot stronger than their subsonic cousins. <S> That was a lesson learned the hard way when planes with suitable engines and aerodynamics were first flown, and Aerovodocody have no wish to kill any more pilots.
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It is not designed either aerodynamically or structurally for supersonic flight.
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Would a stationary WWII fighter fall on its nose with full throttle and brakes on? Would a stationary WWII fighter fall on its nose with full throttle and brakes on? It's a general question, but I am interested in the Republic P-47. <Q> ( Wikimedia ; arrows and CG icon are my additions) P-47 side drawing. <S> The thrust has a bigger moment arm around the tires contact points compared to the weight. <S> It won't nose over below a certain RPM (it will be specified in the training). <S> Below that RPM: The weight will counter the thrust <S> The propeller downwash will produce downward force on the horizontal stabilizer <S> Applied brakes will resist the rotation of the wheels (airframe rotating around wheels) From a training video for the comparable big-engined F6F Hellcat , the narrator says: You can't gun this engine to full takeoff RPM and manifold pressure while holding the plane with the brakes, if you exceed 2,000 RPM the tail will lift and you risk nosing over. <S> Answer is yes it can happen. <S> Note: for comparison, the max RPM is 2,700 for the Hellcat. <A> This was also an issue when doing maintenance. <S> For engine ground running at full power, the tail of the aircraft was weighted down to stop the aircraft tipping over the front wheels. <S> You can see the "saddle bag" and weights hung over the fuselage in front of the tailplane in this still from a video of a WWII Spitfire ground <S> run: ( YouTube ) <A> Depends on the elevator input As long as the stick is held back, as it should be for any kind of runup, then the elevator would be applying plenty of downward force. <S> Now, without the elevator input to cancel it, the pitchover torque might nose over an airplane, and it might not take one of those big WWII engines to do it. <S> There is a force directed aft at the interface where the (brake-locked) wheels meet the ground that is equal to the force forward along the propellor shaft. <S> This force is multiplied by the distance between the extension of the prop shaft and the ground between the wheels to create the torque. <S> It's the same torque, but with opposite magnitude, as that which produces the hotrod wheelie maneuver. <S> (And the torque is there with or without the wheelie, which is why FWD cars don't make good drag racers.) <S> It will be worse for an airplane with long gear legs that sits well off the ground. <S> I've always wondered what would happen if I didn't hold the stick back on runup. <S> Update: <S> Addressing comments ... <S> well, it might take a little unfavorable wind too, certainly airplanes have nosed over, see below, on (perhaps downwind) runups, but note that on the takeoff roll in a tailwheel airplane, the tail comes up quite early on, and that's with neutral stick inputs <S> , so one can only imagine that it could happen pretty darn fast with any reckless amount of forward stick. <S> Apparently, even nose wheel airplanes can do it <S> , I believe this is a Cessna on the runup pad at KSQL:
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If the static thrust or the elevator moment is high enough, it could happen.
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Do parking brakes lock the wheels and airframe together? ( YouTube ) Wildcat undercarriage. For planes with non-truck undercarriages, can they be rotated around the lateral axis of the main landing gear with the brakes applied without causing translation? My answer is no, they must be locked and there must be translation (image below). I had the following comment on a recent answer, and frankly I'm not quite sure, hence the question. [They] are wheels. The whole structure is free to rotate around this 'locked' axle... I don't agree, imagine chocks are placed forward of the main landing gear: A) Frame is locked, blue man can't lift as he can't cause translation. B) Frame is not locked, plane rotates around wheels (from the wheels' perspective, they're free moving). ( Original ) Above shows what I mean by translation, the plane moves forward (blue distance) with the wheel—plane frame (red lines) being locked. (Brakes are applied.) Note: This question has nothing to do with deceleration or a running engine. <Q> Yes, the parking brakes lock the wheel and the airframe together. <S> If the brakes are not applied, the wheel can rotate round the axle. <S> If the wheel's position is fixed to the ground (e.g. by adding chocks, but the brakes are not applied, then the aircraft will rotate round the wheel axle when the tail is lifted by the blue man. <S> Since the contact point moves as the wheel rolls, this results in translation in addition to the rotation. <S> If both the brakes are applied and the wheels are on chocks, the wheels either have to roll over the chocks or something (the wheel, the chock or the brake) will have to slip. <A> If you're asking if an aircraft like a taildragger can be tipped forward rotating about the main landing gear axles, the answer is yes <S> and you do have to be careful of this not to apply too much braking pressure during taxiing or during the landing roll. <A> Let's look at the DHC-2 as an example. <S> Most data is taken from the DHC-2 manual . <S> Here is a basic diagram of the forces involved: F g is from the weight of the plane on the main gear F t is from the weight of the plane on the tail F L <S> is the force applied to lift the tail <S> F x is the lateral force applied to the wheel from friction <S> F N is the normal force from the ground supporting the main gear <S> Gross weight is 5100 lb (2300 kg). <S> The main gear is 25 in (0.64m) in front of the CG, the tail wheel is 244 in (6.2m) aft of the CG. <S> This means that about 4630 lb (2100 kg) rests on the main gear, and 470 lb (215 kg) rests on the tail. <S> The friction force F x can be up to F g <S> μ s , where μ s is the coefficient of static friction, which is about 0.9 ( <S> depending on conditions of course). <S> If the plane is prevented from translating forward, then the airplane will rotate around the wheel axle. <S> The tires are 20.5 in ( <S> 0.5m) diameter, so the moment on the wheel from friction can be up to 3540 lbft (4800 Nm). <S> The tail is about 270 in (6.9m) from the main gear. <S> The force on the tail to overcome the moment on the main gear would be 160 lbf (700 N), which is the equivalent of lifting 160 lb (70 kg). <S> This would be in addition to lifting the 470 lb (215kg) from the weight of the plane. <S> It's also worth noting that right before the tire overcomes static friction, you would need an equal and opposite force to oppose F x , which would be 4160 lbf (18500 N). <S> We would need the mythical frictionless massless (spherical, immovable) chocks to provide this force without adding rotational resistance to the tires. <S> The centerline of the engine is 53 in (1.3m) above the axle, so a thrust force of 830 lbf (3700 N) would be needed to overcome the wheel friction. <S> The tail has 14500 Nm of moment to overcome, which means another 11200 N or another 2500 lb of thrust.
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If the brakes are applied, but the wheel's position is not fixed to the ground, the aircraft will rotate round the wheel's point of contact with the ground.
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Is it technically possible to have nuclear-powered hot-air balloons? Could a balloon use non-fissile isotope, like Pu-238, to heat air in the envelope to stay afloat for years? let's put political and health related problems aside, and consider if it's technically possible at all. Say, as an unmanned, high-altitude scientific/weather station. I know that: Pu-238 has power output of 0.54 watts per gram Its half-life is 87.7 years (power output halves after that time). great most of the energy can be radiated out as heat, and transferred to surrounding air. I don't know what buoyancy can the hot air balloons provide, and what kind of energy input they require to stay afloat. So - would it fly? <Q> Most likely no. <S> RTG does not have enough power. <S> The burner of the hot air balloon requires 2 to 4 MW of power ( here ) so you need at least 4 tonnes of Pu to produce that (2000,0000 / 500 = 4000 Kg), assuming 500 W per kg (0.5 W/mg). <S> From the source, a moderate size balloon can lift few hundred kilograms at most. <S> The true nuclear reactors provide much more power, but they are heavy. <S> Hyperion , for instance, provides 25 MW and weighs 50 tons, so performance per kg is even lower. <S> It could power a cluster of say five balloons, but they would not be able to lift 10 tonnes each. <S> From the other side, nuclear reactors are probably not optimised for the minimal weight, assuming that just a heat output is required. <S> They are built to match different requirements, so some specially built device may be capable of lifting the balloon. <A> Probably not from decay heat as others have said, but ignoring the minor matter of the radiation and toxic byproducts it is clearly doable with a fission pile burning sufficiently enriched fuel. <S> The Soviet nuclear program has had at least one criticality accident with a PU core that ended up in a sort of equilibrium between its thermal expansion and reactivity, so say 10kg of fissile material and a load of heat spreaders to get the heat out into the air, bet you could do it with 50kg or so of machine <S> (But I would not want to be the guy to have to go in and shut it down). <S> There was a proposal for a Venus probe using a nuclear ram jet that may be applicable, thing is once running there was no good way of stopping it because the decay heat would melt the core. <A> The problem with a Pu-238 RTG is that is heavy and low-power. <S> That is to say, the energy is released too slowly. <S> This is not a fundamental problem. <S> Phosphorus-32 is (as the name indicates) almost 8 times lighter, and it has a half-life of just 14 days. <S> This makes it about 15.000 times more powerful per gram as Pu-238 - 8kW/gram ! <S> Typical burners are 3MW, but run at 20% duty cycle for an average power budget of 600kW. <S> This means you only need 75 grams. <S> You can't realistically have 3MW peak power, as this is not a controllable heat source. <S> And using 375 grams for 3MW sustained would mean that you need to get rid of 2400 kW of power on average. <S> Practically speaking, this means that you need a heat buffer. <S> This isn't a big issue, as this heat buffer can surround the P-32 and act as shielding - the absorbed radiation would directly be converted to heat. <S> You'd want a salt melting near 373K, as that's the temperature you're aiming for. <S> Such salts do exist, so that's not a big problem. <S> Technically, this looks feasible. <S> But the practical problem is that your 3MW heat source is a major hassle. <S> It has to be made in a nuclear reactor, and comes out hot - literally. <S> Handling it is a major pain. <S> You need to permanently cool it. <S> That's just not going to be cheap. <A> What would come a little bit closer is some much more powerful radioisotope such as Cobalt-60 for example and that one will produce more than 13 KW/kg through its first years of decay.
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Lockheed Martin is developing a very promising device . It is unlikely that a balloon could use Pu-238 to heat enough air in the envelope to get airborne since Pu-238 is not powerful enough for that.
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Can a US airline add an employee passenger as crew? Suppose an airliner flight is full with passengers and the airline staff realize afterwards that there are employees who the airline wants to send to their shifts using that flight. The airline staff decides to ask for volunteers to surrender their seats in exchange for compensation, but they don't get enough volunteers to make room in passenger seats for their employees to take. Would it be legal for the airline to instead have one or more of the employee-passengers take the flight as "extra crew" (assuming there is an extra seat to strap into in the crew areas)? <Q> First of all it depends on what type of "employee" and if the jumpseat is in the cockpit or the cabin. <S> According to the answers to this question there are no regulations on who may sit in a cabin jumpseat as long as it meets the specifications set out in FAR § 121.211 for proper airline seats. <S> So the airline is free to set policy for cabin jumpseats. <S> As for jumpseats on the flight deck the restrictions are quite stringent. <S> FAR § 121.547(a)(1) allows an on-duty flight attendant to fly in a jumpseat on the flight deck. <S> The person would have to be a certified flight attendant, so you couldn't just make any employee a crew member. <S> Remember also that flight attendants have hours of service restrictions, so any time they are considered on-duty has to comply with the h.o.s. regulations. <S> Certain other types of employees are allowed to fly in the flight deck, but they have to be performing a specific function on the flight that requires their presence in th cockpit. <S> For example, a mechanic could fly in the cockpit if he's there to monitor something on the aircraft. <S> A flight dispatcher could be on the flight deck if they are observing flight operations as a part of training. <S> Even some persons who may be given access to the cockpit for operational need, like air marshals or training personnel, still must have a seat available in the cabin. <S> So they can't put someone in the cockpit just to transport them from place to place and they couldn't just plop a salesman or a ticket agent there and say they are a "crew member." <S> There are regulations stipulating the minimum number of flight attendants on a flight but not a maximum number. <S> So, technically they could make a flight attendant part of the crew, but if that person was just listed as a crew member and wasn't actually performing any duties, the FAA would certainly interpret that as a violation. <A> I used to work for AA and travelled as an employee quite often. <S> The concept of involuntary bumping from a flight has been around for a long, long time, and it only takes simple arithmetic to figure out that if a flight somewhere further along the line cannot depart for lack of crew, to use one possible example, it is much cheaper to bump a paying pax, compensate according to the rules and get the employee where he/she needs to be, than cancel the flight that employee needs to be on. <S> Employees dead-heading to a destination for work are not considered crew by the FAA. <S> The only way to guarantee a seat on an aircraft is to own it, and even then it's not always a sure thing. :) <A> With few exceptions, only pilots and flight attendants can ride in a jumpseat. <S> Pilots can ride in the flight deck jumpseat, and flight attendants can ride in a jumpseat in the cabin. <S> Other types of airline employees are not permitted to ride in a jumpseat. <S> It is my understanding that, contractually speaking, it is up to the employee to decide whether they want to ride in a jumpseat to their destination instead of in a regular seat. <S> There are exceptions in emergency situations where the pilot can, for safety reasons, decide to allow non-flight crew to sit in a jumpseat.
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If the employee is a pilot FAR § 121.547(c)(3) allows off-duty pilots to fly in a jumpseat on the flight deck, so there would be no need to make them an active crew member.
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Why doesn't the US have a flag carrier airline? With the recent United Airlines fiasco, I was reading up on their history and the airline industry and to my surprise I found that United Airlines is not the US flag carrier. In fact, the US does not have flag carrying airline at all! All this time I thought UA was the national carrier for the US. This brings me to the question, why? Why doesn't the US have a national carrier? Is this because of some FAA regulation? <Q> The definition of a "Flag Carrier", although somewhat vague and frequently disputed, is generally accepted to mean: an air carrier that is owned by, or subsidized by, the government of the country of registration, especially for the purposes of flying international routes. <S> Wikipedia : <S> The term also refers to any carrier that is or was owned by a government, even long after their privatization when preferential rights or privileges continue. <S> Business Dictionary : <S> Airline ... registered under the laws of a country whose government gives it partial or total monopoly over international routes. <S> The US has no carriers in this category. <S> All subsidizing of major domestic and international routes ended with the Airline Deregulation Act of 1978 . <S> (Note: there are still some small airlines and routes that are subsidized to serve very small communities... <S> If you want to read more about this program, it's called Essential Air Service .) <A> There are many meanings of "flag carrier", one of which is not addressed in the other answers. <S> In regulated international air travel markets, each pair of countries would agree (via treaty) to let each others' "flag" carriers fly between them. <S> For instance, Britain would allow Air France (France's flag carrier) to fly to London in return for France allowing British Airways (Britain's flag carrier) to fly to Paris. <S> Where a country owned and/or subsidized one particular airline, that was the obvious choice as the flag carrier, but that is the only connection. <S> The US, for various reasons, was allowed to name two flag carriers: Pan-Am and TWA. <S> Later deregulation of the most profitable markets left them vulnerable to destructive competition, and they eventually folded. <S> United inherited Pan-Am's flag status, and American inherited TWA's flag status. <S> That doesn't matter in the many deregulated markets, of course, but it still matters for the many markets that are still regulated. <S> Non-flag carriers, such as Delta, can only access regulated markets via a codeshare agreement with the other country's flag carrier. <A> All US carriers operating on a type 401 certificate are referred to as flag carriers. <S> No subsidy issues are part of consideration <A> We were recently told these were the Flag Carriers of the US, under the Fly America <S> First : <S> Federal travelers are required by 49 U.S.C. 40118, commonly referred to as the "Fly America Act," to use U.S. air carrier service for all air travel and cargo transportation services funded by the U.S. government. <S> My company gave us this list: U.S. flag air carriers: <S> • Airtran Airways (FL) <S> • Alaska Airlines (AS) <S> • American Airlines (AA) <S> • Continental Airlines (CO) <S> • Delta Airlines (DL) <S> • Frontier Airlines (F9) <S> • Hawaiian Airlines (HA) <S> • <S> JetBlue Airways (B6) <S> • Midwest Express (YX) <S> • Southwest Airlines (WN) • <S> Spirit Airlines (NK) • United Airlines (UA) <S> • <S> USAirways (US) <S> With plenty of exceptions relating to international travel. <S> From vanderbilt.edu/ocga/docs/vupolicies/FLYAMERICAACT.pdf <S> U.S. Flag Air Carrier. <S> The term "U.S. flag air carrier" means an air carrier holding a certificate under section 401 of the Federal Aviation Act of 1958 (49 U.S.C. App. 1371). <S> Foreign air carriers operating under permits are excluded.
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A flag carrier is a transportation company, such as an airline or shipping company, that, being locally registered in a given state, enjoys preferential rights or privileges accorded by the government for international operations.
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Do pilots have their own in-flight entertainment? Besides flying the plane and talking to the person in the other seat, what other forms of entertainment are (also legally) available to pilots while on the job? I'm thinking of 'activities' like reading, listening to music, watching a movie, or... playing a flight simulator game on a laptop. <Q> I am not aware of any legal requirements, but rules may differ according to the country of jurisdiction. <S> Generally it is up to the company that a pilot works for to establish their own rules to cover "in-flight entertainment" in the flight deck. <S> Most companies do not allow it. <S> It has been my experience that the rules are generally ignored and common sense rules are used instead. <S> During non-critical phases of flight, pilots will often read newspapers, books, iPads etc. <S> Many will do crossword puzzles or Sudoku. <S> A few will even listen to music or watch a video, but it is pretty rare. <S> In 40 years of flying, I can't recall ever seeing a pilot play a video game or flight simulator. <A> For Part 91 flight operations, many pilots will listen to the radio or music. <S> I have often listened to songs on my iPhone music library fed through an aux jack into my headset. <S> One older option, if the aircraft is equipped with a functioning ADF, is that, since NDBs broadcast in the kilohertz range, pilots can tune an ADF into AM radio stations and put it through to their headsets using the audio panel. <S> The ADF needle will point in the direction of the AM radio transmission tower for that station. <S> AM stations that are tracked this way can be used as a supplemental navaid in VFR operations but are not approved as terrestrial navaids for IFR operations. <S> I can't speak for Part 121 or Part 135 operations <S> but I'd venture a guess that such activity is frowned upon by employers during flight operations. <S> But I'm sure many a 747 or A380 crew over the Pacific at FL410 with another 9.5 hours to go before making Kingsford Smith Intl will listen to the radio or take turns watching outside of the aircraft while the other flight crewmember reads a book or relaxes. <S> It is important to limit these activities to low workload phases of the flight such as long stretches of cruise in low density airspace and maintain a sterile cockpit during attention intensive phases such as takeoff, departure, approach and landing. <S> I will only listen the the radio in cruise and use is terminated at least 10 minutes before a planned descent begins. <S> A pilot should do a realistic self assessment of his/her flying abilities and refrain from the use of these things if they have difficulties with multitasking or are easily distracted from the airmanship tasks at hand. <S> Use of entertainment products during emergencies is unacceptable as well. <A> Having been a couple of times at the flight deck myself I have seen and asked pilots a similar question. <S> The pilots have to routinely monitor the instruments so playing a game reading a book or watching a movie imposes a high risk on "forgetting time" <S> so the pilots I spoke did not do this. <S> They spend quite some time on the flight monitoring part, communicating with ATC and OCC adjusting their course. <S> Then you have the occasional flight attendant visiting the flight deck who stays for a chat or brings food. <S> Newspapers are also read and provide food for conversations and if there is enough staff they can make a short walk though the cabin. <A> Interesting question. <S> I work for an In-flight Entertainment company and none of our in-seat video systems <S> have ever included anything for the pilot to interact with, other than the PA-system. <S> With the PA-system they can entertain themselves with knowing that they're pausing all passenger entertainment for the duration of their prolonged speech. <S> Now for our new WiFi based entertainment systems, there's nothing to stop a pilot with a PED (Portable Electronic Device) from connecting to the entertainment system like a passenger. <S> Personally I would hope a pilot would never do this.
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And many IFDs and integrated GNSS navigation systems often offer XM weather and XM Radio services through subscription that pilots will use to listen to XM radio, as this SR-22 pilot making a flight out to Camarillo, CA does. Use of visual entertainment such as movies, television programs, video games, etc., is not allowed for a flight crew as they are required to maintain visual scanning outside the aircraft, if able, for situational awareness and collision avoidance.
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Why do all commercial aircraft have carpets? When flying I noticed that all the commercial aircraft I have been on use carpets as a floor covering. But why? If you fly in an older aircraft it looks worn out and it is susceptible to stains etc. Why do they not use one of the hard flooring options like linoleum? <Q> helps prevent slips and falls contains spills (your spilt soda won't ruin your neighbors bag) <S> more easily removed and replaced helps reduce cabin noise <A> The answer: High heels! <S> The local pressure of high heels would punch a hole in the aluminium or composite flooring, and a carpet is the lightest way to distribute the loads such that the local pressure from high heels can be tolerated. <S> This is the real reason. <S> From Aircraft Structures Summary <S> On the floor of the fuselage also very high localized loads can occur, especially from small-heeled shoes. <S> Therefore floors need a strong upper surface to withstand high local stresses. <S> Other reasons are improved noise absorption and damping of vibrations. <S> Nobody likes it when the floor panels start to resonate when excited by some engine or pump frequency. <S> With composite panels now in widespread use for cabin interiors, manufacturing flaws need to be covered, and carpets serve this purpose well. <S> From Compositesworld.com : <S> Because sandwich panel facesheets are very thin, core print-through is common. <S> Further, pinholes can form as phenolic resins outgas during reaction and cure. <S> Therefore, panels visible to passengers typically are surfaced with some type of decorative material to cover surface flaws. <S> Floor panels can be painted or covered with flame-retardant carpet. <A> Could you also imagine the difficulty of holding the trolley during turbulence or anything else? <S> It would roll down and run someone over! <S> I also saw a Quora post where someone had pointed out it's also flame retardant, which is a good point. <S> Comfort is important too, not to mention another place to put advertising on some planes <A> Carpet is more pleasant <S> Aside from the practial reasons Greg already mentioned, most if not all people, will consider a carpet as a more pleasant material than ugly linolum. <S> The fact that you have to replace a carpet after some years, counts also for most the interior in a plane (seats, board-entertainment, cover panels and so on). <S> In the good old days TWA rolled out a red carpet for their passengers at the check-in desk :)
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Furthermore a lot of people take their shoes of during long flights and a carpet feels in this situation a lot more comfortable.
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Should I record my helicopter and autogyro time in separate logbooks? I have been flying autogyros for some years now, and I am out to do my license on UL helicopters. I bought a new logbook to log all time in helicopters separately from autogyros. Is that correct? In a few days I will also be taking some lessons in an R22. That's not even UL anymore. Do I have to get another logbook for all flying of non-UL aircraft? Would I log it all in the same logbook? <Q> In the United States, except for that time which is used for certification or currency, the FAA permits you to log your time however you like, or even not log it at all. <S> That means that you can do pretty much whatever you feel like . <S> That said, here are my personal recommendations in order of how much I support them: Get a digital pilot logbook . <S> Log everything in it. <S> Get <S> a professional pilot logbook with plenty of space for various categories and classes of aircraft. <S> Copy all of your records from your old logbooks into it. <S> Archive your old logbooks in a safe location. <S> Use your new logbook for everything from here on. <S> Get a professional pilot logbook with plenty of space for various categories and classes of aircraft. <S> Don't copy all the records from your old logbooks into it, just carry forward the totals. <S> Archive your old logbooks in a safe location. <S> Use your new logbook for everything from here on. <S> Remember which logbook is which. <S> Keep them all easily accessible rather than storing them in a safe location. <S> Worry about whether you lost one. <S> Have a complicated system of adding up your totals from various logbooks. <S> Make it difficult to look up flights chronologically. <S> Feel sad. <A> You would have to make sure your flight time was differentiated into category and class of aircraft. <S> Most logbooks have a blank category on their pages; just fill in ULTRALIGHT or UL in that column and add your hours that way. <S> Now some of those flights can be logged under the columns for PIC, Cross Country flight time, dual instruction, takeoff and landings, etc. <S> as well in the new logbook and can count towards some hour requirements for another certificate. <S> Reference <S> 14 CFR Part 61 for specific requirements <A> There are no regulations governing how many logbooks you may use, nor their exact construction. <S> If it is easier for you to manage your time with multiple logs, that is just fine. <S> If you need a flight review entry, you can always photo copy that entry in one book, and clip or tape a copy into a different book. <S> Personally, when instructing, I use a "critique sheet" which I review with the student at the end of the flight, and we both sign. <S> That sheet becomes my log entry. <S> For other types of flights I may use a traditional log book. <S> While I have several, I avoid the large professional books, because of their size and weight.
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Log your time in whichever logbook is appropriate. Get one logbook for each category/class of aircraft you intend to fly.
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Does the FAA dictate that bridges are closed for the Thunder Over Louisville airshow event? A big tradition here in Louisville is "Thunder Over Louisville". This starts the celebration for the Kentucky Derby. 'Thunder' is an airshow, fireworks, fair, concerts, and a nice day out along the river. This event leads to the closure of bridges over the Ohio River. Some closures are brief, such as I-65. Others are days long because fireworks and other aspects of the theatrics are positioned there. We have a new pedestrian bridge called "The Big Four Bridge" which was opened very recently. This bridge is closed despite being a very obvious attraction to attendees and it can ease car traffic by allowing foot traffic across the river. There are many notices that this bridge is closed, but none of them cite the authority that closed the bridge. Does the FAA hold sufficient authority to close bridges, roadways, or other locations for an airshow? If so, what resources should I use to locate these closure notices? This question is simply a curiosity. There are many logical reasons for the 'Thunder' organizers, local police, state police, and the FAA to close the pedestrian bridge. I want to learn more about what authority the FAA specifically would have in this matter just for the sake of learning. <Q> The FAA has no authority over roads, bridges or any other public roads. <S> Usually, it's the the event organizer who's responsible for requesting and coordinating road closures; think of triathlons, parades etc. <S> And even without the FAA, there are very good reasons for the local police to close the bridges: rubbernecking and accidents caused by distracted drivers; keeping people safe when fireworks are set off from the bridges and so on. <S> But, at least in theory the FAA could indirectly require road closures as part of an airshow waiver . <S> Most airshows require a waiver, i.e. permission from the FAA to 'ignore' certain regulations. <S> The list of regulations that can be waived is in 14 CFR 91.905 and you can immediately see why some of them would be waived for an airshow. <S> These ones in particular seem very relevant: <S> 91.111 <S> Operating near other aircraft. <S> 91.117 <S> Aircraft speed. <S> 91.119 <S> Minimum safe altitudes: General. <S> 91.303 <S> Aerobatic flights. <S> The full instructions for issuing a waiver are long and detailed but there are lots of requirements to ensure minimum distance between aircraft and spectators, and to ensure that the energy vectors of aerobatic maneuvers are not directed towards crowds. <S> I haven't been to Thunder yet <S> so I don't know to what extent the aircraft actually maneuver vs. flying in stable formation down the river. <S> But, it's at least very plausible that the FAA has issued an airshow waiver requiring a minimum distance from spectators that can only be guaranteed if some of the bridges are closed. <S> And, if the park area around River Road is the main spectator area, then any aerobatic maneuvers would have to direct their energy vectors along the river, i.e. towards the bridges. <S> That could require the airshow organizers to request that the bridges be closed. <S> Unfortunately I couldn't find out if airshow waivers are public or not <S> (a quick search on faa.gov didn't find any) <S> so I don't know if it's possible to check which FAA regulations have been waived for Thunder, or what conditions they placed on the organizers. <A> The FAA definitely has problems with the bridges. <S> They don't have authority to close bridges, but they do have authority to refuse the waiver contingent upon things they feel are not safe. <S> It started while the bridge was under construction. <S> They almost didn't approve the waiver due to the cranes. <S> Apparently they were satisfied when the fire dept was able to put flags on them to make them more visible. <S> Last year they wouldn't approve a "box" big enough for the USAF Thunderbirds to do their maneuvers. <S> And it seems that now the bridge is there they probably won't ever approve enough room for the T-Birds. <S> So, it would appear that the bridge closure is a compromise with the FAA. <A> No, the FAA does not have the authority to close a bridge, roadway, or other general public item outside of an airport or airspace. <S> The appropriate regulations are 14 CFR 91.303 Aerobatic flight. <S> No person may operate an aircraft in aerobatic flight-- <S> (a) Over any congested area of a city, town, or settlement; (b) Over an open air assembly of persons; (c) <S> Within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport; (d) <S> Within 4 nautical miles of the center line of any Federal airway; (e) <S> Below an altitude of 1,500 feet above the surface; or (f) <S> When flight visibility is less than 3 statute miles. <S> For the purposes of this section, aerobatic flight means an intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight. <S> I've highlighted the appropriate parts of the regulation that would require a bridge to be closed, however the FAA does not actually do the closing. <S> The show organizers need to coordinate with local/state officials (depending on if it is a local or state controlled road) to have the correct area's closed off so that the show does not violate the regulations. <S> There is a waiver process as noted in Pondlife's answer <S> but I don't believe the FAA will issue waivers for (a) and (b). <S> The most usual waiver is probably for (c) and (e). <S> How they close it is up to them, but it is the organizers responsibility to ensure that the FAR's are not violated.
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So, in short, the FAA cannot close the roads, however it can regulate the airshow which would require the organizers to abide by the FAR's.
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Does the tailwind component always have the same absolute value as the headwind component? If we are on course 360 and we have crosswind from 020 at 20 kts...does the amount of head wind on this leg equal the amount of tailwind on the reciprocal course (i.e. 180)? To amplify the question with an example: TAS: 260kts Wind velocity: 310/35 kts Given the above information, calculate ground speed on courses 240T and 060T. When I use e6b+ aviation calculators, I get the following answers: On a course of 240, the ground speed is 246kts. This is 14kts slower than the true airspeed. On a course of 060, the ground speed is 270kts. This is 10kts fasterthan the true airspeed. Since I believe the headwind and tailwind components should be equal, the question is: why is there a difference of 4kts between the computed headwind component and the computed tailwind component <Q> YES, If the "amount of headwind" was 10 knots due to the crosswind, then the "amount of tailwind" would also be 10 knots on the reciprocal course. <S> BUT, because the 10 knot disadvantage with a head wind will last for a longer period of time than the 10 knot advantage with a tailwind, the entire trip will take longer and use more fuel than a trip in still air. <S> EXAMPLE: <S> The headwind leg is 15 minutes longer, but the tailwind leg is only 10 minutes shorter, so you have a net loss of time. <A> Does the amount of head wind on this leg equal the amount of tailwind on reciprocal course ie 180? <S> In both case the intensity of the head/tail wind component will be $\left\| W_l <S> \right\| = \left\| W \times cos\; W_a \right\|$ <S> where $W$ is the wind intensity, $W_a$ is the angle between heading and wind. <S> For a 20 kt wind at 60° ($cos\; 60° = 0.5$), the result is 10 kt. <S> The cross-wind component is also reversed with the same intensity. <A> My answer comes from the point of view of a cyclist (also being subject to the effects of headwinds and tailwinds).I would suggest that any form of consistent winds on a round trip can only act to make the net effort required greater than in calm wind conditions. <S> Consider the effect of two special cases <S> : Consider a strong cross-wind, blowing at 90 degrees to the path being travelled (say, a westerly wind). <S> In both directions, (north and south), you will face increased head winds. <S> In an aircraft, you would need to aim somewhat west of your intended direction in order to stay on course. <S> Both legs of the journey would be more difficult. <S> Consider a strong head-wind, blowing parallel to your course (head-wind in one direction and tail-wind on the way home). <S> For the sake easy maths, let's assume that the wind-speed is half that of the cruising airspeed of your aircraft. <S> Going into the wind, your ground speed will be only half that of still conditions and so the journey will take twice at long. <S> A one-hour flight (in still conditions) would take two hours. <S> To make up all that lost time on the way home you would need to be moving very fast. <S> However the tail-wind would only make your ground speed 1.5 times your normal speed and you would return along the 1-hour path in only 40 minutes to give a round trip time of 2hrs 40mins. <S> In both cases, and therefore all variations of wind directions and for all wind strengths above 'calm', your total round-trip time will always be longer. <S> If you are only concerned with differences in airspeed (and not how long it will take to cover a certain distance), then a direct tail wind will help in one direction and a direct head wind will hurt in the other direct with commensurate changes to net ground speed. <S> However, as soon as there is any cross-wind component, that will hurt in both directions, hence the 4kt discrepancy mentioned in the question.
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Yes, the intensity of the tailwind will be the same than the intensity of the headwind.
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What is this ring-shaped device behind this DC-8's jet engine? What is this ring-shaped device behind this Douglas DC-8 's jet engine? ( YouTube ) <Q> ( airliners.net ) Ejector on the Rolls-Royce Conway of a DC-8. <S> It's called an ejector. <S> Introduced in c. 1958 by Douglas for their DC-8, it is extended during takeoff and landing, and stowed during the flight because it increases the drag at high-speed flight. <S> In the extended position it acts as a noise suppressor, <S> and it also reclaims thrust that has been lost due to the corrugated exhaust nozzle . <S> Doors within the ejector also close to provide thrust reversal. <S> ( Flight—PDF ) <S> Two views of the device developed by Douglas to suppress the sound and reverse the thrust of the DC-8. <S> The corrugated exhaust nozzle is combined with a cylinder which extends beyond the nozzle during take-off. <S> This "ejector" is claimed to reduce the sound level by 3-4 decibels and increase the thrust sufficient to offset the loss caused by the nozzle. <S> The indentation near the forward lip of the ejector is one of the two doors which close to form a thrust brake. <S> Noise level with the ejector ring and nozzle combined is said to be reduced by 9-12 decibels. <S> (Images from aamalebourget.fr and flightglobal.com ) <S> The image on the right shows a similar installation on the BAC <S> One-Eleven with the positioning screw-jack mechanism. <S> ( YouTube ) Factory testing of the ejector on the DC-8. <A> Normally extended for T/O and landing, it is retracted in flight after T <S> /O because it is no longer needed and creates drag at higher speeds, and then it is extended during the descent/approach phase. <S> It is operated hydraulically to extend and retract, and can be extended by an air bottle in the event of a hydraulic failure. <S> The controls for extending/retracting are two switches on the left overhead panel, one for ejectors on the two outboard engines(1 and 4) and the other for the two inboard engines (2 and 3), and the backup compressed air bottle extends all four and is located on the left side of the throttle quadrant. <S> Individually, the ejectors can be extended by pulling up individual thrust reverser levers on the throttles and the ejectors will retract again when reverse thrust is deselected. <S> The ejector does two things. <S> It reduces noise and improves thrust output up to approx. <S> 150 knots. <S> It also carries the thrust reverser which operates pneumatically to increase descent rate or slow the aircraft inflight and on landing to reduce the landing roll and reduce wear on the wheel brakes. <S> It was developed and fitted on the DC-8 at the factory by Douglas during the flight test phase of the DC-8 program before certification and entry into service and was not an aftermarket hush kit attempt by any third party. <S> I know this because I was a Captain on the DC-8 for 10+ years. <A> People got this one partly right; it's Xenu's ride - a DC-8 (not a 707) fitted with aftermarket hush kits to reduce noise. <S> They included a non-flush clamshell thrust reversers for the hot section fitted to accommodate the hush kit nozzle. <A> The early DC-8 fitted with Rolls-Royce Conway engines had that airframe mounted ejector type thrust reverser system, it was simple, fairly light and reliable. <S> Even though the ejector brought some noise attenuation benefits it was not part of a hush kit. <S> The Conway engine was very responsive but also very noisy. <S> Later DC-8, <S> fitted with Pratt & Whitney JT3D engines <S> had engine mounted fan (bypass flow) <S> reverser doors and engine mounted primary flow clamshell type reverser. <S> These 2 systems were heavy, complex and hardly reliable. <S> Boeing 707 fitted with P&W engine also had complex, awkward thrust reverser systems. <S> Trans Canada Airlines was the ancestor of Air Canada and purchased 11 of the Conway powered DC8. <S> It was the first engine I worked as a 19 year old apprentice mechanic at Air Canada power plant shop in Dorval in 1967.
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It's an ejector and was fitted on the DC-8's equipped with JT3C, JT4A or RR Conway engines.
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What is the physical meaning of Mean Aerodynamic Chord? I have not been able to find a consistent definition of what it really is. I have come across definitions such as: "Physically, MAC is the chord of a rectangular wing, which has the same area, full aerodynamic force and position of the center of pressure at a given angle of attack as the given wing has." which is contradictory with this one "The mean aerodynamic chord is (loosely) the chord of a rectangular wing with the span, (not area) that has the same aerodynamic properties with regarding the pitch-moment characteristics as the original wing." I am very confused and I wonder if you could please give me a precise definition (maybe in relation to an equivalent rectangular wing, as those two definitions I found), that shows intuitively what it is <Q> For tapered wings it is slightly longer. <S> Why? <S> Because the mean aerodynamic chord is the mean chord of a rectangular wing that has the same pitch characteristics as the "real" wing. <S> Pitch characteristics need to include pitch damping, and pitch damping grows with the square of the local chord. <S> That is why the formula for the mean aerodynamic chord divides the square of the local chord by the wing area:$$\text{MAC} = <S> \int_{y=-\frac{b}{2}}^{y=\frac{b}{2}}{\frac{c^2}{S}}dy$$Here <S> $b$ denotes wing span, <S> $y$ the spanwise coordinate and $S$ the wing area. <S> Since the chord is squared, deeper sections of the wing are overrepresented in the result. <S> The resulting rectangular wing will have a larger area than the original, tapered wing but the same pitch damping! <S> In case of a delta wing, MAC will grow to be ⅔ of the root chord, and for an elliptical wing it will be 90.5% of the root chord. <S> The MAC has been invented to convert arbitrary wing planforms into much easier to calculate rectangular wings. <S> By doing all calculations on the correctly sized rectangular version, the more complicated calculations on the real one could be avoided. <S> However, this works only up to a point: <S> if you want to calculate lift, you need a wing of equal area. <S> if you want to calculate induced drag, you need a wing of equal span. <S> if you wand to calculate pitch motion, you need a wing of the correct MAC. <S> This rectangular wing can either have the same area or the same span as the real wing, but not both together, unless the real wing is rectangular, too. <S> You are right, the two definitions you quote are not compatible. <S> The rectangular wing cannot have the same span than the real one, or its area and all associated forces and moments would be higher. <A> On transport aircraft, as you have already gathered the position of its centre of gravity is expressed in relation to the MAC. <S> The definition of MAC, that I will provide is I hope a little clearer. <S> If you were to take a plan view of the wing and draw any number of chord lines over the surface you would notice they're of various lengths, usually longer at the end closest the fuselage (wing root) and <S> shorter at the end farthest the fuselage (wing tip) with different distances from the nose of the aircraft, the shortest distance being again at the root and farthest at the tip. <S> Applying mathematics to find the mean of all those chord lines you have the MAC. <S> This is shown as a single length beginning at the 'reference datum'. <S> For example, an aircrafts MAC may be 520cm in length extending from 2006cm to 2526cm aft of the reference datum. <A> Mean aerodynamic chord is the chord drawn through the centroid (geographical center ) of the plan area.remember <S> it is not the average chord <S> but it ia the chord through the centroid of the wing area..
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The mean aerodynamic chord is only identical to the mean chord for rectangular wings.
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Can a passenger drone perform auto-rotation? ( Source ) The Dubai Drone is an Ehang passenger drone planned to start commercial services in July 2017. If there is a failure, can such an electric multi-copter auto-rotate a landing? I'm wondering, if an electric motor would even allow auto-rotation, and if the autopilot could handle it? Are there regulations for devices like that? <Q> That drone has fixed-pitch rotors, and that pitch is optimized for thrust, not for autorotation. <S> In the absence of power, those rotors won't autorotate. <S> They will stop rotating 'in the right way' and then start windmilling in the opposite sense. <S> That windmilling will cause drag and some deceleration of the fall, but not of the same magnitude as an autorotation, that is a different condition. <A> The 184 is technically an X-8 multi-rotor, meaning that it has four points of thrust, each consisting of two motor-propellers, coaxially aligned—one “tractor” propeller and one “pusher.” <S> This means that if any one of the motors dies, or a propeller disintegrates, the aircraft won’t flip and crash to the ground, although it would need to land rather quickly. <S> The concept has never been tried in an operational passenger service, however, and some feel that without further safety enhancements the drone taxi idea is a disaster waiting to happen. <S> — <S> airspacemag.com <S> The article also discusses how Dubai's hot climate would limit the performance. <S> As for regulations, so far I can't dig up any, but in the US taxi drones are not allowed. <S> FAA regulations prevented it from being legally tested in the US. <S> In Dubai, however, the Civil Aviation Authority partnered with EHang in testing the device. <S> — rt.com <A> Simple answer. <S> No. <S> For autorotation to work the pitch of the blades needs to be variable. <S> At the instant of engine failure, the main rotor blades are producinglift and thrust from their angle of attack and velocity. <S> Byimmediately lowering collective pitch, which must be done in case ofan engine failure, the pilot reduces lift and drag and the helicopterbegins an immediate descent, producing an upward flow of air throughthe rotor system. <S> This upward flow of air through the rotor providessufficient thrust to maintain rotor rotational speed throughout thedescent. <S> Since the tail rotor is driven by the main rotor transmissionduring autorotation, heading control is maintained as in normalflight. <S> - https://en.wikipedia.org/wiki/Autorotation <S> A drone or multicopter with 6 or more propellers can continue flying as long as the thrust provided by the remaining propellers and engines is sufficient to keep it from falling. <S> The aicraft may however begin to rotate around its own axis. <S> In normal flight there are an equal number of clock wise and counter clockwise rotating propellers. <S> If a propeller/motor stops spinning the torque of these engines will no longer cancel each other out so in order to not descend the helicopter may be forced to accept a rotation around the Z axis. <S> This same mechanism is used for turning a multirotor, lower the RPM of the propellers spinning in one direction <S> and you will turn in the other. <S> I fly RC drones myself and have tested how my hexacopter behaves during a motor failure. <S> The conclusion I came to is that if it was close to its carrying capacity it would rotate since it needs all the power it has and can't worry about rotation. <S> But if it only carried a light load it woulden't rotate as it has power left over to compensate for it. <S> There are however a few attempts at making drones with variable pitched propellers <S> This however negates the pure simplicity that a drone provides as one of it's main advantages is that there are only as many moving parts as there are propellers. <S> In my opinion and others ( http://diydrones.com/forum/topics/why-are-we-not-seeing-more-variable-pitch-quadcopters ) the only way to provide a reliable drone is to have 6 or more propellers and lots of power to spare. <A> I am a career helicopter pilot who enjoys watching the development of drone technology. <S> I can tell you for certain that this aircraft is incapable of autorotation. <S> A parachute would be <S> it's best option for pure simplicity. <S> This would not guarantee a safe landing, just avoid a 'splat'. <S> It is very apparent to me that the number one challenge of the drone industry as it relates to increased payload (passengers, cargo, luggage) is power. <S> Drone advancement is highly reliant on battery advancement. <S> If you have a lightweight, high powered battery system, then the sky's the limit for drones, safety and otherwise. <S> Short of that, I'm still waiting for the big breakthrough. <S> For now, I'd just like to see y'all drone drivers get an anti-collision light. <S> Oh wait... <S> more power is going to be needed for that :)
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A drone with fixed wing propellers such as the one you describe can not autorotate. If a single motor fails, it's not unsafe (supposedly).
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How did the 747SR fly from Qatar to London? The following photo on the Boeing 747 Wikipedia article reads: Qatar Airways 747SR-81 landing at London Gatwick Airport in 1996. How did the 747SR manage this flight [on a regular basis]? The only range information I can find for the SR (short range) is from ANA's fleet history , which puts it at 2,590 km. The -SR also had "a 20 percent reduction in fuel capacity." (gcmap.com) Range of the 747SR plotted from Doha and Cairo. Out of the ~520 seats, how many seats were empty to make the trip, or were there stops on the way? I thought maybe a Doha-Cairo-London route, but that falls short as well. This airplane was also seen as far as Bangkok . These probably are not rare trips, i.e., the destinations are likely to have been regularly served. <Q> I was senior cabin crew at Qatar in 1995/96. <S> Flew on the 747 for about 1 year. <S> My first flight was DOH-BKK-MNL Xmas week 1995. <S> 3 pilots, 14 cabin crew and 1 aircraft mechanic, which was the standard crew numbers. <S> We had 57 passengers all the way to MNL as BKK was in a refuelling stop. <S> If I recall there were 20 First Class seats upper deck and 508?+ seat all economy main deck. <S> The configuration never changed from the ex-ANA seating plans. <S> Gatwick was flown both ways via Cairo and was never full each sector. <S> In the period I worked on the 744, Qatar was still a closed country. <S> There were no tourists and our passengers were mainly workers to and from Doha. <S> After BKK started as a drop off port we would have 1-5 transit pax via DOH. <S> Our Bangkok route which was actually to Manila was a refuel stop only at Dhaka. <S> Flight loads were minimal. <S> First we would only ever have 5-10 max pax. <S> Economy I recall ever having over 200 passengers. <S> The 747sr was also used regularly to Khartoum. <S> They were used also around the Gulf on various flights. <S> The 747sp ex Air Mauritius replaced the 747sr for a few months in the DOH to MNL via BKK with Dhaka dropped. <S> I flew the 747sr on a DOH-DXB-DHA-CMB-DOH route, 20+ hour duty. <A> ( Boeing ) <S> Non-stop (2,820 NM) is doable (minus a ~25-tonne limitation). <S> The plane can make it with 396 passengers (compared to the 624 shown above). <S> ANA's figure of 1400 NM assumes a full payload of 624 passengers. <S> (gcmap.com) <S> Doha-Bangkok is almost the same distance at 2,857 NM. <A> If it doesn't have the range on internal fuel, two possibilities remain: Ferry tanks - auxiliary fuel tanks installed in the cargo compartments to give the aircraft the additional fuel to fly the route nonstop. <S> Or, most likely, additional stops along the route of flight for fuel. <S> It could easily make Istanbul, thence multiple options for fuel in Europe prior to flying to London. <S> Now a 747SR has 20% less useable fuel over the 747-100, which, from a simple back of the envelope calculation, would offer a 20% reduction in range over -100. <S> This gives an estimated maximum range of 3,696 miles. <S> A straight line distance from Doha, Qatar to London, UK is 3,242 miles.
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Assuming favorable winds, it is reasonable to believe the airplane could make the flight nonstop with IFR reserves.
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How can seagulls slide in the wind without flapping their wings? There are a lot of seagulls in a park near where I live. Sometimes I can see them somehow "sliding" forward or backward diagonally when flying against the wind, however, their wings aren't flapping. What are the flight mechanics behind this? Can gliders mimic this style of flight? <Q> I've never heard of other birds than albatrosses do dynamic soaring , but since this is over land, it can be simpler ridge soaring —as the sea breezes hits the shore (and obstacles on it), it turns upwards and the birds simply fly in this updraft. <S> They are flying against the wind and gliding down relative to it, but when you add the speed of the wind, they may be stationary relative to the ground—or zig-zag from side to side if the wind speed is a bit less than the forward speed the birds need to efficiently glide. <S> Gliders can do the same, but since they are bigger, they need a mountain range where the seagulls can do with a several feet embankment. <A> If your perception is that the seagulls are pointing straight into the wind but moving sideways to the wind, I suspect that you are mistaken. <S> When the wind is strong and the groundspeed is very low, it only takes a slight difference between aircraft (or bird) heading and wind direction to produce a large crosswind component in the ground track. <S> This is certainly true for gliders (and airplanes) as well as for birds. <S> So "sliding sideways" in relation to the wind is accomplished by steering the aircraft (or bird) to point slightly to the left or right of where the wind is coming from. <S> In strong wind, an aircraft or bird can move perpendicular to the wind direction, with no "forward" progress, while still pointing almost directly into the wind with wings level. <S> Note that this does not actually involve any sideways component to the airflow over the aircraft (or bird). <S> If the seagulls you observed are maintaining altitude while doing this, without flapping their wings, then they are undoubtedly in slope lift. <S> Slope-soaring on a windy day often involves pointing almost straight into the wind, even while the ground track follows the line of the slope, which may be perpendicular to the wind. <A> Perhaps it's the case of the seagulls that you have observed. <S> https://en.wikipedia.org/wiki/Dynamic_soaring
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Some birds 'harvest' energy from the wind gradient.
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Can a low flying jet fighter lift water? Can a low flying but super fast jet spray water from the surface of the ocean? I've seen this visual effect done many times in movies. It's often done to highlight supersonic speed just a few feet above the water. Do the laws of physics even come close to this being plausible? Bonus : Can you provide photograph evidence of this happening? <Q> The visual effect in the picture you found seems to suck water out of the sea, in this real footage the f-18 air shockwave tends to push water down, and makes a trail. <A> And this video gives quite the explanation on how this happens... <S> The way it works: condensation effects: the air speed increases as the air flows around the aircraft <S> this can mean, that the air may travel faster than the speed of sound air pressure and temperature drop, when the airspeed increases this leads to condensation, because the cold air cannot hold the amount of water anymore <S> the cloud the aircraft is seemingly dragging along are condensation effects <S> the cloud is a local effect, it is not dragged along shock waves: <S> they are created, when the air cannot get out of the way of the aircraft fast enough this way, they form a pressure wave that is the sound the aircraft makes generally two waves, one bow and one tail <S> the rocket at the end : <S> the air is cold there are tiny ice crystals in the clouds <S> they make the two pressure waves of the rocket visible <A> I've wondered about this, too. <S> From what I've discovered looking around online <S> (and I am NOT a pilot or physicist) <S> is that it's something of a myth -- at least in terms of the dramatic waterspout-effect like in the painting above and countless movies. <S> The idea may have started because of images like below, where a Blue Angle flies low over water then, as it pulls up, the jet engines directly angled toward the water do indeed blast a huge spray -- but that's very different than sucking up water in level flight. <S> So, the answer is: yes, a low-flying jet can disturb the surface of water, but not quite in the way it's depicted in the movies. <S> https://www.military.com/video/aircraft/jet-fighters/blue-angels-low-pass-over-water/1090049790001
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A fast, low-flying jet may create some shockwaves (not to be confused with the "vapor cone") that would disturb the surface of water, or some updraft that sucks up spray, but nowhere near the massive amount of water depicted.
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How can two planes be on the same taxiway facing opposite to each other? Curious to know how two planes can be on the same taxiway facing opposite to each other at the same time? Please have a look at the satellite view of the following coordinates in Google Maps: ( -27.369843, 153.126482 ) <Q> The taxiway is being used for parking. <S> Specifically, parking of two MD-80s that have attracted press attention—The Australian: Clive Palmer’s <S> $10m in tax-haven jets sitting idle : <S> TWO <S> 155-seat jets owned by Clive Palmer and branded with the name of his controversial and longtime loss-making company Mineralogy sit mothballed in a remote corner of Brisbane airport. <S> The McDonnell Douglas MD-82 jets, worth roughly $5 million each, are registered in the Cayman Islands tax haven and have sat mothballed for months, possibly years. <S> ... <S> A spokeswoman from Brisbane airport confirmed the planes were owned by Mr Palmer and had sat idle for “at least several months”, but was unable to confirm exactly how long. <S> “The space is leased from Brisbane airport and the owner pays leasing fees to have them there,” she said. <S> That article from 2014 shows them parked head-to-tail, but presumably they've been moved since then (the Google maps imagery is from 2017). <S> If you're wondering how I found this, I zoomed in on the satellite image and used 3D mode to get a better view of the side of the aircraft well enough to sort of make out the "Mineralogy" label on the side, and Googled from there. <A> Without knowing the exact date and time that the images were taken and with access to someone on shift at the time, it's impossible to give a definitive answer so here are some "myth plausibles". <S> Mapping images are stitched together from different frames from different satellite passes by software. <S> The software will select two images based on contrast, clarity and other optical attributes or perhaps because of data corruption. <S> Whilst this image is made up of at least two frames from different times, I can see no signs that the two aircraft are from different frames. <S> It's happened before, it will happen again. <S> However, these are tail to tail <S> and I cant think of anyway that this could have happened. <S> The only remaining explanation I can think of, and the evidence points to this being the case, is that the taxiway is being used for temporary parking. <S> The ramp is pretty full and it is plausible that the two aircraft have been parked tail to tail so that either one can get out without having to move the other. <S> Searching Google shows regular NOTAMs which support this, e.g. J0899/13 NOTAMN <S> [ Taxiway ] Q)YBBB/ <S> QMXAU/IV/NBO/A/000/999/2723S15307E <S> A)YBBN B)1303140318 <S> C)1306130700EST E)TWY F3 NOT AVBL <S> DUE ACFT PARKING <S> ** <A> The image is real they have been parked that way for several years and have not moved I know this because they are at the General Aviation Terminal at Brisbane airport <S> and I go by them fairly regularly <S> there is no air controller errors of trick photography anyone looking out the window flying in and out of Brisbane Domestic will see them sitting there.
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A controller made a mistake and cleared two aircraft onto the same taxiway at the same time.
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What is the best word for lateral translational movement in a rotorcraft? I'm talking about movement left and right without changing attitude. This is a motion that can be done with a quadcopter and to a limited extent a helicopter (I presume). On a helicopter a left/right movement of the cyclic will command a roll motion from the rotor, but in a hover the aircraft would only roll slightly then begin to move sideways. Does the pilot just call this a roll or is there another, more appropriate word? I thought of slip or crab, but those describe specific attitudes associated with forward flight. They don't seem to fit the bill here. <Q> (Easy Left/ <S> Easy Right as we got closer to the spot). <S> The FAA term "sideward hovering" suffices, but it is two words. <S> If you want one word, slide is about right. <A> The answer is in the question: lateral, fwd/aft is longitudinal. <S> The cyclic stick directions are cyclic longitudinal and cyclic lateral: move the stick and the rotor <S> tilts, producing direct translational movement. <S> The helicopter fuselage follows the rotor angle and therefore pitches/rolls as well, but more as a (desired) side effect. <S> Desired because they enable instant judgement on the amount of stick applied. <S> In a fixed wing, stick fwd/sideways is pitch stick and roll stick, because stick inputs primarily affect the aircraft attitudes. <S> Longitudinal and lateral are helicopter terms because stick inputs (in a hover) mainly affect translations. <S> And yes on a 6-DoF simulator motion system they are called Surge and Sway. <A> The FAA Helicopter Flying Handbook discusses maneuvering in chapter 9 . <S> Sideward hovering flight may be necessary to move the helicopter to a specific area when conditions make it impossible to use forward flight. <S> During the maneuver, a constant groundspeed, altitude, and heading should be maintained. <S> There are also the forward and rearward hovers, and the hovering turn. <S> These hovers are probably all specific to helicopters, where straight and level flight is designed to be performed in the forward direction. <S> Aircraft like quadcopters are less directional and can generally fly "straight and level" in any direction relative to the quadcopter.
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The term I preferred was "slide" In our NATOPS manuals, and in our trained procedures in both Search and Rescue ops, and cargo ops, in the Navy the crewman would call for us to "slide left" or "slide right" as he positioned us over the pick up point. This movement is called a sideward hover.
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What is the Scaling Factor in ARINC 429? I'm a newly appointed engineer in an avionics company and have been tasked with preparing a report on ARINC429. I understand most of it, and I certainly find it simpler that 664, but I still can't manage to wrap my head around what "Scaling Factor" is.No resource on ARINC429 I have found goes into detail about this, and the best I could find is image below. This is a screenshot from a link discussing the standard. Could anyone please explain what this is trying to convey? <Q> In the example you pasted, the value $1.5_{10}$ is being sent, which has binary representation $1.1_{2}$. <S> The data is sent as an unsigned integer so some kind of multiplier needs to be applied. <S> The value occupies 19 bits, at offset 11 within the packet itself being bit 0 of the data. <S> The default multiplier is such that the "units" bit (ie the one representing $1_{10}$) is in bit 26 in the packet, that is the bit 16 of the value. <S> You can see that in the first example, the lefthand $1_{2}$ is in bit position 16 (counting from 0 from right). <S> This allows only values up to slightly short of 8. <S> Various scalings are applied to values, depending on the label, as this may not be a convenient range for the data conveyed. <S> If a label conveys data in the range 0-6, then it is fine as is. <S> If 0-65 must be conveyed by a label, then the value is shifted right four places (to give more space for the larger numbers, but with less precision). <S> Which scaling is applied is determined by the label. <S> If a negative number is possible in a type, two's complement is applied. <S> The label definition determines the range of its various words. <S> You can see this example effectively repeated immediately with value $1.25_{10}$, which is $1.01_{2}$. <A> The example given is a bit strange in that it explains how to code a specific value as the scaling factor changes. <S> In using A429, we don't often think in terms of how the scaling factor modifies the coding of a specific value as the range (scale) is fixed for any specific A429 label. <S> To code a value, we look at the what the data type is and the range/resolution of the associated A429 label. <S> A429 binary number (BNR) labels are coded using two's-complement. <S> With that, each bit starting at the MSB represents half the value of the previous bit. <S> The scaling of a specific label is defined in Attachment 2B of ARINC 429 Part 1. <S> The 'Scaling Factor' you question is determined by the desired range of values with the resolution driven by the range and the number of significant bits. <S> To scale the data in two's complement binary, the MSB is set to represent half of the +/- <S> range value. <S> Each successive less significant bit represents half the value of the previous bit. <S> The resolution is the value represented by the LSB. <S> So, for example, Label 162 from an ARINC 712 ADF receiver <S> (Equipment ID 012 hex) contains ADF Bearing data. <S> There are 12 significant bits and the range is defined as +/- <S> 180 degrees. <S> Bit 29 is the sign bit. <S> Bit 28 (MSB) is 90, bit 27 is <S> 45, bit 26 is 22.5, <S> etc. <S> down to bit 17 which represents 0.044 (sometimes rounded to 0.05 - I don't know why). <S> So all 0 is 0 degrees (North). <S> All 1 except for sign bit would be 179.95 degrees. <S> A sign bit of 1 and all 0 <S> (-0) equates to -180 in two's complement. <S> For other parameters you need to evaluate the data within Attachment 2B to determine the proper coding based on the range, number of significant bits, etc. <A> The mistake I think the link is making is that number of significant bits determines the position of the LSB. <S> The scale factor can influence the necessary number of sig bits, but the desired resolution does as well. <S> The easiest way I've found to calculate the value that actually gets inserted into the label is as follows: <S> The label you are sending should provide you with the correct number of significant bits. <S> ($SigBits$) <S> The exact resolution can be found by $$ \frac{Range}{2^{SigBits}} $$ and the normalized value <S> is$$ Normal = <S> Value <S> *\frac{Range}{2^{SigBits}} <S> $$ <S> Now you can take that value in binary, place the LSB so that there are the correct number of significant digits by padding 0's on the left. <S> Anything right of the LSB is padded with 0's, to a total of 18 bits (19 for a signed value) - the width of the data field.
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The scale factor (which I'll call $Range$) is usually the value given, unless a $\pm $ is used, i.e. $\pm180$ for labels like heading, in which case you would use the highest value (180).
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How to fly to an uncharted airport? I'm learning X-Plane 11 and started to use an add-on called FS Economy. One of its missions is to fly to small airports that I can't find on skyvector, so I'm unable to plan a direct flight. I usually fly to the nearest charted airport, and fly using the GPS from there. Not knowing any information like runway length beforehand. How realistic is it in the real world that an airport would not be charted, and how are flights planned to such airport? <Q> I know nothing of X-plane, but I fly gliders in real life and often land in fields and "uncharted" airports. <S> Uncharted does not mean the airport does not exist. <S> However, you do need some idea of where it is, GPS coordinates, or some fix from a known point. <S> Even a general description of its location can get you close enough to find it. <S> I have often used "Google Earth" to pinpoint a potential landing area and <S> once I find it there, I have what I need to navigate to it. <S> I check the date of the GE photography <S> some are several years old and things could have changed that make the field unsuitable. <S> GE also has tools that you can use to measure the length and width of the "runway" and its orientation. <S> I look for obstacles that might interfere with my approach. <S> I also check to see if it is fenced because that can complicate getting my glider out of the field. <A> Usually the approach controllers are familiar with local airports, even infrequent use ones. <S> When in an area where there is no approach facility the center controller may be less familiar with the airport. <S> I normally provide the owner's phone as a destination contact. <S> While one could use a lat/long coordinate, a radial and dme is easier to communicate. <S> Depending upon what I am doing, sometimes 20% of my landings are at uncharted airports. <S> One can file VFR and IFR flight plans to them. <S> This doesn't specifically address your use of X-plane 11, but it is intended to describe operations in general aviation in North America, and my less limited experience in South America. <A> If it's not known to the FAA, it's not going to be available in a standard navigational database. <S> You would have to know of the existence of the airstrip beforehand and get the lat-long coordinates for it. <S> If you have those, you can create custom waypoints in a GNSS unit e.g. GNS430, GTN750, etc. <S> to fly to. <S> This can also be done in the air if you locate an airstrip and note the lat-long coordinate or a polar bearing/distance from a know nav beacon like a VOR or NDB, which also can be used to create GPS waypoints as well.
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As a frequent flyer to uncharted airports, I simply use a VOR radial and distance when filing.
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Is there a specific relation between sideslip angle and yaw rate OR how sideslip angle depend on yaw rate? Since, yaw rate is controlled via rudder and sideslip angle can also be controlled by rudder, I want to know if there is any dependence of sideslip angle on yaw rate in fly by wire aircraft as I am working on the SAS design of a/c lateral/directional dynamics? <Q> Since, yaw rate is controlled via rudder <S> No, yaw is controller by many things, and rudder is there mainly to compensate for them to keep the plane flying nose-forward. <S> The usual way to make a control system is that you control (with a PID controller): Move elevator to target vertical (plane coordinates) acceleration. <S> Move ailerons to target roll rate. <S> Move rudder to target zero lateral (plane coordinates) acceleration. <S> Lateral acceleration is measured by the ball in traditional cockpit. <S> Note that each axis is basically independent and rudder is only used to eliminate side-slip, which is proportional to the lateral acceleration unless you have asymmetric thrust or drag—and I have not heard of a FBW that would automatically correct for those conditions. <S> When flying with auto-pilot, the auto-pilot sets vertical speed target from altitude error and vertical acceleration from vertical speed error for the pitch <S> and it sets roll from heading error and roll rate from roll error for roll axis. <S> Autopilots don't set lateral acceleation targets at all—that is always zero. <S> That is why auto-land has much lower cross-wind limit <S> —autopilot does not handle rudder, so it can't de-crab. <A> Sideslip angle β is the "sideways" angle of attack of the aircraft body. <S> In a given time span, sideslip angle is the integrated signal of yaw rate, which is the integrated signal of yaw acceleration, which follows from the yawing moment and the inertia. <S> This is the case in any aircraft, fly-by-wire or conventional control. <S> $r_{dot}$ = <S> $M_β$ / <S> $I_Z$ r = <S> $∫$ $r_{dot}$ dt <S> $β$ = <S> $∫$ r dt <S> Sideslip is an aerodynamic entity defined relative to air velocity (body axes), while inertial entities are defined in earth axes. <S> A transformation matrix describes the relationship of the two axes systems. <S> For flight behaviour the body axes form the frame of reference: a sudden side wind changes initial side slip angle at the start of our time interval, plus the moments acting upon the aircraft. <A> A momentary yaw rate can result in a slip, but a sustained sideslip maneuver will involve a zero yaw rate. <S> Note that a yaw rate is a measurement of rotational velocity while a slip angle is a measurement of relative position. <S> Consider a momentary yaw rate brought about by rudder deflection with the wings held level. <S> That momentary yaw rate will result in a slip of some angle (which angle will depend on a number of factors including but not limited to amplitude and duration of yaw rate), but to sustain a sideslip will necessarily require a zero yaw rate. <S> That is to say, to fly in a sustained sideslip maneuver—as opposed to a slipping turn—the angular difference between the relative wind and aircraft's longitudinal axis must be maintained with a zero yaw rate. <S> While yaw rate or angle can be controlled by rudder, there are several other forces or control inputs that can affect or control yaw rate or angle. <S> As one example, consider an asymmetrical thrust scenario involving a sustained sideslip and zero yaw rate. <S> In that scenario, rudder input opposite the direction of the sideslip may be required to maintain the sideslip.
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No, there is no specific or dependent relationship between sideslip angle and yaw rate.
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Did any aircraft ever use stick twist for rudder control? Did any aircraft ever use stick twist for rudder control like some joysticks for video game flight simulators? <Q> Yes, the RAH-66 Comanche FBW system used a twist control for the yaw channel. <S> It had no rudder pedals. <S> (Yes, a helicopter is an aircraft). <S> Comanche unfortunately was canceled near the end of LRIP (Low Rate Initial Production) in 2004 as the program was moving into EMD (Engineering and Manufacturing Development). <S> There were at least 2 prototypes flying at the time. <S> Test and development flights took place from 1996 to 2004. <S> Extracts : "... <S> the RAH-66 Comanche design incorporated a 3-axis, limited displacement, uniquetrim sidearm controller [replacing cyclic and yaw pedals] for control of the longitudinal, lateral, and yaw axes. <S> A proportional collective with approximately 6 inches of displacement was used. <S> An enhancement tailored to the scout mission was the incorporation of limited control in the vertical (fourth) axis of the sidearm controller. <S> This allowed the pilot to command stabilized climbs and descents with the altitude hold system engaged. <S> This was used primarily for vertical unmask and remask maneuvers, which enabled the pilot to fly through the autopilot without even temporary disengagement." — "Impossible To Resist" - The Development Of Rotorcraft Fly-By-Wire Technology ( PDF—Paywall ) <S> and "The RAH-66 Comanche program has proposed 4-axis controller (Harvey, 1992), but this approach is now questionable." — A Four-Axis Hand Controller For Helicopter Flight Control <S> ( Source ) <S> Note that either the '3 + 1' or '4 + 1' controller configuration would likely have been the ones decided on for the Comanche, on the basis that all the cockpit pictures that have been seen feature a sidestick and a collective stick, but no pedals. <S> As noted in the first text block (Impossible to Resist) the 3+1 (collective) was the final form, although the cyclic had some control authority in the vertical axis (as described). <S> I added the emphasis in bold, and the note on "side arm controller" vs "cyclic" in brackets. <A> ( Source ) <S> Cockpit floor of a Royal Aircraft Factory S.E.5 . <S> The closest thing to a twisting motion was the pre-1919 'rudder bar' shown above. <S> [The] pre-1919 era <S> rudder control was most often operated with by a center-pivoted, solid "rudder bar" which usually had pedal and/or <S> stirrup-like hardware on its ends to allow the pilot's feet to stay close to the ends of the bar's rear surface. <S> A stick twist does not provide a mechanical advantage to control the rudder in a real aircraft. <S> And in case of fly-by-wire aircraft, it doesn't provide the needed input accuracy. <S> (See KorvinStarmast's answer.) <S> Some Russian fighters and trainers however have a 'trigger' brakes lever on the stick, with differential braking being provided by the rudder pedals (that do not have a toe brake motion). <S> PC pilots are heroes for trimming an aircraft without an elevator feedback, and for controlling the rudder with a twisting joystick. <S> Trivial information: <S> the ERCO Ercoupe doesn't have a separate rudder control. <S> That's the equivalent of a flight simulator's auto-rudder feature. <S> Lacking rudder pedals, the Ercoupe was flown using only the control wheel. <S> A two-control system linked the rudder and aileron systems, which controlled yaw and roll, with the steerable nosewheel. <A> Mechanical commands: <S> It's difficult to apply enough twisting torque with your wrist. <S> Using your legs provides a lot more power. <S> Aerodynamical forces on the rudder (or whatever control surface) are quite strong at high speed. <S> You need some large lever arm moment in order to have authority on it. <S> However, there could be some design solutions to allow a twisting stick yaw control. <S> For instance adopting large aerodynamic compensators. <S> Hydraulic or electric commands: <S> Twisting stick yaw control is possible, maybe for a pilot having lost his legs. <S> Otherwise I don't see any advantage adopting this configuration, since 3 axes are mixed, you may lose accuracy.
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The RAH-66 Comanche used a twist in the pilot's stick to control the rudder/yaw inputs.
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What is that black pod on the left wing of a TBM? What is the black pod on the left wing of a TBM ? ( Source ) <Q> That is the front of the housing which encloses the 10" GWX70 Color Weather Radar antenna. <S> Here are some close up shots of a TBM depicting the weather radome. <S> Source: <S> Own work <S> Note the lightning diverter strips : <S> Source: <S> Own work <S> Apart from the simple fact that airborne weather radar is useful, weather radar is a common option due to the equipment requirements imposed on air carriers operating such aircraft. <S> Specifically, in 14 CFR 135.175 , the FAA generally prohibits operation without airborne weather radar equipment along routes where thunderstorm activity is forecast. <S> Many such single engine aircraft include the option for wing-mounted weather radar, as seen on the TBM 900 in the original question. <S> Since weather radar requires a relatively unimpeded area for signal transmission and receipt, the antenna assembly is typically located at the nose of the aircraft, such as on most multi-engine aircraft. <S> In aircraft with nose mounted engines, a mid or outboard wing mounted position makes sense. <S> See the following photos depicting examples of wing mounted weather radar on a Piper PA-46-500TP Malibu Meridian and a Cessna 208B Super Cargomaster , and a nose mounted weather radar on a Beechcraft King Air B200 , respectively: <S> Source: <S> Own work <S> Source: <S> Own work <S> Source: <S> Own work <S> According to the TBM 900 POH , installation of the optional radar system results in a 5 KIAS decrease in maximum cruise performance and a 3 KIAS decrease in long range cruise performance. <S> This change is due to the slight increase in drag from the radar antenna housing. <A> It is weather radar. <S> Most multi-engine aircraft have radar in the nose but single engine aircraft mount it on the wing. <S> They have been doing it since WW II, but with night fighter radar. <S> US Night Fighter Radar <A> The single engine requirement for the engine driveshaft and propeller to be mounted on the aircraft centerline as well as interference from the propeller arc required <S> the radar antenna be offset <S> mounted on the wings like this. <S> Wind tunnel studies showed this configuration minimized parasite drag. <S> This is <S> a fairly common WX radar antenna installation for single engine aircraft and similar designs are found on the starboard wingtip of the Pilates PC-12 and the antenna pod on the Piper PA-46 Malibu series. <S> Source: <S> Pilatus Aircraft Ltd. Source: <S> Piper Aircraft Corporation
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As stated above, it's a dielectric blister fairing which houses the antenna for the GWX70 weather radar.
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Do airlines have freezers? In the latest twist to the case of the dead rabbit, an anonymous "airport worker" has told a reporter that it was killed by leaving it in a freezer locker , contradicting the accounts of United executives who have claimed the rabbit was well treated. United also hastily incinerated the body without the owner's permission, preventing any kind of autopsy from occurring. This all happened apparently at Chicago O'Hare. My question is why an airline would have a freezer at all, and why would they be putting luggage or pets into said freezers. I mean when I make connections I kind of assume they are not putting my bags in a freezer. Do airlines have freezers? <Q> ( Source ) <S> Cool room in a cargo terminal. <S> The rabbit arrived fine but there was some sort of mistake and he was locked inside a freezer overnight. <S> Goods that are perishable and human remains awaiting transport, wait in the freezer before being loaded onto flights. <S> Different rooms for cargo handling can be seen here , they include: <S> Cool rooms Freezer rooms Warm rooms (for e.g. perishable flowers) <S> Dangerous goods rooms <S> There are also specialized ULD 's that come with refrigeration units. <S> ( Source ) Temperature controlled ULD. <A> Parcel services use temperature regulated containers for shipping various products. <S> Pharmaceuticals come to mind. <S> Human organs are normally packed as independent packages, but are sometimes placed in thermally regulated containers. <S> Substantial amounts of produce are shipped via air transport. <S> Hubs have temperature controlled areas for cargo. <S> It can include produce, pharmaceuticals, etc. <S> Even parcel "stations" for ground delivery services have them when they have customer needs. <A> I'm not aware of any American carriers that have freezers onboard that are accessible to the crew during flight. <S> For catering purposes, dry ice has been the accepted means of keeping food chilled until preparation and serving. <S> It's primary use was keeping food at cold temperatures while transporting to the aircraft and while on the ground. <S> It wasn't needed once the food was boarded and usually was removed by the flight attendant when they signed off on catering. <S> Once chilled, the food containers remained that way for the short time until service was started. <S> The exception to this would be if you had a long haul flight with two services then you would keep dry ice the the food carriers for the second service. <S> Refrigerators and freezers for cargo transportation purposes are a separate subject.
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[Depending] on the nature of the goods to be transported, [ULD's] may have built-in refrigeration units.
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Do helicopters need to use yaw pedals to fly a coordinated turn? I recall years ago, when I took a helicopter tour, I noted the pilot simply moved the cyclic left or right to bank the helicopter and initiate a turn. No pedal input was made whatsoever, and the ride seems completely fine. In many fixed wing aircrafts, if rudder is not applied during the entry of a turn, the airplane will have a tendency to yaw to the opposite direction due to the drag induced by the ailerons. Is pedal (rudder pedal? what are they called in a helicopter?) input necessary for turns in a helicopter? <Q> Many helicopters have different flight characteristics, but for general information you can always look in the FAA Helicopter Flying Handbook , this is from Chapter 9 : <S> This is from a section on the four fundamentals of flight (straight-and-level, turns, climbs, and descents): <S> Anticipate the following characteristics during aggressive maneuvering flight, and adjust or lead with collective as necessary to maintain trim and torque: <S> Left turns, torque increases (more antitorque). <S> This applies to most helicopters, but not all. <S> Right turns, torque decreases (less antitorque). <S> This applies to most helicopters, but not all. <S> So some (most) helicopters do require some torque pedal movement for aggressive maneuvering, but the pilot may have anticipated this and added the correction prior to beginning the turn. <S> You may not have noticed as much pedal movement as you would in a coordinated turn for an airplane, or the helicopter you were riding in had different flight characteristics and was not maneuvering aggressively enough to need it. <S> Many helicopters "wind vane" <S> pretty well, that is that they stay aligned with the relative wind at high speed. <S> For an example of how speed cancels out the need for anti-torque control, see this article about a helicopter pilot that lost the tail rotor and continued to fly for half an hour to a proper landing site. <A> Coordinated flight means that the airflow over the fuselage flows along the longitudinal axis of the aircraft. <S> The main risk of uncoordinated flight in an airplane is the possibility of entering a spin. <S> But helicopters don't spin, and uncoordinated flight is not dangerous in them in the same way as in fixed-wings. <S> This means that helis can fly at any angle to the direction of flight, which is one of the main benefits of flying them. <S> That being said, helis are equipped with a flight instrument invented by the Wright Brothers -- the yaw string. <S> They are taped to the bubble, and in forward flight the pilot keeps the yaw string aligned with the fuselage by using the pedals. <S> The main benefits of coordinated flight in a heli are fuel efficiency and passenger comfort. <A> Fixed wing aircraft that deflect their ailerons experience adverse yaw: the aileron deflecting downwards experiences more drag than the one deflecting upwards, and this creates a yawing moment in the wrong direction. <S> The magnitude of the effect depends on variables like aspect ratio, wing span, airspeed etc. <S> It is this yawing affect that would be compensated by pedal input. <S> Helicopters effectively tilt the lift vector to the side where they need to go to, there is no adverse yaw effect that requires compensation from the pedals. <S> Both fixed wing and rotary wing aircraft experience side slip when only stick and no pedals are applied in a turn - to a limited extent due to directional stability in forward flight. <S> The vertical fin provides this stability, and in helicopters the tail rotor as well: increase in side slip angle causes a change in angle of attack at the tail rotor, which results in a stabilising thrust change. <S> But self stabilisation needs a slip angle to create force. <S> Like Simon says, a true coordinated turn always requires pedal input.
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It could be that the helicopter you were in was travelling at a high enough rate of speed that a large (or any) correction was not needed to maintain proper alignment.
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Do flight regulations prohibit sleeping on the floor of an airliner? During a recent trip in a Finnair A350, a couple traveling together was occupying 1 row of three Economy Comfort seats. During the 12 hour flight, one of the couple stretched out on the seats, the other one on the floor in between the seat rows, leg room being sufficient to allow this. A flight attendant was overheard stating that sleeping on the floor was not allowed due to safety regulations. What safety regulation would prohibit this? update During cruise condition, no Fasten Seatbelt sign. EASA regulations. Yes you're out of your seat but we're allowed to walk around aren't we. Where is the hard, written, safety regulation? <Q> That depends on the air carrier and the regulatory body they're certified by. <S> Finland is part of the EU <S> so I'm assuming that Finnair's certificate is under EASA aviation safety regs . <S> Specifically, a quick Google search finds: CAT.OP.MPA.165 Passenger seating: <S> The operator shall establish procedures to ensure that passengers are seated where, in the event that an emergency evacuation is required, they are able to assist and not hinder evacuation of the aircraft. <S> Finnair would also write their own SOPs to ensure they meet all the EASA regs. <A> Essentially this has been explained to me as "you're a trip hazard." <S> 'Additionally, inferences that if power/lights go off, you'll be stepped on and trip people, particularly people in your row (don't know how this applies so much if you're a couple/by yourself), and in the way in the necessity of evacuation, or in the case of a flight attendant needing to rush to the window to look out. <S> How they'd do that with your legs in front of you in a seated position, I don't know. <S> In my experience it's pretty common to hear the captain or stewardess announce or tell a passenger if you're on an overnight or long flight. <S> ADD: <S> Just got off a QANTAS flight, this is more of less what they said. <S> The flight attendants need to be able to rush to a window or an overhead locker/passenger in a window seat in an emergency situation, so bags cluttering floors, people sleeping on floors isn't ok. <A> This will vary based on jurisdiction and the stage of the flight, but in the US under the FAA this is prohibited (most likely for multiple reasons) for at least some stages of flight and flight conditions. <S> This is most likely an EU issue but here in the US... <S> They can't do it during taxi <S> take off and landing: § 121.311 Seats, safety belts, and shoulder harnesses. <S> (b) Except as provided in this paragraph, each person on board an airplane operated under this part shall occupy an approved seat or berth with a separate safety belt properly secured about him or her during movement on the surface, takeoff, and landing. <S> And the flight attendant was well within their rights if the fasten seat belt sign is on thanks to <S> § 121.317 Passenger information requirements, smoking prohibitions, and additional seat belt requirements. <S> (f) <S> Each passenger required by § 121.311(b) to occupy a seat or berth shall fasten his or her safety belt about him or her and keep it fastened while the “Fasten Seat Belt” sign is lighted. <S> (k) <S> Each passenger shall comply with instructions given him or her by a crewmember regarding compliance with paragraphs (f), (g), (h), and (l) of this section. <S> I'm still looking for the letter of the law on if you need to be seated in an approved seat during the cruise stage of flight with the "fasten seat belts" sign off.
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I do know it's not allowed on QANTAS (and Jetstar), Emirates, American, Virgin Blue, or North West (now defunct). Also mentioned was the danger to passenger in case of turbulance, etc, the comparison with sleeping on the back seat floor of a car in motion was mentioned vis a vis unexpected swerving or breaking.
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Why do some fighters have two engines? Some countries (e.g. Russia) develop fighter aircraft (e.g. Sukhoi ) with 2 engines. Is it for maneuverability, or is it because they can't build an engine that would meet the power requirement? <Q> Taking the Sukhoi Su-35 <S> for example, it has two engines, each capable of producing 86.3 kN of dry thrust, combined they produce 172.6 kN. <S> With afterburner they produce <S> 284 kN <S> (142 kN each). <S> The jet engine on the American F-22 produces 156 kN with afterburner, close to the 142 kN of the Su-35. <S> Soviet Union / Russia made the Kuznetsov NK-32 military jet engine, capable of 137 kN (dry) and 245 kN (wet). <S> So, the ability or technology to make a powerful jet engine is not the reason. <S> It's just powerful engines are much bigger. <S> Redundancy, in case one fails, especially important for big fighters. <S> Afterburners are easier to make for smaller diameter engines. <A> The general purpose was redundancy. <S> Splitting the power demand of the airframe and payload made for smaller engines and the ability to stay airborne and RTB <S> (return to base) if one engine suffers a failure. <A> As pilots, we very often go right for the aerodynamic reasons, but one glaring reason has been omitted from the discussion - price. <S> Governments have to choose between having a smaller number of more expensive, likely more capable, aircraft and having a larger number of smaller, lighter, less expensive aircraft. <S> This applies not only to initial cost, but also to ongoing maintenance, parts and fuel cost to operate the aircraft. <S> The F-16 is a great example of an economically efficient aircraft that can be operated by nations on a budget due to its small size, single engine and availability of parts versus an engineering marvel like the F-22 <S> which is no longer in production due in no small part to the difficulty of obtaining parts, a better explanation of which follows here: <S> https://www.defenceaviation.com/2016/05/why-did-the-united-states-stop-f-22-production-could-lockheed-martin-restart-the-production-line.html <S> Also, along economic lines, a quick visual price comparison is found here: https://www.popularmechanics.com/military/weapons/news/a25678/the-cost-of-new-fighters-keeps-going-up-up-up/ <S> Price issues aside, from a pilot's perspective <S> I don't think there is a pilot alive who would not want a second engine for many reasons, but we aren't the ones buying the jets.
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The main reasons for selecting a twin engine design are: Slimmer design, two smaller engines make for a slimmer profile than one big engine.
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Can the APU provide emergency thrust? By David Monniaux (Own work) [ GFDL , CC-BY-SA-3.0 or CC BY-SA 2.0 fr ], via Wikimedia Commons Many larger airplanes have gas turbine APUs ( auxiliary power units ). It seems that their exhaust is oriented to the rear and might provide some thrust. How much thrust does an APU provide and would it be enough to keep flying an airplane if the main engines went out? <Q> An APU lacks the critical component that produces thrust, a propelling nozzle . <S> A propelling nozzle converts a gas turbine or gas generator into a jet engine. <S> and Most modern passenger and military aircraft are powered by gas turbine engines, which are also called jet engines. <S> There are several different types of gas turbine engines, but all turbine engines have some parts in common. <S> All gas turbine engines have a nozzle to produce thrust, to conduct the exhaust gases back to the free stream, and to set the mass flow rate through the engine. <S> The nozzle sits downstream of the power turbine. <S> ( NASA ) <S> Would it be enough to keep flying an airplane if the main engines went out? <S> It would, in the sense that it will provide electrical and pneumatic power for the different aircraft systems, but no thrust. <S> Or airplanes would have just been built with a few of those tiny APUs. <S> :) <S> Another alternative for backup systems power when airborne is the Ram Air Turbine . <S> RE comment about turboprops having some exhaust thrust, they also have nozzles, which an APU still lacks. <S> ( NASA ) <S> Before entering the nozzle (...) <S> the exhaust velocity of the core is low and contributes little thrust because most of the energy of the core exhaust has gone into turning the drive shaft. <A> The Antonov An-26B cargo aircraft (produced in the Soviet Union) has a Tumansky RU19A-300 combined APU and jet engine mounted on the wing behind the right main engine. <S> This unit provides additional thrust up to 800 kg to improve takeoff and safety in case of engine failure. <S> This information is from the accident investigation report of Polish aircraft An-26B SP-FDO in Tallinn, Estonia on March 18. 2010. <S> During the flight from Helsinki to Tallinn, 9.5 NM from Tallinn the left engine failed, and the thrust-providing APU could not be started. <S> The aircraft was not configured for landing, flew over the runway and made landing on snow- and ice-covered lake Ülemiste (main supply of drinking water). <A> The amount of thrust available from an APU would be minuscule as it is designed drive various aircraft systems and adding on a nozzling system geared for propulsion would reduce the power available for doing it's intended work. <S> Even if an APU was re-purposed for propulsion, it most likely would not be enough to have any significant role. <S> While horsepower and thrust are dissimilar terms that do not have a simple conversion, we can do some comparisons to show how under-powered an APU would be An Airbus 350 has a pair of jet engines which combine to produce about 195,00 lb-ft of torque. <S> This same aircraft has an APU which can produce up to 1700 equivalent shaft horsepower. <S> The Airbus 400 has 4 turboprops that combine to produce 45,000 HP, and has a max takeoff weight roughly 1/2 that of the A300. <S> While I am in no way an aeronautical engineer; and these comparisons are on the order of apples and oranges, I don't think it is a grasp to say "it ain't happening" to an APU providing propulsion. <A> Not alone, but APU can help to get more thrust by taking over the duty to supply the bleed air from the main engines. <A> It is an issue of power (as well as having that power effectively converted to thrust). <S> The APU is designed to provide electrical, bleed air (for environmental control, and for starting other engines), and in some cases they may run other accessories. <S> It may be possible to have more power available to the main engine(s) if the APU is used for electrical, bleed air, etc. <S> Normally, this is not done in most aircraft. <A> Thanks to pots and Federico for their answer mentioning the Tumansky RU 19A-300 combined APU and jet engine. <S> Further search found a NASA paper from 1968 using a GE TF-34 "convertible" turbine that could unload the generator shaft and redirect the power output with "variable inlet guide vanes" to a turbofan. <S> Around 8000 lbs of thrust could be created as a turbo fan alone. <S> Combinations of thrust and shaft power were also possible. <S> Generally, an engine out/landing emergency will be in a speed range where a turbo fan (or prop) will be effective (around 150 - 250 knots). <S> So, maybe the tri-jet isn't dead, it just needs to be tweaked a bit. <S> There are tales of using the 3rd top mounted jet to control pitch-up as well.
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Practically speaking, APUs are not sufficiently powerful to provide the thrust necessary to maintain level flight.
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Why do some aircraft have pods on their wing tips? By JetPix [ GFDL 1.2 or GFDL 1.2 ], via Wikimedia Commons Why do some aircraft have pods on their wing tips, like this Cessna 414? <Q> Wingtip pods or winglets differ in installation reason from aircraft to aircraft. <S> Here is a non exhaustive list of possible reasons: <S> Fuel tanks Whitcomb bodies to enhance the area rule of the aircraft also known as Kuchemann Carrots Vortex generators and relievers - used to enhance aircraft aerodynamics and modify fuel consumption Mass balance - in particular on forward swept wing aircraft Housings for sensors or landing gear <A> Many aircraft have had fuel tanks mounted on the wing tips. <S> These were sometimes main tanks, but often were auxiliary tanks, or even "Drop Tanks" which could be jettisoned for combat. <S> The tip tanks on the Cessna 414 pictured above are the MAIN fuel tanks. <S> They hold 50 US gals each. <S> In addition to the 50 gal mains there would be 2 smaller auxiliary fuel tanks in the wings, and 2 optional "wing locker" fuel tanks in the wing lockers behind the engines. <S> All early Cessna 300 and 400 series aircraft shared this rather complex fuel system which required using fuel from the 50 gal mains first before using the auxiliary or wing locker tanks. <S> Later versions of the Cessna 400 series aircraft went to a much simpler "Wet Wing" fuel tank system with only 1 tank in each wing. <A> Another example of an aircraft with wingtip tanks is the T2-C Buckeye. <S> They hold approximately 102 gallons each, and so add to the total fuel capacity of the aircraft. <S> There are a number of reasons that the wingtip tanks might be part of the design of an aircraft. <S> Decreasing flutter is one reason that you might add wing tips, and this hasn't been mentioned in any previous post. <S> Reducing flutter will decrease drag, and that offset the increased drag of adding external tanks. <S> I think one of the things that made the T2-Buckeye ideal as a trainer is that the wing tips reduce roll rate. <S> That is good for training but not so good for bombing or aerial combat. <S> It also reduces airflow escaping off the tip which creates vortices. <S> The wingtip tanks also help in the distribution of weight, which effects the center of gravity. <S> It was the only jet aircraft that the Navy permitted spins in, and it was therefore used for training in spin recovery procedures. <S> This was the US Navy's basic jet trainer. <S> It was also the only jet that you were allowed to intentionally spin. <S> That was a lot of fun. <S> It had a very tight turn radius. <S> It was where a pilot got their first hop in formation flying, rendezvousing, and the gunnery pattern. <S> Carrier qualifications were done here as well, although one didn't always get to trap aboard a carrier. <S> First time a pilot did a lot of consecutive solos as well. <S> Very cool flight time in the training program here.
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Weight at the end of the wing will offset the bending of the wing due to lift.
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How is an ILS approach conducted when following a heavy aircraft? I'm following a much heavier aircraft on an ILS approach to a large airport. Ideally I'd like to stay a bit above the glide path and land late, both to avoid the turbulence and also get off the runway quicker. Is that actually a good idea, and how would I do that in IMC? <Q> Other bodies may advise differently but I will answer for the FAA. <S> The FAA covers this in their wake turbulence handbook as well as many other scenarios you can look over. <S> As in similar situations, separation services may be provided, load permitting. <S> 2.10.5.1 Air Traffic Control Assist Air traffic controllers are able to provide sepa- ration distance information to pilots <S> when workload permits and they have radar <S> dis- <S> plays in the control tower. <S> They can provide airspeed differential between aircraft and may advise pilots following another aircraft when they are overtaking the preceding aircraft. <S> The document outlines some other methods and is worth a read. <A> Your concerns are valid and any competent approach controller is going to provide adequate spacing for light aircraft flying an approach. <S> However if you don't feel comfortable accepting an approach clearance, request additional spacing to minimize wake turbulence hazards. <S> A good controller will offer additional radar vector or send you to a hold in order to provide acceptable sequencing. <A> To avoid danger due to wake turbulence by preceding aircraft <S> the so called Wake Turbulence Separation is used by ATCOs. <S> This takes into consideration the wake turbulence categories of both you and the preceding aircraft by this table: <S> (ivao.de) <S> If a case (eg. light - light) is not on the table normal radar separation (3nm) is used.
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Basically you can fly above the glide slope as you have assumed but you should always take precaution as it cant be known if the leading aircraft is at or above slope.
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What's the reason for pilots wearing uniforms? Just came across an interesting answer to a question on uniforms for PPL Human Performance and Limitations: Pilots wear uniforms: a) so they can be easily recognised b) so that they can be perceived to be important c) so that they can feel important Apparently the correct answer is b (I said a). Is this so that their authority is respected, is this a valid reason? <Q> The Smithsonian's National Air and Space Museum says: By the early 1930s, airlines were introducing distinctive uniforms for their employees, and women were entering the ranks of flight attendants. <S> Pilots were given military-style uniforms to reflect their status. <S> Pan American emulated luxurious ocean liner service by calling its flying boats "Clippers" and its pilots "Captains," and attiring its crews in naval-style uniforms with white hats and navy-blue, double-breasted jackets and rank insignia on the sleeve cuffs. <S> Other airlines followed suit. <S> Many of these customs continue today. <S> This is why choice b is the correct one. <S> A military-derived uniform projects importance / reflects [high] status. <S> While a flight jacket —or a cap that reads 'pilot' for that matter—might adequately serve the purpose of identification (choice a ). <S> Look no further than Wilhelm Voigt , an imposter in an officer's uniform can command real soldiers, place people under arrest, and make away with a treasure. <S> ( Navy Officer , Pilot ) <S> Side-by-side comparison. <A> If you don't understand, just imagine someone saying "Hey, that pilot looks elegant and professional! <S> He sure knows what he's doing." <S> This is why most airlines require pilots to cover up their tattoos, etc. <S> Pilots are also required to take good care of their uniforms for the same reason. <A> YouTube channel Mentour has a good video on this subject. <S> He says Pan Am introduced the Navy style uniforms to pilots in the 30's when they operated flying boats to calm the passengers down.
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Airline pilot uniforms started being used by Pan Am in the 1930s to make the pilots look more professional and experienced which would calm nervous fliers down.
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What is the fatigue life of a fuselage based on? The fatigue life of the fuselage is based on the number of what? Pressurization cycles? <Q> Most (large) aircraft life times are measured in cycles. <S> "Aircraft lifespan is established by the manufacturer," explains the Federal Aviation Administration's John Petrakis, "and is usually based on takeoff and landing cycles. <S> The fuselage is most susceptible to fatigue, but the wings are too, especially on short hauls where an aircraft goes through pressurization cycles every day. <S> " <S> "There are 747s out there that are 25 or 30 years old," says Petrakis. <S> But that only applies to pressurized aircraft, there are large planes that are un-pressurized and their life is generally measured in flight hours. <S> However most large aircraft like say the DC-3 don't have any imposed hourly limit on the fuselage but other parts may be hour/life limited. <A> The safe/fatigue life of a structure is the number of eventsduring which there is a low probability that thestrength will degrade below its design ultimatevalue due to fatigue cracking. <S> The events maybe flights, flight hours, landings, pressure cyclesor engine cycles. <S> Safe life may be determined by using a similarstructure (usually called a fatigue specimen)which is tested to establish the minimum numberof events which should elapse before a majorstructural failure occurs. <S> For example the safelife of the Cessna 310 wings is 19,190 flyinghours. <A> Metal fatigue is measured in cycles, indeed, but not necessarily in flight cycles. <S> However landing cycles are a good measure of fatigue life, as can be seen in an iron bird set-up at an aircraft manufacturer. <S> Complete cycles are simulated: A row of actuators are connected to the wing. <S> They start with a bit of rumbling downwards pressure, simulating taxiing. <S> Then more pronounced rumbling, followed by a sharp wing up deflection, simulating take-off. <S> You can hear the structure groan when this occurs. <S> A hissing sound gets more and more pronounced: the fuselage is being pumped up like a beach ball. <S> More groaning, it's literally a strain. <S> When pressure differential is at maximum cruise altitude, we're descending again, after a while we can hear the air escape and the fuselage settle in. <S> SLAM! <S> A sudden sharp downwards kick on the wing, we've touched down. <S> And back to the beginning. <S> These birds make hundreds of flights a day, simulating all that happens during a flight. <S> The wing experiences lots of smaller cycles during taxiing, and two huge ones during TO and landing. <S> It is the number and the magnitude of these cycles that determine fatigue life. <S> Your question was specifically about fuselages, they are subject to taxiing cycles and pressure increase/decreas cycles. <S> So if we take a decent cross section of runway surfaces and average taxi time, we can tie the taxi cycles to a flight cycle, and continue flying the iron bird again and again...
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Aircraft used on longer flights experience fewer pressurization cycles, and can last more than 20 years.
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What were the U.S. Air Force's first 2-crew fighter planes? The Navy has had 2-crew planes since at least as early as 1944 with the Grumman F7F Tigercat but when did the U.S. Air Force adopt 2-seaters. Does the Navy prefer 2 crew and the Air Force prefers 1? Was the McDonnell F-101 Voodoo one of the first AF 2-crew? <Q> The first two-crew fighter aircraft to enter service with the US Air Force <S> was the Lockheed <S> F-94 Starfire . <S> Source: Wikipedia Public Domain <S> The aircraft's first flight was on April 16, 1949 and entered service in May of 1950. <A> The US Army Air Corps has flown bombers with 4+ crew members since the 1920s, for example the Huff-Daland LB-1 introduced in 1927. <S> As aircraft speeds increased through the 1930s, the open-cockpit flexible gun mount became less practical and the weight penalty of a second crew member in an enclosed turret was rejected for fighters. <S> During WWII the introduction of radars small enough to put on a plane led to the development of "night fighters" or all-weather fighters with a second crew member dedicated to operating the radar equipment. <S> ( This Q&A discusses the tradeoffs between single-crew and multicrew designs in more modern combat aircraft.) <S> The long-range <S> P-82/F-82 <S> Twin Mustang entered USAF service in early 1946. <S> Early models had two identical crew cockpits allowing pilots to alternate control on long flights; later night fighter versions introduced between 1946 and 1948 put the radar operator in the right cockpit. <S> The Black Widow wasn't a traditional dogfighter, but carried radar and heavy guns to intercept bombers at night. <S> Similarly, the P-70 was a night fighter in USAAF service from 1942, but it was a conversion of a light bomber design. <A> I would have to agree that the P61 Black Widow, which carried the formal designation of Pursuit (fighter), was the first multi-crew FIGHTER in the US inventory. <S> It was a dedicated night fighter, and like most multi-crew intercepters, carried additional crew to work the complex weapons systems (or radar, in the case of the P61). <S> Interesting note: due to special wing flaps, the P61, while not much smaller than a B-25, could roll at about the same rate as a Mustang, though obviously it would lose a lot of airspeed from sharp turns, and take longer to get that speed back. <S> During the war, a 2 seat night fighter variant of the P38 Lightning, the P38M was produced in small numbers (75 total). <S> The British did field the Bristol Fighter in WW1, and it was quite successful. <S> They tried this again in WW2 with the Boulton Paul Defiant <S> that was a dismal failure. <S> Plus the German BF 110 , which wasn't as bad, but not really competitive with single seaters.
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Depending on what you consider a fighter, the Northrop P-61 Black Widow night fighter entered service with the USAAF in 1944 with a crew of 2 or 3 (pilot, radar operator, and optional gunner). In the WWI and interwar era, a few biplane fighters carried an observer/gunner; the Berliner-Joyce P-16 introduced to the USAAC in 1932 was one such.
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How much lift is created by a half-sized rotor? I wonder if lift is directly proportional to the diameter of the rotor disc. For example, if an engine spinning a 26 ft diameter rotor can lift 635 kg, will a 13 ft diameter rotor using the same engine lift 318 kg? The power absorbed by the rotor is the same in both cases. <Q> Thus, $L = f(P,D,\rho)$ <S> where $f$ is a function to be determined. <S> From dimensional analysis, the lift $L$ can be easily derived: <S> The variables are Lift $L$, dimensions $MLT^{–2}$; <S> Power $P$, dimensions $ML^2T^{–3}$ <S> ; Rotor diameter $D$, dimensions $L$ and air density $\rho$, dimensions $ML^{–3}$ <S> The variables form a non-dimensional product $k$ <S> $k = <S> L^a\cdot P^b\cdot D^c\cdot <S> \rho^d$ <S> where $a,b,c,d$ are numbers to be determined. <S> Let’s form now a parallel product $k^*$ with the dimensions: <S> $k^ <S> * = <S> (MLT^{–2})^a (ML^2T^{–3})^b (L)^c (ML^{–3})^d$ Clearly, $k^* = <S> M^0 L^0 <S> T^0 <S> $... <S> We now take the exponents for each dimension: $a + b + d = 0 \\a + 2b + c – 3d = 0 <S> \\–2a – 3b = <S> 0 <S> $ <S> We make $ <S> a = 1$, since $L$ is the variable we’re going to solve for. <S> $b = –2/3 \\ d = –1/3 <S> \\c = <S> –2/3 <S> $ <S> Then, $k = <S> L^a\cdot P^b\cdot D^c\cdot <S> \rho^d \rightarrow <S> k = <S> L\cdot <S> P^{–2/3}\cdot <S> D^{–2/3}\cdot \rho^{–1/3}$ Solving for $L$ <S> $L = <S> k\cdot <S> P^{2/3}\cdot D^{2/3}\cdot \rho^{1/3}$ <S> where $k$ is a constant Hence, for rotor diameters $D_1$ and <S> $D_2$, and for the same power and air density, the corresponding lifts $L_1$ and $L_2 <S> $ are: <S> $L_1/L_2 = <S> (D_1/D_2)^{2/3}$ <S> For the case of $D_1 = 13 ft$ and $D_2 = 26 ft$, <S> $L_1/L_2 = (13/26)^{2/3} = 0,63 <S> $ <S> In other words, the smaller (13 ft) rotor gives you, for the same power and air density, just 63% of the lift attained with the larger (26 ft) rotor. <S> That's for the hover. <S> For the climb, you'll need extra power. <S> In order to move 635 kg vertically upwards at 1200 <S> ft/min (6,09 m/s) <S> you would need $635 \cdot 9,8 <S> \cdot 6,09 m <S> /s = <S> 37,9 kW... <S> $ <A> No, it won't be half. <S> It will be much less than that. <S> The area of lift is circular, so halving the diameter decreases the area of the circle to 25% of the original. <S> Area = <S> πr 2 . <S> Besides the effective rotor area, there are also losses for the body of the aircraft being in the center, though the rotor doesn't generate lift near the center because of low blade speed and not having the blades go all the way to the center. <S> I would look for a helicopter design rule-of-thumb to find the answer. <A> Using momentum theory and assumption of uniform inflow distribution, rotor thrust T can be expressed as $$ T = C_T * ρ <S> * A <S> * (ωR)^2 $$And power P as $$ P = <S> C_P <S> * <S> ρ <S> * A <S> * <S> (ωR)^3$$ From empirical data, for rotor solidity = 0.1: <S> Case 1: R = 13 <S> ft = 3.96m, <S> A = π <S> * $R^2$ = <S> 49.32 $m^2$, <S> $T_1$ <S> = 635 <S> *9.81 = <S> 6229.4 N, assume ρ = 1.225 kg/$m^3$ and tip speed = <S> ωR = <S> 200 <S> m <S> /s = <S> > <S> $C_T$ = <S> 6229.4/(1.225 <S> *49.32*(200)$^2$) = 0.0026; $C_P$ = 0.00025; P = <S> 120.8 <S> kW Case 2: R = <S> 6.5 ft = 1.98m, <S> A = π <S> * $R^2$ = <S> 12.32 <S> $m^2$ <S> , P = <S> 120.8 kW, assume ρ = <S> 1.225 kg/$m^3$ and tip speed = <S> ωR = <S> 200 <S> m <S> /s = <S> > <S> $C_P$ = <S> 120,800/(1.225 <S> *12.32 <S> *200$^3 <S> $) = 0.001, $C_T$ = 0.0105, $T_2 <S> $ = 0.0105 * 1.225 * 12.32 <S> * 200$^2 <S> $ = <S> 6338.6N <S> According to momentum theory and uniform inflow assumption, the smaller rotor delivers 2% more thrust at equal power. <S> The rotor runs at twice the RPM and the blade is at maximum angle of attack, may even be stalling. <S> It is the absolute maximum thrust it can deliver. <S> Surprised because it is counter-intuitive? <S> So am I. Source : Principles of Helicopter Aerodynamics by J. Gordon Leishman section 2.5
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For the hovering rotor, the stationary case, it can be safely assumed that the lift $L$ is a function of the input power $P$, the diameter $D$ of the rotor and the air density $\rho$.
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Where can I find registration information of a private aircraft registered in Germany? Is there any way (website, database etc.) where I can get the registration information of a privately-owned general aviation aircraft registered in Germany? (Germany has pretty extensive privacy laws, but it would seem that aircraft registrations should be a little bit transparent and verifiable...) <Q> I don't think the information is accessible on a public website. <S> On their website (in German) they state that they do release information to members of the public at a fee (they love that here). <S> A little bit of link-clicking later you will find that you have to pay 40 euros. <S> I am not sure whether they can release the name of the owner. <S> The law (Luftverkehrsgesetz) governing the information in the register can be found here . <A> So, while this site is not officially sanctioned by any government, it is quite extensive. <S> Accuracy and currency of data can vary, but there are other websites you can use to verify the source. <S> Finding single aircraft is the easy part. <S> However getting an entire list of a specific country's registry, whilst I know is possible, may require you subscribe at a certain level to gain that functionality. <S> AeroTransport Data Bank (ATDB) http://www.aerotransport.org <A> Airframes could be worth a try. <S> Doesn't provide all the information you're looking for, but it's a beginning at least. <S> I'm myself using it on work whenever I have to know an aircrafts type. <S> http://www.airframes.org
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According to the German wikipedia the Luftfahrtbundesamt (LBA, the German Civil Aviation Authorities) cannot publish the information for data protection law reasons.
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Is a one foot landing possible? This video shows an aircraft touching down like a helicopter on some gravel, is this possible or is the video a fake? Are there any other videos out there? Facebook video Similar one on YouTube <Q> It's a STOL (short takeoff and landing) plane, landing in strong headwind. <S> It's perfectly possible. <S> You can find more examples on YouTube . <A> With a STOL aircraft like a Carbon Cub or Aviat Husky and brisk headwinds, it sure is. <S> Alaskan bush pilots have held landing competitions with these to see who can stick a landing - literally set down and hold the wheels in that spot. <S> UPDATE: <S> this guy officially set the world record for a fixed wing STOL aircraft landing in still air with a 10ft, 5in ground roll! <S> https://www.facebook.com/valdezflyin/videos/10155067657750071/ <A> Imagine you have a 60 knot headwind. <S> You have to fly an indicated airspeed of 60 knots and you can hover over the ground. <S> If you want you can try it out in flight sim, it makes lots of fun. <S> That's called a STOL.
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The videos you reference are real.
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Why are holding patterns in an oval shape? Why are holding patterns in an oval shape? Why not circular or more square-like? <Q> I don't have any definitive information on why the oval shape was chosen. <S> However, it seems to me to be the most practical shape given the navigational equipment available when holding patterns first became necessary. <S> VOR, DME, and GPS technology did not exist. <S> Holding patterns were flown, often by single pilots hand flying, with reference to an ADF needle, maybe with a little marker beacon help. <S> I don't know if a square-like pattern was considered, but if it was I think it would have been rejected for at least the following; <S> a rectangular pattern would involve 4 turns, better to keep it simple with only 2 turns. <S> flying any kind of a leg perpendicular to the holding radial would mean getting farther away from the radial than necessary with no advantage to be gained, and it might involve more terrain clearance problems. <S> even, not even rotating ADF cards at first), than an oval. <S> Worse, though, is what could occur in some wind conditions. <S> For example, let's say you're supposed to hold north of a fix on the 360 radial (inbound course 180). <S> Further, lets say there's a significant north wind. <S> You're approaching the fix on a course of 180. <S> You cross the fix and then fly a circle with respect to the air you're in. <S> In a no-wind condition, you'll come back to the fix. <S> However, with a north wind, you'll come back to the course south of the fix, and will have thus violated where you were supposed to hold. <S> With today's navigational technology, we can of course easily fly any kind of shape we want, but the disadvantages previously mentioned would still apply. <A> An IFR holding pattern is along some bearing (typically, a VOR radial). <S> By flying a racetrack pattern, the plane is flying inbound on the radial for a period of time (straight line), making a standard turn (semi-circle), flying outbound on the same heading, slightly offset from the radial (straight line again), and making another standard turn to come inbound again. <S> On each pass, the pilot has time to verify his heading and alignment on the radial, and correct as needed. <S> If instead he were flying a circle, he'd never be established on any fixed heading for more than a moment. <S> His heading would always be turning, which is a chance to get disoriented, uncertain, and off course. <S> A constant circle would also be less comfortable for passengers. <S> With a standard hold, they get a couple minutes of straight flight before a gentle turn. <S> Imagine trying to turn a perfect circle, at night, in clouds, in stormy, turbulent weather. <S> Without GPS, you could never be sure you were in the right spot. <S> (aviation techniques were created long before the days of GPS) <A> According to various sources I've seen, the original purpose of the 'racetrack' holding pattern was to eliminate cumulative precessional error in gyroscopic intruments such as simple attitude indicators. <S> As was well explained in this answer to another question, in a good gyro there should not actually be any cumulative error in continuous turns because, at each point in a 360° turn, the error introduced by the gyro's 'erecting mechanism' should be precisely cancelled 180° later. <S> But, in early instruments there certainly were cumulative errors (eg. <S> due to frictional forces on the gimbal), and the racetrack pattern was a simple answer to that problem. <A> Wind correction in a "parallel" course racetrack pattern is much less complicated than in a circular pattern. <S> This is the number one reason. <S> Square patterns would require steep turns, inconsistent with the concept of a standard rate turn in instrument flight. <S> It's not about comfort, it is about navigation and maintaining the aircraft reliably in a specified region.
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Flying a circular pattern makes it more difficult to keep track of where you are in your head (no glass cockpits, indeed no HSIs Basically, the straight legs of the track allow the gyros to settle down again after a turn, and (just as importantly) allow the pilot to check that the instruments have settled down again, before starting the next 180° turn.
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Why are autonomous vehicles not used at airports for on-ground services? Autonomous vehicles have been around for over an decade, other industries such as the maritime industry have already been using unmanned vehicles at ports. Curious to know why airports are reluctant to implement this despite the clear benefits it has. <Q> Many of the ground vehicles need to have a trained human to make it useful for the plane (for example the fuel truck, mobile stairs, ...) <S> so it makes sense for it to cart the trained human around. <S> If you do that you may as well make said human drive. <S> This means there is a high ratio of human controlled vehicles mixed with the autonomous vehicles. <S> There are also the firetrucks that need priority, giving it to them sometimes needs human intuition in where you stop or move to to make a path. <S> You don't want the vehicle to path underneath an airplane and cause damage, or potentially end up in the jetblast. <S> Someone needs to monitor them and coordinate with the ground controller whenever they need to access/cross the taxiways. <A> It would be too complicated to develop vehicles that fit into the environment of an airport. <S> Airplanes are very sensitive. <S> If something gets damaged, the plane needs to stay on ground. <S> For the pushback it would be maybe possible. <S> But again, many sensors and supervision by a human is needed. <A> Frankfurt Airport is currently testing two autonomous busses from french company Navya. <S> While during the first test run they are only to be used by employes, future tests near the active runways might follow. <S> Unfortunately, most articles on that are in German, but I found one in English here . <A> Most likely because autonomous vehicles are brand new; Google and other companies are in the process of perfecting the technology just for regular street use. <S> I suppose as time goes by more ground vehicles are going to be automated, including ones at airports. <A> Full autonomy is still in it's infancy. <S> The consequences of an autonomous vehicle malfunctioning and crashing into an airliner fully loaded with both people and fuel are... a lot worse than an autonomous vehicle malfunctioning and crashing into the side of a ship. <S> Same can be said for one that goes haywire and wanders out onto a runway that has airliners on final approach or taking off.
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Autonomous vehicles are great, but they do not fit to an airport.
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Was the F-4 Phantom the only fighter to be in service for the US Navy, Air Force and Marines? As is stated here : Furthermore, the F-4 came in both ground- and carrier-based models and served in the U.S. Air Force, Navy and Marines. The only other frontline fighter to serve in all three services before or since is the F-35. Is that correct? Was any other fighter used by all three services? <Q> The statement is accurate. <S> Here is a list of all U.S. Fighter Aircraft, in service and retired on Wikipedia . <S> The following is an excerpt from that list for relevant aircraft. <S> F-4 Phantom (Air Force/Navy/Marines) <S> F-5 Freedom Fighter (Navy) <S> F-6 Skyray (Navy/Marines) F-7 <S> F-8 Crusader (Navy) <S> F-9 Cougar (Navy) <S> F-12 Lockheed (Air Force, A12 Variant) <S> F-14 Tomcat (Navy) <S> F-16 Fighting Falcon (Air Force) <S> F-17 Cobra (Air Force) <S> F-117 <S> Nighthawk (Air Force) <S> F-18 Hornet/ <S> Super Hornet (Navy/Marines) F-20 <S> Tigershark (Prototype, cancelled) <S> F-21 Kfir <S> C-2 (Navy) F-22 Raptor (Air Force) <S> F-23 Black Widow II (Air Force, cancelled) F-35 <S> Lightning II (Navy/Marine Corps/Air Force) <S> F <S> /P-80 <S> Shooting Star (Air Force/Navy) <S> FH-1 <S> Phantom (Navy/Marines) <S> F2H Banshee (Navy/Marines) FJ-1 <S> Fury (Navy/Marines) F-86 Sabre/Super Sabre (Air Force) <S> F-82 <S> Twin Mustang (USAF) F7U Cutlass (Navy) F-102 Delta Dagger (Air Force) <S> F-106 <S> Delta Dart (Air Force) F-104 <S> Starfighter (Air Force) <S> F-101 Voodoo (Air Force) F3H Demon (Navy) FJ-2/FJ-3 <S> Fury (Navy/Marines) F-89 Scorpion (Air Force) <S> F-84 <S> Thunderstreak (Air Force) <S> This list includes fighter aircraft introduced or in service after 1949, when the US Air Force was created until the end of 1960 when the F-4 Phantom came into service. <S> Table image was removed because the data is out-of-date. <S> You can view the original image here . <A> Maybe not technically a fighter, but the A-1 Skyraider was (in different variants, like the F-4) also used by all services. <S> It was even used in air to air combat, shooting down at least one North Korean and one Chinese aircraft during the Korean war and several North Vietnamese MiGs during the Vietnam war. <S> Not sure if that makes it a fighter according to whatever definition you're using. <A> The A-7 was used by the Navy and Air Force, but I don't think the Marines ever flew them (fighter?).And going back further, and in the non-fighter category, the B-24 had a Navy variant in the PB4Y--not Marines again.
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The FJ Fury is actually a Navy/Marine derivative of the Air Force F-86 Sabre. F-15 Eagle/Strike Eagle (Air Force) Sea Dart (Navy) F-10 Skynight (Navy/Marines) F-11 Tiger (Navy) Variants of the Northrup F-5 were also used by all services, although mostly in adversary training roles.
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Was differential thrust used in the P-38 to improve turn performance? In the P-38 Lightning could differential thrust be used to improve turn performance ? If so what was the procedure ? <Q> According to WW2 pilots, no. <S> Aside from the dangers in adjusting 1600hp on one side of the aircraft on the fly in the midst of a dogfight... With the P38, they didn't need to. <S> The P38 had an inherent advantage over single engine prop fighters of its era. <S> Its engines (and propellers) rotated in opposite directions, canceling out any torque effect. <S> The counter rotating engines and props were considered a big secret on the P38 when it was first designed. <S> (as if anyone couldn't look at the angle of the props on each side and tell that.) <S> The pronounced torque of the 1600hp-2000hp single seat fighters played a major role in aircraft handling: both in takeoff and power on maneuvers, something WW2 flight simulators never seem to reproduce. <S> Single engine fighters would roll left far quicker than they could roll right, due to the immense torque of the engine/prop combination, aiding in the left roll but inhibiting a roll to the right. <S> This was most evident at lower altitudes, where the air is thicker and the torque effect more pronounced. <S> Not so with the P38 - contra rotating engines and props canceled the torque, and the P38 could roll right far quicker than any single engine fighter. <S> While the P38 did have several issues at high altitude, WW2/Vietnam ace Robin Olds held that nothing could beat a P38... down low. <S> (revisit the Dogfights/Air Ambush episode for that) <S> So, no, they didn't use asymmetrical engine power for maneuvering with the P38 - they didn't need to. <S> Just roll right and turn - no single engine fighter of that day could stay with you. <A> I know this question was asked years ago. <S> Irv Ethel used differential thrust to escape a gaggle of 109s over Africa after his flight was jumped near Lake Bizerte in Tunisia. <S> He taught the maneuver to other 38 pilots who then used it both offensively and defensively. <S> The idea was to chop throttle on the side that you wanted to roll to. <S> This could be used offensively to beat an enemy aircraft into a split-s, or could be used to rapidly reverse direction as if spinning the plane around a vertical pole. <S> The P-38’s counter-rotating props combined with the prop’s airflow over the wings, which supplemented lift at lower speed made the Lightning capable of fantastic low airspeed and high angle-of-attack maneuvers that single-engine aircraft watched in disbelief. <A> In flight, differential thrust has only adverse affect. <S> The only benefit of asymmetrical thrust would be to facilitate yaw in stalled condition or during taxi. <S> A stalled example of using asymmetrical thrust would be facilitating a hammerhead maneuver. <A> It depends how you want to turn I reckon. <S> If by rudder only and if both engines are not flat out <S> , then yeah <S> you could up the outer engine thrust and yaw faster. <S> But that is an uncomfortable and slow way and generally not how it is done, usually pilots bank the aircraft, tilting the lift vector. <S> That is a big vector and can provide much more centripetal force than the yaw scenario: the wings provide lift, and increasing the AoA a bit creates much more force. <S> The vertical tail is dimensioned to fly with one engine out, the wing is dimensioned to support the weight of the aircraft. <S> Difference between engine thrust and weight is easily a factor 5, often more.
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But yes, differential thrust was used and was a trick up the sleeve of 38 drivers.
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What's the UX in modern airliner avionics for diversion choices, and does it integrate to autopilot? This question mentions a flight that had to divert, in that case to Iqaluit (YFB) . I was wondering: in modern large airliners, what is the user interface like when diverting? How is the case of "what is the nearest airport/runway we can divert to now?" handled in the avionics displays? Does the computer system know at all times what the nearest runway or airport is? Does that information appear when needed, or perhaps it's just continually displayed and updated at all times? Does the system understand subtleties such as which one is best based on your current heading, altitude and so on? Or do pilots just have to quickly look up the nearest one with no special help from the avionics? Or, is it figured out for each stage, as part of the preflight planning? Do they have it written down as part of a flight plan? Or does the crew have to program in a list of suitable diversion airports along the coming route, and if the worst happens the system will tell you which one (of that set) is nearest now? In fact, is there just a big red button marked "Divert Now", and the plane immediately changes course to whatever it decides is the nearest and/or best diversion prospect at that moment? To be clear, I'm talking about how it works in this sort of cockpit: (To a civilian, most modern airplane controls look like that: touchscreens with some sort of graphical user interface.) <Q> There are a few options for this and it depends on the type of plane you are in, for the most part it looks like the information must at least be proactively navigated to in what ever NAV system you are using. <S> Every pilot should study their route before hand and identify possible diversions or at least understand where they are. <S> For pilots flying common trans ocean routes there are some pre-arranged diversion airports that the pilot should know . <S> If you are using some kind of tablet as your source of navigation information (maps) most of the modern apps have a function for this . <S> If you have some kind of in panel GPS like a Garmin GNS system <S> there is also a page for that very information . <S> According to this doc FMS systems may have this info as well. <S> For example in the 737 <S> This extremely useful page takes a couple of minutes to calculate but will list the nearest airports in the database in order of DTG. <S> Once again, line selection of 1R to 5R will give more useful diversion information as shown below. <S> ( source ) <S> You can also program in you <S> alternates <S> You can enter up to 5 alternates here, selecting 1R to 5R against any entered alternate will show the info below... <S> ( source ) <S> The FMS will compute data to those points from the aircrafts current location. <S> All the diversion data is now shown based on you flying direct to this alternate from present position (VIA DIRECT). <S> Selecting MISSED APP will show the same data but calculated from the missed approach point. <S> Selecting nearest airports will give... <S> ( source ) <S> Even the more modern airbus cockpits contain a traditional FMS input or possibly a keyboard and mouse. <S> To my knowledge airlines have not really adopted touch screens yet. <S> ( source ) <S> Some of the smaller panel avionics are starting to incorporate touch screens like Garmins GTN series however some pilots prefer the tactile feel of hard buttons. <A> It's the quickest way to get the info IMHO. <S> Of course this data needs to be corroborated with the nearest airport in the NavData and once a suitable airport is chosen, it can be quickly entered into the modified route - activate, execute and fly direct to. <S> ND showing nearby airports. <S> EFIS Control Panel with ARPT button to switch airport display ON/OFF. <A> I believe on Garmin systems, the pilot can simply hit 3 buttons: "Nearest" , "Direct-To" , "Enter" , and the flight computer will immediately show a line straight to the nearest airport. <S> If they configured their settings before, they can set certain parameters, such as minimum runway length, and excluding grass runways.
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On a Boeing 777, the pilot can select to have nearby airports displayed on their navigation display (ND).
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Which engine type requires the shortest take-off run: a turboprop or a turbofan? If two fixed-wing aircraft almost identical except for the engines, one turbofan and one turboprop, which one would need less runway to take off? <Q> Even with similar weight, turboprop and turbofan aircraft will have different design characteristics. <S> A turboprop will fly at lower altitudes and airspeeds, resulting in different aerodynamic designs. <S> A turboprop also burns less fuel per hour, so it will need less fuel capacity. <S> That being said, we can look at some aircraft to get an idea of what the trends might be. <S> The best example is probably the Dornier 328. <S> It's a turboprop aircraft that seats about 30 passengers. <S> There also happens to be a version of the plane with jet engines. <S> This is probably about as similar as you can get in both weight and aerodynamics. <S> According to Skybrary, the figures are as follows: Dornier 328 MTOW <S> 13990 kg <S> Distance 1000 <S> m <S> Dornier <S> 328JET MTOW <S> 15200 kg Distance 1382 <S> m <S> You can see the the jet derivative is a bit heavier but requires a much longer takeoff distance. <S> The trend is similar between other aircraft. <S> Dash 8-300 <S> Turboprop MTOW 18600 <S> kg <S> Distance 1085 <S> m <S> ERJ-135 <S> Jet MTOW <S> 20000 kg <S> Distance 1580 <S> m <S> CRJ-200 <S> Jet MTOW <S> 21523 kg <S> Distance 1527 m <A> In general, and for the same power, thrust at low airspeed is higher the lower the 'disk loading' is. <S> That's why helicopters have big rotors... <A> A shorter take-off run equals a greater acceleration in order to reach take-off speed earlier, which means applying engine's power output (converted into thrust) to the greatest possible surface of air, from 0m/s to take-off speed. <S> Imagine a 10 meter race starting at 0 <S> m/s , helicopter ( R44 ) accelerates faster vertically, than an airplane ( Cap 10b ) <S> does horizontally when releasing the brakes. <S> Yet Robinson R44 and Cap 10b have the same power to weight ratio. <S> Turboprops move a greater frontal surface of air at a slower speed, turbofans move a smaller frontal surface of air at a higher speed. <S> Most force application surface you have, most efficent thrust you get. <S> A 1kg steel sphere sinks faster in water, than a 1kg steel disk displacing a lot more water.
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Everything else being equal, and for the same engine power, a turbofan will need more distance, since turboprops give more thrust than turbofans at small airspeeds.
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How many four-engine commercial passenger jetliner types are currently in use? Just heard following somewhere: It is easy to distinguish four-engine passenger jetliner type, because there are only three of them: if it has "hump" upper deck then it is Boeing 747, if it has two decks then it is Airbus A380, otherwise it is Airbus A340. Is this statement true? I'm asking about commercial passenger jetliners only. So no cargo, no military etc. <Q> Well, the 3 points you make are easily demonstrable to be true, and also a fairly unique feature of all three if looked at side-by-side. <S> The 747 is the only one with an obvious hump towards the front of the aircraft. <S> This upper row of windows is unlike either of the other two Photo Aldo Bidini:: source: http://www.airliners.net/photo/Alitalia/Boeing-747-243B/1200648/L?sid=f499b3169d12a0d4f410846e6512443a <S> The A380 has an entire upper row of windows - it does indeed have 2 full decks. <S> Richard Vandervord source: <S> http://www.airliners.net/photo/Etihad-Airways/Airbus-A380-861/2574151/L <S> If it has 4 engines, but neither a half upper deck and hump or a full upper deck <S> (and it's an airbus!) <S> then yes it is an A340 Aero Icarus source: https://www.flickr.com/photos/46423105@N03/5445375360/ <S> However, that is not all the 4 engine passenger aircraft. <S> It is also the only one of the bunch with a high wing. <S> Adrian Pingstone source: https://commons.wikimedia.org/wiki/File:Lufthansa.rj85.arp.jpg <S> And then we're into the Ilyushins. <S> The Il-96, is easily distinguishable from the similar(ish) A340 as it is considerably smaller - hard to tell from a close-in photo, but in real life if one were parked next to the other <S> the IL-96 is smaller. <S> Anna Zvereva source: <S> https://www.flickr.com/photos/130961247@N06/31268448486/ <S> The Il-86 has 4 engines but does not fit your criteria, as it only remains in service with the Russian Military, but the Il-62 is still in commercial service. <S> It's very easy to distinguish by having its 4 engines mounted on the tail <S> Tim Rees source: http://www.airliners.net/photo/LOT---Polish/Ilyushin-Il-62M/1033235/L <A> You can add the BAe 146 to the list. <A> Boeing has B747 with 4 engines. <S> Airbus has A380 and A340 with 4 engines. <S> Antonov has an-124 with 4 engines and an-225 mriya with 6 engines. <A> Well... we should not forget legacy aircraft still in use. <S> You might also spot some Douglas DC-8 still in use. <S> In this link <S> I have been able to find 8 planes still in use. <S> This figure via wikipedia : <S> In order to identify this old model just look to the engines, old fashion slim hets and look to the wing tips, there is no wing tip device. <A> There's still John's 707 flying around - not commercially granted. <S> There's the VC-10 that could be confused with the IL-62. <S> Only military now but was commercial. <S> And the Avro 85/100. <S> Same but different from the BAe 146.Bit too picky? <A> As stated in other answers, there are quite a few more 4 engined jet liners than just the three types stated in your claim. <S> Identification of the 747 <S> and A380 is pretty simple indeed and correctly asserted in the claim. <S> Other types will all have their own characteristics, which would have to be found by studying photos and/or drawings of the aircraft in question (and possibly knowledge of which types can be expected at a specific airport, e.g. you're not going to find Il-62s in western Europe because they're banned there for noise abatement reasons).
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The BAe 146 is a 4 engine regional airliner, and you could add to your distinguishing features "has a T-tail, must be a 146".
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What can trigger the ELT on GA aircraft? Does the Emergency Locator Transmitter (ELT) on smaller aircraft activate automatically in case of an accident? If so, what triggers it? Is it a certain amount of G's that triggers it or are there other parameters taken into account? <Q> There are four different types of ELTs: <S> Automatic fixed ELT (ELT(AF)). <S> An automatically activated ELT which is permanently attached to an aircraft. <S> Automatic portable ELT (ELT(AP)). <S> An automatically activated ELT which is rigidly attached to an aircraft but readily removable fromthe aircraft. <S> Automatic deployable ELT (ELT(AD)). <S> Manual deployment capability is also provided. <S> Survival ELT (ELT(S)). <S> An ELT which is removable from an aircraft, stowed so as to facilitate its ready use in an emergency,and manually activated by survivors. <S> All the aircraft I fly in (all two of 'em) have the third type. <S> If the aircraft is submerged or experiences a high G-force, the ELT will be triggered. <S> There's also a button on the panel to activate it manually. <S> I'm not sure what G-forces are required to set off the ELT, but they must be fairly significant—I've slammed my plane down pretty hard while misjudging my landings, and never had it go off. <S> According to https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_91-44A.pdf : To meet the "g" force requirements of TSO-C91, automatic fixed-type inertially activated ELT's (except overwater type) must activate at any inertial force, parallel to the longitudinal axis of the aircraft when installed in accordance with the manufacturer's instructions, of 5(+2, -0)g and greater for a time duration of 11 (+5, -0) milliseconds or longer. <S> So, there you have it. <S> You need 5–7 Gs for 11–16 milliseconds—but only in the direction the plane is pointing. <S> Misjudging your landing flare and stalling the plane 20 feet off the runway won't set it off, as that's not on the axis they're measuring. <A> There is another way that an aircraft ELT (or for that matter, any ELT) can be set off: By a mechanical or electronic failure of the unit. <S> This is usually caused by corrosion and is more common on maritime ELTs than on ELTs designed for aviation use. <S> Believe me ... <S> it is more common than you might think. <S> As a USCG pilot, I have many times located an active ELT that did not appear to be activated by any of the previously mentioned methods. <S> If your ELT mysteriously activates (especially if that activation is intermittent), consider that possibility. <S> We once flew over 800 miles to a large freighter where the ELT appeared to have been deliberately activated (i.e., manually turned on) only to have the surprised crew discover the ELT safely untouched in its bracket. <S> They were impressed that we came that far to see if they were okay; we had left Shemya Island in the Aleutians in the middle of the night and just wanted to go back to sleep. <A> I believe that it is a requirement that the ELT transmitters have an ON switch on the transmitter housing. <S> I don't have a cite, but I might be able to dig it out. <S> There is a similar requirement for marine emergency beacons.
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An ELT which is rigidly attached to an aircraft and which is automatically deployed andactivated by impact, and, in some cases, also by hydrostatic sensors.
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As a plane gets slower, why does a certain bank angle make you turn faster? In the video "Maneuvering during Slow Flight" the narrator states that while flying slow the airplane will be less responsive to aileron and other control inputs. He also says that the plane will turn quicker at a certain bank angle than it would if the plane was flying at normal speed. My question is: why does the plane turn quicker when flying at a lower speed? So basically what I am asking is, as a plane gets slower, why would it start turning faster then it was when in fast flight? The part of the video I am confused about is at 1:16 <Q> Rate of turn is dependent on the following two items: <S> The horizontal component of lift (centripetal force) <S> The tangential velocity of the aircraft (true airspeed) <S> The rate or turn is directly proportional to the horizontal component of lift and inversely proportional to the tangential velocity of the aircraft. <S> For a given angle of bank, the vertical and horizontal components of lift will be the same, regardless of airspeed in level flight. <S> Consequently the airplane will experience the same centripetal acceleration, regardless of airspeed. <S> Since the tangential velocity is slower, any kind of centripetal force will produce a greater rate of turn for a slower flying aircraft as opposed to a faster moving aircraft and this can be shown by the centripetal acceleration equation $$ <S> a_c = \frac{v^2}{r}$$ <S> so both slow flying airplane with a true airspeed $v_s = 100$ knots and fast flying airplane with a true airspeed $v_f = 200 <S> $ knots experience the same centripetal acceleration. <S> $$\dfrac{v_s^2}{r_s} = \dfrac{v_f^2}{r_f} = 4\ <S> \dfrac{v_s^2}{r_f}$$ <S> or, $$\dfrac{1}{r_s} = <S> \dfrac{4}{r_f}$$ <S> Consequently <S> $r_s < r_f$; in this case $ <S> r_f = 4\ <S> r_s$ <S> Since the angular velocity is equal to the tangential speed divided by the radius. <S> $$ <S> \omega = v <S> /r$$ the angular speed of the slower aircraft will be greater than the faster aircraft. <S> $$ <S> \omega_s = v_s/r_s$$ and <S> $$\omega_f = <S> \dfrac{v_f}{r_f} = <S> \dfrac{2 \ v_s}{4 \ r_s <S> } = \frac{1}{2}w_s$$ <S> So our twice as slow airplane turns twice as fast as the faster one does under these conditions. <A> Another way of explaining it in simpler terms would be: Two vehicles, driving at 10m/s and 100 m/s respectively, both execute 180 degree turns to the left. <S> The catch is that each car must do the turn so that the driver only experiences 0.5G lateral acceleration. <S> For the car traveling 10m/s this will mean a turn radius of 20m. <S> This car will complete the turn in just over 6 seconds while covering 62.8m. <S> For the car going 100m/s, a turn radius of 2000m will produce the same sideways force. <S> It will complete its U-turn in 63 seconds while covering a distance of 6283m. <S> In short, the slower moving car can make a U-turn much quicker. <S> The same thinking can be applied to flying. <A> The key word is "rate" of turn. <S> It means that if you are travelling slower, it will take less time to complete a 360 degree turn than if you were going fast. <S> It's the same as when driving a car. <S> If you want to complete the turn quickly at a high speed, you need a steeper bank angle compared to the angle you'd need at a low speed. <A> Weight does not change for different speeds, so lift does not change, too, if you maintain the same bank angle. <S> At lower speed, however, the kinetic energy, the direction of which needs to be changed in a turn, is smaller, so the same lift force has less work to do. <S> A banked wing creates a side force which is used as the centripetal force in a turn. <S> This force is actually pulling the aircraft sideways into the new direction of movement. <S> When banking into the turn, the centripetal force will accelerate the aircraft sideways and will decelerate its original speed component, such that the direction of the speed vector continually changes while its scalar value stays constant. <S> If there is less speed to convert, turning can be made more quickly. <A> Please pardon my one-liner: because it is very hard to turn a speeding bullet. <S> Same bank angle = <S> > same turning force. <S> Much less inertial energy to turn around when the plane flies slowly. <A> When you turn, acceleration is used to redirect your direction of travel. <S> If your initial velocity is low (slow flight) then less acceleration (bank angle * time) is needed to redirect your travel. <S> If your initial velocity is high (SR-71 Mach 3.2 flight) then more acceleration (bank angle * time) is needed to redirect your travel. <S> Bank angle describes acceleration here because it effectively revectors some portion of "lift" into a horizontal direction, which causes the change in direction. <S> Of course flying straight and level, the lift is used to exactly counteract the force of gravity. <S> In a level turn, some of the wing's lift is used to cause the direction of travel to change (horizontal acceleration), and also back elevator is added to increase the angle of attack, and cause a temporary increase in lift while turning. <S> (That might slow you down a little in the turn by the way.)
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So the simple answer is that there is less energy (acceleration * time) spent in turning a slow object than a fast object.
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Is it legal for an SEP airplane to fly above its service ceiling? Let's take a Cessna 172R for example. According to the POH this airplane has a service ceiling of 13,500 ft. I know that the service ceiling is the maximum altitude where a 100 foot per minute climb can be maintained.So that would mean that it can technically continue the climb and fly well above his service ceiling, until full power is required for level flight (Correct me if i'm wrong here). My question is, besides the physical barrier, is there any regulations that would prevent and aircraft to fly higher than his certified service ceiling? <Q> You didn't say which country you're asking about, but in the US it's legal. <S> Your definition of service ceiling is correct , and there's no regulation that I know of that requires you remain below it. <S> Exceeding limitations in the POH is a violation of 14 CFR 91.9(a) : <S> Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards <S> The AIM 5-3-3 requires you to report to ATC if you can't maintain a 500ft/min climb rate, so I suppose that not doing that could get you in trouble somehow. <S> There are other, contrived scenarios that you could invent. <S> If exceeding the service ceiling would require specific equipment or training that you don't have, then you could be in violation of various regulations, but that isn't because of the service ceiling itself. <S> And finally, there's the catch-all 91.13 : <S> No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another. <S> If you do operate above the service ceiling and something goes wrong, then the FAA could bust you on that. <S> Trying to get over mountains at or close to your service ceiling could be an example. <A> It is not illegal unless ceiling is listed as a limitation in the limitation section of the POH or AFM. <S> Simply mentioning a service ceiling <S> does not make it a limitation, the service ceiling has to be a published limitation in the limitations section. <S> If your cruise performance tables only give numbers for 2700, 2500, and 2300 RPM can you run the engine at 2400 RPM? <S> Of course you can. <S> These values are not limitations, they're merely performance expectations (just like the ceiling figure). <A> As far as I know there is not FAR that requires you to abide by the POH numbers. <S> However a case could most likely be made that this is careless or reckless operation, §91.13 <S> Careless or reckless operation. <S> (a) Aircraft operations for the purpose of air navigation. <S> No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another. <S> There are some other limits that could be imposed. <S> First off FL180 and up is class A airspace and requires you to be going IFR. <S> Subsequently you need to be equipped for IFR to do so, in turn you could not take a VFR only aircraft above FL180 in most scenarios. <A> Service ceiling may be exceeded in the US, not withstanding operational restrictions from the manufacturer and regulatory altitude restrictions such as O2 requirements, ATC, etc. <S> In general your chances of exceeding the service ceiling are greater with a light load, and in cooler temperatures, where your performance is better. <S> Flying in the middle of a low helps as well, because there is a light updraft. <S> It is a somewhat common occurrence when flying in some mountainous regions (particularly in South America), where mountain wave will provide additional lift. <S> The conservative pilot may choose to take the altitude from the wave, figuring that when they are out of it, there will be a strong downdraft. <S> Flying unforecast mountain wave I have encountered -2000++ VSI readings flying at Vy in the downdraft region, and +2000++ VSI readings flying near Vmo or Vne in updrafts. <S> Bottom line to remember, your practical service ceiling is impacted by atmospheric conditions, and to a larger extent loading.
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But there's no actual regulation, as far as I can see. The only clear case I can think of would be if the POH says that the service ceiling is an actual limitation and you shouldn't operate above it.
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How can you identify the upwind side of a thunderstorm, and why should you fly there? When flying around a thunderstorm, it is advised that you fly in the upwind portion of the thunderstorm. First off, how do you figure out which side is the upwind and downwind of a thunderstorm? Second, why fly in the upwind? <Q> The "anvil" of a Thunderstorm is always on the downwind side. <S> Airline pilots routinely deviate around the upwind side in hopes of a smoother ride. <S> photo source: <S> CRAZY CLOUDS: <S> The Thunderstorm Anvil <A> You don't figure out which side of the storm (mature stage) has updrafts or downdrafts. <S> You simply don't fly near, in, or under a thunderstorm. <S> It's too dangerous. <S> The FAA advises that you stay at least 20NM away from intense radar echos associated with thunderstorms in order to avoid clear air turbulence and hailstones. <S> These factors may be present on all sides of a mature thunderstorm. <A> One reason that you stay away from the downwind side is hinted at by the funny quote by @psmears: <S> If you are downwind of a cheese factory, you will smell it, but if you are upwind of it, you won't. <S> Here is my take on it: <S> If you are downwind of a thunderstorm, you will get hit with hail, but if you are upwind of it, you won't. <S> Of course, it is possible there is no hail on the downwind side, but still it is a risk that is not usually necessary to take, and it is almost always possible to deviate as needed. <S> Below is an image taken from Professor Frank Ludlam's (Imperial College) 1961 article in Weather. <S> The storm is moving right to left and affects are out to 20 km. <S> You can see the large area of hail downwind. <S> I remember coming in to NAS Beeville in an A4 finishing up an instrument training hop. <S> We were in a slow descent at 25k feet heading east at 250 kts. <S> It was around sunset, with the sun behind and encroaching darkness in front of us. <S> There were numerous large thunderstorm cells around us, some as high as 60-70k feet. <S> As I looked up towards their tops I could see the lightning arcing from one side to the other of a cell in that weird, mesmerizing twilight. <S> It was like a fireworks show, and quite impressive. <S> There wasn't anybody out there that evening and we asked to deviate around weather. <S> We got approval and did these lazy turns in our descent to the approach. <S> One of those most pleasant fligths I visit often in my memory. <A> Simply put, flying downwind of thunderstorms increases your risk of hail. <S> The downwind portion of the thunderstorm is characterized by an anvil cloud. <S> It is not uncommon for anvil clouds to extend a hundred miles down wind from larger cells. <S> Hail may be can be obscured by precipitation. <S> Hail can damage an aircraft even though other flight conditions such as turbulence are benign.
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Typically the downwind side has a much higher probability of hail.
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Why does it feel like a plane accelerates just before touching down? On commercial flights it often feels like the plane gets faster just before touching down. What creates that sensation? <Q> The aircraft flares just before touching down. <S> It descends with a constant velocity, and just before touching down pulls the nose up to reduce the descent. <S> This results in a higher angle of attack, more lift, and a vertical deceleration of the airplane. <S> A passenger perceives this vertical deceleration as a force. <S> Direction of the force is straight down and the aircraft is nose up, you're leaning back, so there is a component of (gravity + vertical deceleration) that pushes you into the back of your seat. <S> This same effect is used in flight simulators with a motion base. <S> Upon accelerating, the simulator pushes forward like the aircraft does, but also slowly rotates backwards so that the pilot feels sustained seat back pressure. <S> He cannot see the leaning back angle inside the simulator because the horizon of the projected outside visual image does not move. <S> As happens in the aircraft: look forward in the aircraft and your view of the inside of the aircraft is always the same, irrespective of aircraft angle. <S> So for your eyes there is no apparent tilt, the inner ear senses rearwards force, and there is increased pressure from the seat backrest. <S> The brain translates this into perceived forward acceleration. <A> Aside from the sensory effects already mentioned, there are also occasions when the pilot does indeed add a bit of power shortly before touchdown. <S> See, for example, comments #5 , #16 , and #17 from Adding Power Just Before Touchdown . <A> Visual perception of your perspective; as the aircraft gets closer to the ground your field of view constricts and you are closer to terrain and other structures, making them appear to move faster past the jet than at altitude. <A> I think what you're feeling is the brief float due to the ground effect. <S> Within about 10 feet of the ground the air being forced down by the wing encounters the resistance of the ground. <S> It actually arrests the downward motion unless the angle is pretty steep and that float gives a slight sinking feeling that feels like acceleration. <S> Sometime too the pilot will add a little throttle to transition out of the ground effect a little less abruptly. <A> Power from the engines will translate into speed, if not height. <S> I don't know if it happens often in real world landing configurations, but it's certainly possible. <S> To make it happen for sure, set the power so that the plane is just barely descending, and when it gets into ground effect, it will certainly speed up measurably.
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As the plane descends into ground effect, it may actually accelerate if the engines are producing enough thrust, since in ground effect the plane requires much less power to keep "flying".
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Is it possible (not practical) to create a liquid nitrogen jet? Would it be possible (though not practical) to create a jet that runs on liquid nitrogen that is heated, creating the expansion effect? I believe nitrogen takes up 674 (about) times as much space in gaseous form as in liquid, but if it were somehow evenly heated, could it provide a similar effect to combustion without the carbon emissions? <Q> At best, the mechanical energy you can release by evaporating liquid nitrogen would be about its heat of vaporization , which is 5.56 kJ/mol or roughly 200 kJ/kg . <S> (Converting this energy to useful thrust probably requires you to use the expanding nitrogen to drive a turbine that drives a fan or propeller, but that's a Simple Matter of Engineering, at least comparatively). <S> The chemical energy density of jet fuel is about 46 MJ/kg . <S> Even if we suppose the efficiency of your nitrogen engine could be a bit better than that of hydrocarbon-burning engines, this still mean that you would need to carry about a hundred times more nitrogen (by weight) than jet fuel for the same result. <A> You could if you would cool the N$_2$ on the ground and then let it expand, you would then not need the compressor amd the turbine in your turbofan drawing, just an exhaust nozzle. <S> In a way you would use the liquid nitrogen as an energy storage source, like a battery. <S> Possible, yes, practical, no, like stated in the question. <S> A practical problem being the fuel tank that needs to be kept below -159 deg C for the nitrogen to remain fluid. <S> Another practical problem is that it would be a rocket engine, not a combustion engine. <S> Rocket engines bring all their propellants on board, while a jet is an air breathing engine: most of what streams out of the jet exhaust is air, which was floating around in the atmosphere just where the plane was, now bound to carbon atoms from the fuel. <S> That's what you need all the compressor and turbine blades for, to first compress outside air and then extract energy to run the compressor. <S> Rocket engines have an issue with how long the fuel lasts. <S> All of the mass you're propelling to create thrust with, you carried on board and took off with. <S> It could be an amusing exercise to compute how many passengers would be able to sit around the huge nitrogen tank with very cold feet from the -159 C fluid inside, ready for a flight of 3 minutes. <S> There was a clever Frenchman who sold licenses for compressed air vehicle motors some time ago, a wonderful scheme to extract money from people with more money than sense. <S> It hasn't worked in a car yet due to <S> it all being a bit inefficient - can't see it work in an aeroplane where weight is so important. <S> But perhaps I'm just overly pessimistic, these could one day be just practical design problems that were overcome. <S> Edit <S> The question turned into a discussion that is more interesting than what I initially expected. <S> A string of half-truths may look like a proper necklace at first glance. <A> You run into several major problems that make your entire assertion fundamentally flawed: <S> The liquid nitrogen needs to be constantly cooled and kept in heavy containers to remain liquid, greatly increasing the mass of your fuel tanks AND requiring some form of active cooling system that needs a source of energy to run on. <S> You then need to heat up the nitrogen as it enters the engine proper (through thick and heated pipes to prevent the pipes from getting quickly coated with a layer of heavy water ice, requiring more heating systems that require more energy), this requires a source of energy and thus more mass and fuel. <S> This would likely have the same mass, size, and fuel requirements roughly as the jet engine you're thinking to replace with a nitrogen expansion vessel. <S> And on top of that your fuel system for the main engines just got a lot more complicated, prone to failure <S> (cryogenic systems are very prone to failure as all but the most exotic materials tend to not last very long at cryogenic temperatures, certainly when compared to normal temperatures), and heavier. <S> All these problems were encountered during the 1990s and early 2000s when several manufacturers (including Airbus <S> and I think Boeing) started drawing up plans for aircraft fueled by liquid hydrogen. <S> Turned out that just the tanks and cooling/heating systems would take up the entire cabin space of say a 747 while giving the range and performance of something smaller than a 737 (while leaving it with no room for passengers or cargo). <A> Liquid nitrogen could be heated by the coming air (-50 celsius at flight altitude is not the best temperature but still way above the temperature of liquid nitrogen) and then expand. <S> The engine would need lots of air to heat the nitrogen, so may actually need the air intake, compressor (compressing air raises the temperature a lot). <S> Higher flight speed may be optimal, as such an engine would likely want higher intake temperature. <S> There is no need for such an engine to be pure rocket, it can have also bypass, using fan to accelerate some air bypassing the core, same as most of jet engines do. <S> Storing liquid nitrogen is also not a problem, as the process of evaporation (that must be even accelerated by the engine) <S> should cool it enough. <S> Some thrust seems possible. <S> Mathematical analysis by specialist in physics is required to figure out if the thrust would be sufficient to sustain the flight.
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In the end you're going to need a large generator running some kind of fuel to produce the electricity needed to cool the liquid nitrogen, heat it up in the engine, and prevent icing on the nitrogen pipes.
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Why were the speed records set by seaplanes in the early thirties? For nearly all of the 1930'ies, the fastest aeroplanes were all of the seaplane category (as opposed to landplanes, to use the terminology of FAI ). Presumably, the designers of the two categories had access to more or less the same technology (engines, materials, aerodynamics, etc.) given the large interest in the subject and funding available. If we for a second rely on Wikipedia for the record listing , we see that the speed record for a seaplane set in 1931 is 655.8 km/h ( Supermarine S.6B ), while the record for a landplane set in 1935 (4 years later) is "only" 567.1 km/h ( Hughes H-1 Racer ). Seeing how fast aviation technology developed in that period, it is remarkable that four years after the Supermarine record, the fastest landplane was still significantly slower than the fastest seaplane. I would expect the large pontoons on the seaplanes to provide more drag compared to a simple landing gear, and hence by logic the seaplane should be penalised and achieve lower maximum speeds. All things being equal. However, since the speed differences are so pronounced, all things obviously are not equal. So what are the differences between the two categories (or their designers and manufacturers) that can explain the gap in maximum speed? <Q> The answer: Fixed-pitch propellers. <S> Until the 1930s propellers were fixed pitch only. <S> From Wikipedia : The first practical controllable-pitch propeller for aircraft was introduced in 1932. <S> French firm Ratier pioneered variable-pitch propellers of various designs from 1928 onwards, relying on a special ball bearing helicoïdal ramp at the root of the blades for easy operation. <S> This means all speed records were flown with fixed-pitch propellers, which needed to be optimised to the top design speed to coax as much thrust from the engines as possible. <S> In turn, this means that most of the propeller blade was stalled at low speed, so take-off thrust was low. <S> To achieve high speed, a high wing loading was needed and, in combination with low thrust, the take-off length of such an aircraft was beyond of the length of airfields back then. <S> On water, however, the maximum field length is close to infinity. <S> Yes, drag with floats is especially high when transitioning from buoyancy to dynamic lift (the "hump"), but that can be overcome when that hump occurs at high enough speed so the propeller delivers enough thrust. <A> This may only be part of the story, but the Schneider Trophy was the most prestigious air trophy of that era, and it was initially reserved for seaplanes only. <S> In I Could Never Be So Lucky <S> Again , the famous aviator Jimmy Doolittle (writing about events in 1925) said: The Schneider Cup race, to be held at Baltimore two weeks after the Pulitzer [air race] , was reserved for seaplanes only. <S> The race had first been run in 1913 and was sponsored by Jacques P. Schneider , pilot son of a wealthy French industrialist. <S> It was considered the most important international air race at the time and received much press coverage in the flying nations of the world. <S> So at that time, the way to bring the most attention to your aircraft - or your country's aviation capabilities - was to enter the most famous air race, which happened to be restricted to seaplanes only: <S> The word came down from Washington that we could attempt to set or break records and make cross-country flights that were considered newsworthy and would project a favorable image of the Army Air Service . <S> I'm sure there were other factors involved, but publicity and prestige seem to be two big ones. <A> No source on this, but my gut feeling is that it's a funding issue. <S> The Air Force wasn't an independent branch and the navy was quicker to invest in aviation and didn't share with the army, and definitely had a larger budget then private citizens. <S> The army definitely delayed emphasizing their Air Force (based on Rindlesbacher/rickenbacker's experiences).
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So again, no source other than books like The Aviators, but I would say funding in the Navy was higher and aircraft carriers weren't yet perceived by the navy as a whole as the dominant force they became in the early years of world war 2 (hence the pontoons).
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Can you file an open-ended IFR flight plan? Say you are doing an instrument training flight with a CFII and you are practicing IFR navigation. You will be taking off and returning to the same airport, but you are not certain exactly where your CFII might have you go. For instance, your CFII wants to see how you handle deviations in flight. Ths is just an example as I'm sure there are other reasons one would need to be IFR without a specific routing or destination. How would you file such a flight plan? Can you file an IFR flight plan without a specific routing? Another reason I can think of would be a test or acceptance flight that needs to be conducted in class A airspace. You would have to be on an IFR plan to fly there, but your ultimate destination would be right back where you came from. You might not be able to indicate specific waypoints, etc., instead you would be requesting block altitudes, etc. if you need room to perform maneuvers. <Q> If operating within a single area (TRACON) then file from KABC - <S> > <S> KABC and <S> in remarks put "Practice APCHS KXYZ KDEF". <S> The controller will be asking you what your next approach will be at some point. <S> Another tactic is to file to ABC VOR (or some other fix) and request a hold. <S> I like this method, as the student gets a hold with an EFC and that gives me time to decide how many orbits they will need as well as the next approach request. <S> I normally have the student ask for the next approach, as it keeps their workload up. <S> The first suggestion is generally preferred because in the event of lost com, in a true IMC environment, it is clear that you will be returning to KABC, unless you encounter VFR first. <S> Remember that an IFR clearance can end at a fix (even a pilot defined fix) and when you are in VMC that can be useful. <S> Similarly, an IFR clearance can begin at a fix, and that can be accomplished in a non-radar environment. <A> JScarry's comment is the answer. <S> The system has multiple levels of safety and assumes that if communications are lost, you'll fly the last clearance. <S> For instrument training or test flights, you can file a flight plan from airport A to airport B via VOR XYZ or airway V-99. <S> Fly the clearance you receive, then, before you land at B, ask for more clearances to fly to airport C or repeated approaches to B or whatever you want to do. <S> You will get clearances that always have a valid ending and allow ATC to work out what you will be doing and keep other traffic away from you should communications be lost. <S> The system was designed when radar coverage was not as extensive as today and radios were not as good as today. <A> ATC will generally clear this depending on the airspace, workloads, etc.
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You usually file a local IFR for this kind of flying, usually with a flight plan indicating the airports you will be flying approaches into or other details about your flight.
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How do I remind myself to run in-flight checklists? When flying a basic light aircraft with no "modern" instrument the pilot needs to remember to do various checks on a regular basis (FREDA every x minutes, change fuel tank every Y minutes etc.). Just flying the plane can be consuming a lot of attention (especially without auto-pilot or if you become unsure of your position) and it's easy to forget to run those checks. I wouldn't want to forget changing fuel tank so I was wondering: What are the tools that I can use to make sure that all checks are done on time? <Q> In my view, the best tool for reminding yourself of recurring "household chores" is by using a timer, if the noise profile of your aircraft allows it. <S> (Try it! <S> You can probably hear more than you think, even in a loud prop). <S> Either use a kitchen timer (which has a really simple physical interface, although two hands may be required) or your smartphone (a bit more complex interface, typically allows for single hand usage, with the added benefit that you can run multiple independent timers, and that the alarm will not stop sounding until you dismiss it). <S> Modern GA EFIS (for example G1000) typically have timing facilities built in. <S> (For example "Check the tank every time <S> the minute-hand passes the 0, 15, 30, 45 marks"). <A> I guess I have just been flying too long. <S> I just have chores that I do every five minutes, and I lookup my watch/clock probably two times a minute. <S> So it's pretty hard to miss things. <S> Even when flying an aircraft without an electrical system. <S> On my knee board I keep a list of things that I have to do in Zulu time, such as reports, fuel changes and things like that. <S> I don't like relying on smartphones, tablets or specific equipment in the plane with the exception of a timer, which almost every plane has, and a clock. <S> I have a back up to the timer and the clock on my knee board. <S> As of yet the math is still something I can manage. <S> I encourage you to consider the same, because a reliance an electronic systems will create inconsistencies if you move between different aircraft. <S> On the other hand if you rely on simple timekeeping instruments, which you carry backups for with you on every flight, then you can move from one aircraft to another with confidence that you can still manage the temporal tasks. <A> train yourself to look at the watch (wristwatch,cockpit,etc) at least once a minute, just like part of the instrument scan. <S> Pro: It gives you an awareness of the time elapsed, and also helps with lost comms scenarios,etc. <S> Cons: might develop into OCD pick a visible landmark ahead along your route. <S> "when we pass that large hill, I will check fuel, and contact radar". <S> It works surprisingly well (at least for me), as the brain instinctively/subconsciously recognizes passing abeam a landmark and raises the alarm on it's own. <S> Pro: easiest to train and execute. <S> Cons: well, you need landmarks <S> you can use a timer/alarm (wristwatch, phone, tablet). <S> Pro: works every time. <S> Cons: you become reliant on that phone/tablet, and having that alarm going off while on final approach can be annoying if you use a flightplan with waypoints pick some of them (usually 30-60 mins apart) and circle them with a big red pen. <S> ( if you have the FMS capability draw a circle arround them on the ND and an abeam <S> line).Pro: well, it works. <S> Cons: doesn't work well on VFR flights, since there aren't so many waypoints and they are too far apart. <A> Every flight has different phases. <S> For example, climbing, enroute, before landing, take off, landing, and others. <S> When you are in a phase of flight, then you do the chores that you learn to do when you are taking flight lessons.
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If you are unable to use an actual timer, determine the interval of the task (for example every 15 minutes), and use your normal watch. Using a checklist allows you to not forget anything that needs to be done, like lowering the landing gear!
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What is the procedure when an aircraft with an emergency can't land due to a blocked runway? This is a hypothetical scenario, but I'm interested to know if there are any regulations/guidance for what ATC should do in this situation. The hypothetical nightmare scenario: The runway is blocked by a crashed airliner and can't be cleared quickly. The airliner is full of injured passengers who will take time to move. The next aeroplane in line to land has an engine failure and is gliding to the runway (so can't go around). You're in a hilly/built-up area so other options for landing are limited. Clearly, you can't have one aircraft landing on top of a crashed aircraft, so what should ATC do? Some of the options I can come up with (in roughly ascending order of how crazy they sound): Switch him to a different runway e.g. LHR has two parallel runways (but if he's close to the airport making the sudden move across to another runway might be dangerous without power?) Empty a taxiway (but you'd probably struggle to empty it fast enough at a busy airport?) Point him towards a grassy bit of the airport Allow him to land, but aim to land before or after the crashed aircraft (crash is probably at start or end of runway, so might just work) Wish him good luck and tell him to find somewhere else to land (you know that's possibly going to result in him crashing, but at least he won't crash into the already crashed aircraft). So is there any advice for the controller and if so what is it? Note the source of this question was listening to a recording of the ATC when BA38 crashed at LHR . The controller asks the next aircraft to go around - it made me wonder what would happen if they had said no! <Q> What's the procedure? <S> The procedure is, be creative to save as many lives as possible! <S> Really. <S> Period. <S> It is as simple as that. <S> There are infinitely many scenarios, and one cannot be trained for everything. <S> However, pilots and controllers are trained to remain calm. <S> When we look at the accident report years later, reading the document, we can easily say " if the pilots had done that, people would have been saved... ". <S> The important thing is that the people who were responsible at the time had to <S> remain calm enough to look at the big picture instead of focusing on a particular problem, otherwise they can easily overlook a solution. <S> During training, it is common to throw multiple failures / emergencies together. <S> The purpose is not to train the trainee to react to this exact combination of failure, since that is rather unlikely. <S> Rather, the purpose is to simulate a stressful environment, under which one has to make sound and logical decisions. <A> It is up to the pilot in command, in cooperation with air traffic control, to decide what to do. <S> There are generally very few specific procedured defined for handling emergency situations. <S> Handling unusual situations is exactly why there are pilots and air traffic controllers at all. <S> We come up with solutions to problems that no one has ever seen before, or even thought about - it's what we get paid to do. <S> If there was a rule for how to handle every single hypothetical scenario, we would be long gone, replaced by computers. <S> But that is not possible - at least for now. <A> An example of how the title situation was handled in real life. <S> UA497 took off from the KMSY (New Orleans International) 2011-04-04 7000 ft runway and 4 minutes after wanted to return. <S> The Longer runway (10104 ft) was closed at the time for lengthy repairs with equipment on the runway. <S> Pilots wanted the longer runway but it couldn't be cleared in time. <S> They eventually landed on the 7000 foot runway, and veered a bit off to the side and were stuck for some hours. <S> http://flightaware.com/resources/airport/MSY/APD/AIRPORT+DIAGRAM/pdf <S> Overview of aftermath <S> (plane ran off side of runway and took time to clear) http://www.cnn.com/2011/US/04/04/louisiana.emergency.landing/ "United Airlines pilot, control tower conversation: 8 minutes and 44 seconds of steely calm" http://www.nola.com/news/index.ssf/2011/04/united_airlines_pilot_airport.html <A> It's a hypothetical scenario, perhaps, but one that has actually been considered and legislated for in at least one case. <S> If you're flying to Easter Island, you're not allowed to commit to it until any previous traffic has landed. <S> As with so many things in aviation, it's a lot easier to get out of this sort of mess when the system prevents you from getting into it in the first place :) <A> Like was said, there is no standard for a scenario like that. <S> The pilot in command will take the decision. <S> If none: We start praying and looking for a place to land. <S> After choosing one, we communicate to the ATC in order to send the rescue. <A> There is a simple rule that allows pilots to do whatever is necessary in an emergency. <S> So what happens in such a case is that the pilot declares an emergency , tries to figure out (together with the ATC) what to do but finally decides on his own what the best possible solution is. <S> He is allowed to disregard even ATC commands in an emergency (although he is still held responsible for his actions!). <S> So even though ATC can advice, they're "not the one in charge". <S> The pilot would most probably land on the blocked runway and turn sideways into the green to not collide with the other airplane.
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No, there is no standard procedure for handling a scenario like the one you describe. The procedure is to determine a course of action which will likely result in the best outcome for everyone, utilizing all resources and given all constraints. If there is another runway or taxiway available to land, the ATC will send the aircraft there.
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What happens when disengaging the electricity generators on a B747? This answer says: If let's say, you [...] disengage the electricity generator of every engine (which cannot be re-engaged without mechanical maintenance), [...]. What exactly happens in the aircraft when disengaging the generators and what benefit does it have to be not able to engage them again? Is it only the B747 that works like that or also other Airliners? <Q> This is how it works on all aircraft with a Constant Speed Drive (CSD) Generator or an Integrated Drive Generator (IDG) - doesn't matter who the airframe maker is. <S> When you press the disconnect button (the red arrow), the disconnect circuit is completed and the solenoid pulls the pin out of the pinion shaft (the blue arrow) which then engages the worm gear on the drive shaft (the green arrow) and causes that gear to disengage from the drive mechanism. <S> This causes the generator to stop turning. <S> To reset the mechanism you have to pull the "RESET HANDLE". <S> This drive mechanism is attached to the gearbox on the engine which means that it can only be done on the ground with the engine off <A> You have 3 questions: <S> What exactly happens in the aircraft when disengaging the generators? <S> What benefit does it have to be not able to engage them again? <S> Is it only the B747 that works like that <S> or also other Airliners? <S> What exactly happens in the aircraft when disengaging the generators? <S> As mentioned in the other answers: A solenoid removes a retention pin. <S> This allows a spring-driven pawl to engage a worm gear on the drive input shaft. <S> This causes the inner input shaft to disengage from the engine drive. <S> Thus the generator drive rapidly coasts to a stop. <S> Source: <S> k-makris.gr/AircraftComponents/CSD/C.S.D.htm <S> What benefit does it have to be not able to engage them again? <S> The primary reason to disconnect the generators is when some mechanical problem causes a risk of serious mechanical damage to them. <S> From <S> the Boeing 747-400 Abnormal Procedure Checklists <S> Word Doc : <S> Condition: <S> Low IDG oil pressure or high IDG oil temperature. <S> Crew Response: <S> Affected GENERATOR DRIVE DISCONNECT switch PUSH. <S> Note: <S> This action prevents damage to the IDG. <S> DRIVE DISC message is displayed. <S> ELECT GEN OFF message is displayed. <S> A lesser reason might be to prevent a seized-up generator drive from adversely affecting an otherwise operable engine. <S> Since whatever caused the loss of oil (pressure) <S> and/or overheating almost never can be corrected in the air , then there is no point in being able to reengage the generator drives in the air. <S> Furthermore, to provide that capability would require complex mesh gears, clutches, and mechanisms that would add considerable weight and more points of failure -- all to cover a contingency that is both rare and very unlikely to be critical (discounting sabotage). <S> Is it only the B747 that works like that <S> or also other Airliners? <S> Most large jet aircraft use some form of Constant speed drive (CSD) to power their electrical generators, as the alternatives are not well suited to the large electrical demands of jetliners. <S> From Wikipedia, we see that newer Boeing and Airbus models use a single-case variant of this called an "IDG" . <A> The button I was talking about is the "Drive Disc" button, circled in red here: source: http://www.meriweather.com/flightdeck/747/over/elect.gif <S> This button mechanically disconnects the Integrated Drive Generator (IDG), a generator for providing electricity, from the engine. <S> The button above it disconnects the IDG electrically from the buses, but keep the IDG connected to the engine (so it is spinning as the engine spins). <S> A similar configuration exists on Airbus as well, see for example this YouTube video where disconnecting the drive is part of a procedure for abnormal engine indications. <S> As a result of disconnecting the drive, the electricity output of the plane is reduced.
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The disconnect button is pushed when there is reason to believe that continue operation of the generator may lead to engine damage, for example when there is a low oil pressure or high temperature indication of the IDG.
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What is the efficiency of running an electric motor from a gas generator? If you were to run an electric motor from a gasoline or diesel generator, how big would the generator have to be to run something like the Siemens electric engine? Is this a viable model for replacing a heavy piston engine or is it too inefficient? The link below says standard portable generators are capable of 6.13 kWh per gallon of gas. The Siemens only weighs 50kg and delivers a continuous output of 260kw. Does that mean I'd need a generator 42.4 times as powerful than most portable generators and be burning a gallon of gas a minute? I know a lot of small aircraft engines weigh around 150kg and several use gear boxes as well. So Does this mean you could save the weight to make the plane electric but not battery powered or is the generator simply going to be too inefficient? https://www.google.com/amp/s/settysoutham.wordpress.com/2010/05/26/portable-generators-about-half-as-efficient-as-power-plants/amp/ <Q> I know a lot of small aircraft engines weigh around 150kg and several use gear boxes as well. <S> Almost no piston aircraft use gearboxes. <S> The only one that I know of that ever did was the Porsche Powered Mooney PFM which was largely a failure overall, with the gearbox being often cited as an issue. <S> Smaller turbo-prop planes do use gearboxes due to the super high RPM range of a turbine but those are generally larger than the ones that seem to be in question here. <S> So Does this mean you could save the weight to make the plane electric but not battery powered or is the generator simply going to be too inefficient? <S> As mentioned the issue here is simply weight and line loss. <S> You are taking mechanical energy converting it to electrical, bussing it somewhere <S> then converting it back to mechanical. <S> There will always be line loss in a process like that when you don't really need it (since you need to spin the prop to begin with). <S> You are also introducing at least 3 major points of failure (engine -> generator -> motor) to a system that previously only had one. <A> Analogous to train powertrains :). <S> The great characteristic of electric motors is the large torque generation at standstill, compared to combustion engines. <S> We all tend to look at power output for engine comparison, but it is Newton's second law that provides the acceleration to achieve the end velocity: <S> force (or torque) does that. <S> Power equations just make the computations easier, especially if torque is a function of rpm and if there are gearboxes with selectable gears. <S> The four stroke petrol (gasoline) engines provide zero torque at standstill and a pesky amount of torque at idle. <S> Two-stroke engines, diesel pistons, gas turbines, electric motors all provide more torque at standstill or idle. <S> Ships have 2-stroke diesels for all the torque that the propellor must provide. <S> Trains indeed use the combustion engine-torque motor combination for better torque control for heavy trains, the alternative is a slipping clutch which has obvious drawbacks. <S> Cars now have combustion - torque combination with batteries to regenerate energy that would otherwise be lost from deceleration. <S> So if we treat your question as a design question, we can see the reasons why electric motors were successfully applied in other vehicles: to overcome a dominant design issue. <S> In aircraft there are three dominant design issues: weight, weight and weight. <S> And safety. <S> An aircraft that is too heavy simply will not fly. <S> Sure a B747 freighter can lift a tank, but the skin is made from aluminium, the engines are twin axle gas turbines (high torque, low weight!), and everything in the aircraft has been designed for low weight first. <S> Aircraft don't need slip clutches, the air itself does that already. <S> They just need a light way to create a lot of torque and output power. <S> They also need redundancy: if you have one gas turbine providing electricity for four motors, and the turbine fails, all four motors stop. <S> If you have 4 separate gas turbines, failure of one of them is not catastrophic. <S> For preventing failures aircraft need simplicity. <S> Converting kinetic energy to electrical to aerodynamic propulsion is too complicated. <S> All of this will be a different story once we can generate electricity in huge amounts from light weight fuel cells, but we haven't cracked that nut yet. <A> What you describe sounds like a gas-electric transmission (gas/diesel engine drives generator, generator drives one or multiple electric engines that propel the device). <S> Such systems are sufficiently efficient and very common in trains, ships and other big, heavy and powerful machinery. <S> Seems that nobody ever attempted to build a plane like that, but, to my opinion, it should fly. <S> There may not be enough benefits to justify the additional weight of the generator and powerful electric engine. <S> For instance the possibility to place the larger and heavier gas engines anywhere in the plane and distribute their power evenly between all (multiple) propellers may be an advantage.
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Gas-Electric (be it diesel or gasoline) is advantageous as you can drive full torque at 0-RPM which is useful when getting a giant freight train rolling but does not provide a ton of benefit to light aircraft.
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Why the moment arms in x-direction are considered as -x? Thanks for anyone reading this question. I am able to understand the signs of the forces, but I could not understand why a negative sign is added to the moment arm in x-direction (please check the last line in the picture).Thank you! <Q> In your drawing, force is defined positive when upwards. <S> By convention, pitching moment is defined positive in aircraft nose up direction. <S> Origin of the moment is the wing leading edge, so a positive force yields a nose down moment which is negative. <S> Horizontal forces result in a nose up moment when above the origin, and nose down when below the origin. <S> That is assuming: Positive is up, for force and position. <S> Positive is aft, for both force and position. <S> Positive is nose up, for moments. <S> That is the sign convention for which the equation in the book holds. <S> The book should state the sign convention it is using, perhaps you can post that as well. <A> Also, the value of Y for the lower side forces should be negative while it is positive for the upper side forces. <S> The author selected to subtract the lift force terms while he added both drag force terms even when one of them has a negative lever arm. <S> This is sloppy. <S> The reference point of the moment is the leading edge, so all lift forces N act at a point behind this reference point. <S> Positive is up and to the right, so a positive moment is trailing edge down. <S> A positive lift force behind the reference point produces a negative moment, so to achieve a positive number the lever arm has to be negative. <S> In mathematical terms: Positive x is backwards, but you need to go forward in X to move from the force to the reference point. <S> Hence a negative x. <S> But there should not be a minus sign for the variable in the equation. <A> I think the confusion stems from an incomplete understanding of reference systems on an aircraft. <S> The forces and moments are arranged according to the right hand system. <S> A way to determine what direction the moments point is to use the your right and make a fist. <S> Then point out your thumb. <S> As in the image below: Source <S> If you put your thumb on the positive direction (so let's say +X force), your fingers curl in the direction of the positive moment (thus in the direction of the arrow that says 'L'). <S> Similarly for your question, we are talking about pitching moments (rotation around the Y-axis), so we have to point are thumb in the positive Y direction. <S> Our fingers then curl with the clock (as seen from the Y-axis). <S> The N force is in the opposite direction, making for the - sign. <S> Source <A> I'm not an aviation engineer, but a physicist, and see it like this:There is a pressure $p$ acting perpendicular onto the airfoil, and $\tau$, which seems to be drag, acting parallel to the airfoil to the trailing edge. <S> Right? <S> If this is so, one can express the horizontal force $dA$ and vertical force $dN$ on the upper side as: $$\begin{eqnarray}p_x&=&-p\sin\theta\\p_y&=&-p\cos\theta\\\tau_x&=&\tau\cos\theta\\\tau_y&=&-\tau\sin\theta\\\hlinedN&=&p_y+\tau_y=-p\sin\theta-\tau\sin\theta\\dA&=&p_x+\tau_x=-p\cos\theta+\tau\cos\theta\end{eqnarray}$$ <S> Note: <S> The direction of $dN$ is upwards, and that of $dA$ is to the right. <S> The value of this expressions can be negative, making them effectively pointing into the other direction. <S> But we don't have to care about this, math does for us. <S> Now, in physics, a momentum trying to rotate something counter-clockwise is positive, and a momentum trying to rotate clockwise is negative. <S> But it seems in aviation a moment trying to lift the nose is positive, which in this case means that clockwise rotation is positive. <S> Then, one gets: An upwards pointing $dN$ tries to turn the wing counter-clockwise, and must give a negative momentum, <S> i.e. $\int -x\cdot dN$. And $dA$ tries to turn the wing clockwise, and gives a positive momentum $\int <S> +y\cdot dA$. (Please excuse that I'm a bit sloppy about that infinitesimal stuff)
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You are right, technically the equation should have only plus signs, and the value of X would be negative.
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Do the pilots have to recalculate the balance when 6 passengers show up last minute in a 737? Few years ago me and my mates forgot the checkin time and were late for flight. We were late for check-in counter closure (30 minutes before flight if i'm not wrong) but the staff allowed us to go on. We had no checked luggage. There were 6 of us so at least 400 additional kilograms to be carried. Do the pilot need to recalculate mass and balance or is it within the allowance? <Q> Loadsheets have a section called ' last minute changes' . <S> As the name implies, pilots can record last minute changes here. <S> What constitutes 'minimal' depends on many things, principally limits set by the operator or manufacturer. <S> I can't verify this but think 400kg would fall within these limits, unless the aircraft was already at its performance limits. <A> Chances are pretty good that the W&B was recalculated automatically as soon they decided to let you board. <S> Pax manifests have to be accurate and just about everyone uses software tools to manage this. <S> Once you have a pax & bag count, you plug the numbers into whatever zone they're in and boom done. <A> It depends. <S> If the pilots had already completed the loadsheet, or received it from the handling company (more likely for a larger operator), then yes, they do have to recalculate, or request a new, updated loadsheet. <S> Otherwise, since no loadsheet has been issued, there is nothing to recalculate, for the pilots, but WHEN the loadsheet is calculated, it WILL include the latest numbers. <S> Bottom line is: you will be included. <S> 400 kg is enough to make a noticeable impact on performance (engine thrust setting) and take off speeds for a 737. <S> As another poster implies, there is often a last minute change (LMC) section for, <S> well LMC's. <S> There is also an upper limit of how large this LMC can be (ranging from 500-1500kgs for the 737-operators <S> I have been with). <S> An LMC usually takes about a minute.
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If the changes are minimal, there is no need to recalculate the mass and balance, and trim settings.
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Why are fighter pilots seated and not reclined? I have always wondered about this one. Pulling high G-forces is, I assume, the most physical challenge the pilot of a high performance fighter aircraft needs to be able to sustain without blacking out or worse. Indeed, in most countries in the world would-be fighter pilots cannot qualify for jet-jockey status without first passing the dreaded centrifuge test. Further, modern jets can in fact pull much higher G-forces than the pilot without damage to the aircraft. Indeed, I read somewhere once that one of the issues with auto-missile-avoidance systems is that the aircraft is limited to performing maneuvers that the pilot can withstand. As I understand it, the issue with high-G turns is that the blood is drained or driven from the body to the lower (and upper when undergoing high negative-G) extremities of the body resulting in starvation of the brain and consequent blackouts or even embolism in the negative-G case. I realize pilots wear tight G-suits which have air pumped into them to restrict the amount of blood that can accumulate in their lower extremities, but that doesn't reduce the stress on the heart trying to pump blood up to the head. It seams rather obvious to me that much of the issue with high-G is caused by the seated position of the pilot. It is an established fact that the more vertical you are the harder it is to withstand G-forces. Why then are modern jets not designed with the pilot in a more reclined position? For example, the position used by Formula-1 race car drivers: Don't get me wrong, I understand F-1 drivers do not need to withstand the same kind of sustained vertical forces that a fighter pilot does, however the legs-up reclined position seems to be far more practical for a high-G environment. I do realize that the whole ejector-seat mechanism would need to be redesigned to eject the pilot differently, and that the pilot's ability to see behind himself would be compromised without technical aids, but surely the increased turn rates and lower profile cockpit would outweigh those issues. NOTE: I have seen other posts on using the head first "prone" position, including this stack-exchange link but nothing on reclined. ADDITION: Found this image of a Foka-5 glider pilot position too... note how wonderfully streamlined it is. <Q> But seat angles are limited by the need for good visibility. <S> Pilots frequently need to look to down-and-sideways, down-and-forward, and towards their back-quarters. <S> These are angles that your F-1 Driver couldn't possibly see. <S> Also, High-G maneuvers are quite rare. <S> Most modern military planning is about making sure pilots are never even in a position where they need to evade a missile or dog-fight another plane. <A> The F-16 in fact has a relatively large recline (compared to other fighters). <S> From the main F-16 Wikipedia The F-16's ACES II zero <S> /zero ejection seat is reclined at an unusual tilt-back angle of 30°; most fighters have a tilted seat at 13–15°. <S> Subsequent U.S. fighters have adopted more modest tilt-back angles of 20°. <S> Albano, J. J. and J. B. Stanford. " <S> Prevention of Minor Neck Injuries in F-16 Pilots". <S> Aviation, Space and Environmental Medicine Issue 69, 1998, pp. <S> 1193–1199. <S> From this archived DTIC Article from 1962 it appears to confirm a lot of what the other answers said. <S> As noted in the comments this in regards to the prone position and not a reclined position. <S> From the summary page: The prone position of the pilot in high-speed airplanes has certain advantages <S> (higher g-tolerance of the pilot, reduction of drag due to decrease of frontal area, improved instrument visibility) and drawbacks (narrowing of field of vision, decrease of visual acuity, aggravation of claustrophobic tendencies, discomfort encountered in this abnormal position). <S> Spacecraft routinely have their pilots in the reclined position but their main objective is a fairly narrow scope compared to a fighter pilot. <S> It seems the wrap-up answer is that other positions are useful in the context of the specific mission of a given platform but for military aircraft it doesn't seem to offer an advantage. <A> A pilot position as reclined as pictured would have the pilot upside down with blood rushing to the head whenever the plane is in a steep fast climb such as takeoff and many dogfight maneuvers. <S> Probably not a great position for maintaining orientation and consciousness. <S> It feels natural to move forward while seated upright. <S> Even climbing vertically is a similar G sensation pressing you into your seat. <S> But people are not accustomed to being dragged skyward by the feet. <S> Without it, the inertia of a helmeted head would carry the head forward causing grave injury in a crash, and to a lesser extent during hard braking. <S> The reclined position starts you out closer to the limit of your safe range of motion. <S> HANS prevents you from reaching that limit, but it also prevents you from looking down. <S> That can be a useful skill if you are the type of pilot that likes to.. uh... land. <S> A HANS type device isn't required in the glider pictured because it lacks the capability to rapidly accelerate or decelerate, thus leaving the pilot free to look around. <A> This question is pretty similar to this one <S> but you provide a slightly different position so there may be some variances. <S> Some things to consider, In the F1 like case, blood would still have the ability to pool in the gluteal region as well as the feet since they are lower than the head. <S> In the more reclined, feet forward position one would need to have the instrument panel over their legs (and a significant amount of it) lest it be quite far and possibly out of reach. <S> This could potential cause a problem in an ejection scenario. <S> A good, practical example of this position is <S> the Bede Jet <S> a not so popular kit plane famously flown by James Bond . <A> The Recline was to get the seat in the jet... <S> that is the primary reason. <S> On long ferry missions not much pressure is on your sit bones and back. <S> G tolerance and endurance is about hitting the gym.. <S> not really the 30 degrees of recline :) <S> Also ejection out of the jet.. which can be career ending... <S> your knees have to clear that dash on the way out... <S> so they had to make sure the seat gets you clear of the suns-shield /dash and the vertical tall as you are fired toward it...
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The tilted seat can accommodate taller pilots and increases G-force tolerance; however it has been associated with reports of neck ache, possibly caused by incorrect head-rest usage. Fighter pilots are far more reclined than you might think. A very critical device in a F1 car that allows for that extremely reclined position is the HANS head and neck restraint system.
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Why is a sweeping second hand required for IFR? The reasons why a clock is necessary for IFR have been explained elsewhere , but I haven't seen the reason that the clock has to have a sweeping second hand. It seems like when timing things it would be more useful to have a ticking second hand, why is it expressly required that it be a sweep? <Q> As @fooot mentions in the comments it means that the hand must be concentric with the hour and minute hands , it is not a reference between the difference of deadbeat and sweep seconds as many watch brands commonly reference now. <S> This is a regulation that is intended to clarify the difference between a second hand that references the main dial and one that is on a sub dial. <S> Historically planes may have had more complicated nav clocks like this hamilton <S> where the large second hand is for the chronometer and not the elapsed time clock. <S> ( source ) <S> You can find what looks like one of the early AC's on digital clocks here . <S> It references FAR 91.33 (which seems to no longer be in place) <S> you can find the original verbiage here . <S> I can not find any FAA legal interpretation that further defines "sweeping seconds". <S> On a bit of a side note, wrist watches (in any form) are not a legal substitute for a mounted clock . <A> In IFR flight you sometimes need to accurately time seconds for approaches or turns. <S> Early watches did not have a "seconds" hand. <S> Some watches had a small secondary dial for seconds, but because of the small size it was hard to read. <S> As "fooot" says above, it does not refer to the type of motion the hand makes. <S> I have seen some aircraft equipped with digital clocks and often wondered if I needed to wear a "sweep-second hand" watch to be legal. <S> Photo Source <A> FWIW, local DPEs and the FAA FSDO agree that a digital clock with a seconds display may be used as an equivalent of an analog clock with a "sweep second" pointer. <S> This was a big deal, perhaps in the 80's, but everyone has come to accept the digital clock as acceptable for flight operations and flight tests. <S> The point about a clock aircraft mounted is a MEL / 91.213 issue that should be understood by wanna-be instrument pilots. <S> Practically, installed GPS satisfies the clock requirement.
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The rule was written "sweep-second hand" meaning a seconds hand that swept around the main dial so that a pilot could accurately time seconds.
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Where can I get airport diagrams of non-towered airports? I'm trying to find a couple of airport diagrams for right now: X26 and X59 . Neither of them are listed in the Chart Supplement or on the FAA site.All I could get were those shabby diagrams presented by Airnav and Skyvector and sorts, and Google Earth images, both of which are not current. (The runway numbers are different from what are actually designated (painted) and used.) Does anyone have a better idea about where to find the airport diagrams? Plus, what the heck is the order of those airport diagrams listed in the Chart Supplement?! I couldn't find any rules. <Q> Many non-towered airports have diagrams in the Chart Supplement, and there is an airport diagram for X26 but not for X59 . <S> The difference appears to be that X26 has instrument approaches <S> but X59 doesn't. <S> It looks to me like the airport diagrams are considered part of the terminal procedures . <S> But I have to say that the FAA is as clear as mud on this. <S> The airport diagrams legend <S> says: selected towered airport diagrams have been published in the Airport Diagram section of the A/FD <S> But obviously that's completely wrong, because a) many non-towered airport diagrams are in there, and b) <S> the A/FD doesn't exist any more. <S> By inspection, it looks to me like airports without an instrument approach <S> have no airport diagram (X59, X25, 2RR) and ones with an approach do have one (X26, X07, AVO). <S> But I only spent a few minutes looking, so I may well be completely wrong on this. <S> As for your question about the order of diagrams, the legend says : Diagrams will be listed alphabetically by associated city and airport name <A> Try contacting the airport manager at those airports for this or more info: X59: 321-952-4590 X26: 772-228-7013 <A> Does anyone have a better idea about where to find the airport diagrams? <S> For U.S. airports, consider using the AOPA Airport Directory . <S> It's searchable by anyone without charge. <S> I just checked, searching using X26 as the input string and then X59, and it has airport diagrams for both.
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ForeFlight makes a basic airport diagram for X26 and for X59.
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Can state or local laws regulate where aircraft can take off and land? Say you have as private strip, but your neighbors get tired of hearing your plane. Can the local authorities pass, and enforce a law saying you can't take off and land there? Or do FAA rules override local authority as to where you can and can't land? <Q> As any licensed pilot knows, the FAA and the US military are the "de-facto" regulators of 99.9% of what goes on in the air over the US (see: <S> https://aviation.uslegal.com/government-regulation-and-control/state-aviation-regulations/ ). <S> Still, state and local governments are not entirely powerless here. <S> The general theory being more or less that, in cases where there is no obvious conflict with the FAA, or the US military, then local jurisdictions may still have some small level of control over certain very limited "air-spaces" (see: http://caselaw.findlaw.com/us-6th-circuit/1140229.html ). <S> Suggestion: 99.9% of the time, the FAA wins, but <S> hey, don't let that slow you down! <S> (Still, in view of the findings of the second case I just listed above, if I were you, I might try keeping peace with my neighbors over trying to save just a few steps on the way home.) <A> In cities where a public helipad has been established, flight operations are often severely restricted by annual movements, or specific hours of operation. <S> With that said, here is an extract from a piece written by Matt Thurber for Business Jet Traveller Magazine, in October 2010: <S> The FAA doesn't prohibit helicopters from operating most places, so you should be able to land one in your backyard if you can do so safely. <S> And no law says you have to build a helipad to land. <S> The regulations do, however, "require notification to the FAA for any permanent landing area; private versus public use does not matter," according to FAA airports airspace specialist Angie Muder. <S> City, county and state requirements may present greater obstacles, so be sure to check these, too. <A> Say you have as private strip, but your neighbors get tired of hearing your plane. <S> Can the local authorities pass, and enforce a law saying you can't take off and land there? <S> The short answer is yes they can. <S> You are allowed to build such a strip as is answered here . <S> However the city may have a thing or two to say about it and there are things they can do. <S> A lot of big cites have noise abatements that prevent aircraft from being bothersome. <S> In reality they legally could have the noise abatement be in effect all the time preventing you from ever flying in and out of your strip. <S> An appeal to a higher court may rule in your favor on a case like that. <S> However towns can have all sorts of strange regulations that may prevent you from storing an airplane on your property like this case from LI NY . <S> Some states may chose to not regulate it like Kansas at a state level, Kansas has no inspection program and makes no apologies for allowing private airport owners to operate free of bureaucracy. <S> "We in Kansas love the sound of aviation," says Mike Armour of the Kansas Department of Transportation. <S> There are lots of jurisdictions here in the US and it will vary heavily from one to the next. <S> Or do FAA rules override local authority as to where you can and can't land? <S> Generally no, however the airspace in this country does fall under the federal purview and you are allowed to use it as long as regulations are followed. <S> With that in mind the FAA sure does have a lot of regulations about where you can't land but generally does not mind you landing on your own property. <S> In some cases the FAA may even be on the cities side such as we have tragically seen in the case of the Santa Monica Airport .
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Civil Helicopter Operations are greatly stilted by local county, and municipal laws that in many cases, prohibit helicopter operations.
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Why is there a helicopter visibility reduction restriction for this approach? For the RNAV (GPS) RWY 17 approach at KSMN, why does it say "Helicopter visibility reduction below 3/4 SM NA."? Looking at the LNAV, there is a 5 mile visibility requirement and if we cut that in half per AIM 10-1-2 , wouldn't there be a 2 1/2 mile visibility requirement? If so, then a helicopter couldn't fly the approach with 3/4 mile visibility anyway. <Q> Helicopters may operate under special VFR when in flight visibility is less than 1 SM. <S> Therefore, the approach can be flown at lower visibility than that published on the approach plate. <S> However, the note must be published to further restrict these types of operations: <S> "The procedure is annotated with 'Visibility Reduction by Helicopters NA.' <S> This annotation means that there are penetrations of the final approach obstacle identification surface (OIS) and that the 14 CFR Section 97.3 visibility reduction rule does not apply and you must take precaution to avoid any obstacles in the visual segment. <S> " <S> 1 <A> Even though it's obvious from the (non-helicopter) 5 mile min <S> vis (reduced to 2.5 miles for helicopters), the issue of 3/4 SM is never relevant. <S> The same goes for the "DME/DME RNP-0.3 NA, which is irrelevant also since in order to fly a RNP -0.3 approach (which an LNAV approach is), you must use a properly certified GPS system to achieve the RNP -0.3 performance accuracy (DME/DME RNP can never be used). <S> I think both are just a charting convention. <S> This question has been asked before on another forum (can't remember which one) and this seemed to be the accepted most reasonable answer. <A> Remember that the helicopter visibility restriction also applies to IFR departures. <S> under part 135, you can depart IFR without a takeoff alternate if you have the visibility to shoot the approach straight in, and all the equipment is working... <S> this visibility can be cut in half unless it says helicopter vis reduction N/A. <S> So, looking at this approach plate alone would still not answer your question. <S> But, if you look at the other VOR/DME B approach you can see that the required vis is 1.25sm vis. <S> Helicopters would usually be allowed to cut that in half and therefore depart IFR without a takeoff alternate if the vis was .625sm <S> vis. <S> I looked it up, but they seem to have removed the limitation as of me writing this. <S> But I would be curious if they had that limitation on all of Lemhi's approaches in order to limit the IFR departure to 3/4sm.
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My understanding is that similar to the notation on the chart that "DME/DME RNP-0.3 NA, the helicopter notation (Helicopter Visibility Reduction less than 3/4 SM NA) is just a charting convention.
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Why is an approach that relies on both LOC and PAPI not considered a precision approach? I am an aviation layman. I am reading about PAPI lighting system and it seems like it provides vertical guidance, just like the glideslope component of an ILS. Coupled with a LOC, both vertical and lateral guidance are available to the pilot. Why isn't such an approach considered a precision approach? Thank you. <Q> I think you're overlooking the primary reason pilots fly instrument approaches: the conditions do not permit flight by visual reference. <S> The fact that a PAPI provides vertical guidance is more or less useless if you can't see it. <S> Most ILS approaches involve a descent of at least 1500' from glideslope intercept. <S> If you break out from the clouds at ILS minimums, you can be as low as 200' above the runway surface; at 3°, that's around 3/4 miles from the touchdown zone and the PAPI. <S> It's highly unlikely that the PAPI would be visible prior to that point, meaning the approach would be made with purely lateral guidance. <A> The latter allows you to spot small deviations or trends much earlier and with significantly higher precision. <A> A precision approach is one where vertical guidance is provided. <S> ILS, (former) MLS, and other approaches where there is electronic vertical guidance may qualify as a precision approach (there are some other criteria). <S> PAPI is not electronic guidance, and therefore would not meet the requirement of vertical electronic guidance on an instrument approach.
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In addition to the issue of visibility, consider that a PAPI consisting of 4 red/white lights only lets you distinguish between five different states (ranging from all red to all white), whereas an ILS glideslope component will give you a continuous guidance.
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