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Have jet engines ever "Sheared" off? I have read that jet engines, at least the under-wing ones, are attached to the airplane by shear nuts and bolts so that in case of unstable forces in or on the engine, the engine would fall off to prevent further damage to the airframe. Have there been any incidents and or accidents where the engine has fallen off the plane in accordance to this design feature? <Q> Engine shearoff, though rare, has happened in a number of cases. <S> Boeing 747F experienced a number of engine falloffs: <S> On Dec 1991, China Airlines flight 358 , a 747-200F, lost an engine near Taiwan and crashed. <S> Another 747F from Evergreen Airlines lost an engine over Anchorage, Alaska soon after. <S> On October 2004, a Boeing 747-132SF of Kalitta Air lost an engine while climbing and landed without further incident. <S> Engine separation has been reported on 737s too: <S> In November 2007, Flight CE723, a Nationwide 737-200 lost an engine during takeoff; the aircraft was landed without further incident. <S> On December 1987, USAIR FLT 224 , B737, lost an engine during climb; the aircraft was landed successfully. <S> There are cases where engine separation has occurred in B707 , B727 , and DC-10 . <S> aviation-safety.net has a list of engine separation incidents. <A> ELAL flight 1862 crashed in Amsterdam on the 4th of October 1992 as a result of 2 engines shearing off. <S> The number 3 engine sheared off shortly after take-off due to metal fatigue related failure of the fuse pins. <S> After separation, the number 3 engine hit the number 4 engine, shearing it off as well. <S> Combined with damage to the leading edge of the right wing the aircraft became difficult to control at low speeds and subsequently crashed on the attempt to return to Schiphol Airport. <S> Official accident investigation report <S> (PDF) <A> The Boeing 727 acquired a reputation for shedding engines. <S> The process was ice buildup on the right side due to leaking lavatory plumbing, the ice falling off and into the No. 3 engine where it caused damage to the fan blades. <S> The resulting imbalance lead to vibrations, and the engine was designed to shear off in that case. <S> This New York Times article describes one case where a 727 lost its engine over Florida. <S> The article continues: Cases of engines falling from airplanes are rare. <S> In 1974 a National Airlines 727 lost an engine near Sierra Blanca, Tex. <S> In 1985 an American Airlines 727 flying from Dallas to San Diego lost an engine near Deming, N.M. <S> I would expect this happened also to some Russian airplanes, but here the reporting is less up-front, so I know of none. <A> In addition to the cases where engines fell off in flight, there have also been cases where the engines sheared off due to impact forces during a crash, which is the primary reason for attaching to the wing with shear pins. <S> This helps to prevent excessive loads from breaking the wing structure, which would cause a fuel leak from the tanks in the wings. <S> Some examples: July 2013 , <S> an Asiana 777-200ER crashed short of the runway. <S> Both engines separated. <S> April 2013 , a Lion Air 737-800 crashed short of the runway. <S> The right hand engine sheared off. <S> February 2009 , a Turkish Airlines 737-800 crashed, both engines separated. <S> December 2008 , a Continental 737-500 departed the runway on takeoff. <S> One engine separated.
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On October 1992, a El Al 747-200F crashed after takeoff due to engine separation, at Amsterdam, the Netherlands.
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What are the advantages or disadvantages of a mid wing design? Are there advantages or disadvantages to a mid wing design for a monoplane? If so, how would this design compare to a high wing or a low wing monoplane design? What might be the aerodynamic advantages or disadvantages? What might be the design or structural advantages or disadvantages? What might be the control or flight characteristic advantages or disadvantages? <Q> The mid wing is mostly used in combat aircraft and rarely in passenger jets. <S> The reasons are mostly structural. <S> Aerodynamically, the mid wing is the best option as it is much more streamlined and has less interference drag compared to the high and low wings. <S> The mid-wing also has neutral roll stability, which is good from the prespective of combat and aerobatic aircraft as it allows for the performance of rapid roll maneuvers with minimum yaw coupling. <S> The mid wing has certain disadvantages when it comes to structural design as far as passenger and cargo aircraft are concerned- the wing will have to either pass through the fuselage, eating into usable volume or the structure <S> has to be strengthened around the fuselage to carry the loads. <S> This is the main reason this type of wing is rarely found in commercial airliners. <S> There are some aircraft which do have mid mountedwings, like the Piaggio Avanti , which has the wings passing behind the cabin and canards and the Hansa jat , which solved the problem by sweeping the wings forward and thus passing it through the rear fuselage. <S> These types are rare, however. <S> Image from hansajet.de <S> This type of wings are used by a number of combat aircraft, however, for example, the Dassault Rafale . <S> Image from <S> http://indiandefence.com <S> For combat aircraft, the adoption of mid wings means that the landing gear have to retract into the fuselage for keeping the length under check. <S> The mid wing allows for the carriage of weapons and fuel tanks in underwing pylons however. <S> Also, the pilot's visibility is not affected during turns as in the case of high wing. <A> A mid wing design is mostly used on aerobatic and combat aircraft. <S> The wing spar carry-through would be where the payload needs to be in transport and passenger aircraft, so a mid wing is the worst choice for these types of aircraft. <S> When Boeing turned the B-29 into an airliner (the 377 Stratocruiser ), they needed to add a second tube on top of the original fuselage, turning a mid-wing design into a low-wing. <S> Boeing 377 Stratocruiser <S> (picture source ) <S> Aerodynamic pros and cons <S> Pro: <S> A mid wing position adds the least amount of interference drag. <S> This is the main reason for using it on high-performance gliders. <S> Pro: <S> Ground effect is less than for a low-wing layout … <S> Con: … <S> but higher than for a high wing design. <S> Structural pros and cons <S> Pro: Puts the wing spar at the widest point of the fuselage cross section, so the load transfer is straightforward and the bulkheads can be lightweight, if no engines are in the way. <S> Pro: Leaves more space for wing-mounted ordnance or engines and allows a shorter fuselage-mounted landing gear … Con: … but if the landing gear is wing-mounted, it needs to be longer and heavier than that of a low-wing configuration. <S> Con: <S> In fighter jets with fuselage-mounted engines the air ducts and engines are in the way of the wing spar, so it needs to be built around the intake duct(s) and engine(s). <S> This makes the bulkheads heavy. <S> Con: <S> The spar will be where the payload needs to be in transport and passenger aircraft. <S> Flight characteristics pros and cons: <S> Pro: The inertial axes run through the center of the airplane, so any roll maneuvers can be performed quickly and without much change in the flight characteristics between upright and inverted flight. <S> Note that most high-performance aerobatic airplanes use this layout. <S> Con: <S> In single- and tandem seaters with a cockpit close to the CG the wing blocks much of the pilot's view in the lower forward region, which makes take-offs and especially landings harder. <S> Patty Wagstaff's Extra 300 over Florida (picture source ). <A> They have a main structural advantage: Mid mounted wings have the advantage of being structurally efficient when aerospace engineers desire to incorporate a swept or tapered wing design on the aircraft. <S> This increase in structural integrity is essential for aircraft that perform extreme maneuvers or aerobatics Source: Student Pilot News <S> They also leave the aircraft free of spars on the belly and room for cargo. <S> And they reduce the induced dragThe main disadvantage is the speed. <S> The fastest planes use low-wings. <S> Also many of this aircraft use spars in the middle of the fuselage, so you have to have a bigger fuselage and thus more weight. <S> It is common on high-performance types such as sailplanes. <S> A low wing allows the pilot to have a good visibility and a lighter structure because as it is below fuselage, it doesn't have to carry more weight. <S> But there's also a main disadvantage which occurs when landing; it produces a strong ground effect compared to the high and mid-wing. <S> In case of an emergency you can step out and can be used as overwing exits. <S> And finally, they have better flexibility. <S> A high wing provides also good visibility and lateral stability. <S> Also increases ground clearance for the engines and cargo. <S> More info can be found here and here .
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It is aerodynamically the cleanest and most balanced, but the carry-through spar can reduce the useful fuselage volume near its centre of gravity, where space is often in most demand.
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Can multiple helicopters be used to lift a heavy load? If the load is heavier than a single helicopter could lift, how possible is to use multiple helicopters for this task? I have only seen this in some movies. The biggest doubts are If we attach two ropes to the single point of the load in a V shaped way, a side force will be created pulling the helicopters together into collision. Even without this, the flight of the two machines probably needs to be very coordinated. In movies like "Pacific Rim" a whole swarm of helicopters lift a heavy robot. How realistic are these visions? <Q> This video on YouTube apparently shows that it has been done at least once. <S> A rigid beam was used to counter the forces that would draw the two helicopters together. <S> Screen grab: <S> I also found this fascinating report <S> (.PDF link) from Piasecki (now part of Boeing Defense, Space & Security) that studied the feasibility of attaching two CH-53D helicopters to each other, including interconnected powerplants and flight controls! <A> Each helicopter probably does not weigh more than the woman being lifted. <S> The two helicopters are tilted such that the forces are in equilibrium with no collisions. <S> Both are coordinated as two pilots are flying these by Line-of-Sight. <A> The Soviets tested this for very outsize cargo - spacecraft components. <S> The developers considered using a couple of Mil Mi-26 helicopters to "bundle" lift the Buran, but test flights with a mock-up showed how risky and impractical that was. <S> This site (cited in the quote above) goes into a little more detail: <S> The newly developed MI-26 helicopter of the weight-lifting capacity of 26 tons was offered for delivery by helicopter. <S> According to this project, bulky cargoes of high mass (airframe and rocket bays) tied with cables had to be carried by 2 or 3 helicopters, and such ‘bundle’ had to move along the route, at the best fit height and flying speed. <S> As the basis for such version the example of helicopters application for ‘crane’ operations was brought, but there was still no experience of flights ‘in bundles’. <S> Test flights with mock-up cargo having the configuration of a tank section of the rocket were carried out at LII. <S> The tests revealed a complexity and risk of such kind of delivery. <S> During one of the flights at a suddenly arisen weak turbulence of atmosphere, a ‘pendulous’ swing of cargo on the cables started which caused a disturbance of the helicopters flight stability, owing to what the crews were compelled to dump the cargo. <S> Three would complicate it even more!
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Yes, this is possible, as demonstrated in this video from almost 2 years ago: Video The natural way to lift something like this would seem to be seperate slings at the two ends, which would counteract the side force problem but at the cost of having the two helicopters very close.
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What happens to Flight Testing Aircraft after Testing is over? Are aircraft used for flight testing typically sold to Airline customers after their use for flight testing is over? e.g. The aircraft shown in this SE Aviation Question: Why are these windows on some airplanes red? Sounds like a lot of money to waste so I expect they would be sold for some revenue but to what end use is the question. <Q> It depends. <S> In most of the cases, the aircraft have been instrumented and pushed so much that it not possible to modify them for commercial flight. <S> In these cases, they are either preserved or continued to be used as test aircraft. <S> In other cases, the aircraft are modified and delivered. <S> On the other hand all the 747-8 s were converted back after test flights and delivered to customers. <S> Boeing 777 <S> - The first 777s were considered production models , not prototypes and were delivered to customers after testing. <S> Boeing 787 - It is kind of a mixed bag here- <S> Boeing is still using one as a testbed, while one more is in storage. <S> Another aircraft used for testing was later modified and sold to the Mexican Air Force. <S> Airbus A350XWB - Right now, Airbus is holding all the five testing aircraft and using them for testing or demonstration flights. <S> Airbus A380 - Airbus has all the test aircraft. <S> You can check out the production lists of various aircraft here <A> Prototype aircraft are generally of less value than the production counterparts, since they are heavier and may not have the normal design configuration. <S> Boeing 737 <S> : The original -100 ended up going to NASA as a research aircraft as NASA 515. <S> Boeing 747: At the Museum of Flight. <S> Boeing 757: <S> Nicknamed "Catfish" <S> , it is an experimental avionics testbed registered N757A. <S> Airbus A320: One retained and continued to be used for the type's winglet/engine testing. <S> Boeing 737-800 prototype went to commercial service, now operating as TC-SNY. <S> Boeing 737-900 prototype went to Alaska Airlines as N302AS <S> Boeing 777-200 prototype went to Cathay Pacific as B-HNL. <S> However, not every aircraft can be sold if the aircraft is too unattractive and end up in a museum so many have been scrapped. <A> Like many of these answers mentioned, it depends. <S> For instance, the 787 program did write off the airframes for the first 6 aircraft due to the extensive number of modifications that were required to those airframes. <S> They do go to museums of strategic importance to either the manufacturer or the kick-off customer and their country. <S> Some of these aircraft end up going into lifecycle fatigue testing or are maintained in the ownership of the manufacturer for follow-on testing that would be for upgrades or newer subsequent models. <S> If the program is a brand new model or significant technological change to an existing model, it has to go through stability and control testing and flutter testing. <S> That literally beats the airframe to hell. <S> It will most likely experience an over-G loading in these tests, and therefore, cannot and should not be used to carry passengers. <S> There would be a potential for cargo in these cases, but then there would be added maintenance costs and operating costs from being structurally modded and heavy. <S> There aren't many that would want to purchase a 'new' aircraft that had gone through the beatings these aircraft take. <A> In order to reduce the certification time needed, manufacturers usually manufacture more than one testing aircraft, this way several flight tests can be done in parallel. <S> Once the airplane is finished, keeping those airplanes is a cost and there is no business case to keep all them. <S> However, an airplane model is a living design and during its lifetime (could be more than 50 years, as B737 for example) the airplane design will be updated. <S> Things as simple as obsolescence of equipments, small improvements, new technologies... <S> not just re-engining the airplane. <S> Those modifications must be certified as well, and some of the means of compliance require a flight test. <S> So, in this context: Manufacturer usually keeps always one of each airplane model, and likely more than one during a period of time. <S> Those having less damages and usable for commercial flights (like long haul testing) are usually sold with a discount (and actually very early...) <S> Finally, those that are too expensive to keep and not usable for commercial flight are scrapped or sold/donated to institutions. <S> Anyhow, is a significant amount of money what is lost, but is part of the development cost. <S> Finally is a business case... you can extend the certification period by 1 year and save 2 testing airplanes? <S> Having 1 year more the manufacturing line stopped waiting for the certification? <S> Finally using several testing airplane is a possitive business case.
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Particularly new aircraft (and derivatives thereof) tend to go to customers as testing becomes more refined and the cause of less design changes: Boeing 777-200LR prototype went to Pakistan International Airlines as AP-BGY Boeing 747 - The first ever Boeing 747 was used exclusively as a test aircraft and was later handed over to museum. The first three 787s are in museums across the world (two in the US, one in Japan).
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Can a passenger plane stand still in the air, or hover at a fixed location above a ground? This Gizmodo link shows that a commercial passenger aircraft can stay at single location without any movement with respect to ground. (Is it real, an illusion, or faked?) I have heard a friend saying that this happens for flights into Heathrow airport when the runway is busy with many aircraft required to land. I have argued with him about the holding circuit which basically requires airliner to follow a path around a airport, he is for sure that he has experienced such a thing happening when he was on board and also saw it live many times. <Q> NO , at least not during landing. <S> And especially not an Airbus. <S> Two reasons: <S> While up in the jet stream <S> a 150 knot wind is normal, wind over 100 knots (185 km/h, 115 mph) near the ground only occurs in hurricanes (and tornadoes) and would be so turbulent that landing it it would be most likely out of question. <S> When landing in strong head wind the pilots will use higher air speed. <S> This is because strong winds have a nasty habit of changing in strength or direction quickly and if the head wind reduced suddenly, the plane would loose lift and crash. <S> So the pilots maintain some minimum ground speed to have a safety margin for that case. <S> Airbus even has a minimum ground speed warning exactly to keep the pilots out of this risky flight regime and that would be blaring in cockpit if the A330 in the video really almost stopped in midair. <S> There must be something wrong with it (the linked article does not link to a video, only a screencap and one can't tell from screencap what is going on). <A> can a commercial passenger aircraft stay at single location without any movement with respect to ground? <S> In theory it could, with strong enough headwinds, low weight (no passengers nor cargo or baggages), deployed high-lift devices. <S> i have heard a friend saying that this happens for flights in Heathrow airport when the runway is busy with many aircraft's required to land. <S> This is simply false <S> i have argued with him about the holding circuit which basically requires airliner to follow a path around a airport <S> That is correct <S> he is for sure that he has experienced such a thing hapening when he was on board and also saw it live many times. <S> Either he as flown in an An-2 (see linked question) or he simply dreamt about it. <A> An airplane cannot stand still in the air as it requires air flow over the wings to create lift. <S> A lightly weighted aircraft can fly slower than a heavy one, but even flying just above stall speed you would need a headwind well over 100mph in order for a jet to be stationary with respect to the ground. <S> In this video the airplane appears to be flying must slower than it actually is due to the angles viewed and other factors. <S> It was never stationary with respect to the ground. <S> Commercial jets don't "hover". <S> What does happen when there's traffic is that they are put into a holding pattern. <S> This is generally away from the airport, not around the airport.
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An airplane can be stationary over the ground if the air is moving over the ground quickly enough. In the video it does not happen and I seriously doubt it has ever happened in real life.
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What is the purpose of eyebrow windows? Nowadays they are no longer needed but why do they cover them up like in this photo? What is their purpose and why aren't they used anymore? Source <Q> Wikipedia answers this on the Boeing 737 page : <S> Most 737 cockpits are equipped with "eyebrow windows" positioned above the main glareshield. <S> Eyebrow windows were a feature of the original 707 and 727. <S> They allowed for greater visibility in turns, and offered better sky views if navigating by stars. <S> With modern avionics, they became redundant, and many pilots actually placed newspapers or other objects in them to block out sun glare. <S> They were eliminated from the 737 cockpit design in 2004, although they are still installed at customer request. <S> These windows are sometimes removed and plugged, usually during maintenance overhauls, and can be distinguished by the metal plug which differs from the smooth metal in later aircraft that were not originally fitted with the windows. <A> To add to Steve's correct answer, Boeing has historically designed aircraft with less than ideal visibility for the pilot. <S> Case in point: Their first all-metal passenger aircraft, the Boeing 247 . <S> Its design was ahead of its time and prompted TWA to convince Douglas to build the DC-1 and -2, but was marred by two details: <S> The wing spar was not below the cabin floor level; instead, Boeing expected passengers to climb over the spar on their way to their seat. <S> Many airlines were less enthusiastic and rejected the aircraft in favor of the DC-2 and -3, which also offered more seats. <S> The second detail was the cockpit window: It was sloped forward, so the visibility in the upper hemisphere was severely restricted. <S> In turns the pilots were basically flying blind. <S> The idea was to angle the window glass such that the instrument lighting would not reflect in the glass, but Boeing soon realized that this was creating new problems, and from the 247D on the window was sloped aft. <S> Forward fuselage of the Boeing 247 <S> (picture source ) <S> When the 247 was offered to Lufthansa, it was rejected for this particular reason. <S> I guess Boeing engineers were very sensitive to get the visibility right after the 247. <A> I'm an MD-80 pilot (they have huge eyebrow windows). <S> However, nowadays, it doesn't really add that much visibility. <S> All it really does is just have the sun shine into the pilots' eyes. <S> I'e usually cover them up with IFR charts, or checklists. <S> They look cool on the outside. <S> But they're not great on the inside. <S> In addition, the more windows you have on an aircraft, the more time you spend cleaning, checking them, etc. <S> So, by removing the eyebrow windows, some maintenance time was saved. <A> A major point in removing the 'eyebrow panels' is reduced costs over the life of the aircraft. <S> Also in most of the aircraft I've been in they're usually blocked with paper or similar for most of the flight if its sunny! <S> I've heard they reduced noise as well <S> but I haven't been in the newer ones yet and <S> what with the rules on jumpseating getting stricter looks like I'll never have the chance!
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The eyebrow windows were originally used in tight turns to help the pilots align with the runway.
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What is this line found above the door on many aircraft? Many aircraft have this line above the door as seen in the photos below. What is it, and what is its purpose? Source Source <Q> This is a close up of the rain gutter over the main cabin door of a Beechcraft King Air B200, showing the channel that would catch and redirect water flow to the side of the door opening: <S> Source: own work <S> A jet-bridge may partially deflect rainwater in some cases, but the gutter helps mitigate water exposure for the aircraft interior and passengers. <S> Even gutters cannot completely eliminate such exposure since their size is necessarily limited by aerodynamic constraints. <S> Many operations do not have the luxury of jet-bridges, making the rain gutter especially helpful in reducing the amount of water that might otherwise enter the cabin and pose a hazard to the aircraft or onboard systems. <S> "Rain Gutters" is the technical name, at least for Boeing aircraft, such as the B777 depicted in the photos in the question. <S> Here is a Boeing reference to such gutters on the 787: Rain gutter : When customers found that water was not being properly deflected over a passenger entry door, they requested a change. <S> Boeing relocated the gutter to function more efficiently. <S> The solution means happy customers, who had fewer water and maintenance issues, and happier and drier passengers. <S> This was a significant enough change to process to require certification work with the FAA. <A> It's for the passengers on a rainy day. <S> If this strip would not be diverting the rainwater flowing from the upper fuselage, a curtain of water would soak the passengers upon entering or leaving the aircraft, and the cabin floor. <A> These rain gutters are for deflecting the rain from entering the cabin. <S> Even with Jet-bridges, the door itself might be covered, but since the whole cylindrical fuselage is not. <S> The rain that falls in the uncovered area at the top of the fuselage would roll down, then going under the jet bridge's cover. <S> This is to redirect that water that would have gone into the doorway off to the side.
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They are designed to catch rain that runs off the upper surface of the aircraft fuselage and channel it away from the open aircraft door so that the water does not enter the cabin. These are rain gutters .
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Why doesn't the A320 have a dorsal fin like the 737? The A320 doesn't have a dorsal fin, but the 737 does. If the 737 is more or less a similar aircraft, why doesn't the A320 have a similar dorsal fin? By Bill Larkins [ CC BY-SA 2.0 ], via Wikimedia Commons <Q> Boeing learned the value of a dorsal strake the hard way: On their civilian version of the B-17, the Boeing 307 Stratoliner , the first Boeing aircraft with a pressurized cabin, the lack of a strake ahead of the fin caused the rudder to lock in the hard-over position when the pilot demonstrated the capability of the aircraft to fly with two dead engines on one side. <S> The aircraft entered a spin and crashed, and that was on a demonstration flight for prospective customers. <S> Early Boeing 307 with the two right engines off and props feathered (picture source ). <S> Note the deflected rudder and the rectangular windows in a pressurized fuselage . <S> It worked because the pressure difference was small. <S> Late Boeing 307 in flight <S> (picture source ). <S> The vertical was enlarged and had the strake added; the same vertical was also used on later versions of the B-17. <S> With today's hydraulically operated controls the risk of an uncontrollable hard-over is reduced, but exactly this happened to several early Boeing 737s . <S> From the 737-300 on the strake was added and the control system (PCU = power control unit) was exchanged for a modified version. <S> Airbus never had those issues and did not see the need to add a strake since the existing vertical could do its job in all conditions. <S> A strake is worthless at small sideslip angles and will only help when the vertical is close to stalling due to extreme sideslip. <S> Adding a strake will increase the wetted surface area and add friction drag, so Airbus did not include one. <A> Adding to PK's very informative answer: The 737 Original series did not have this dorsal fin. <S> When the newer series was introduced (737 Classic) with the new 1.6x more powerful engines , the dorsal fin was needed "to cope with greater asymmetric thrust potential." <S> Source: <S> Flight , (1982). <S> The design remained with the 737NG and 737 MAX to keep the cost down: machining, suppliers, R&D, testing, etc. <A> Adding a dorsal fin, increases surface area. <S> The plus theoretical side is that it increases directional stability. <S> The minus theoretical side is that it adds weight, drag, and manufacturing complexity. <S> Early 737s did not have a dorsal fin. <S> Presumably, at some point Boeing decided that adding one would provide better performance. <S> Airbus apparently does not see the need for on in the A320. <S> They are all design decisions. <A> In addition to ymb1 's answer, I found this video of a B737 Pilot that specifically explains why is added in new models. <S> The short answer is very similar to that already provided, but explained in details and with some examples, maybe could result easier for someone to figure out reasons. <S> Boeing had two options " to cope with greater asymmetric thrust potential " increase tail height or enlarge its surface horizontally, but existing customers preferred second option because they already had hangars designed for previous B737 series with not enough height. <S> Continuing comparison to A320 family, we can also say that in A318 (the shortest of the family), Airbus too needed to enlarge tail surface ( increasing its height in this case) because shorter fuselage caused less torque that should be compensated by additional force at the end. <S> For those that are more technicians, physical explanation could be the following: Since the torque on a body is defined as T=F x d , where " F " is the applied force at a point P of the body, " d <S> " is the distance from P to the center of the rotation and " x " is the cross product, it's clear that by reducing d <S> we need to proportionally increase F to keep T constant <A> Note in your photos that the A320's tail in general is wider than the 737's. <S> So it can be argued that Airbus met the same need with a different tail design. <S> They didn't use a strake, they made the whole vertical stabilizer larger.
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The fact that the 737 was originally designed in the 1960's for turbojet engines, while the A320 was designed in the late 1980's with the more powerful turbofan engines, may be the reason that Airbus made the whole vertical stabilizer wider.
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Can you help me identifying an A-4 Skyhawk-like jet? I'm having trouble identifying a jet and am hoping someone can provide some help. Here is the best picture I've been able to capture. The closest similar jet I've been able to find is the A-4 Skyhawk , which shares many of its features, but even in looking through the variants, I can't find an exact match. The next two pictures aren't as clear, but they show the profile and wing shape, respectively. There are three features I've noticed which set it apart from the A-4 variants I've found. Wing shape - It's very curvy, almost Concorde-like. Vertical stabilizer - The forward section of the top of the vertical stabilizer is very sharp, whereas on the A-4's I've seen, this is curved. Antennae - There are two antennae; one swept-back antenna directly behind the cockpit and a vertical antenna farther back where the vertical stabilizer begins. I appreciate any guidance you can provide. Thank you. <Q> They are A-4 Skyhawks all right. <S> They are operated by Draken International and provide adversary training for USAF (among others); here's a closeup photo of them. <S> Image from edwards.af.mil <A> Those are Draken International A-4K KAHU Skyhawks, based of of Lakeland regional airport. <S> They have 8 or 9 of them, unfortunately, one was lost last year outside Las Vegas. <S> They are former Royal New Zealand Air Force strike fighters. <S> These are not your typical A-4 <S> Skyhawk - they are true wolves in sheep's clothing. <S> They have the HOTAS, MFD, radar, and war computers of an F-16 Falcon. <S> Project KAHU was undertaken in late 1980's to early 1990's. <S> All of New Zealand's Skyhawks had their air frames zeroed and then brought into a generation 3+ strike/fighter, almost a 4 a few weapons shy. <S> However with a software upgrade they could have carried the AIM-120 BVR air-to-air missile. <S> But she could carry all the other air to air or mud moving gear of the F-16. <S> The ones with a hump and tail extension were acquired from another contractor that was bought out by Draken. <S> Those are H models from the IDF. <S> A-4K Showing the underside, with some Sidewinder and Maverick missiles. <S> All the assembled A-4Ks and TA-4Ks <S> one T-Bird was lost. <S> A-4 Skyhawk over Christchurch, NZ <A> It's the two-seat training version of the Skyhawk. <S> You can see this in the photo:there are two pilots seated in tandem. <S> According to the A4 Skyhawk Association , there were several two seat models built: U.S. versions of the two-seat Skyhawk were the TA-4E, quickly changed to TA-4F, the TA-4J, and two special variants, <S> the OA-4M and EA-4F. Export variations of the two-seater were TA-4G {Australia), TA-4H (Israel), TA-4 <S> K (New Zealand), TA-4KU (Kuwait), TA-4PTM (Malaysia), and TA-4S (Singapore). <S> The ones shown above are probably the US version. <A>
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Looks to be a pair of T-A4K Skyhawks carrying a center-line droptank
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Is there a relationship between control surface deflection and a particular turn radius or bank angle? I am making a project which includes automation of aileron, rudder and elevator deflection. Is there a quantifiable relation which can tell me the amount of deflection required for any radius of turn if the other parameters are put constants. <Q> You need the ailerons only to bank the aircraft; once the bank angle is reached, the aileron deflection is mostly close to zero. <S> I assume we are talking about stationary turns, so speed and aircraft mass will not change significantly over the duration of the turn. <S> While turning, several moments need to be balanced to keep the roll angle constant, and a good design does this without requiring aileron input: <S> The rotation around the vertical axis causes more airspeed over the outer wing, increasing its lift. <S> This causes a rolling moment into the turn. <S> The rotation around the vertical axis causes a sideslip condition at the vertical tail which causes a yawing moment against the turn. <S> The inertial forces try to pull the wings level. <S> This causes a rolling moment against the turn. <S> However, the elevator needs to be held at a slightly more negative angle than in level flight to pull the required load factor $n_z$. <S> In a turn, the load factor is proportional to the bank angle $\Phi$:$$n_z = <S> \frac{1}{cos \,\Phi}$$Radius $R$: <S> $$R = <S> \frac{v^2}{g\cdot tan\,\Phi}$$Angular velocity $\Omega$ (rad/sec): <S> $$\Omega = <S> \frac{v}{R} = <S> \frac{g\cdot <S> tan\,\Phi}{v}$$The amount of elevator deflection needed depends on the stability margin (expressed as $\frac{c_{m\alpha}}{c_{L\alpha}}$) of the airplane, its pitch damping (expressed as $c_{mq}$) and elevator effectiveness (expressed as $c_{m\eta_H}$). <A> (Assuming a coorinated turn.) <S> Depending on various parameters, some small amount of rudder and elevator deflection may be necessary to maintain coordinated level flight once established in the turn, and depending on the aircraft, you may need some rudder input while the ailerons are deflected. <S> That's all pretty well specific to whatever aircraft you're modeling. <S> In a swept-wing jet, significant rudder deflection is not required (and what little deflection is needed is often provided by the yaw damper rather than the pilot), while in a long-winged glider with considerable adverse yaw, adding a fair bit of rudder along with aileron is required for coordinated flight. <A> Probably the relevant answer as a pilot: <S> No <S> What you want to achieve is most probably more complex, flying a certain curve depends on so many things and is a dynamic process. <S> True answer as a physicist: <S> Yes, of course <S> Whenever you have a given situation with the exact same parameters (as you described, all other parameters are put to constant, including wind, power, airspeed, density, etc.), you will end up with the same turn radius. <S> It's deterministic... <S> Problem: Your premise of holding the other parameters constant is unrealistic <S> Combining the two <S> : You never fly a curve, like the second answer suggests, where you have "a certain deflection" of the aileron, but change it during the turn to start and stop it as well as during the curve because you never have all the other parameters constant. <S> You use, within other things, the rudder to compensate for other, changing parameters. <S> So the question is, are you interested in making a whole turn (look at the first answer) or do you only care about the artificial steady state (second answer)? <S> Actually, I think your problem has been solved already by a lot of autopilots... <S> I'd recommend to have a look at the state-of-the-art implementation of those. <A> Yes there is a relationship between control surface deflection and bank angle, but it is a complicated one, with a feedback loop, aerodynamic forces and inertia, double integrators, <S> transformation from aircraft to earth axes etc. <S> Since it is a dynamic relationship, it is best characterised by the response to a step input. <S> Start with control wheel at 0, set a sudden deflection at let's say wheel 30 deg for 5 seconds, then briskly return wheel to zero. <S> Meanwhile, measure the aircraft bank angle response. <S> This is the way that the flight dynamic model in flight simulators are tuned. <S> There is more information on this link (figure 5), although that explanation considers roll rate. <S> In order to get to bank angle you need another integrator and axes transformation. <S> An autopilot will compare actual bank angle with a setpoint, and vary control wheel input until the required bank angle is reached. <S> You may find source code examples in open source simulator programs such as FlightGear.
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Aileron deflection affects your roll rate , but you can roll rapidly or slowly to whatever chosen angle of bank... and the angle of bank (along with true airspeed) is what determines your turn rate and radius.
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In what manner was the Vympel R-73 (AA-11 Archer) a game-changer in comparison with NATO's missiles? I have heard that when the Vympel R-73 air-to-air missile was introduced it was a game-changer. I have also heard that after the collapse of the Soviet block it was tested by NATO (via re-united Germany) and NATO was quite impressed by it. According to one source, in close combat the MiG-29 was better than the F-16 by 2:1 and better than the F/A-18 by 1.5:1. What was so special about it? How did they make it? Did they have better experiences? Or ideas? <Q> The Russians brought some new ideas to the missile warfare when they mated the Vympel R-73 with Mig-29. <S> The most important of these was the high offset sensor lock mode, which allowed the pilot to 'lock on' to the targer regardless of where the nose was pointed at. <S> The Archer in [sensor lock] mode.” <S> Introduced in the mid-1980s, <S> the Archer AA-11 is a very capable heat-seeker with a greater range than the U.S. Sidewinder. <S> “A simple monocular lens in front of my right eye enabled me to slew the seeker head of the missile onto my adversary at high angle off [target].” <S> The Fulcrum’s ability to lock a missile even though its nose was pointed far away from its target “watered many eyes,” ... <S> The image below shows the missile aiming sight mounted on the helmet of a JG 73 pilot. <S> Image from <S> airspacemag.com <S> This off boresignt advantage was not achieved by the western forces till they introduced the AIM-9X missile and the Joint Helmet-mounted Cueing System in 2002. <S> Aircraft-wise, the Mig-29 was a revelation to the west as the previous Russian designs have not been so sophisticated, so as to speak. <S> The West was concerned enough with Mig-29 to start looking for new fighter ideas. <S> Another important equipment in Mig-29 was the Infra Red Search and Track System (IRSTS), an idea for which the US is just warming up. <S> Most of the exchange pilots, who flew the Mig-29 against the US F-15s and 16s were quite surprised and initial engagements usually went the 29s way, though techniques were later devloped exploting the Mig-29s' weaknesses. <S> From an USAF exchange pilot : From BVR (beyond visual range), the MiG-29 is totally outclassed by western fighters. <S> Lack of situation awareness and the short range of the AA-10A missile compared to the AMRAAM means the NATO fighter is going to have to be having a really bad day for the Fulcrum pilot to be successful. <S> In the WVR (within visual range) arena, a skilled MiG-29 pilot can give an [F-15] Eagle or [F-16] <S> Viper driver all he <S> /she wants. <A> Yes, the Russians had the better ideas. <S> The key was the slaving of the radar system to the pilot's helmet, called sight-controlled missile targeting : The missile would lock to whatever the pilot was looking at. <S> In combination with the wide off-boresight capabilities of the aircraft's radar and the missiles, it even allowed to get a lock on aircraft flying actually behind it. <S> When US F-16s met ex-GDR MiGs in exercises in the early 1990s, they were shocked to find how much superior the Russian design was. <S> From the second link: With the Phazotron NIIR N019 Doppler radar (NATO designation "Slot Back") capable of detecting a target more than 60 miles away, infrared tracking sensors, and a laser rangefinder carried on the MiG-29, a pilot could track and shoot at aircraft flying below him. <S> Also, the pilot's Shchel-3UM-1 helmet-mounted aiming device turned the MiG-29 into a very dangerous threat once opponents came within visual range. <S> No longer did a pilot have to turn his aircraft toward a target and wait for his missiles' sensors to "lock-on" before firing. <S> Now, the pilot simply turned his head toward a target, and the helmet aimed the missile's sensors toward the target. <S> This "off boresight" procedure gave the MiG-29 pilot a great advantage at close range. <A> According to this article, the main reasons were its exceptional mobility and accuracy. <S> It can maneuver well enough to hit an aircraft in a 12 G turn, and has incredible accuracy, due to a direct connection with the pilots HUD, sophisticated infrared targeting, and a system called a "transverse control engine" (the details of which are apparently classified) to ensure that the target can't out maneuver it at the last second.
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According to Peter “Stoini” Steiniger a JG 73 Pilot, who flew Mig-29s in East Germany, The nice airframe in combination with one weapon was the killer:
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Why do pilots need the ceiling, time, and dew point in the ATIS? For example: Ceiling: what is the ceiling? Why do they need to know the ceiling? Zulu time: what is the zulu time? Dew point: why do they need to know the dew point? <Q> The ceiling is the lowest altitude where clouds cover more than half of the sky. <S> This is important because climbing above that altitude means you will most likely have to fly through clouds. <S> This makes navigation more difficult and pilots are required to have special training to fly in low visibility. <S> If the ceiling is too low, pilots can't be at a safe altitude above the ground and out of the clouds at the same time. <S> Low ceilings are also critical for landing, and may require pilots to make an instrument approach and landing . <S> Zulu time refers to UTC time, which is the universal coordinated time. <S> The ATIS will contain the Zulu time that it was updated so pilots know how recent the information is. <S> The dew point in relation to the temperature gives the pilots information about the humidity, and can affect visibility. <S> If the dew point is close to the temperature, humidity is high, which can cause hazy conditions, or even fog. <S> As with the ceiling, this can warn pilots of possible changes in conditions that will make it harder to see the ground or other aircraft while in flight. <S> A high dew point means a higher density altitude, which reduces aircraft performance. <S> Dew point is also very important in certain helicopters with carburetors, like the Robinson R-22 and R-44 helicopters, which are subject to carb icing even during take-off because they only use as-required power rather than full throttle. <S> In this case, carb heat needs to be applied whenever the temp/dew point spread is 15C or less. <S> Here is the citation from the R-22 POH : <A> Dew point can most certainly be used for performance. <S> High humidity can cause a longer take off roll. <S> When combined with a high altitude airport and hot temps, it can be a struggle to get airborne. <S> Cooler, less humid air is more dense--there's more "air" for the wing to bite into. <S> So, a pilot listening to ATIS would want to know the temp, dew point, and temp for the airport to determine (in this example) takeoff roll distance. <A> To add to the above, in all carbureted A/C dew point is needed for indication of carburetor icing. <S> Dew Point relative to temperature is a useful indication of weather conditions .
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In terms of aircraft performance, the dew point is also needed to determine the true density altitude , when combined with the pressure and temperature . Zulu or UTC time is helpful as a worldwide reference in fields like aviation, to avoid issues like dealing with changing between local time zones.
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Why do some airports have to put 2 jetbridges on one aircraft? At a gate in Denver Int'l there is a United plane with 2 jetbridges. Why do some airports have to put 2 jetbridges on a plane? Is it necessary? <Q> It is not strictly necessary. <S> But it is done in order to save time. <S> More points of passenger loading leads to faster loading, potentially reducing delays, airport charges etc. <S> In some cases, there is a seperate jet bridge for first/business class. <S> For large aircraft like A380 etc, is quite common to use multiple jet bridges as use of a single one may lead to quite large loading time. <A> It saves much more time than loading the plane from one jetbridge and in the case of the A380, there are 2 full wide-body decks to fill. <S> Passengers also like getting on and getting off the plane quicker as well. <S> Interesting that there is this similar question on travel.se <A> In addition to Aeroalias' answer, some airports adopt a Multi Aircraft(Apron) Ramp System. <S> The gate may be used by multiple small or a single large aircraft. <S> It allows airport planners to make their gates more flexible and efficient. <S> In such a case two or more jet bridges are needed for a single gate. <S> Some of the busiest airports including Beijing Capital, London Heathrow and New York JFK have already adopted such a system. <S> More details can see this article . <A> So that economy class passengers can also see at least one of the higher classes (when they exit) and wish they booked that! <S> :-/ <S> Trust me <S> you sure will wish that <S> and that someday can mean more $ for the airline Source: <S> Original picture was taken from this very question Joking aside <S> I have seen it happen on many airlines. <S> The people on left Aisle go out from the first one and people on the right aisle take the longer route to exit from the gate that's closer to cockpit. <S> Primary reason must be to transfer people faster to make the jet available for crew as soon as possible specially after a landing when the jet has to fly again in an hour.
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The reason they use 2 or sometimes even 3 (A380) for wide-body aircraft (I have seen 2 on a B757, but that is rare) is because the more entrances to facilitate faster boarding and unloading passengers from the airplane.
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Has Air Traffic Control ever had to talk a first time pilot through a landing due to an emergency? This question deals with the plausibility of the Hollywood cliché of a passenger on a commercial jetliner landing a passenger plane. My question is related but broader, and less hypothetical: Has anyone ever found themselves in an emergency with no piloting experience (e.g., the amateur pilot of a small plane dies or is incapacitated, and the only other person in the plane has never flown anything before) and been talked down by Air Traffic Control? <Q> The answer is yes. <S> One example was on April 2, 2012. <S> Helen Collins, an 80-year old Grandmother was forced to take the controls of her husband's CE-414 and land it at Door Country Cherryland Airport (KSUE) after her husband had a massive heart attack at the controls and died. <S> She managed to circle the airfield and call 911 on a cell phone. <S> The emergency dispatcher contacted the FAA who got in touch with ATC. <S> A KSUE based private pilot named Robert Yuksonavich took off and joined her in formation, talking her through what was about to happen and flew her wing on several practice approaches prior to the landing attempt. <S> On landing the Cessna 414 skidded off the runway and came to a stop in the grass, breaking the nose gear off. <S> Helen survived with only minor injuries; her husband was pronounced dead on the scene. <S> A brief piece by the CBS morning news featuring commentary by Capt Chesly Sullenberger about the incident. <S> This is the full ATC of the accident <A> There was another incident in the UK where a passenger landed a Cessna 172 after the pilot had a heart attack, but I do not have a source for that. <A> John Wildey was in a Cessna 172 when the pilot became incapacitated and was successfully talked down by ATC in October 2013. <S> He had worked as a clerk for the RAF and been on several GA flights, but had not had any flight training. <S> His story was featured in The Daily Mail and became an episode of Mayday . <S> There also happens to be a Wikipedia page on this subject . <A> As many others have said, there was, most notably when a man in his seventies died while flying his friend back to their home airport in the west parish of London, <S> when night fell and the first time Cessna 172 pilot became nervous and was thankfully able to land the aircraft at a local international airport.
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In 2009 the pilot of a Kingair 200 ( Registration No. N559DW ) fell unconscious and died during flight while flying over South Florida, and a passenger took control and landed at Fort Myers International Airport.
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Who sells aviation fuel to airports? I want to ask about the jet fuel purchasing cycle. Is it the airport that buys the jet fuel from refineries and then sells it to the airlines? Or do airlines buy fuel directly from refineries? <Q> The airport is buying fuel and selling to airlines. <S> And more over, they provide different types of fuel on prior request by the airliner. <S> Reference : VCBI <A> Airlines make direct contracts with the major petrol companies eg Chevron, BP, etc. <S> for large quantities of JET-A, often years in advance of its use. <S> It is the best way for them to buy fuel in bulk like that and <S> it is traded much like stocks are. <A> It depends. <S> Airlines have contracts either directly with say Shell or they have a contract with a 3rd party that handles their fueling requirements. <S> That 3rd party may or may not be the airport, it could be another company servicing the airport (and maybe others as well). <S> And such contracts may well differ depending on location. <S> E.g. at their home base(s) they may draw directly from Shell, but at remote locations where Shell does not supply fuel to they may buy fuel from Joe's oil and lube supplies.
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Airports themselves will fuel airliners with on-hand supplies of JET-A and be reimbursed for it by the petrol companies.
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How do stealth aircraft get ATC? I believe that all aircraft must be controlled under ATC's instructions to fly safely especially when take-off and landing. And, most ATC instructions are conducted by ground radar which controllers use. But I know that the stealth aircraft (including B-2, F-22 etc.) aren't captured on radar display owing to their stealth ability. If so, how does a controller give instructions like radar vectors to stealth aircraft? I know that there's are primary and secondary target when using radar, and the controller must use primary target to vector aircraft. I guess stealth aircraft can be captured by secondary radar but not primary target. <Q> The concept of ATC is based on primary radar targets, secondary radar targets and radio communication being used to determine the position of aircraft and establish separation. <S> The concept of stealth aircraft is to reduce production of primary radar targets and being able to turn off transponders to disable secondary radar targets being visible. <S> Stealth aircraft also do not communicate on frequencies during tactical missions, they are designed and meant to reduce radio emission to enable the stealth features. <A> First off: "I believe that all aircraft must be controlled under ATC's instructions to fly safely especially when take-off and landing." <S> Not true. <S> When I fly my small Cessna from an untowered airport in VFR conditions, I don't file a flight plan, and I don't talk to ATC. <S> I do make annoucments on the CTAF, but that is not even required. <S> I would be completely legal to take off, fly and land, never turning on my radio or talking to anyone. <S> "See-and-avoid is the rule. <S> Secondly: Stealth aircraft are stealthy only when they are trying to be. <S> Something as simple as lowering the landing gear would provide a strong radar return. <S> The transponder can indicate position, ADS-B can provide precise updates, and the pilot can verbally describe their position to ATC. <A> ATC concept is based on cooperative targets (i.e. willing to send their position to the ATC radar). <S> I suppose that they are equipped on board with a transponder that is switched on when there is a need for air control.
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If they are not on a tactical mission and stealth is not required, they will simply turn on their transponders and communicate with ATC on the required frequencies.
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Is it possible for a plane to use cameras and screens instead of a clear windshield? I was just wondering: is it possible to have a commercial plane with no cockpit windshield, just external cameras and video screens? The question come in my mind after reading the nth occurrence of laser in pilot's eyes . Moreover, a structure without windscreen is surely lighter: when there are not passenger, we avoid to put windows! Which are the limits and the opportunities to this solution? With "ever" I don't mean "in centuries" but in 30/40 years. <Q> It's entirely possible to do this now, it's simply not a good idea. <S> If you have no cockpit windows an electrical or systems failure would leave pilots totally blind, without any references whatsoever. <S> The "mark I eyeball" works in a wide variety of conditions and does not require electrical power of any kind. <S> Plus, there's usually 4 of them in the cockpit, and chances are at least one of them will work. <A> Is it possible? <S> certainly yes. <S> Airbus has applied for a patent for a windowless cockpit in which the external view is displayed in the cockpit using cameras and screens. <S> The technology itself is available and some significant progress has been made in recent years in the related equipment. <S> Will it become a reality? <S> Maybe. <S> Why fix something that ain't broken? <S> In the future this may well be used, maybe in supersonic aircraft (For example, spike aerospace has proposed a design without cabin windows; interestingly, the design still has cockpit windows). <S> Addition of cameras and displays adds one more layer of complexity, which is at present unnecessary. <S> Also, there are other issues to consider. <S> In order to give the pilot with a view at least as good as the exiting aircraft, images from multiple cameras have to be 'stitched' and displayed. <S> The system should be able to do this without any lag (F-35 had a similar problem while joining feeds from its DAS). <S> Unless there is a compelling reason for the addition of cameras and displays, the windscreen is here to stay. <A> That should be ... exciting ... during an electrical failure. <S> Good luck getting it approved for use anywhere in the world <S> , you can't even build a pure glass cockpit in many jurisdictions. <S> Likewise you can have all the cameras you like provided you can still look out the window. <S> It's certainly technically feasible <S> but it's not a good idea. <A> Somewhat, but the lack of depth perception may be an issue on the taxiways. <S> But if lasers is the concern, I think they should install something similar to the auto darkening lenses used by welders to the front windows.
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At present, there is nothing wrong with windshields in aircraft (pointing laser at aircraft is illegal; anyway, lasers can damage camera sensors too). The drawbacks to safety outweigh the benefits of doing so.
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What are the guidelines for call signs for aircraft dealing with US ATC? Suppose a general aviation aircraft is operating VFR under part 91. When they call ATC they'd normally use their tail number as the call sign. Something like "November 1-2-3 Foxtrot Uniform." What if they called up as "little piggy 27?" Are there guidelines or regulations about this? Does a custom call sign require anything or can you just make one up? <Q> According to JO 7210.3Y , Air Traffic Organisation Policy , section 4-4-2 there are several requirements from both the FAA and FCC. <S> The FAA requirements are (paraphrased from the JO): <S> Comply with FCC regulations (remember that the FCC is responsible for radio communication technical regulations, not the FAA) <S> Get FAA approval "to avoid possible duplication or conflictwith air−ground call signs assigned on a nationalbasis to other aircraft operators" The FCC requirements are in 47 CFR 87.107 (not 87.115 as the JO says): <S> (a) Aircraft station . <S> Identify by one of the following means: (1) Aircraft radio station call sign. <S> (2) <S> The type of aircraft followed by the characters of the registration marking (“N” number) of the aircraft, omitting the prefix letter “N.” <S> When communication is initiated by a ground station, an aircraft station may use the type of aircraft followed by the last three characters of the registration marking. <S> Notwithstanding any other provision of this section, an aircraft being moved by maintenance personnel from one location in an airport to another location in that airport may be identified by a station identification consisting of the name of the company owning or operating the aircraft, followed by the word “Maintenance” and additional alphanumeric characters of the licensee's choosing. <S> (3) <S> The FAA assigned radiotelephony designator of the aircraft operating organization followed by the flight identification number. <S> (4) <S> An aircraft identification approved by the FAA for use by aircraft stations participating in an organized flying activity of short duration. <S> In reality, if you call up ATC as Little Piggy 27 <S> you'll either get a laugh and a "no, seriously?" <S> or - in the worst case - you'll just annoy them. <S> There are also military call signs in use <S> but I know nothing about them. <S> I do remember being in the pattern while an Air National Guard aircraft out of Memphis, TN was doing touch and goes using the call sign Elvis 1. <S> But I have no idea how that call sign was set up between the ANG and FAA. <A> Operator call signs are generally established with the FAA <S> > <S> In addition, operators can establish local call signs with their ATC facility. <S> E.g. <S> News Chopper 10. <S> The FAA has established aircraft types in call signs at well. <S> You can't just make up a call sign. <A> From ATC's point of view... If a pilot calls up as "little piggy 27", the controller may respond initially with "little piggy 27". <S> When ATC establishes communication with a GA aircraft, they state the prefix "November" followed by the phonetic numbers/letters of the aircraft registration. <S> As a pilot, you could replace "November" with aircraft type, the model, or the manufacturer’s name, and ATC can respond in kind going forward. <S> [Info from JO 7110.65 , 2−4−20. <S> AIRCRAFT IDENTIFICATION]
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In other words, your call sign must be approved in advance by the FAA, otherwise you can't legally use it per FCC regulations.
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Why is it called "Dry Thrust"? When reading the specifications of a jet aircraft anywhere on the Internet, it usually states that its engine produces X pounds of "dry thrust". Why is it called "Dry" Thrust? As opposed to what? <Q> Dry thrust usually means the non-augumented thrust i.e. thrust without the use of afterburners or liquid injection. <S> The maximum thrust produced by jet engines w/o afterburner is sometimes called military thrust. <S> The thrust of a jet eingine can be increased by using methods like water(+methonol) injection (mostly in older turbojet engines) or by using afterburners (reheat). <S> In such cases, the (higher) thrust produced is called wet thrust. <A> The figures you mention usually refer to the maximum thrust without afterburner. <A> One interesting case of actually wet thrust, as opposed to afterburners, is the Harrier Jump Jet , which can inject water into its engines for up to 90 seconds to increase performance for vertical takeoff and landing without melting its turbine blades. <S> The use of water in jet engines is interesting because it not only cools the turbine, but simultaneously adds thrust through the added mass and steam expansion.
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Dry thrust refers to an afterburning engine running without afterburner .
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What is the difference between the Maximum Glide and Minimum Sink ratios? In this comment a brief explanation is made of the differences between Max Glide Ratio and Min Sink Ratio: Sink rate is how much altitude you lose over time, for example, how many feet per second. So minimum sink is the lowest sink rate you can get. Glide ratio is how much distance you can travel per given loss of altitude, for example, how many feet per feet. So max glide ratio is the shallowest angle you can glide at. However, I don't understand how the lowest sink rate you can get isn't the same as the shallowest angle you can glide at . If I can design wing A to sink at only 1 foot per minute, wouldn't that automatically get me a longer glide ratio from altitude X than wing B that sinks at 2 feet per minute? <Q> Glide ratio is the ratio of the distance a glider can travel horizontally to the altitude lost in transit. <S> For instance, if a glider can travel 40 miles horizontally while losing one mile of altitude, the glide ratio is 40:1 (typical for a medium-high performance glider). <S> The best glide ratio or maximum glide ratio is simply the best ratio a glider can achieve. <S> Best glide ratio is achieved at a specific airspeed, which varies depending on the glider type. <S> One flies at best glide speed in order to maximize the distance covered. <S> When gliders are flying in a straight line and want to go as far as possible, they fly at best glide speed (typically 55-65kts). <S> Minimum sink is the minimum vertical speed the glider is capable of flying at in still air ( <S> typically 100-200ft/min). <S> Minimum sink is also achieved at a specific airspeed, depending on the glider type (typically 40-50kts). <S> One flies at minimum sink speed to maximize altitude gain when flying in lift. <S> If you're circling in a thermal that is going up at 500ft/min, and your minimum sink speed is 100ft/min, then the glider will go up at 400ft/min. <S> Best glide ratio is achieved at a higher airspeed than minimum sink <S> Any aircraft can be a glider with its engines out, so this applies to all aircraft. <S> However, I don't understand how the lowest sink rate you can get isn't the same as the shallowest angle you can glide at. <S> Remember that minimum sink comes at a lower airspeed than best glide. <S> At minimum sink speed, the glide ratio is worse because even though the aircraft is sinking slower, it is also moving forward slower. <A> However, I don't understand how the lowest sink rate you can get isn't the same as the shallowest angle you can glide at . <S> Look at a Polar Curve : <S> The lowest sink rate you can get is the maximum value of the curve, as illustrated in this image taken from the wiki article above: <S> The shallowest angle you can glide at is given by the tangent to the curve that passes through the origin (another image from the wiki article) <S> If I can design one wing to sink at only 1 foot per minute, wouldn't that automatically get me a longer glide ratio from altitude X, than another wing that sinks at 2 feet per minute? <S> As we see from the images above, the answer is not a clear yes/no, because it depends on the Glide Polar of the aircraft. <S> Having a wing that sinks at 1 ft/min vs another that sinks at 2 fts <S> /min is no guarantee that the polar is shifted upwards, giving you a better glide ratio. <S> It will depend also on wing loading, as Peter wrote in this answer . <A> You compare different things. <S> Me can use your example. <S> Wing sinks 1 foot minute and goes forward 10 foot. <S> Another sinks 2 foot minute and goes forward 30 foot. <S> You start with 10 foot. <S> 10x10=100 and 5x30=150. <S> You can see that second wing though sinking at 2 foot per minute was going faster and moved 150ft instead of 100ft. <S> So the angle is shallower. <S> The same is in real live. <S> If you look at the glider manual it will have two speeds. <S> Max Glide speed and Min Sink(endurance speed, always lower). <A> Just something to consider (#'s are approximate for a C172SP) <S> At 60kts, your sink rate is 300fpm: - You travel 1.0nm forward over the ground in 1min- <S> You descend from 1000’ to 700’ in 1min - <S> At this airspeed and sink rate, you have lost 300’ in 1nm of forward travel over the ground, OR, you have lost 300’ in 1min of elapsed time At 70kts (best glide), your sink rate is 500fpm:- <S> You travel 1.2nm in 1min- <S> You descend from 1000’ to 500’ in 1 min (i.e <S> , you lose 500’ in 1min of elapsed time, OR you have lost 500’ in 1.2nm of forward travel over the ground) <S> NOTE: at 70kts airspeed and a 500fpm sink rate <S> , you would have lost 300’ in .69 <S> nm of forward travel over the ground <S> OR you would have lost 300’ in 36 seconds Airspeed-- <S> Sink rate (FPM)--Distance traveled in 1 min (nm)--Distance traveled with the loss of 300’ (nm)--Time elapsed with the loss of 300’ <S> (secs) <S> 60KTS -- 300 -- 1 -- 1 -- <S> 60 70KTS -- 500 -- 1.2 -- <S> .69 -- <S> 36 <S> With these notional numbers, with an engine out scenario, I would fly at 60kts (vice 70kts) because I would lose, on average, 300’ after gliding 1nm…if I flew at 70kts, I would lose that same altitude in a shorter distance traveled (.69nm)…I gain more gliding distance per foot of altitude lost at the lower airspeed
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To review, the key differences are: Glide ratio specifies how "flat" the glide angle is Minimum sink specifies the minimum vertical speed the glider can fly at One flies at best glide speed to maximize the distance covered vs altitude lost One flies at minimum sink speed to maximize altitude gain in lift
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Can we eliminate the center tank of large passenger planes? This is a safety question about fuel and fires. This all regards commercial aviation for large passenger planes. Most fuel is stored in the wings, but in the largest planes, there's also a center tank for the longest flights. It's this center tank I'm concerned with. In the event of a fire, this seems to be the most dangerous tank. I'm obviously concerned with fires in the fuselage, or very close to it. Obviously this is where all the people are and we don't want smoke or flame there, but remember also there are overhead oxygen canisters that if heated or fueled, will explode. Jet fuel is flammable by its nature. This cannot be changed because its purpose is to combust in an internal combustion engine. So it seems the best we can do is to keep the fuel as far from the fuselage as possible, to make it unlikely that fuel will cause a fire there (initially). Isn't there someplace we can move this center tank? Some ideas I thought of: store fuel in anti-shock bodies on the wings (or they could be just small sears-haack bodies on the wings); store fuel in the empannage; store fuel in nacelles that have a larger diameter than the engine itself, to make room for fuel. Another exotic idea: Is it possible to engineer the wing such that the most likely structural failure will happen first near the wingtip rather than the wingroot? This would spill the fuel farther from the fuselage. (I got this idea from a really wierd Boeing 747 crash in Netherlands where one engine jumped off then fell back into the other engine, causing 2 engine losses. They said some pins were designed to fail first for a more "benign" failure, but apparently those pylon pins were engineered wrong.) There's one more tricky caveat, though: the cross feed line to balance fuel loads in the wings. If we eliminate this line, we increase the dangerous consequences of a fuel imbalance. But, it's interesting to think of what might cause a major fuel imbalance other than a leak, in which case the cross feed valve should not be opened. I can't think of anything so I'm leaning toward the opinion that this line can be eliminated too. EDIT: Thanks to bodargpd for pointing this out. Losing an engine in flight means the consumption rates will be hugely different. Without a cross-feed line, all that fuel in the other wing is unavailable and we may have to ditch early. So the cross-feed line is still necessary. I still say this is much less dangerous than a center fuel tank, however. It would also be nice if we engineered the cross-feed line to be weakest at the sides, so any leak will most likely be as far to the outside of the fuselage as possible. To sum up, the basic question is, can we viably move the center tank volume of fuel somewhere outside the fuselage? EDIT: I'm not primarily worried about fuel explosions. I'm concerned mostly about fuel leaks during hard emergency landings. I'd rather have a fuel leak out on the wing than in the fuselage. <Q> I'm assuming you're talking passenger safety in the event of a ground impact - if anything happened midair, it wouldn't really matter if it were in the fuselage or one of the wings. <S> Moving the fuel somewhere else is going to have center of gravity implications. <S> Moving it to wing pods or lager nacelles in particular would increase drag, which would require the plane to have even more fuel on board, which seems counterproductive to decreasing the fuel risk to passengers (and, of course, would substantially increase the cost of operating the flight). <S> However, that's less a safety design and more the lack of anywhere else to put the extra fuel on a small aircraft. <S> If an engine fails, the rate of fuel consumption is going to be different on each side of the plane. <S> Although both are rare, you likely have far more situations where different wings use fuel at different rates than situations where having fuel feed under the body would be dangerous. <S> If that's true, then removing the cross-feed line would be more dangerous than leaving it in. <A> Extending bogardpd's answer: moving the fuel from the center to the wings will also upset the weight and balance. <S> When the plane rolls, since the mass is further away from the rotation center, the moment of inertia is increased. <S> Which means slower response and a need for stronger wings, which means more weight, which means even stronger wings...... <S> You get the idea. <A> Yes the fuel from the centre tank can be moved to another place in the aircraft. <S> It's a lot of fuel though. <S> Some ideas I thought of: Store fuel in anti-shock bodies on the wings <S> (or they could be just small sears-haack bodies on the wings). <S> Technically possible, but there will be a large amount of pods. <S> Store fuel in the empannage. <S> This is already done for cruise trim drag elimination. <S> Store fuel in nacelles that have a larger diameter than the engine itself, to make room for fuel. <S> These would be huge and the fuel would be directly around the heat source of the combustion chamber. <S> All of this is technically possible, but is there really a problem to solve? <S> The centre tank is the first one to be emptied, since the fuel in the wing provides bending relief. <S> All solutions would introduce economical issues: the extra drag makes our tickets more expensive. <S> Is it possible to engineer the wing such that the most likely structural failure will happen first near the wingtip rather than the wingroot? <S> The root of the wing has the largest stresses due to bending moment, and will unfortunately fail first. <A> Probably safer in the belly than anywhere else due to stress, bending, and weight balance issues. <S> The wings would be closest to pitch CG, but loading them with fuel would affect the roll rate as well as a possibility of creating a sickening uneven "sloshing" motion that could affect passenger comfort. <S> The solution is called "inerting" or eliminating one of the spark, oxygen, fuel components thata fire needs. <S> Nitrogen will not support combustion of jet fuel, so filling the fuel tank with nitrogen greatly improves safety. <S> Nitrogen is cheap, and a gentle flow into the tank will keep even volatile liquids from igniting.
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Some military aircraft do carry fuel in removable underwing fuel pods (particularly fighters being ferried somewhere, where increased endurance/time between refuelings is more important than performance for that particular mission).
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How do door seals work? The pressurization in the cabin requires the doors have their seals working properly. How do they prevent pressurized air from leaking from the doors? <Q> How do they prevent pressurized air to leak from the doors? <S> They don't. <S> The seal does not have to be perfectly airtight. <S> The requirement is that it will create enough impediment to the air that wants to gush out, where "enough" is defined by the capability of the conditioning system to input new air into the cabin. <S> In other words, everything is fine as long as the air mass that gets out of the doors is less than the maximum air flow that the air conditioning system can input into the cabin. <S> Note also that, as stated on Wikipedia , aircraft are equipped with one (or more) "out-flow valve(s)" and "pressure relief valves": these valves intentionally let air out of the cabin to avoid over pressure in the cabin and thus they prevent possibly dangerous scenarios. <A> You can find one of Boeings patents here which covers door seals. <S> Some smaller planes (and unpressurized GA planes) use inflatable seals, the door is closed and then the rubber boot is inflated to form a tighter seal. <S> You can find an interesting discussion on the seals here but in general they may have tiny leak issues. <S> This was the cause of at least one A380 diversion recently , but it looks like airbus is working through it and has a solution. <S> Since the cabin has an outflow valve to keep it properly pressurized a tiny leak in the door will be compensated by the outflow valve. <S> This airbus briefing warns that they can be hazardous and hard to detect if one does occur the crew may not know until the O2 masks deploy. <S> Slow/ <S> Insidious decompression involves a very gradual decrease in cabin pressure. <S> Slow decompression may be the result of a faulty door seal , a malfunction in the pressurization system, or a cracked window. <S> Slow decompression may not always be obvious. <S> The cabin crew may not notice the changes in the cabin, until the oxygen masks drop down from the Passenger Service Units (PSUs). <S> It has been noted that leaky seals on both pressurized and unpressurized doors can lead to a very loud noise in the cabin. <S> The seals do at least to some level try to keep water out. <S> This is mainly because excess water may build up and then freeze as the airplane climbs. <S> This ice build up in the door could in theory cause an issue (although I cant find any cases where it has). <A> A lot of aircraft with pressurised cabins have plug type doors which press against the fuselage when in closed position. <S> There is a (silicone) rubber seal where it touches against the fuselage, which minimizes air leak. <S> The image below shows the seal in an aircraft door. <S> Image from aviationtroubleshooting.blogspot.in
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Like any pressure seal they are generally rubber seals.
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What are the pro/cons of polyhedral cranked wings? Dihedral wings seems to be very common (almost if not all low-wing airliners, many modern gliders,...). Polyhedral seems to be less common and mainly found in relatively old aircraft (F4 Phatom, F4U Corsair, DR400,...). By polyhedral, I mean at least 2 dihedral angle with a sharp discontinuity between both. I don't include wings whose diheadral angle varies smoothly along the wingspan (such as this B787 ). But I was surprised to discover that this design (polyhedral with sharp angle between the distinct diheadral sections of the wing) was elected in at least 2 project whose first flight was in the last 10 years (namely the solar impulse and the qinetiq zephyr ). I do realize that both examples I gave have similar missions (stay airborne as long as possible, and thus fly slowly; gather as many sun-energy as possible, and thus fly as horizontally as possible) and may thus have similar design. Given recently-designed aircraft with polyhedral wing exist, what are the pro/cons of such design over well spread dihedral wings and over the smoothly varying dihedral angle? EDIT: note that the polyhedral does not necesseraly increase the dihedral angle as we go away from the wing root ( Be 12 , Habicht ,...) <Q> While dihedral wings offer increased stability in the roll axis, they also decrease the lift that the wings provide. <S> Therefore, a polyhedral wing allows the best of both worlds for a wing design. <S> Other applications of a polyhedral wing are utilitarian; the gull wing on the Vaught F4U Corsair is designed so that the landing gear is positioned close to the ground while maintaining roll stability and aerodynamics. <A> Polyhedral wings are used in aircraft for various reasons, mainly to improve roll stability without significant change in the overall wing design. <S> The original design of the F-4 Phantom (which started as a 'super F3' had a constant swept wing with anhedral. <S> By U.S. Navy - U.S. Navy National Museum of Naval Aviation <S> photo <S> No. 1996.253.7320.028, Public Domain, https://commons.wikimedia.org/w/index.php?curid=24564607 <S> However, wind tunnel tests indicated stability problems, which were were overcome with giving the outer wings a 12$^\circ$ dihedral, corresponding to a 3$^\circ$ overall (with changes in wing sweep too). <S> This saved a major redesign of the wing, while also allowing the spar to pass below the fuselage. <S> Another example of this is the Antonov An-12 'Cub' . <S> The early prototypes had a straight high wing. <S> However, test flights showed the aircraft having poor lateral and longitudinal stability, which was remedied by increasing anhedral on the outer wing panels. <S> By Sefjo - Own work, CC BY-SA 3.0, <S> https://commons.wikimedia.org/w/index.php?curid=29397593 <S> The F-4U Corsair had polyhedral wings as the the designers had to keep the landing gear short enough, while at the same time have enough ground clearance for the huge propeller used. <A> Lets consider the dihedral angle from three points of view: Stability, the more conventional one, it mainly influences spiral stability, which is the tendency of the aircraft to enter into a spiral due to a perturbation (i.e.: gust): The aircraft should not enter this spiral, it is allowed to enter in a spiral only when the motion is slow enough for the pilot to safely recover. <S> Reduction of induced drag, a more "unconventional" aspect to analyse the dihedral angle, requires higher dihedral angles. <S> Integration, keeping clearance between the ground and the wing tip and/or engines/propellers. <S> This is specially important for the ground phases. <S> From the stability point of view the dihedral main effect is on the $C_{l_{\beta}}$ (and $C_{l_{r}}$ ) derivative. <S> This derivative plays a major role (along with other such as ( $C_{n_{r}}$ $C_{l_{p}}$ , $C_{n_{p}}$ , $C_{n_{r}}$ ) in defining the spiral and dutch-roll modes. <S> These other derivatives usually depends heavily on the design of the vertical stabilizer design (except $C_{l_{p}}$ , which is mainly influenced by aspect ratio). <S> Since the vertical stabiliser design is more complex than trading the dihedral angle (whose main influence is on $C_{l_{\beta}}$ ) , the latter can be used to " adjust " the desired spiral and dutch-roll modes, to desired values. <S> The dihedral angle, when exaggerated, has a secondary effect on induced drag as well. <S> This can be seen from the configuration on the bottom right in the figure below. <S> Here it can be noted how a ( very ) high dihedral angle has a positive effect on the aerodyanmic efficiency factor $\epsilon$ . <S> Generalizing, the higher the displacement of the wing (the dihedral angle) <S> the better it is for induced drag (think about the new B787 or A350 designs). <S> Since induced drag is the main component of drag in low speed, and since the aircraft you mentioned (solar impulse, kinetiq zephir), are solar powered and flying slowly I can imagine that they have a stronger use case to minimize drag. <S> Finally the dihedral angle can be used to mitigate "integration" problems. <S> The other example you mentioned I think fall in this category. <S> On the Beriev Be 12,the propellers would be too close to the water, expecially when the aircraft is floating (see here ). <S> And similar the Habicht wihtout the gull wing would have a wing tip too close to the ground.
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A polyhedral wing provides a compromise: a steep dihedral at the tip of the wing in order to maximize stability, and a shallower dihedral angle closer to the root in order to maximize lift.
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Where does the final approach segment begin on an ILS approach? Where does the final approach segment begin on an ILS approach? It may not be as simple as it sounds to answer. The reason I ask is because I've found some support for at least two answers. One is that final begins when passing the glide slope intercept point a the last no lower than altitude for the approach. This is the point denoted by the lightning bolt arrow on government charts. Another answer I've heard is that it begins when glide slope has be intercepted within the limitations of the glide slope and on an approach segment. For the example plate above, this would mean that if the glide slope were intercepted between SILKY and JAKOR the pilot would be considered to be past the final approach fix for all intents and purposes and might even configure the airplane for landing at that point rather than passing JAKOR at the published glide slope intercept. I think there are valid arguments for both, but I'd apprecate more insight and references on the topic. <Q> No arguments needed, it's very specifically defined. <S> According to the FAA's Pilot/Controller Glossary under SEGMENTS OF AN <S> INSTRUMENT APPROACH PROCEDURE : <S> c. Final <S> Approach− <S> The segment between the final approach fix or point and the runway, airport, or missed approach point. <S> (See ICAO term FINAL APPROACH SEGMENT.) <S> So it starts at the FAF, which is defined in the same document as: FINAL APPROACH <S> FIX− <S> The fix from which the final approach (IFR) to an airport is executed and which identifies the beginning of the final approach segment. <S> It is designated on Government charts by the Maltese Cross symbol for nonprecision approaches and the lightning bolt symbol, designating the PFAF, for precision approaches; or when ATC directs a lower-than-published glideslope/path or vertical path intercept altitude, it is the resultant actual point of the glideslope/path or vertical path intercept. <S> In your example, that means the final approach segment starts at JAKOR. <S> I may be wrong here, but your original thought might have been that the final approach starts when you're established on the glideslope, which could be outside JAKOR. <S> That makes sense in a general way, but it isn't how the term is defined. <A> It's pretty easy to answer as best <S> I can determine: The Final Approach Segment begins at the Final Approach Fix. <S> On FAA/NACO charts this is shown on the profile view with the Maltese cross: <S> The "lightning bolt arrow" (or as the FAA calls it, the "zigzag line") designates the precision approach glideslope intercept altitudeThis is usually coincident with the final approach fix (and the specified altitude serves as the minimum crossing altitude for the final approach fix if the glideslope is inopertive or not in use), but it does not appear on non-precision approach charts, as shown above. <S> The final approach fix may also be marked in the plan view with the annotation (FAF) . <S> You may have intercepted the glideslope before the FAF as you describe in your second scenario (particularly on a continuous-descent profile) or you may have done a dive-and-drive to that point because the glideslope is out of service before starting your final descent as in your first scenario, but for purposes of the approach segments the FAF marks the beginning of the final approach segment . <A> The lightning bolt is the final approach fix for precision approaches and the Maltese cross is the final approach fix for non-precision approaches. <A> My 2014 AIM 5-4-5 Instrument Approach Charts says: The ILS glide slope is intended to be intercepted at the published glide slope intercept altitude. <S> This point marks the PFAF and is depicted by the “lightning bolt” symbol on U.S. Government charts. <S> Intercepting the glide slope at this altitude marks the beginning of the final approach segment and ensures required obstacle clearance during descent from the glide slope intercept altitude to the lowest published decision altitude for the approach. <S> Interception and tracking of the glide slope prior to the published glide slope interception altitude does not necessarily ensure that minimum, maximum, and/or mandatory altitudes published for any preceding fixes will be complied with during the descent. <S> If the pilot chooses to track the glide slope prior to the glide slope interception altitude, they remain responsible for complying with published altitudes for any preceding stepdown fixes encountered during the subsequent descent. <S> So basically, the Final Approach Fix is when you intercept the glideslope at the lightning bolt or after the lightning bolt. <S> Outer marker beacons are usually (but not always) <S> co-located with the conjunction of intercept altitude and glideslope. <S> If there are no marker beacons, you can expect to see an annotation stating RADAR REQUIRED. <S> As shown below, the PFAF for the ILS part of the approach is 3100'. <S> The Maltese cross would be the FAF if the approach is being flown as a localizer. <A>
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Final approach segment begins no sooner than the Final Approach Fix or Final Approach Point, however, it can begin later if you intercept the final approach course below the FAF/FAP published altitude, in which case the Final Approach Segment begins at the point of glide slope capture/intercept.
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In the traffic pattern, what is the appropriate distance from the runway for the downwind leg? Specifically for a piston general aviation aircraft, is there a recommended distance from the runway to fly the downwind leg? Does this change based on the speed of the aircraft? <Q> AOPA has a nice over view of non towered airports here . <S> This FAA brief states it should be flown 1/2 to 1 mile out <S> (page 7-4 of FAA Airplane Flying Handbook, FAA-H-8083-3B). <A> There are multiple considerations, among them: Other aircraft in the pattern (that may be slower or faster than you): you want to maintain your position, not getting too close to planes ahead of you, nor slowing down planes behind you. <S> The descent rate of your aircraft: <S> I was taught to descend 25% from TPA on downwind, 25% on base, and 50% on final. <S> (typically from a 1,000 ft TPA, that is 250ft / 250ft / 500ft) <S> The turning rate of your aircraft: You want to make rectangular shaped patterns. <S> If you are too close, your patterns will be more oval shaped. <S> If you are too far, you will have a very long base leg. <A> "Within gliding distance" is one common rule that many instructors teach. <S> It would be embarrassing to have an engine failure in the pattern and not make it to the runway :-) <S> More seriously, you tend to make a lot of configuration changes in the pattern so the risk of something going wrong is higher, therefore within gliding range is usually a good place to be. <S> That doesn't mean being in a position to glide the remaining downwind, base and final legs to land neatly on the numbers: it means gliding to <S> somewhere on the runway you can safely land (or even to a taxiway if need be). <S> (The FAA's commercial pilot test standards require the applicant to glide to a landing from the downwind leg starting at 1000 AGL.) <S> Of course, there are lots of variables and you may have to fly a wider (or tighter) pattern at certain times or at certain airports for any number of reasons: traffic, ATC instructions, noise abatement etc.
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This leg should be approximately 1/2 to 1 mile out from the landing runway, and at the specified traffic pattern altitude. Most instructors say that (in a low wing plane) you should see the runway on the tip of the wing or between the tip and 1/4 in the wing.
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Why are modern regional jet designs shifting towards under wing engines? Historically regional jets (eg, MD-95/B717 , CRJ-700/900 , ERJ-145 , etc) have had their engines mounted near the rear of the fuselage. But, recently, regional jets are increasingly using an under wing configuration ( E-170/175 , Sukhoi SJ100 , Mitsu MRJ700 to name a few.) A couple related questions: Why might this configuration be advantageous for small jets as opposed to the rear mounting configuration commonly used before? If it's advantageous, I assume technical problems are what stopped it from being implemented before. So what has changed that allows manufacturers to use this configuration now? <Q> The underwing engine location allows for a lighter airframe. <S> Placing the engines under/ahead of the wings brings these benefits: <S> Bending relief: Engine mass is closer to where lift is created, so the structure has less stress to carry around. <S> Flutter suppression: Placing the engines ahead of the elastic axis of the wing shifts the flutter speed up <S> , so the wing can be built less stiff. <S> Better evacuation: With wing-mounted engines a rear door is possible to create a second point for emergency egress. <S> Lower noise level in the rear cabin. <S> More useable cabin space at the rear. <S> Easier access to the engines for maintenance. <S> Shorter piping for fuel and bleed air. <S> Especially in the narrow fuselages of regional jets the air ducts for ventilation take a lot of valuable space. <S> And don't discount psychology <S> : The underwing engine design looks more like the bigger jets, which can be a big factor for some passengers. <S> The airplane looks safer and more mature. <S> With modern CFD it is much easier to reduce the interference between the engine nacelles and the wing, so the biggest disadvantage of an underwing engine location can be reduced. <S> Note that early designs for the Boeing 737 used rear-mounted engines. <S> By relocating them under the wings, the structure could be made 700 kg lighter. <S> Quote from <S> www.b737.co.uk : <S> Overall, the wing-mounted layout had a weight saving of 700Kgs over the equivalent “T-tail” design and had performance advantages. <S> The rear-mounted engines were a fad from the late Fifties (started by the Sud Aviation Caravelle ) to the mid-sixties and driven by the concern about the higher risk of low-mounted engines ingesting debris and the higher asymmetry in engine-out conditions. <S> With more operational experience and more reliable engines, these concerns proved unfounded. <S> Citing www.b737.co.uk again: <S> Initial worries about the low mounted engines ingesting debris proved unfounded, this was demonstrated by the Boeing 720B whose inboard engines are lower than the 737's and had been in service for four years without significant problems. <S> Small business jets still prefer rear-mounted engines so they can operate from more airfields (on which the runway might not be as clean as those of big airports) and because the weight penalty of rear-mounted engines is less pronounced. <S> Instead of bending and thrust loads, handling loads and manufacturability drive the minimum skin gauges on smaller jets. <A> There are a few reasons for the placement of the engines under wings. <S> As most of the pros and cons have been already discussed elsewhere, I don't want to go into them, but I'll just point out some reasons for this trend. <S> One important shift in the last two decades in airline industry is the use of high bypass engines, which have higher diameters and are quite difficult to place in the rear. <S> As the trend appears to be towards higher bypass ratios, it makes more sense to put the engines under wings where engine size increase could be better accomodated. <S> Another point is that the aircraft today are not developed seperately for regional and national use, but developed as part of a family, which can be used in a variety of roles. <S> Flighglobal points this out on its article on the Embraer E170: <S> The response reflects the shift in emphasis since 1998 away from a product geared solely to the regional airline market to a more robust family design with equal appeal to traditional mainline carriers. <S> Note that the 170 is not called ERJ 170, just the E-170 <S> ; the dropping of the regional moniker is significant. <S> Embraer considerd using a tail mounted engine for 170, but went with a wing mounted one as this design proved better. <S> The mounting of engines on the wing helps in reducing weight. <S> Mounting engines on the tail needs beefier fuselage for thrust transfer and usually necessiates a T-tail due to engine location. <S> This is somewhat cancelled by a shorter landing gear, but as the aircraft size increases, the weight savings become significant. <A> To answer your WHY, these are larger regional jets. <S> Most regional jets are too small for engines under the wing. <S> As theses jets get larger (mini-737) <S> there is such room. <S> Thus these designs can take advantage of the benefits of wing mounted engines. <S> It's unlikely you will see many jet aircraft of the size of the Embraer ERJ series (30-40 passengers) with under wing engines.
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From the airline/customer point of view, the mounting of engine on the wing is better in two respects- reduced maintenance due to engine accesibility and reduced noise in cabin.
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How do I determine the center of gravity on aircraft? What are the parameters considered and what formulas are used to find the Center of Gravity on an aircraft? <Q> You ask particularly about the Center of Gravity (CG), but not the weight. <S> Any CG calculation will necessarily include the weight as a component of the calculation; therefore I refer to the calculations as weight and balance (or CG) calculations. <S> The two primary ways that weight and balance measurements are determined are by physically weighing the aircraft and by mathematically calculating based on additions or subtractions to the previous weight. <S> The former is performed by maintenance personnel and forms the empty weight and CG for any given aircraft. <S> The later may be performed by either flight operators or by maintenance and uses the predetermined empty weight and CG as the basis for the calculations; this may be needed due to the installation of new equipment, for example, or a pilot may do such a calculation to determine the weight and CG for a given flight with, for example, fuel and passengers. <S> For maintenance operations, most aircraft have a section in the maintenance manual or operating handbook that prescribes the process. <S> One necessary parameter is an established reference datum . <S> The basic formula is: $$C_G=\frac{(W_1\cdot A_1)+(W_2\cdot <S> A_2)}{W_1+W_2}$$ <S> Where: $W_n$ is the weight of the aircraft scale's measurement, predetermined empty weight, fuel, or payload, etc. <S> $A_n$ is the moment arm, in reference to the datum, of the of the aircraft scale's measurement, predetermined empty CG, fuel, or payload, etc. <S> $C_G$ is the solution to the center of gravity for the aircraft. <S> The cancelled FAA Advisory Circular AC65-9A contains an entire chapter ( Chapter 3 ) dedicated to the subject of weight and balance, including exactly what you ask, the parameters that must be considered and the formulae used to perform the calculations. <S> Though cancelled, the AC is still available online <S> (I have a print copy). <S> EDIT <S> : See the comment below from @voretaq7 referencing the excellent "Aircraft Weight & Balance Handbook" quoted here: <S> In addition to AC 65-9A the current Aircraft Weight & Balance Handbook (FAA-H-8083-1A - available here) contains more than you ever wanted to know about computing weight & balance. <S> This is currently the direct link to the PDF of that document. <A> It is not fully clear to me whether you are interested in determining the CG (Center of Gravity) of a new design or an existing one, I guess is the latter. <S> In this case the main parameters are: The Payload (i.e.: people, cargo, other (e.g.: ammunitions)) <S> The Fuel <S> The manufacturer provides you with tables to determine the CG due to the different loading condition (combination of the aircraft payload and fuel). <A> First you put it under the front/tailwheel, note the force F1, and then do the same for one of the main wheels. <S> You note the force and take double that value, F2. <S> The CG is in a point of a line along the fuselage, where the moments of F1 and F2 have the same value. <S> It's elementary algebra for 10-year olds... <A> Very simple answer, but one familiar with modelers, is to lift it off the ground. <S> Keep in mind your horizontal (front to back) <S> CG is normally slightly forward of your Clift, and is "balanced" by the angle of incidence, or trim of elevator. <S> There is also a vertical CG (top to bottom) <S> whichshould be compared with your center of frontal drag. <S> Note most aircraft tail designs are assymetric, withmore "up" than down, also adding to the up trim. <S> The drag from the vertical stabilizer is thereformore efficiently used, saving some up trim on the horizontal. <S> For full scale, there are formulas in the POH basedon the CG before loading fuel, people, luggage, etc. <S> Very important pre-flight task to check this.
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For flight operations, most aircraft have an information manual or operating handbook that will prescribe the calculation. For light planes, you can get a good approximation with a bathroom scale.
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What are the uses of gyroplanes? From my understanding, a gyroplane (autogyro): Is a rotocraft . Uses an unpowered rotor for lift generation, instead of wings. Uses a propeller for horizontal translation like an airplane. Cannot take off vertically or hover contrary to an helicopter. Can land vertically like an helicopter using rotor inertia. Maybe simpler to build and maintain than an helicopter or an airplane. ( Source ) Are gyroplanes a technology that works but without particular application? Or do gyroplanes have well known uses for which they have significant advantages over airplanes and helicopters? <Q> Gyroplanes have quite a few applications , but the problem is that anything they can do, others (helicopters/fixed wing aircraft) can do better. <S> The main advantage of a rotorcraft is that they can hover at a location; the gyroplanes are unable to do this, which is kind of a deal breaker. <S> However, most of the autogyros available in market are small ones and as the size scales up, this may vanish. <S> The gyroplanes are used mainly for low speed surveillance operations due to their low stall speed. <S> Of course, helicopters can be used to do this, albeit at a higher cost <S> So basically, the autogyro can do most of the things the helicopters/small GA aircraft can do at a lower cost. <S> This low operational cost may be its main advantage. <S> I'm not aware of anything the autogyro can do which the others cannot do though. <A> I also want to mention these advantages (in addition to the lower operational cost): <S> Easy to fly and enjoy the flying experience. <S> Because it is in constant autorotation it can't stall. <S> It's simpler than a helicopter or plane Because it's simpler and can't stall: <S> With a proper design It can be safer than a helicopter or plane. <S> Mix that <S> and you find the perfect recipe for sport/pleasure flying for people that have been dreaming of flying. <S> Also this is the foundation of the bad safety reputation (with is not the fault of autogyros) as amateurs are building and flying this aircraft without the proper preparation. <S> Also: With a prerotator and rotor pitch control it can do jump takeoffs, taking off vertically. <S> It can not hover <S> but it can land within a very short distance (practically none) <S> In conclusion, private usage is the perfect application for Autogyros. <A> The gyrocopter is cheap, versatile, and as easy to operate as an off-road motorcycle. <S> What can it be used for? <S> For everyone's daily ride to work. <S> The owner of Quobba Station in Western Australia owns a gyrocopter and uses it to patrol his land, and to muster the sheep and goats when time comes to sell them. <S> He operates a barren "sheep station" the size of a small country, and has built the gyro himself. <S> A Robinson R22 would be prohibitively expensive. <S> A small plane would not be able to land anywhere on his property. <S> The off-road motorcycle ride is slower and less comfortable.
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The main advantage of the gyroplane is that they cost less and are easier to maintain, compared to other type of aircraft.
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Does a request for a Pop-Up IFR clearance constitute filing a flight plan? Introduction Pop-up IFR clearances are an accepted way to transition from VFR to IFR flight by obtaining an IFR clearance. They are well documented from a controller's perspective in this Tarrance Kramer article appearing in AvWeb and from a pilot's perspective in this Rick Durdan article appearing in AvWeb. These related Aviation.SE questions also address the topic: How do you request a “pop up” IFR clearance? How do you open and get a IFR clearance while in the air? How should I request an IFR approach at the end of a VFR flight? Clearly, this is an accepted way to obtain an IFR clearance; I have made use of the option myself plenty of times. Legal Background Now, pop-up clearances are often requested and granted with no previously filed IFR flight plan which, on the face of it, would seem to be in violation of 14 CFR 91.173 which states (emphasis mine): No person may operate an aircraft in controlled airspace under IFR unless that person has— (a) Filed an IFR flight plan; and (b) Received an appropriate ATC clearance. 14 CFR 91.169 gives the information required for filing that required IFR flight plan, which states, in part (emphasis mine): Unless otherwise authorized by ATC , each person filing an IFR flight plan must include in it the following information: [...] (I omit the long list of actual information) The Question The first part of my question is: Does a request for a pop-up IFR clearance constitute filing a flightplan? Is there an unwritten (or perhaps written) understanding that the request for the IFR clearance constitutes filing a flight plan to the extent required by 14 CFR 91.173? The second part of my question is: Why is the full list of information requiredfor filing an IFR flight plan not required, in fact, of a pilotrequesting a pop-up IFR clearance? If ATC issues an IFR clearance without this information, is that a tacit, but legally valid, authorization to exclude the information otherwise required by 14 CFR 91.169? Is all this actually codified somewhere that I am not aware of? <Q> I think Porcupine911 nailed the first question perfectly with the reference to JO 7110.65W : <S> ATC considers it an "airfiled" flight plan (VFR-to-IFR), and the controller talking to you will take at least the bare minimum information necessary to enter you into the ATC system and generate a flight plan / strip for your aircraft. <S> Your second question is a little more complicated, but the short answer is that pop-up IFR clearances aren't "tacit authorization to omit information required by 91.169", but controllers are busy people and don't have time to key all that into the computer when they're supposed to be working traffic. <S> The longer version is that what you probably should be doing to get an IFR clearance in-flight is calling the local flight service station over the radio and air-filing your IFR flight plan with them, then checking in with ATC (who will have <S> all the information Flight Service took from you and entered into the computer, without having to tie up their frequency interrogating you for it). <S> The FAA (or at least the ATC organization) is not without a heart though: They understand that if you're calling them for a pop-up IFR clearance it means you're in a bit of a situation (like IMC closing in on you with no good "out" that will allow you to remain VFR) and you need to get into the system before you hit the ground, a building, or another aircraft. <S> Giving the controller the bare minimum skeleton of a flight plan allows them to get you into the system and under positive ATC control to ensure you're operating at a safe altitude without any traffic conflicts, which satisfies the first of the three ATC operational criteria ("Safe") -- the other two (Orderly & Expedient) are a lower priority and can be dealt with later. <A> Here are two relevant definitions from the FAA's Pilot/Controller Glossary (my emphasis): <S> FLIGHT PLAN− Specified information relating to the intended flight of an aircraft that is filed orally or in writing with an FSS or an ATC facility. <S> And: <S> ABBREVIATED IFR FLIGHT PLANS− <S> An authorization by ATC requiring pilots to submit only that information needed for the purpose of ATC. <S> It includes only a small portion of the usual IFR flight plan information . <S> In certain instances, this may be only aircraft identification, location, and pilot request. <S> Other information may be requested if needed by ATC for separation/control purposes. <S> It is frequently used by aircraft which are airborne and desire an instrument approach or by aircraft which are on the ground and desire a climb to VFR-on-top. <S> So according to the FAA's own definitions, a flight plan may be filed orally with ATC, and an abbreviated flight plan is specifically intended for pop-up clearances. <A> To add on to voretaq7's excellent response, the bottom line for ATC is that full flight plans and IFR pop-ups will be handled the same way for separation and sequencing, etc. <S> Pop ups are more work for the operational controller trying to separate airplanes, but they will almost always grant them workload permitting. <S> Filing the full flight plan through FSS or DUATs is the best for everybody. <S> The controllers get the proposed plan 30 minutes prior to departure and don't have to play 20 questions on frequency. <S> The pilots get better service and more complete search and rescue data on file, which may sound trivial but is actually really important! <S> BTW - you can actually file an IFR flight plan to begin mid flight. <S> I've seen many times when a flight will have VFR legs before and after the IFR segment. <S> Kind of handy if you are anticipating weather down the road but want to remain VFR as much as possible. <A> One additional aspect of pop-ups. <S> Air filing a flight plan with FSS, and then going to ATC to pick it up, saves the controller typing, and makes friends. <S> You might be talking with FSS already to get updated <S> Wx if you don't have a fancy cockpit.
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A "pop-up" IFR clearance counts as filing an IFR flight plan.
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What is the need for TCAS? Isn't it the job of the air traffic controller to assign altitudes and make sure airplanes do not collide in mid-air? Is having TCAS mandated or optional? If it is a mandate, then is there a mechanism to notify other airplanes that TCAS is off? <Q> TCAS is part of a defense in depth strategy to reduce air accidents. <S> ATC does not cover all areas, so TCAS adds protection where ATC coverage is missing. <S> ATC is not infallible: humans can make errors and computers can go down. <S> With TCAS pilots can get life-saving warnings even in zero visibility, without reliance on any ground based system. <A> It is the job of the ATC to assign the aircraft altitudes and ensure their safety. <S> But consider the following situations: <S> There is no ATC coverage. <S> (one of the) <S> The aicraft fails to respond to the ATC directions. <S> The aircraft follows the ATC directions, but there is an error either in the aircraft systems/pilot actions or in the ATC directions. <S> In these situations, the TCAs acts as the next layer of defence against mid-air collisions, acting independently of the ATC. <S> Most of the regulatory authorities (FAA, EASA etc) mandate <S> TCAS (usually TCAS II) in the civil aircraft beyond a certain capacity, though the requirements vary from country to country. <A> An air traffic may be distracted or occupied elsewhere and so no instruction is given to the two aircraft. <S> The TCAS overrules any instruction given by air traffic control and the pilots must specific that they are following TCAS over the radio. <S> For example if an aircraft is instructed to descend by air traffic control and TCAS is requesting the aircraft to climb the aircraft will begin a climb. <S> TCAS will order one aircraft to climb and the other aircraft to descend to safely end the conflict between the two aircraft.
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TCAS is used as a last line of defense to avoid a collision.
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How much effect does the ground have on flight control when flying low? In this awesome video, shot at the "Mach Loop" in Wales, F-15Cs fly down the valley, then cross a ridge very low to the ground. While it's difficult to tell from the video just how low they really are, they seem to be fairly close. How much effect on flight characteristics do the pilots feel as the ground comes up to meet them, then falls away? To clarify a couple of points from the comments, I'm interested in any effects on flight control that are caused by flying fairly low over that ridge and through the valley ( to grandmother's house we go ). <Q> At the high speed of the F-15s in the video ground effect is almost negligible. <S> Ground effect is about the restriction of downwash by the ground, and at high speed and air density downwash is rather small. <S> Also, the duration of close proximity to the ground is too short for ground effect to fully develop. <S> The biggest effect will be air turbulence. <S> Since air will neither flow into the ground nor out of it, the vertical speed of atmospheric turbulence is greatly reduced when flying close to the ground. <S> Also, the scale of turbulence will get smaller with proximity to the ground. <S> While gusts may rock your wings when flying high, at very low altitude (less than one wingspan) the turbulence will average out over the wing. <S> When flying over a ridge, any wind speed component perpendicular to the ridge line will mean updrafts on the windward side of the ridge and downdrafts on the leeward side. <S> This will be the strongest effect in this particular case of F-15s flying over a ridge at Mach 0.7 to 0.9. <S> Now back to that ground effect meme which seems to find wide agreement here: Ground effect is a stationary process which is strongest at low speed, when the downwash behind the wing is strong. <S> In the case shown here, the aircraft is only momentarily in close proximity to the ground. <S> The pressure field around the aircraft will never reflect that proximity because it is gone before the aerodynamics could start to react. <S> This is completely instationary aerodynamics, and air, having mass, will take some time to respond. <S> However, it is never given this time. <A> This generally occurs with in one wing spans length from the ground and manifests its self as reduced drag on the airframe, lower stalling speed and a general floating feeling. <S> In this specific case the planes appear to be flying low in a relatively mountainous area. <S> The pilots may experience certain mountain related wind conditions while flying this low as well. <A> Ground effect is defined: ... <S> the increased lift (force) and decreased aerodynamic drag that an aircraft's wings generate when they are close to a fixed surface. <S> Source: <S> Wikipedia <S> The effect is that the aerodynamic drag is decreased and subsequently lift is increased giving the ability for the aircraft to fly at a lower speed than normally it could. <S> It is also a reason why overloaded planes can get off the ground but then stall as soon as they try to get some altitude. <S> Ground effect happens when the aircraft is at an altitude that is less than the wingspan of the aircraft. <S> For an F-15, this means that they would need to be within 43' of the ground. <S> Having watched the video its difficult to determine the exact altitude <S> but I'd hazard to say that they are more than 50' off the turf. <S> But the other part of your question is: How much effect on flight characteristics do the pilots feel as the ground comes up to meet them, then falls away? <S> It can be significant, especially in low-wing aircraft. <S> However the composition of the surface has a large effect on this. <S> Soft earth or water has a lesser effect than a hard surface like pavement. <S> Passing over peaks at 250 <S> + mph is probably going to have little effect <S> whereas coming in to land will be much more noticeable. <S> There are a few fighter pilots that hang around here that may be able to tell you what it feels like in a fly-by-wire aircraft, but in a cable and pulley system its definitely noticeable. <S> So much so that it can make an otherwise un-flyable aircraft fly. <S> There are aircraft designed to operate solely in ground effect and has been a factor in aircraft crashes .
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Low is of course a relative term but at a sufficiently low altitude a plane will physically experience ground effect . Speaking from a GA perspective, the controls become lighter and the airplane floats or doesn't want to touch the ground.
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What are the advantages and disadvantages of mixing the bypass flow with the core flow? Many Aircraft engines mix the bypass air with the core gases before exhausting to atmospheric pressure through a propelling nozzle. However, some do not mix and have separate nozzles for the flow of each. What are the advantages and disadvantages of each? PS: I hope that I am clear now. Sorry if the question wasn't clear earlier. <Q> In simple terms, mixing the exhaust flow (with any bypass ratio) is good for all the reasons except for construction and weight. <S> It is aerodynamically more efficient; it reduces noise (exhaust noise makes most of the jet noise); it cools combustion chamber (and other downwind parts) more efficiently, etc. <S> However, making the mixing chamber on a high bypass / big engine would require enormous outer nacelle to cover the whole engine (and extend somewhat beyond), and the weight penalty and complexity/cost negates all the benefits. <A> Advantage improved propulsion efficiency, stream Mn is affected by increase in temperature ie speed of sound changes. <S> Disadvantages longer nacelle required to mix cold and hot streams, this increases bypass scrubbing loss, nacelle drag and weight & cost. <A> Early jet engines were called turbojets where all flow went through the turbine. <S> In other words there is no bypass. <S> These are the cigar shaped engines you see in early airliners and military fighters. <S> These types of engines are very loud and whiny and required high fuel flows to achieve the amount of thrust required. <S> so you don't overheat your nozzle. <S> The combination of the two exhausts can also see gains in thrust for given fuel flows. <S> One of the most significant gains of bypass flow is noise reduction by having this outer flow "masking" the turbine noise. <S> This is desirable in airliners. <S> There are two types of bypass: <S> Low bypass is where there is more turbine flow than bypass flow. <S> This is common in business jets and military fighters with a ratio of around 1.5:1 or 2.0. <S> High bypass where there is more bypass flow than turbine flow. <S> This is common in modern airlines with bypass ratios upward so 10.0:1. <S> Low bypass: <S> High Bypass: <S> In low bypass, the flow is remixed prior to exiting the nozzle, giving the cooler exit temperature typically to save the nozzle material. <S> In a high bypass, the bypass air is allowed to flow outside of the engine after its high bypass compressor section, giving a very efficient airflow and adding to the overall thrust by moving a large volume of air outside the combustion and turbine section. <S> This give greater fuel efficiency and much quieter engines for airplanes that can use them due to their size. <S> Below is an example of a low bypass F-100 engine which is found on F-15 and F-16 fighters. <S> This is the GEnx high bypass engine found on 747-8 and 787.
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Bypass allows a few things, it provides a cooling flow of air to mix with turbine exhaust and lower the overall exit temperature
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Can passengers tell (without GPS etc.) where the aircraft is heading to? I was watching Mayday Varig Flight 254 and at minute 38 it said that some passengers noticed that the plane was flying in the wrong direction. This accident took place in 1989 , so my question is: without 'modern' aids like GPS, smartphones, in-flight entertainment system maps etc., can a passenger really notice where the aircraft is heading to? (I suggest you watch that minute of the video if you have the time. It will help to understand the question.) <Q> can a passenger really notice where the aircraft is heading to? <S> Passengers can rely on visibly observed phenomena such as stars, moon, sun, ground topology, or major landmarks (interstates, cities, facilities etc.). <S> General familiarity with flight routes and runways, coupled with attentiveness to significant changes in roll, pitch, and yaw can bolster an understanding of the flight's direction. <S> Items such as a compass (built into Casio calculator watches?) <S> could also be used to get an approximation of direction. <S> They may be affected by other instrumentation and mechanical features along with being really cheap. <S> Some passengers will be able to note which runway they took off from and a divergence from a typical path. <S> While still ascending they can more easily notice landmarks that are likely familiar, and recognize that no significant change in direction has happened since orienting themselves. <S> It's possible too that cognitive bias may be another explanation. <S> The media, and documentaries like this, seem to embrace an event as predictive or accurate despite a long history of inaccuracy or patterned behavior. <S> That passenger who makes 98% incorrect assertions of plane direction is only recorded or listened to after the fact and appears to be 100% accurate in their vastly under sampled assertion set. <S> How does it go? <S> A broken clock is right twice a day? <S> Also, thanks to all the comments, tried to cover most of those notes/ideas here. <A> Absolutely you can. <S> I have been doing this since the 1980s when I started flying. <S> I love maps and love looking at the earth from 30000 feet up. <S> When I see interesting features I want to know what they are and where they are. <S> Nowadays with google maps it's very easy to do this without getting into a plane but back in 1989 <S> your best opportunity to see the earth from up high was a plane flight. <S> Every trip for me was an opportunity to explore <S> and I'd prepare for the flight by having a look at a map and gaining an understanding of the significant landmarks we'd be flying over and the potential routes. <S> When you know what to expect and what things generally look like from altitude <S> it's easy to keep track when over land. <S> Working out the exact heading is trivial if you can see the sun or a few key stars. <S> Most plane flights are above any clouds giving you great astro-navigation cues (learning how to determine compass directions from the stars is easy in both hemispheres). <S> Once you progress to being a frequent flyer you tend to know exactly where you are. <S> I've flown Sydney to Cairns, Auckland and Melbourne enough times now that I can pick out all the cities, towns, rivers, lakes, damns, harbours, bays, open cast mines, wind farms, power stations etc. <S> Over the ocean it's just dead reckoning <S> (ssw for 2.5 hours from Sydney... should see the NZ coast soon. <S> oh yeah <S> there's the entrance to Kaipara harbour). <S> I would suggest that there is a subset of the passengers on board who know exactly where the plane is currently and where it is heading. <S> They're the ones in the window seat spending the flight staring out the window like they think the view outside is more interesting than the movie.... <A> There is a way to determine North with your wristwatch, if the sun is visible through the windows (see here ). <S> This would help to notice if the plane is heading in a completely wrong direction. <S> Many hikers know this trick. <S> Of course, it is even more obvious if the sun is ascending in the morning on the completely wrong side. <S> If it is in the night, many people know where the North star is, and some more skilled in astronomy may guess its location even if they see some other piece of the stellar sky. <S> All this is not likely for a single random chosen individual, but if there are say 500 passengers on a plane, it may a hiker between them, and it may be an astronomer between them because even finding a certified pilot between passengers is not completely unheard of.
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A wide variety of observable phenomena and general attentiveness can lead to an approximate understanding of which direction the aircraft is heading in.
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Why is this 777 with doors and windows covered? It's in the desert somewhere and it has its windows and landing gear and doors covered. Why is it that? Of course, it's not in service anymore... Source <Q> The aircraft is in storage. <S> The Boeing 777-212(ER) seems to operated by Singapore Airlines under lease from Pembroke before being withdrawn from use in Dec 2014 . <S> After that, the aircraft is under storage at Southern California Logistics Airport . <S> The windows are covered in aluminium foil for storage; however, the engines appear to be still there (which will usually be removed), which indicates that the storage was planned for only a short time. <A> The reason why it is stored in the desert is because the environment would not cause some structural damage to the airframe. <S> All those doors and windows are covered to keep animals, dust, and even sunlight out so that they would not damage the airframe either. <S> You can read more about storing aircraft in the desert here and here . <A> The aircraft was previously operated by Singapore Airlines but has been returned to Pembroke Leasing. <S> It is probably in storage because it is not economical to sell or lease at the present time. <S> Here are some possible reasons why it may be uneconomical to sell or lease: 1) <S> excessive supply of aircraft for market conditions 2) cabin or seating configuration 3) <S> excessive hours on the aircraft, engines or components 4) age of the aircraft (14 years)
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Currently that airplane is in storage per planespotters.net .
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How do you convert true airspeed to indicated airspeed? Is this something found in the POH? I know there is a IAS and CAS chart. <Q> Short Answer Getting to grips with Aircraft Performance and Calibrated Airspeed are two good places to start! <S> The short answer: From TAS to IAS $IAS= <S> f(TAS)$: <S> $$IAS = a_0 <S> \sqrt{5\left[\left(\frac{\frac{1}{2} \rho {TAS}^2}{P_0} + 1 \right)^{\frac{2}{7}}-1\right]} <S> + K_i <S> $$ From IAS to TAS $TAS= <S> f(IAS)$: <S> $$TAS = <S> \sqrt{\frac{2 P_0}{\rho}\left[\left( \frac{ (\frac{IAS - K_i}{a_0})^2 + 1}{5} \right)^{\frac{7}{2}} + 1 \right]} $$ WARNING: <S> the units should be taken as SI, ($\frac{m}{s},\frac{kg}{m^3},Pa$). <S> In particular: $a_0$: speed of soundat sea level in ISA condition = $290. 07 \; \frac{m}{s}$ $P_0 <S> $: <S> static pressure at sea level in ISA condition = <S> $1013.25 \; Pa$ <S> $\rho$: density of the air in which you are flying $\frac{kg}{m^3}$ $IAS$: indicated Air Speed $\frac{m}{s}$ $K_i$: is a correction factor typical of your aircraft. <S> How to get to this formula, see the long answer below. <S> Long Answer <S> From the definition of dynamic pressure: <S> $$ q_c = \frac{1}{2} <S> \rho v^2 $$ <S> Where $v = TAS$ <S> , I am assuming you are interesting in subsonic speeds (cross-country flight), so we don't consider compressibility effects for the CAS: $$CAS = <S> a_0 <S> \sqrt{5\left[\left(\frac{q_c}{P_0} <S> + 1 \right)^{\frac{2}{7}}-1\right]} <S> $$ <S> Substituting the dynamic pressure definition in the $CAS$ as a function of $TAS$ $$CAS = <S> a_0 <S> \sqrt{5\left[\left(\frac{\frac{1}{2} \rho {TAS}^2}{P_0} + 1 \right)^{\frac{2}{7}}-1\right]} <S> $$ <S> Where $a_0$ is <S> $295.070 \; <S> \frac{m}{s}$ and $P_0 <S> $ is $101325 \ <S> ; Pa$. the density <S> $\rho $ is the density at your altitude <S> that day, you can get it from International Standard Atmosphere calculator or table/formulas .If <S> you measure it from your aircraft <S> instruments <S> $\rho = <S> \frac{P}{RT}$, with $R=287.058 J kg ^{-1} <S> K^{-1}$. <S> You should give in Pressure in Pascal (not $hPa$) and most important temperature in Kelvin <S> $K$.Reverting the formula above (double proof is appreciated): <S> $$TAS = <S> \sqrt{\frac{2 P_0}{\rho}\left[\left( \frac{ (\frac{CAS}{a_0})^2 + 1}{5} \right)^{\frac{7}{2}} <S> + 1 \right]} $$ Being $$IAS = <S> CAS + <S> K_i <S> \\CAS = IAS - K_i$$ <S> Where $K_i$ is a correction factor typical of your aircraft. <S> You should find it in the POH. <S> Finally we get TAS as a function of IAS $TAS=f(IAS)$ <S> So:$$TAS = <S> \sqrt{\frac{2 P_0}{\rho}\left[\left( \frac{ (\frac{IAS - K_i}{a_0})^2 + 1}{5} \right)^{\frac{7}{2}} + 1 \right]} $$ <A> I just dial in the OAT, look for the TAS in the white window, and read the IAS on the black scale. <A> Complementing GHB’s answer, an exact formula for converting CAS to TAS that takes compressibility effects, indicated altitude, and static air temperature into account is $$ \text{TAS}= \sqrt{ \frac{7 R T}{M} \left <S> [ \left( \left( 1 - \frac{L h}{T_{0}} \right)^{- <S> \frac{g M}{R <S> L}} \left <S> [ \left( \frac{\text{CAS}^{2}}{5 a_{0}^{2}} + 1 \right)^{\frac{7}{2}} - 1 \right] <S> + 1 \right)^{\frac{2}{7}} - 1 \right] }.$$ <S> In this formula (which is valid only for subsonic speeds), the inputs are $ \text{CAS} $ — the calibrated airspeed ( $ \text{m}/\text{s} $ ), $ h $ — the indicated altitude ( $ \text{m} <S> $ ) up to $ 11,000 ~ \text{m} $ , <S> $ T <S> $ — the static air temperature ( $ \text{K} $ ); <S> the output is $ <S> \text{TAS} $ — the true airspeed ( $ \text{m}/\text{s} $ ); and the various physical constants are $ a_{0} = <S> 340.3 <S> ~ \text{m}/\text{s <S> } $ is the speed of sound at sea level in the ISA, $ g = 9.80665 ~ <S> \text{m}/\text{s}^{2} $ is the standard acceleration due to gravity, <S> $ L = 0.0065 <S> ~ <S> \text{K}/\text{m} <S> $ is the standard ISA temperature lapse rate, $ M = 0.0289644 <S> ~ \text{kg}/\text{mol} <S> $ is the molar mass of dry air, $ R = 8.3144598 ~ \text{J}/(\text{mol <S> } \cdot \text{K}) <S> $ is the universal gas constant, $ T_{0} = 288.15 ~ \text{K} <S> $ is the static air temperature at sea level in the ISA. <A> It's a common questions... <S> you get a TAS from your POH based on an RPM setting in your cruise performance chart. <S> Some Navlogs have a TAS/IAS box. <S> If you can determine the IAS then you can look at the Air Speed Indicator to insure everything is correct (from an airspeed perspective). <S> You still need to do a ground speed check because the TAS/IAS question doesn't help you with Navigation and confirming the forecasted winds. <S> But this is a commonly asked question. <S> And yes, using your E6B and working backwards to your CAS and the chart in the POH for you IAS is how you do it. <S> It's faster with an electronic E6B for sure. <S> PS - thanks for the math above, which will be way more accurate than the E6B, but I doubt I'll be doing the math! <S> haha <A> You read your TAS from your POH. <S> Then you get to your CAS by using a flight computer, such as the E6-B. <S> Then you use your POH to convert from CAS to IAS.
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You should find it in the POH.
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What is the exact meaning of CAVOK and CAVU? How are they used by pilots and ATC? Do CAVOK (ceiling and visibility okay) and CAVU (ceiling and visibility unlimited) have formal definitions worldwide? CAVOK, source: formercaptain.ca Are they used in ATC communications? <Q> CAVOK is formally defined in ICAO Annex 3 ( APP3-2 2.2 Use of CAVOK ) . <S> You can hear it at the airports where there is no ATIS , when ATC communicates the weather info. <S> When the following conditions occur simultaneously at the time of observation: <S> a) visibility, 10 km or more, and the lowest visibility is not reported; b) no cloud of operational significance; c) no weather of significance to aviation as given in 4.4.2.3 and 4.4.2.6; information on visibility, runway visual range, present weather and cloud amount, cloud type and height of cloud base shall be replaced in all meteorological reports by the term “ CAVOK ”. <A> CAVU means: "CLEAR OR SCATTERED <S> C LOUDS <S> A ND V ISIBILIY <S> U NLIMITED <S> (GREATER THAN <S> TEN MILES) <S> " CAVOK means: " <S> C LOUD <S> A ND V <S> ISIBILITY <S> OK (METAR). <S> " <S> This military document , has a little more background: <S> Overseas locations may use the contraction “CAVOK” (ceiling and visibility OK). <S> CAVOK is used when there is no significant weather, the visibility is 10 km or greater, and the ceilings are greater than 5,000 ft . <S> I have never heard them used in verbal ATC communication, and they are not listed in the Pilot/Controller Glossary <S> so should not be used on the radio. <A> Actual Definition From Annex 3 <S> When the following conditions occur simultaneously at the time of observation: <S> a) visibility, 10 km or more, and the lowest visibility is not reported; Note 1.— <S> In local routine and special reports, visibility refers to the value(s) to be reported in accordance with4.2.4.2 and 4.2.4.3; in METAR and SPECI, visibility refers to the value(s) to be reported in accordance with 4.2.4.4.Note 2.— <S> The lowest visibility is reported in accordance with 4.2.4.4 a). <S> b) <S> no cloud of operational significance;c) <S> no weather of significance to aviation as given in 4.4.2.3, 4.4.2.5 and 4.4.2.6 <S> ; information on visibility, runway visual range, present weather and cloud amount, cloud type and height of cloud base shallbe replaced in all meteorological reports by the term “CAVOK”.
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CAVU is not formally defined in Annex 3 .
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How does an airline open a new route? How do they manage to open a new route? For example Dubai-Panama. Do they have to open new airways? <Q> No. <S> You do not need to create new airways. <S> You stick up to the already existent waypoints or not, if the route flies through a segment of free-route airspace. <S> Also, the engineering department of the airline studies the route, for instance: computes the MSA (Minimum Safe Altitude) for every point, engine failure and depressurization simulations are done in order to avoid possible hazards in critical points, if the aircraft is ETOPS certified they will decide which alternative airports are available for the route, fuel computations, chart generation for arrival and departure (most of the airlines use their own charts instead of those provided by the ANSP), et cetera. <A> In addition to Airman01's answer , opening a route goes beyond flying from point A to point B, you also need to: get landing and departure slots at each of the airports. <S> At some with lots of spare capacity, this is easy. <S> At others, such as the largest and busiest airports, this is very difficult, and is a process that can sometimes take years. <S> Airlines have been known to buy competitors just to get their slots. <S> arrange ground handling (jetways or stairs, loading/unloading luggage, refuelling, possibly catering and light maintenance, check-in and gate personnel). <S> Sometimes this may be provided by the airport itself, sometimes it will be outsourced to specialised companies doing so in many places, sometimes to local companies, and other times it will be handled by the airline itself. <S> have all the relevant licenses/authorizations from countries overflown as well as source and destination, and arrange for the payment of relevant taxes and fees to the appropriate authorities. <S> and then you need to insert this into the rotation of the planes and crews in order to minimise downtime while still trying to find the most convenient times for your customers. <S> EDIT <S> I forgot to mention that in the case of international flights, there's the issue of the Freedoms of the Air . <S> Overflying, stopping, flying to, from or between countries other than your own is not automatic, and is usually subject to state-level agreements. <S> Overflying another country (First Freedom) is nearly universal (though the two states must either both be signatories of the IASTA, or have a bilateral agreement). <S> The Wikipedia page on the topic also lists examples of flyover fees. <S> Further freedoms are a much more complex issue, though relatively recent changes like the EU–US Open Skies Agreement changed things a lot on many of the most competitive (and restricted) routes. <A> Maybe this is an exception which proves the rule, or maybe this is not exactly a valid answer because it doesn't relate to the design a new complete route, but sometimes new airway segments are created, e.g. this discussion between IATA and FAA for opening two new polar segments: Summary of Discussions of the Sixteenth Meeting of the Cross Polar Trans East Air Traffic Management Providers Working Group (CPWG/16) 3-6 December 2013 – Ottawa, <S> Canada 8.1. <S> Based on ideas and proposals from IATA member airlines, State ATM Corporation developed two new route proposals that would supplement the existing cross polar routes and provide additional flexibility. <S> The routes presented were: a. 7957N16858W – <S> RODOK to join G495 <S> b. 7457N16858W – LUTEM – OLMIN – TURAN – <S> ASKIB 8.2. <S> The FAA agreed to review the routes and make an effort to limit restrictions. <S> These routes will be added to the ATS Route Catalogue. <S> The routes were later discussed at ICAO , but seems to be still waiting for their implementation. <S> However in the same document other routes are adjusted in the Sea of Japan:
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Each airline has its own policy and the process may vary but fundamentally the procedure done is to make a study of all the parameters that can affect to guarantee safety and efficiency.
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Are there any cockpit indications when an engine has separated from the aircraft? On this answer, there is a comment that asks if there is an alerting alarm of some sort when an engine falls off an airplane. Is there a direct alarm from the engines specifically saying "You lost an engine" to warn that an engine has fallen off from the aircraft? <Q> This is the indicator that shows you when one engine falls off in a multi-engine aircraft: <S> If the right engine falls, off, the little ball will move left. <S> If the left engine falls off, the little ball moves right. <S> If you only have one engine, or both engines fall off, you need to use a different indicator that looks like this: if both engines fall off, this white pointer will start to move towards the "40", and you might hear an alarm, a voice shouting "stall, stall", or feel the stick shake. <S> if you have one engine and it falls off, the white pointer will move, but in an indeterminate direction. <A> The B-737 has a checklist for engine separation, but no specific alarm for it. <S> The absence of all engine indications might be a hint, though. <A> aircraft work a bit different when it comes to alarms and advice. <S> There is indeed an alarm and an indication of an engine failure. <S> You would notice that the indicators of the respective engine, like Exhaust Gas Temperature (EGT), N1 Thrust and N2 Thrust will all drop. <S> You will also get an EICARS warning (or several), that lead to the conclusion, that indeed an engine has failed. <S> There is yet another indication if there is an engine fire. <S> Along with an alarm the engine fire extinguisher handle will light up. <S> However, there is no indication as of whether the engine has just failed or flamed out or separated. <S> At least not from an instrument point of view. <S> A good pilot however will at least suspect that an engine separation has occurred. <S> For example, if an engine is failing, its indicators are going down slowly. <S> N1, N2, fuel flow, everything is going down slowly until it reaches zero. <S> An engine separation will also lead to a fuel leak, since the fuel will spill out of the pylon. <S> Maybe there also have been engine issues before, like overheating, that led to the failure. <S> On the other hand, if an engine separates, all indicators will go to zero pretty much right way. <S> As all sensors are gone. <S> Usually a missing engine will also change flight behavior. <S> Another way to find out would be the cabin crew or a passenger telling the flight crew. <S> Of course this does only work with wing mounted engines. <S> Aircraft like the Boeing 717, which have tail mounted engines make it impossible for anyone in the cockpit or cabin to notice a separation. <S> In addition, it helps to know what happened before... <S> maybe a sound of an explosion, touching something with the wing, etc. <S> would also lead a pilot to think that an engine could have been separated. <S> but there is no alarm for an engine separation. <S> It will just be an engine failure alert. <S> However, there are indications and signs which a good pilot will recognize to at least suspect the separation.
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So to summarize: There is an alarm for engine failure and engine fire I've never heard of any aircraft with such an alarm, but I don't know about all of them out there.
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What happens if you exceed the maximum speed on a C172? The airspeed indicator has a red marking that means: "never exceed this speed" ($V_{NE}$, around 160 KIAS). Why can't you exceed that speed? <Q> You can, but you have to live with the consequences. <S> There are several things that can happen: <S> Depending on the vertical gusts ahead, you might not even get close to v$_{NE}$. <S> There is another speed limit for gusty weather called v$_B$ , and exceeding this will run the risk of overstressing the wing structure. <S> Going above v$_B$ will overstress the wings in a gust of more than 50 ft/s, and <S> more than 25 ft/s when flying above v$_D$. The exact values can be found in the flight envelope diagram of the flight manual. <S> On a calm day, you can fly v$_{NE}$ and even a little faster, but once you fly fast enough, flutter will become very likely. <S> Note that flutter needs some initial excitation , so you might fly well into the flutter speed range before flutter occurs. <S> When it does, control surfaces will be ripped from their fittings which will make the aircraft pitch up. <S> At that point the wings will break off. <S> The engine on a C 172 is not powerful enough to sustain level flight at v$_{NE}$. <S> You need to dive the aircraft, which requires some altitude. <S> Maintaining the speed will mean that you dive into the ground, so you need to pull out of the dive in time. <S> On really fast aircraft <S> the pitch trim will get more nose-heavy when the aircraft approaches the speed of sound. <S> You don't run that risk in a C 172, but faster aircraft found themselves locked into a dive which they could not end . <A> You can exceed the never exceed speed $V_{NE}$, but doing so will most likely result in damage to the structure. <S> From FAA handbook of pilot knowledge : <S> $V_{NE}$ —the speed which should never be exceeded. <S> If flight is attempted above this speed, structural damage or structural failure may result. <A> Because above that airspeed, the airframe is increasingly likely to fail. <S> Failure would likely start with control surfaces like the ailerons, elevator and flaps, then the wings and tail are likely to separate, resulting in total catastrophic failure. <A> In other words, parts of the airframe - which is critical for controlled flight cannot be guaranteed to perform as designed. <A> There are both aerodynamic and structural reasons for Vne. <S> Aircraft controllability is impacted (for specific impacts on a specific make and model, consult with the manufacturer and perhaps they will share their findings from testing) and you may encounter difficulties with control authority (your ability to move control surfaces), airflow (e.g. the Clark-Y airfoil is designed for its lifting capability far more than it is designed for speed), and you may exceed the structural limits of aircraft components (control surfaces, wing spars, windshield, landing gear.) <S> Operating above Vne now places you in the role of de-facto test pilot and any damage you cause to your aircraft may manifest itself that same flight or many hours later when the results of stresses you induced on the airframe or cables, pulleys etc. <S> cause a failure of the aircraft structure. <A> The answer depends on how much you exceed V_ne. <S> I do not have the information for this particular aircraft in front of me, so I can not say what will happen at a specific airspeed. <S> Cessna spent a lot of money and time on engineering and flight testing to come up with the maximum airspeed (V_ne). <S> There is a safety factor built in to this calculated and tested speed. <S> One situation is flying level at a high altitude, then go in to a steep dive. <S> This may cause an overspeed condition. <S> One of the first problems as a result of overspeed, will start out as a vibration of control surfaces and controls. <S> The chance for loss of control by the pilot due to mechanical failure or metal fatigue will increase exponentially, as does the airspeed. <S> The C172 has airfoil designs meant for low speed. <S> Depending on the exact plane and loading this could differ slightly, but the stall speed is 49 KIAS. <S> With its straight, high lift wing structure, the airfoil may actually completely loose its lift at a very high airspeed. <S> As the airspeed increases, farther above the V_ne, the craft will basically start to tear apart and disintegrate. <A> As stated in another response the stock engine in a C172 isn't powerful enough to sustain Vne in horizontal flight. <S> Establishment of the various speeds is part of the aircraft certification process and usually includes a safety margin of 10 to 15 percent and there are many factors that go into determining these numbers. <S> For example, I have <S> a Beachcraft Baron and one of the important speeds is Vr or V Rotate. <S> It's not that the aircraft cannot take off at a slower speed <S> it's just that if you have a critical engine failure at takeoff power and a slower speed you don't have enough control authority to compensate. <S> There are many factors that go into determining these numbers and structural integrity <S> is just one of them. <A> To add to previous answers, Vne is usually set at near ideal conditions, therefore the 10% - 15% mentioned above really becomes nothing if there are air pockets or other phenomena usually not meaningful, let alone minor fatigue or skin imperfections, hence, as the name implies, never exceed this speed with standard issue airplanes.
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Think of $V_{NE}$ as the speed at or beyond which the structural integrity of the airframe is not guaranteed.
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What is the difference between a leading edge flap and a slat? I always thought that the definition of slat was: "Lift modifying and adjustable wing element on the leading edge of main airfoil." and the definition of flap was: "Lift modifying and adustable wing element on the trailing edge of main airfoil." However, there are also leading edge flaps, also known as Krueger flaps, and they are located on the leading edge. What gives these elements the name of "flap"? What is the main difference to slats? <Q> Slats are leading edge devices on aircraft that enable higher angles of attack. <S> Flaps are devices on the leading (Krueger) and trailing edge which increase camber and the depth of the wing. <S> Both are mainly used in the low-speed situations of take-off and landing. <A> First of all, slats produce a slot (not slat) somewhat aft of the leading edge in order to allow high-speed air from below the wing to pass through and maintain laminar flow to a somewhat higher angle of attack. <S> They are a low-speed device. <S> There are also mid-wing slats which both produce drag and decrease lift and are used to slow down and get down, and, used on one wing at a time, cause roll. <S> They may be used at high speeds. <S> Both trailing edge flaps and LEDs (leading edge devices, be they leading edge Kreuger flaps or slats) <S> increase camber in order to allow the wing to produce the same amount of lift at a lower airspeed (takeoff and landing). <S> They do not increase lift; if they did the aircraft would go up (and slow down rapidly) which is not the point. <A> Not all leading edge flaps are Kreuger flaps, which rotate out from the lower forward wing surface. <S> There are simple hinged leading edge flaps, as well. <S> The example with which I am most familiar is the Chance-Vought F-8 Crusader. <S> The entire leading edge droops simultaneous with trailing edge flap extension -- the inner wing section <S> 25 degrees, <S> the outer section 27 degrees on all US models except the F-8J. Lower stall speed and carrier approach speed are the reward. <S> ref: <S> F-8H NATOPS Manual.
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Slats create a "slat" between the slat body and the wing leading edge so the air can pass from the bottom to the surface to hold off a stall to a higher AoA, flaps merely extend it fore and aft and direct the flow downwards for more lift.
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Is it possible to detect a pitot static failure (blockage) of air data probe during flight and alert the pilot? Loss of static and pitot tubes affect the display of airspeed, altitude, vertical speed information. Loss of this information can be catastrophic for flight. How are the pilots communicated about the failure of these ports (ex: when they get blocked). Or is there a system in place already that detects the blockage and unblocks it. Even if such system exists, what is done to ensure that pilot does not trust the airdata information displayed during the time when the ports are blocked? <Q> The crew checks the pitots and static ports before the flight to ensure they are in good condition and not blocked by objects or insects. <S> Pitot tube (pitot-static) can be obstructed in-flight. <S> Static ports are less affected. <S> Unblock a blocked pitot: <S> In some cases <S> yes: <S> Melt ice or snow by heating the tube in flight, but the tube may be frozen for a minute from time to time. <S> Some pitots are not heated and must be deiced naturally, which will be longer (while cruising in -50°C air, friction prevents aircraft skin to be cold. <S> Concorde skin was about 100°C, meaning air friction just increased its temperature by 150°C). <S> Drain water using drain holes in the pitot. <S> Redundancy for pitots: Yes , two or three exist on most airliners. <S> Alert for blocked pitot: Not a direct alert , since a blocked pitot is not detected, but air data processors compare the different pressure values received from the different pitots, and in case of significant difference alert the crew and disconnect the automated units relying on pitot pressure (like the autopilot). <S> A message is displayed to emphasize that airspeed is unreliable Dangerous ? <S> Yes because if the unreliability of airspeed is not taken into account by the pilot, then stress and inappropriate actions can occur because the aircraft is apparently not reacting to attitude changes. <S> AF447 disaster is sadly a perfect demonstration of the stress that can be generated. <S> If the crew detects correctly the situation, then there is nothing special to do, they just need to continue (manual control) at the same altitude and with the same aircraft attitude until the speed becomes reliable again. <A> Loss of this information can be catastrophic for flight. <S> It is certainly a risk factor, but pilots have to do many mistakes before it really becomes catastrophic. <S> There are procedures to get the plane safely to the ground even without that information. <S> How are the pilots communicated about the failure of these ports (ex: when they get blocked). <S> Failure of the ports specifically, rather than the system as a whole, can't be detected and if it can't be detected, it can't be communicated either. <S> So it isn't. <S> Aircraft with three redundant systems and flight computer have the computer compare the readings and display appropriate message (airspeed disagree, altitude disagree, vertical speed disagree) and sound master warning if it detects mismatch larger than normal measurement error. <S> Or is there a system in place already that detects the blockage and unblocks it. <S> It is not possible to detect the blockage. <S> The only unblocking mechanism is anti-ice, which simply heats the pitot tube to prevent ice buildup. <S> Only the pitot port, which faces forward, can be blocked in flight. <S> The static ports face sideways and are almost impossible to get blocked in flight. <S> Even if such system exists, what is done to ensure that pilot does not trust the airdata information displayed during the time when the ports are blocked? <S> Nothing. <S> Even if the system does detect a fault by comparing the values from the separate system, it does not know which of the systems is wrong. <S> The pilots must decide themselves by combining other information they have and their understanding of physics of flight. <S> They have pitch-power tables and other procedures to diagnose the problem. <A> Some planes are set up with triple redundancy (often found on Airbus planes ) ( source ) <S> In this case the system can reject the bad reading (caused by a blockage or bad probe etc.) by using the data from the 2 other sensors. <S> The basic logic is that if all 3 probes are in agreement (same reading) they are all working. <S> If at any given time one of the probes readings differs from two of the others then the reading is rejected. <S> Of course this does open you up to the issue where two of the 3 probes fail and only a single probe is correct. <S> However the chances of two probes failing and giving the same incorrect reading is low. <S> In modern planes things like GPS and INS units can be used to cross check the system but it will not necessarily be connected to all the same systems. <S> I don't know of any system that unblocks a pitot tube if a physical blockage is present, but if this is in reference to Air France 447, modern airplanes have a heater that can be applied to pitot tubes to de-ice them. <A> In general, unless there is a system in place to specifically detect this, pitot blockages are generally detected through erroneous readings on the instruments. <S> Blocked pitot tubes can generally be spotted with unresponsiveness of the airspeed indicators or display tapes to throttle inputs while holding a level attitude or slower than normal displayed airspeeds at lower altitudes and faster than normal displayed airspeeds at altitudes higher than where the pitot tube became clogged. <S> A little experimentation and cross checking between the Captain’s and FO <S> ’s gauges can quickly determine the faulty system.
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Detecting a blocked pitot or static port: This is not done , but is possible (e.g. send some air from the back of the tube in a pitot, and see if it can exit the tube at a normal rate (which is dependent on several parameters). In smaller aircraft that don't have redundant pitot-static systems (light singles usually don't) and in older aircraft without flight computer it is up to the pilot(s) to spot the problem. The good news is that most large jets have dual pitot static systems, one for the pilot’s displays and the other for the first officer’s.
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Why is New York-London used in time measurement for aircraft? Looking around aviation news and history, I see that many commercial aircraft are touted to have this or that much time fly between New York and London. What caused the route between these two cities to be used in measuring the "speed" of the aircraft? <Q> They are (and historically, were even more so) <S> two of the biggest cities in the business world (ranked Alpha++ ). <S> That specific route has some of the highest rates of business travel and is, therefore, a fairly prestigious, famous route which is popular with fairly wealthy, prestigious people. <S> They are also two of the most famous cities in the world, and most people know roughly where they are on a map. <S> The fact they're separated by an ocean which is large but was just small enough to be possible to cross safely in the early days of aviation also helped, because it gives the impression of being further than it is. <S> For example it's a comparable distance to London-Dubai, but that doesn't "feel" as big due to being overland through Europe. <S> Equally while many people know roughly where Dubai is nowadays, it wasn't anywhere near as famous 30-80 years ago. <A> English speakers read easily left to right. <S> I believe that commercial aircraft pilots and air traffic controllers around the world speak English at least as a second language. <S> The particular route is typically perceived to be longer than many other routes that are the same length yet nearer the equator. <S> Perceptions can be misleading. <S> For instance, on a Mercator projection map, Greenland appears about the same size as Africa, but actually Africa is 14 times the size of Greenland. <A> Once a benchmark is set up, it's usually preferable to add data to it and continue using it, than to create a new benchmark, because it permits a comparison between current and previous samples. <S> So even if the two cities are not the most logical choices now, they were in the past. <A> New York to London is a route which benefits from a strong tail wind - it takes 6 hours (British Airways, in a 777) in that direction, but 8 hours from London to New York.
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I suggest that the particular international air route is used because (1) both countries speak English and (2)
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MD81: Why are there so many lights on the fuselage? Looking at this photo I can see lots of lights on the fuselage of this MD81. It can't be a reflection, can it? Source: Airliners.net Why are there so many lights? <Q> <A> On the fuselage, only 3 per side (discounting the red anti-collision which is above/below): <S> Ground flood aka runway turnoff lights. <S> Leading edge for inspecting the wing and for higher visibility on ground to other vehicles. <S> Nacelle. <S> ( airliners.net ) <S> And here they are from an MD-80 flight manual: <A> I'd say they're reflections. <S> You can see the reflection of a building or something like it on the fuselage, and if you look close enough, you can see the poles of the 2 first lights. <S> Also most of them are at or near the windows' corners. <S> There aren't any housings or mounts to lights on those spots.
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I think they are reflection from some light posts in the background environment (green line above the blue "horizon" light), and the reflection of the wingtip position light.
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Where can I get aviation weather information? Where can I get weather information (preferably something similar to what pilots get) for a non-pilot? I usually use flightradar24 for flight tracking, would love to see weather data as well. <Q> NOAA collects <S> METAR s (current weather) from all over the world and publishes them at http://weather.noaa.gov/pub/data/observations/metar/stations/ . <S> They also collect TAF s (forecasts) and publish them at http://weather.noaa.gov/pub/data/forecasts/taf/stations/ . <S> These reports are what the information told to pilots by controllers or broadcast in ATIS is based on, written in shorthand format designed for efficient transmission over teletype. <S> If you look around the directory structure, there are also decoded versions. <S> The above links are complete, but intended more for machine consumption, being plain text files. <S> You'll find many other sources that look more like normal web pages if you google for some airport code and “METAR” or “TAF”, but different parts of the world will be available at different places. <S> The above links are most comprehensive source. <A> The Aviation Digital Data Service (ADDS) is an excellent source for aviation weather information within the US. <S> This website is free and completely open to non-pilots (as opposed to 1800wxbrief , for example). <S> The other pages include many other useful weather products, including forecasts, pilot reports, and satellite or radar images. <S> As a pilot, this is a website that I use frequently, and have used throughout my career. <S> To a non-pilot some of the products may seem incomprehensible, but the website does provide help pages . <S> Perhaps most importantly for a non-pilot, many of the coded textual products are available in a decoded, normal language format. <A> You can also search in your state, or a specific airport using this site <S> https://www.faa.gov/air_traffic/#weatherWidgetContainer <S> It pulls up a map and a list of airports and their automated info type, example of the first 3 of 20 entries for MA <S> Automated Weather Observing System <S> (AWOS) Automated Surface Observation System (ASOS) https://en.wikipedia.org/wiki/Automated_airport_weather_station <S> KBED <S> Bedford Middlesex <S> MA <S> ATIS - 124.6 (781) 274-9733 <S> ASOS KBVY <S> Beverly Essex <S> MA <S> ATIS - 119.2 (978) <S> 921-5042 <S> ASOS <S> KBOS <S> Boston Suffolk MA <S> ATIS - 127.875 (617) 567-5762 <S> ASOS <S> I carry the list of numbers for my state in my flight bag so I can call from on the road and see what conditions are like nearby, along with a call to Flight Service (1-800-weather) for the broad picture and NOTAMS, etc. <A> Since you are asking as a non-pilot, I would highly recommend this particular site that I use for every single flight that I make, it is Sky Vector . <S> Not only does it provide METARS and TAFs , it provides graphical depictions of: TFRs DROTAMs PIREPs <S> SIGMETs <S> AIRMETs <S> It also provides graphical depictions of MRMS Weather Radar , IR4 Satellite and Cloud Top Heights. <S> Besides all of the weather services, you can plot a flight plan and overlay enroute hi and low IFR or VFR charts as well as selected sectionals. <S> I have sent several of my simulator-only pilot friends to this website for fast, accurate and up-to-date weather information and flight planning. <S> FOr non-pilots <S> it has all of the same weather information that we pilots use but in a nice, graphical format that is easy to readn and understand.
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The METAR page gives up to date weather observations for airports throughout the US.
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Why is angle of attack information not displayed in the cockpit? Would not it be useful to have the angle of attack information displayed on the flight display? I know that we have shakers that alert pilot when the critical AOA is exceeded, but still we have cases of pilots stalling the aircraft (sometimes stalling one wing more than other).I am sure designers have considered this but not chose to display AOA. I am curious what the reason could be. <Q> For example a modern 737: <S> A Garmin G1000 (one of the more common General Aviation glass cockpits): Specifically the part that looks a bit like this <S> And a more traditional analog/mechanical gauge: <S> The problem is that usually when someone stalls, it's because they've made a mistake - <S> not because they can't see the AoA. <S> Either they're disorientated, or they've made a mistake with airspeed or an obstacle and are exceeding the aircraft's performance envelope. <S> Typically, the lack of an AoA dial isn't the reason you stall. <A> Slightly off-topic, but I recently came across the "side string" which gives a direct reading of AoA. <S> Every gilder pilot is familiar with the yaw string , but in two years of learning to fly gliders, I'd never heard anyone mention the side string. <S> Now, in the ultralight / open-cockpit world they use a single piece of yarn mounted on a stick, which acts as a combination yaw and side string. <A> It strongly depends on the aircraft we're talking about. <S> As an example, this is the Head Up Display of an F/A-18 <S> "Hornet": <S> The number near the α is the angle of attack (AoA or α) measured in degrees. <S> I presume that only in certain conditions knowing the exact value of the AoA may turn out to be useful (when nearing the limits maybe...). <S> Usually, exceeding the maximum AoA is a the result of a mistake, not the mistake itself. <S> Fly-By-Wire systems usually do not allow the pilots to exceed the max AoA (Airbuses' Alpha Floor for instance) during normal operations. <A> As others have noted many aircraft do have AOA indicators. <S> Military A/C tend to have them next to the HUD on the left side. <S> The advantage using AOA over stall speed is that the stall AOA is constant while the stall speed depends upon weight. <S> Greater weights = <S> > <S> lower stall speeds. <S> This difference will be important when there are large differences in A/C weights. <S> If your F-18 has 4x2000lb bombs <S> the stall speed is much different depending upon whether those bombs are dropped or not. <S> With your average cessna, the weight change of the A/C/ does not change the stall speed significantly. <S> An AOA indicator does not provide as much value relative to its cost and weight.
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Many aircraft do include them, because it's very useful.
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When should a pilot use the word "takeoff?" I've been taught before that the word "takeoff" should only be used when reading back a clearance, and that when requesting a clearance pilots should advise "ready" or "ready for departure." Here's the really critical point to the question. I've always believed that the word "takeoff" should only be used when reading back a clearance for such an action . Not when requesting a clearance for that action. I've also heard it taught that this is true only for IFR flights but it's okay to ask for a clearance with the word "takeoff" when VFR. I don't see why the difference between VFR or IFR flight would be a factor here. Has the ICAO, FAA or any other controlling organization released any written guidance on radio communications that covers this procedure? <Q> "Departure" should be used in all other circumstances, and as far as I'm aware whoever told you you could use the word Takeoff for VFR was wrong. <S> Anybody saying the word "takeoff" intends for an aircraft to enter, accelerate along, and then leave a runway in the immediate future: never anything else. <S> Anybody saying otherwise should be immediately directed to the Wikipedia article for the Tenerife 747 disaster . <A> ICAO Doc. <S> 4444 specifies standards for ATC communication. <S> " <S> DEPARTURE" is used for taxi-ing etc, and "TAKE-OFF" is used when actually taking off. <S> In Europe, this EASA guide specifies much the same thing. <A> There's no definitive FAA statement one way or another that I could find. <S> Outside the US and per ICAO, "take-off" is only used when accepting a take-off clearance and you should use "departure" in other situations. <S> There's nothing I could find about departure vs. take-off phraseology in the P/CG or AIM . <S> The ATC orders 4-3-1 do mention it, in the context of clearances: 4−3−1. <S> DEPARTURE <S> TERMINOLOGY Avoid using the term “takeoff” except to actually clear an aircraft for takeoff or to cancel a takeoff clearance. <S> Use such terms as “depart,” “departure,” or “fly” in clearances when necessary. <S> The AIM uses "departure" in its examples but makes no comment about avoiding "take-off" and an FAA runway safety publication doesn't have anything to say about it either. <S> AOPA has an article (from 1999, admittedly, so perhaps it's now considered outdated) <S> that says that pilots can use "take-off" to tell ATC they're ready: <S> When you're ready for takeoff, use the same "who, where, and what" format for your initial call to the tower - " <S> Anytown tower, Trainer zero-zero-zero-zero-Yankee , ready for takeoff Runway three-three." <S> That phraseology is commonly used at my local airport in the US <S> but it would be a major no-no in South Africa, where I learned to fly. <S> And Jon's answer is based on UK experience (only because it's in his profile), so it looks like an ICAO vs. US thing, at least to some extent. <S> And indeed, ICAO document 4444 uses the word "departure" as part of "preparation for take-off", and "take-off" itself for "take-off clearances" (see sections 12.2.4.10 and 12.3.4.11). <S> 12.2.4.10 says that pilots only need to say "ready" to inform ATC that they're ready for departure: "Tower, N12345 is holding at 18, ready". <S> It doesn't address uncontrolled fields, but the usual call I was taught was "N12345 is departing runway 18". <A> "Take-off" indicates to others on frequency that a potentially high-risk operation is about to be undertaken by another aircraft, which they should take a special interest in for situational awareness and conflict management. <S> Procedures vary by field, but standard ICAO phraseology (or equivalent for the jurisdiction) should be employed for all the radio telephony. <S> Assuming the aircraft is waiting on a taxiway at the active runway, a typical notification to the tower that the crew are ready to depart might be: Some Tower. <S> Speedbird Niner Juliet. <S> Holding runway 27 left, ready for departure. <S> Typical responses from the tower would be: <S> Cleared for takeoff [runway], wind [...] . <S> The aircraft is cleared -- at the crew's discretion -- to taxi onto the designated runway, apply power and lift off. <S> Runway [identifier], line up and wait. <S> Cleared to taxi onto the designated runway, DO NOT commence take-off roll, await further instructions. <S> (Delays typically for spacing / sequencing, conflicting traffic movements, departures taking place behind arriving aircraft, ...) <S> No immediate action. <S> The aircraft cannot enter the active runway for some reason, so continues to wait at the hold-short line until further instructions or clearances are provided. <S> At some fields, it may not be necessary or desired to provide an indication of departure readiness. <S> Ground may provide such indication on the pilot's behalf and advise at switchover to simply monitor the tower frequency. <S> Non-standard RT phraseology does often creep in. <S> I sometimes hear either "[Callsign] rolling", "rolling [runway identifier]" or a combination announced upon commencing the roll. <S> This is particularly the case if there has been a delay between issuing the take-off clearance and the departure commencing. <S> It's a courtesy and notification to others on the field or in the pattern to watch out for the metal about to be thrown along the tarmac at high-speed. <A> The ICAO Common Taxonomy Team defines take-off as : From the application of takeoff power, through rotation and to an altitude of 35 feet above runway elevation. <S> This phase of flight includes the following subphases: <S> • <S> Takeoff. <S> From the application of takeoff power, through rotation and to an altitude of 35 feet above runway elevation or until gear-up selection, whichever comes first. <S> • <S> Rejected Takeoff. <S> During takeoff, from the point where the decision to abort has been taken until the aircraft begins to taxi from the runway. <S> So, the term 'takeoff' should be used only if the intention is to acclerate, rotate and leave the runway. <S> Use of takeoff in any other sense would result in confusion, with potentially dangerous consequences.
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The word "Takeoff" should only be used when clearing somebody for takeoff, acknowledging your takeoff clearance, or cancelling/acknowledging a cancelled takeoff clearance.
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How does pregnancy affect airline pilots operating under FAA regulations? Female airline pilots have an area of medical concern that male pilots don't deal with: reproductive issues. If a female airline pilot operating at an air carrier in the United States of America under the Federal Aviation Administration (FAA) were to become pregnant, how would this affect her standing with a first class medical and in general with operations at most airlines? <Q> I'm not aware of any FAA regulations that prohibit pilot ing during pregnancy. <S> The closest it comes is in <S> 14 CFR § 61.53 - Prohibition on operations during medical deficiency , which says (noting that pregnancy is not a medical deficiency in any way and the regulation is taken here in the widest sense) <S> that: (a) Operations that require a medical certificate. <S> Except as provided for in paragraph (b) of this section, no person who holds a medical certificate issued under part 67 of this chapter may act as pilot in command, or in any other capacity as a required pilot flight crewmember, while that person: (1) Knows or has reason to know of any medical condition that would make the person unable to meet the requirements for the medical certificate necessary for the pilot operation <S> As long as the pilot feels that she is medically fit and has a valid medical certificate, they can't be legally prevented from flying the aircraft. <S> In case of other regulattions (like EASA), pregnant women are not allowed to pilot after 26 weeks of pregnance. <S> For example, UK Aviation Authority says: (c) <S> Pregnancy (1) <S> In the case of pregnancy, if the AeMC or AME considers that the licence holder is fit to exercise her privileges, he/she shall limit the validity period of the medical certificate to the end of the 26th week of gestation. <S> After this point, the certificate shall be suspended. <S> The suspension shall be lifted after full recovery following the end of the pregnancy. <S> (2) Holders of class 1 medical certificates shall only exercise the privileges of their licences until the 26th week of gestation with an OML. <S> There are a number of medical issues that the pilot should be aware of while pregnant, so that appropriate measures could be taken, like, Ability to move the controls to their full extent. <S> Ability to wear seat belts. <S> Effect of high altitude operation on the foetus among others. <S> The airline policy will vary and they have to consider a number of other conditions- for example, the ability of flight crew to egress during a crash etc. <A> Here is a decent article from AOPA on the matter (covers the topic from an FAA/USA standpoint). <S> Looks like legaly they dont have to say anything and they cant legally be pulled <S> The law is on their side, too. <S> In the early 1990s, the U.S. Supreme Court ruled that unless a woman voluntarily disclosed her pregnancy to her employer, she couldn't be switched out of her job to one that carries less risk to her fetus. <S> Essentially this means that a woman has the right to decide when to declare she is pregnant to her employer, and to stay in her position even if it may cause harm to the developing fetus. <S> It also seems like the regulations vary from airline to airline, <S> Few airlines today ban first trimester flying (from the time of conception through the first 12 weeks of pregnancy). <S> Most, along with the military, permit flying through the second trimester (24 to 28 weeks) during an uncomplicated pregnancy. <S> A few companies have no written policy and handle their pilots' pregnancies and leave issues on a case-by-case basis. <S> The article goes on to cover most of the topics related to this pretty comprehensively and is worth a read. <S> Of course there are some general medical concerns that any mother should take into account. <A> This is not specific to aviation, and I don't know the rules for countries other than Germany. <S> I was just starting to argue about radiation doses, but this turns out not to be an issue in most cases: An average pilot / FA receives a dose of about 2 mSv / year (worker in nuclear power plant: 1mSv/y). <S> An embryo / fetus is not allowed to collect more than 1mSv during the entire pregancy. <S> This would not happen if the much larger mother collects 2mSv in one year, but there are still special precaution requirements. <S> For example, the received dose has to be measured weekly instead of monthly. <S> But our law gives even more. <S> For example, after the 3rd month, a pregnant woman is not allowed to work on any means of transport, which an aircraft definitely is. <S> And in general, pregnant woman are not allowed to do a job where they have to lift / push / move weights over 5kg permanently or 10kg occasionally. <S> Due to this laws, pregnant women have to be grounded immediately, no matter what the airline says. <A> I am a pregnant pilot with an ATPL in Australia where we are allowed to legally fly until the end of our 30th week. <S> I'm currently at my 27th week and definitely still feel fit to fly, I just had <S> my Class 1 medical Renewal and my Doctor said he would be more than happy to sign me off to fly for longer but the CASA regulation is firm. <S> I myself still feel fit to fly and am lucky that I have crew that load bags and do the heavy lifting so to speak.
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As long as the pilot is having a first class medical, her pregnancy should have no effect on the operations, at least legally, though the regulations differ from country to country.
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How do you know if a VOR is High, Low, or Terminal? Is there any way of telling on both a VFR and IFR chart what type of VOR we are looking at? <Q> Typically terminal VOR's do not have compass roses around them if they are strictly terminal VOR's. <S> I can't find an example of one <S> so I don't have an image for it. <S> Edit <S> I found an example: <S> Source: <S> SkyVector <S> The DEN VOR has no compass rose, so its either a terminal VOR or they omitted the compass rose for clarity. <S> There are two other VOR's in close proximity, MILE HIGH on the North East side of the field and Falcon to the east of Buckley AFB. <S> According to AirNav NavAid Info its a high VOR. <S> As far as high/low VOR, one way to tell is to look at the High/Low enroute IFR charts. <S> For example, here is a portion of a low-enroute IFR chart: <S> Source: <S> SkyVector <S> You can see two VOR stations on here labeled Minot Intl and Devils Lake Rgnl with a victor airway between them (V430). <S> Here is the same area from the high enroute <S> IFR chart: <S> Source: <S> SkyVector <S> You can see that the VOR symbol around Devils Lake Rgnl has disappeared and (although its difficult to see) the VOR symbol has also disappeared. <S> NavAid Website lists DVL (Devils Lake) as a LOW VOR and also lists MOT (Minot International) as a HIGH VOR . <S> There is no differentiation between the VOR high/low symbols on a VFR chart because low altitude VOR's can serve aircraft up to 18,000 feet where you would need to file an IFR flight plan anyway, so all VOR's regardless of high/low are available to VFR flights. <S> Putting it another (technical) way is that high/low VOR's have the same service volume for VFR and low-enroute IFR flights, so they do not need to be distinguished on VFR or low-enroute IFR charts. <A> The range of the VOR is included in the Airport/Facility Directory data. <S> High altitude VORTAC: <S> ( Source ) <S> Low altitude VOR DME: ( Source ) Terminal VOR DME: ( Source ) <A> From the chart you can understand what type of VOR is that <S> But there are also other ways . <S> There are basically two types of them and they are Terminal VOR(TVOR) and Airway VOR. <S> The whole VOR frequency range is VHF-108 to 117.95MHz. <S> ILS frequency shares some portion of the TVOR. <S> TVOR frequency band are from 108.00 to 112.00MHz. <S> In details, TVOR uses even first decimal and even first decimal <S> +50KHz upto 112MHz. <S> Like 108.00MHz, 108.15MHZ, 108.20MHz, 108.25MHz etc and the ILS uses odd first decimal and odd first decimal <S> +50KHz upto 112.00MHz. <S> Like 108.10MHz, 108.15MHz,108.30MHz, 108.35MHz etc. <S> Airway VOR uses the remainder of the frequency band 112.00MHz to 117.95MHz. <S> other than this <S> you can understand the VOR type from the chart the people has already shown.
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The terminal VOR are mainly of low and the airway VOR are mainly of high type. By checking the frequency band you can also understand the type of that VOR.
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What are these grilles in the passenger cabin of this 787? Below the windows, ahead of the seat, there are small grilles. Look: Source: Airliners.net What are those for? <Q> The answers to this question indicate that these are the exhaust vents for the cabin air circulation. <S> I think they appear to be much too large for just that purpose. <S> I don't have a technical reference for this, but I believe those vents also prevent the cabin floor buckling in the event of a sudden pressurization failure. <S> The cargo hold is beneath the passenger cabin, and both are pressurized because the cylindrical hull can resist pressure better than the flat cabin floor. <S> If the cabin suddenly loses pressure the air in the hold could buckle the floor upward, or if the hold loses pressure the air in the cabin could buckle the floor downward. <S> The floor must be generously vented to prevent this. <S> US patents # 6129312 and # 5137231 claim systems for combining the cabin air circulation vents with the depressurization relief vents. <S> From the '9312 patent: <S> An air return grille mounted below the passenger cabin sidewall comprises openings to allow return airflow from the air conditioning system. <S> The grille openings are covered by a single thin baffle with cutouts within its periphery that slip over and are held in place by fasteners on the molded grille. <S> During normal operation, the thin baffle restricts flow through a small opening in the grille. <S> During a sudden decompression of the cargo compartment, the baffle is dislodged from the fasteners. <S> This allows the airflow to pass through all of the molded grille openings in order to achieve rapid pressure equalization. <A> In the architecture lingo, the dado is the lower part of a wall below the dado rail . <S> The grille portion of a passenger aircraft wall is called the dado module. <S> It consists on a louvered air grille over a decompression panel (sometimes called the dado panel) which can be open or closed. <S> Boeing patent for a decompression panel, source <S> The cargo compartments on a pressurized aircraft are not always fully heated, but they are always pressurized, being part of a single pressure vessel (a cylinder sealed by two bulkheads ). <S> Air from the packs (conditioning system) enters the cabin usually from the ceiling and leaves it by the dado modules, e.g. (A320): <S> Cabin air distribution, source <S> Airbus <S> There are recirculation ducts in the cargo section with fans drawing air from the cabin. <S> Air is then reconditioned and sent back to the cabin. <S> A fraction is dumped overboard though the outflow valves to regulate pressure in the aircraft. <S> In case of decompression <S> In case of rapid decompression in a cargo area, there is a risk of cabin floor collapsing due to the pressure difference above and below it. <S> This happened in 1972, as @krmezljavKuza mentioned. <S> The related NTSB investigation report included this recommendation: <S> Require the installation of relief vents between the cabin and aft cargo compartment to minimize the pressure loading on the cabin flooring in the event of sudden depressurization of the cargo compartment. <S> The decompression panels open to act as pressure relief vents and allow a larger quantity of air to flow into the cargo compartment. <S> Pressure can equalize before the floor is damaged. <S> There are similar decompression panels in the triangle areas indicated in the picture above, between the different sections of the cargo level. <S> There are also louvers in various panels, e.g. lavatory doors. <A> As far as I know, the design feature stems from two consecutive accidents with the DC-10, American Airlines 96 on 12 June 1972, and Turkish Airlines 981 on 3 March 1974. <S> Though the cause of both of these decompressions was a poorly-designed (and poorly-maintained) cargo door, in both cases, the real damage was caused by the collapse of the cabin floor, which severed control cables, and on Turkish Airlines, broke hydraulic lines. <S> After these accidents, the grilles were added to equalize pressure and prevent the floor from collapsing. <S> The floor itself was also strengthened. <S> If I remember correctly, one of these accidents was the subject of an episode of Air Crash Investigation. <A> Air Crash Investigation S7E1 "Shattered in seconds" about China Airlines flight 611 on 2002-05-25 <S> (decompression due to fuselage rupture caused by a faulty repair after a tail strike on 1980-02-07) mentions dado panels and an accident with a Turkish Airlines flight in 1974 (together with reconstruction footage of that accident), and it is said that the Turkish Airlines accident led to a NTSB recommendation about adding more dado panels to the cabin. <S> All of this is in sum a good indication that there also is an episode about that particular crash.
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The grilles are almost certainly meant to equalize pressure between the cabin and cargo bay, particularly in case of rapid decompression.
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How can I get General Aviation flight data on smartphone and/or tablet? Is it possible to in-flight receive navigation data on an electronic device (like smartphone and/or tablet) present in the cockpit?I refer to General Aviation aircraft and navigation data like airspeed (not groundspeed), GPS and AHRS data. <Q> Garmin has a product called Connext that allows you to stream in-flight avionics data to mobile devices. <S> They are pushing that product as a move towards connected components and a "Bring your own device" approach to cockpit automation. <S> So is it possible in general to receive it? <S> No, not really. <S> Not unless the avionics package was designed to broadcast it out. <S> The other side of it is that if you are a passenger you still probably won't be able to pair with the avionics. <S> Connext allows you to modify the flight plan via a mobile device, and I'm not sure I would want any of my passengers doing that. <S> On top of that, pilots are trained to interpret the data at hand, you don't want a passenger seeing a faulty artificial horizon after a vacuum failure and think that the aircraft is tumbling out of the sky. <S> There is a lot of security concerns as it is over being able to hack into commercial aircraft (I know you are talking about GA), but I still don't want a passenger to have the ability to connect to my avionics. <A> EDIT: <S> This answer applies to large commercial aircraft. <S> As a normal passenger? <S> No. <S> As @mins said, this data is captured, processed, and displayed within the aircraft's avionics system, but this data is not available to passengers (it's not transmitted outside the avionics system). <S> When aircraft are being developed and the manufacturers perform flight tests, then they will install special gateways into the avionics, allowing the test engineers in flight and on the ground to monitor aircraft parameters outside the cockpit - but this equipment is removed long before aircraft are sold to an airline. <S> The best you can do is to use your own sensors - e.g. the GPS on your phone, a separate accelerator/gyro module - to generate your own position and attitude data. <S> However, it will have a worse accuracy than the aircraft-level sensors, and there are certain parameters (e.g. airspeed) which you won't be able to obtain. <A> Yes but only with certain avionics. <S> Avidyne recently released an SDK that allows third party developers (tablet/smart phone) to interface with their IDF440 and 540 units . <S> There are two levels of access (read only and read/write) that an app can have for the data stream.
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As other answers have said, a simple GPS and AHRS integration of the sensors in your tablet/smartphone can give a pretty good approximation of the data you are asking for, but things like airspeed, navigation waypoints, and other on-board sensor data are not generally available without a product like Connext.
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For calculating $V_{stall}$, why should be used $C_{L,max}$ and not $C_{L,min}$ (that would be more prudent)? Premise: In level unaccelerated flight we have relation $W=L=\frac{1}{2}\cdot\rho\cdot V_{stall}^2\cdot S\cdot C_{L,max}$ (taken from book Daniel P Raymer "Aircraft Design: A Conceptual Approach" equation (5.5) at page 85). Question: Why $C_{L,max}$? Why not $C_{L,min}$? In fact in case the $C_L$ in use is not $C_L,max$, and speed is little more than $V_{stall}$ (valued for $C_{L,max}$), it happen that Lift is not enough and anyway stall happens on aircraft. If using $C_{L,min}$ the calculation is more cautious. <Q> The stall speed is the speed at which you can still fly the plane in level flight . <S> This is important, because strictly speaking, stall happens at a certain angle of attack, not at a certain speed. <S> In other words, you can safely fly a plane way below stall speed - the problem is that you'll be doing it nose-down in order to keep the angle of attack to a minimum (and that as such you will quickly exceed the stall speed again - hey, we just did a stall recovery maneuver!) <S> So, let's see what happens when we approach stall speed from a higher speed, while flying level. <S> As we slow down, we must increase our angle of attack to maintain level flight - this way, we are increasing the $C_L$ of the wing, as to keep the lift $L(=W)=\frac{1}{2}\rho VSC_L$ constant when reducing our $V$. Ideally, we'd like to keep increasing our $C_L$ as we reduce our $V$ - however, this means we keep increasing our AoA (angle of attack) until it gets past a critical point, where the airfoil stalls due to flow separation at the suction side of the airfoil. <S> So really, using $C_{L,min}$ would be nonsensical - if your wings would have a lift coefficient so low at such a low speed, I can guarantee you that $W> <S> L$, i.e., you plummet from the skies. <S> We need to increase our $C_L$ to maintain level flight, and the stall speed is exactly the point where we can no longer increase our $C_L$, or in other words, we arrived exactly at $C_{L,max}$. <A> There are multiple stall speeds that have been defined. <S> For example, the 14 CFR §1.2 Abbreviations and symbols lists the following stall speeds: <S> $V_{S}$ means the stalling speed or the minimum steady flight speed at which the airplane is controllable. <S> $V_{SO}$ means the stalling speed or the minimum steady flight speed in the landing configuration. <S> $V_{S1}$ means the stalling speed or the minimum steady flight speed obtained in a specific configuration. <S> $V_{SR}$ means reference stall speed. <S> $V_{SRO}$ means reference stall speed in the landing configuration. <S> $V_{SR1}$ means reference stall speed in a specific configuration. <S> $V_{SW}$ means speed at which onset of natural or artificial stall warning occurs. <S> In short, as $V_{stall} \propto \sqrt{\frac{1}{C_{L}}}$ , $C_{L_{max}}$ gives the minimum speed at which the aicraft is controllable. <S> Consider an aircraft in a level flight, If the pilot wants to reduce the speed, in order to maintain a steady, level flight, he/she has to increase the angle of attack i.e. increase the $C_{L}$ . <S> He can do this till the $C_{L}$ <S> reaches $C_{L_{max}}$ , where the speed becomes minimum while the aircraft is still in a steady, level flight. <S> If the speed is reduced any further, the aircraft loses lift; this speed gives the stall speed of the aircraft. <S> You can get the stall speed for any configuration by using the $C_{L}$ at that configuration; but the values have to be realistic. <S> Setting the $C_{L}$ to very low values to get large <S> $V_{stall}$ makes no physical or practical sense. <S> For example, the aircraft can be set to have zero (or even negative) $C_{L_{min}}$ , in which case, the stall speed has no meaning. <A> In the equation $W= <S> L=\frac{1}{2}\cdot\rho\cdot <S> V_{stall}^2\cdot S\cdot C_{L,max}$ <S> the goal is to find minimum flight speed which can produce lift equal to weight. <S> This speed varies in different configuration but the minimum would be at maximum angle of attack producing $C_{L,max}$ (lift coefficient). <S> The lift coefficient is a function of angle of attack, airfoil and wing geometry. <A> The general equation during level unaccelerated flight is <S> $L=\frac{1}{2}\cdot\rho\cdot <S> V^2\cdot S\cdot <S> C_{L}$ <S> : <S> For a variety of speeds V between the stall speed and the Never Exceed speed. <S> For a variety of altitudes, between under sea level and the stratosphere. <S> For a variety of Angle of Attack of the aeroplane, equating to a range of $C_L$ Resulting in a variety of lift forces <S> L. <S> There are three independent variables in the one equation, chose all three and the lift will be found, choose the lift and two others and the third one will be found. <S> This latter thing is what Raymer is doing. <S> He sets lift to weight W for steady unaccelerated flight; he sets $C_L$ to $C_{L,max}$ ; and he then finds the minimum speed <S> $V_{min}$ <S> that the aeroplane can fly with at a certain altitude. <S> Note that for normal level unaccelerated flight $C_L$ is always > 0. <S> The minimum $C_L$ is a negative value for negative AoA, and would mean that the aeroplane is flying upside down.
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What you're asking is the $V_{S}$ , the minimum flight speed at which the airplane is controllable.
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Why don't we get more user-friendly weather reports than METARs? This question is not about how to decode METARs or what software or tools can be used to decode METARs. It is about why we are still using METARs today. Given that we have smartphones with video messaging capability, cloud services with machine learning today, I struggle to understand why we are still reading METARs: It is difficult to read. Sure it is not hard to learn, but the fact that you have to learn it means it's not intuitive It is designed at an age when text are transmitted by telegraph and every character counts It is trivial to program a parser and render more friendly messages For me I always feel that METARs are meant for machines; there has got to be something better for pilots which happens to be human. Instead of having this on my flight plan: KSFO 111456Z 16015KT 9SM RA FEW012 SCT030 OVC070... Why not just: Station: KSFO Time: Mar 11 14:56 UTC Wind: 160 degrees, 15 knots Visibility: 9 statue miles Weather condition: rain Clouds: few at 1,200 feet; scattered at 3,000 feet; overcast at 7,000 feet ... The problem is not about decoding them. Most pilots can read them, and by the time a new pilot completes his PPL training he should have no trouble reading either. The point is everybody around the world is reading them, today, in the 21st century! I don't know if I'm the only one, but processing the METAR string during flight prep takes a couple of instruction cycles away from my brain (and I have a tendency to check whether the software got it right if I happen to be using one, so I will be processing it anyway, which is a good habit I suppose). I am sure some of that brain power can be better spent somewhere else: reading section charts, route planning, picking an alternate, etc. Scaling this to the global scale? It means every pilot is paying more attention to other things, as opposed to reading coded weather strings which really is the job of a machine. The result? Better flight safely. So, why haven't we began the move? <Q> For that purpose, METARs are user friendly in the sense that they are expert friendly. <S> For example, a friend invited me to fly with him today on an Angel Flight mission that would have required a landing at Nashville. <S> We had to scrub because the weather is unfavorable and not getting any better according to the TAF and ADDS METAR Data : <S> Data at: 1616 UTC 11 Mar 2016 KBNA 111553Z <S> 36006KT <S> 1SM <S> R02L/4000V6000FT -DZ BR <S> OVC005 14/12 <S> A3024 RMK AO2 DZB51 SLP239 P0000 T01390122 <S> $KBNA 111541Z <S> 35005KT 1SM BR OVC005 14/12 <S> A3024 RMK AO2 SFC VIS 1 1/2 <S> $KBNA 111527Z <S> 01006KT <S> 2SM BR OVC005 14/12 <S> A3022 <S> RMK AO2 SFC VIS 2 1/2 <S> $KBNA <S> 111453Z 02008KT <S> 3SM <S> BR OVC005 14/12 <S> A3021 RMK AO2 SLP227 <S> T01390122 53015 <S> $KBNA 111451Z 02007KT <S> 3SM <S> BR OVC005 14/12 <S> A3021 RMK AO2 $KBNA 111434Z 01007KT <S> 2SM BR <S> OVC004 14/12 A3020 <S> RMK AO2 $KBNA 111353Z 02007KT 5SM BR <S> OVC004 14/12 <S> A3019 RMK AO2 SLP219 T01390122 <S> $ A subsecond scan confirms that the low overcast ceiling is stuck at four to five hundred feet AGL for the past several hours. <S> Try outdoing that using the same information in decoded METAR format . <A> If it ain't broke... <S> For what its worth many new aviation apps like ForeFlight and the such display the information in user friendly formats. <S> ( source ) <S> To be honest I have not decoded a METAR in some time. <S> You are correct that the system comes from a time when transmission bandwidth was not what it is today. <S> Keep in mind things in aviation are slow to change and many other nations also report weather in the METAR format so its useful to know how to read one if you fly abroad where they don't have the kind of infrastructure and applications we have available here in the US. <S> Since official bodies like NOAA and the FAA broadcast METARS <S> its far easier for a company like ForeFlight to parse and display what they can already get than try to make the government change the format. <S> I would love to see a broadcast of the METAR data in easy to read JSON format.... <S> There are some packages out there for dealing with them in software if you need to. <S> There is also something to be said for a format that can easily be transmitted over various communication mediums. <S> While morse code is not that popular anymore and most things are broadcast digitally <S> the METAR format would still allow the information to be transmitted as is, in the event one of the more modern systems failed. <S> Since the question has been edited a bit ill expand my answer to reflect. <S> While it has been pointed out there are some quick things that can be determined from reading them in their current format there is no information that is planed to be added to them <S> so there is no reason to change (or expand) the format. <S> A great deal of infrastructure exists around producing and decoding them as is, which would be a large task to overhaul and in the end produce nothing different than what exists now. <A> Because the METAR format is standardized and a large number of systems know how to read and process them. <S> Lots of applications consume METAR data, from weather websites to ACARS terminals in cockpits to pilots' brains. <S> An application can read in METAR data from many stations and use it to produce, say, a map of winds across a region or a graph of temperatures over time. <S> This all works because everyone has a common understanding of the format, and there are a number of code libraries for major programming languages that assist in generating and parsing the METAR format. <S> If you change the format to be human readable, all of that breaks. <S> As with many popular standards, changing it would require the immediate global cooperation of everyone at once. <S> It makes far more sense to keep the METAR format as it is (or to extend it with new elements to accommodate new reporting needs) and build tools to present the information in user friendly ways, as ForeFlight and many others do. <A> Other answers have addressed some of the reasons why the METAR transmission format should stick around. <S> I'll add that there is a lot of machinery in place that would be expensive to replace in order to make such a change, so it wouldn't happen even if we wanted it to. <S> If something was going to change, it could be to eliminate the testing requirement that all new pilots are able to read and interpret METARs. <S> So it's dubious reasoning to assert that a person cannot be a competent pilot unless they can interpret a METAR without assistance. <S> Useful skills should be trained, but only skills and knowledge required to be competent should be tested.
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As has been pointed out, there are many applications both for devices and on the web that can translate them for you, including aviationweather.gov. There really is no reason to change the format since most places you get the METAR from decode it for you anyway these days. One use case where the compact METAR format is tough to beat is rapidly scanning meteorological trends.
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How can I find out the best time to practice within towered airspace? I would love to practice within towered airspace (approaches, touch and goes, ect.) However, I do not want to upset operations within the airspace. What is the best way to determine when the best time to practice these maneuvers would be? Should I contact both the tower and TRACON? <Q> Simplest answer: Call the tower. <S> Or ask instructors/schools in the area if the controllers care when you arrive and want to practice. <S> Usually if you arrive during the busiest time, you'll likely be accommodated as best as they can, but there's a chance you could be told to just do a full-stop taxi-back operation if that helps out or told to go fly around elsewhere for a bit. <S> It depends on what airport you're thinking about going to. <S> If you want to go to ATL, well, you'll be vectored in a gap, and told go as fast as you can for as long as you can, and be told to land(or if you go around, expect a long delay to find a new gap). <S> If it's just a general aviation airport, anytime is fine. <A> I did most of my training at a towered airport in Class D airspace ( KPNE ). <S> Running laps in the pattern when no one was around did not really build up my communication skills with the tower as they basically would just clear you for the option every time. <S> When there were other planes in the area they might extend a leg of your pattern or have you do a 180, and these scenarios were better practice in my opinion. <S> Crowded radio frequencies also keeps you on your toes and gets you better practice (especially if there are some similar tail numbers in the area). <S> You will not be upsetting operations by any means. <S> ATC is there to handle you and frankly it's always good to practice being diverted (if that's what happens) in a busy airspace so you will know how to handle it when you get out on your own missions. <S> Class C/D space airports generally run a lot of large private traffic and some scheduled carriers. <S> I found that KPNE and KABE (if I wanted to practice in class C) were heavier later in the day and early in the morning as would be logically expected. <S> But to be honest there were plenty of times a bunch of planes would come in all at once mid day <S> and it would be quiet the rest of the day. <S> If you are a student pilot (you did not say in your question) you can identify yourself as such when entering the airspace and when getting on with the tower. <S> In most cases it will make them a bit more forgiving if you ask for an instruction repeat or don't understand something. <A> I did all my training in the NYC area from airports with towers. <S> KMMU and KCDW. <S> There was no such thing as a good time (other than 2am to 5 am). <S> For my first solo, I was number 14 to land. <S> Both of those airports share the same approach control frequency as KEWR. <S> If you want to do an approach, you had to do it in traffic. <S> You'd be the only person doing the LOC or ILS at KMMU/KCDW <S> but you'd be sharing the frequency with non-stop approaches to KEWR. <S> I'd suggest getting some training with an instructor at a busy airport with a tower.
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From my experience there is no "best time" (although there are times when the airspace is more empty) and for what it's worth I found it better to train when the airport was busy as it offered me the chance to practice some real world scenarios.
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Why does the Falcon 900 have anhedral wings? Why does it have anhedral wings and not "normal" wings? Many other similar aircraft with low-wing have dihedral wings. Source: DassaultFalcon.com Edit: This is about the Falcon 900, which apparently has a low-wing design and it's not used for cargo like the An-225 <Q> For the same reason why the Lockheed F-104 <S> Starfighter had such a pronounced anhedral <S> : It is the size and location of the vertical tail. <S> Lockheed F-104 <S> Starfighter (picture source ). <S> In both cases, the vertical tail is large relative to the wing and fully above the roll axis. <S> In a sideslip it produces a high rolling moment, so any more rolling moment from the wing would reduce the handling qualities of the aircraft. <S> Especially in case of the F-104, the raised position of the horizontal tail shifts the center of pressure on the vertical tail upwards, exacerbating the offset location of the vertical tail. <S> The rear-mounted engines on the Falcon 900 move the center of gravity backwards, so the wing is more backwards than usual for aircraft with wing-mounted engines. <S> Therefore, the part of the fuselage ahead of the center of gravity is large, requiring a larger vertical tail to overcome the destabilizing yawing moment of the fuselage. <S> The same is true for the Tupolev 134 and 154 , and - surprise! <S> - they also have no dihedral, even though both are low-wing configurations. <S> Tupolev 154M of the Polish Air Force <S> (picture source ) <A> Picture source <S> It may seem so when on ground, but in flight the wings flex up. <S> Judging from the photo, the wings seem to have the tiniest bit of dihedral. <S> They also have wing sweep, which provides sideslip-to-roll stability as well. <A> It's because anhedral wings remove one of the biggest disadvantages of dihedral wings - maneuverability. <S> But anhedral wings don't come with such a problem.
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Although dihedral wings give roll stability by pushing up on the wing which is lowered while banking, it also means that whenever the pilot is rolling to one particular direction, the wings have a tendency to oppose that by rolling the aircraft to the opposite direction, giving the aircraft reduced maneuverability.
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Is is possible to land a midsize commercial plane on an Ford Class aircraft carrier? I'm story-boarding a novel. I'm toying with the idea of contriving a situation in which a midsize commercial aircraft is forced to make an emergency landing on an aircraft carrier. I read here that the largest plane to land on an aircraft carrier is a C130 Hercules, which it did as a series of tests. Its maximum weight when performing these tests was 121,000 lbs. At this weight, it required only 460 feet to land. And it did so without use of a tailhook, or any other arresting mechanism. The brand new Gerald R. Ford class carrier is 1,106 feet long. The landing strip on the carrier is somewhat shorter. I couldn't find numbers on this, but from photos, I would estimate that the landing strip is a little more than 800 feet long. Which leads me to my first question: In an emergency situation, could an aircraft use the full length of the aircraft carrier's deck to land? Assuming the answer to the above is yes, this means that our commercial aircraft has somewhat more than twice the distance to make its landing than the C130 did. Let us assume that the commercial aircraft is a B737 Classic, weighing aobut 140,000 pounds, just a little more than the C130 did during the tests. This leads me to my main question: Could a 737 Classic safely make an unarrested emergency landing on a Gerald R. Ford Class aircraft carrier? By safely, I mean without any passenger death. I expect that any such landing attempt would result in significant damage to the aircraft and the carrier. On one hand, the numbers seem to suggest that if a C130 can do it, so could a B737. On the other hand, I would expect that the C130, as a military aircraft, is more robust than a commercial aircraft, and perhaps able to better meet the conditions required to land on a carrier. Also, I realize that in an emergency situation it may be safer for the aircraft to make a water landing near the carrier, and then for the passengers to evacuate onto inflatable rafts, finally to be brought aboard shortly thereafter. I will have to invent a situation which requires the plane to land on the carrier. <Q> A classic 737 MAX landing weight is about 114,000# for a -300, less for a -500, more for a -400. <S> But that is max. <S> Down to "almost empty" gas tanks, knock another 8 or 10,000# off of that. <S> Less than full pax/cargo load, several more thousand pounds off. <S> With a stiff breeze, say 20 knots, plus the carrier at max speed, you have maybe 50 knots of headwind. <S> With that sort of headwind, can you stop a mid- to light-weight 737 in 1000' using full flaps, max reverse, and max brakes? <S> I don't have the charts with me, but I suspect you totally could, and in fact it wouldn't even be all that close. <S> No margin for error if equipment fails, but if everything works right, those jets can stop quite well. <S> And 50 knots on the beak is a LOT of headwind... "groundspeed" over the deck would be like 60 or 70 knots, and you can lose that in a lot less than 1000'. <S> I've flown <S> C-130's and 737's, and the rate of descent on an assault landing in the Herk is nothing the 737 couldn't handle. <S> So... <S> carrier landing... <S> good to go? <S> Not so sure. <S> Compared to carrier aircraft, the 737 wingspan in WIDE -- even for the "little" -500. <S> That limits where you can plan your rollout so that you don't have an unacceptably high risk of clipping the island. <S> Without playing with scale drawings of a 737 and the Ford's deck, I couldn't even guess if or how the geometry would or wouldn't work out. <S> Alternate plan that is probably no more risky for the passengers and might be a LOT safer for the carrier: ditch your (nearly out of fuel) <S> jet close to the carrier, and have the carrier's helos and the small boats of the battle group pull the survivors off the wings or out of the water. <S> With calm water, you get a "Sully" scenario (except with wings filled mostly with air, rather than jet fuel... <S> Better buoyancy). <S> In rough water, the risks go up. <S> Way up. <S> But in that sort of weather, the deck landing gets lots more risky as well. <S> I suspect the deck landing would neither be allowed nor requested, but not for reasons of stopping performance. <A> B737-500 required landing runway requirement is around 975m, while 300/400 model needs longer. <S> Although actual landing runway requirement is 3/5 of required landing runway requirement(dry) <S> (FAA standard), Ford Class does not have such a long runway. <S> On the other hand, Boeing had proposal to develop T-43 Carrier Onboard Delivery. <S> If Boeing won the USN contract, we may see B737-200 landing on aircraft carrier. <S> More details can be seen here . <A> In addition to the other posts: it depends on how much notice the carrier has. <S> The C-130 landed on an empty deck; during normal operations the edge of the flight deck is lined with aircraft. <S> This goes double if you decide to use the full deck length instead of just the landing area. <S> The bow area is often used for parking. <S> So in order to land a 737, you need to launch pretty much every aircraft that's currently on deck (which can be ~50 depending on what the carrier is doing at the moment). <S> Launching 50 aircraft takes a while: a carrier can launch 4 planes/minute maximum, and that's if everything has been lined up just so <S> beforehand, every aircraft already has fuel and crew on board, etc..
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Without modification of b737, it is not likely for a b737 to land on a Ford class carrier.
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Does adding flaps during ground roll perform better in short-field takeoff? In most POHs, the flap configuration for short-field is usually recommended as partial flaps, for instance 10˚ for C172. I remember the arguments are that full flaps would reduce the acceleration rate, and in no flaps the airplane would have to accelerate to higher speed to off the ground. In either case, the ground roll distance is longer than the optimal partial-flap configurations. However, this assumes a fixed flap setting during ground roll. How about let the airplane accelerate to a certain speed (in zero flaps) before adding to full flaps? We could achieve best acceleration as well as best lift-off speed? <Q> I found this answer is a good analysis. <S> 13.3 - Obstructed-Field - Skimming versus Wheelbarrowing or Flap-Popping " Another possible procedure (which is usually not recommended) is to keep the flaps retracted until you are ready to leave the runway. <S> Less flaps means less incidence. <S> A big disadvantage is that “popping” the flaps like this increases your workload at a time when there are lots of other things you should be attending to. <S> Another disadvantage is that you run the risk of extending the flaps past the takeoff position to the landing position, creating lots of drag, which is really not what you want in this situation. <S> If your POH calls for this procedure, go ahead, but be careful. <S> Make sure you have some sort of detent to block inadvertent over-extension. " -- John S. Denker, See How It Flies <A> Flaps have the dual function of increasing lift and drag. <S> When they are fully extended, the drag greatly outweighs the extra lift. <S> So whilst you might have a slightly shortened takeoff run (though I doubt that there is a significant reduction in a C172), you could very well struggle to clear any obstacles. <S> And not forgetting that the takeoff distance required is defined as the distance to climb to 50ft, climbing out on full flaps could actually increase this distance. <S> You might be tempted to say you should extend the flaps just in time to rotate, then retract them immediately once airborne. <S> Retracting flaps at such a low speed and altitude is incredibly risky. <S> Plus this is a lot of extra work for the pilot at an already critical phase of flight. <S> Always follow the POH - it's written by the folks who know the aircraft and its performance better than anyone. <A> Yes. <S> But only partial flaps will help; full flaps are almost always a poor choice for takeoff. <S> What you describe was the standard operating procedure for the Messerschmitt Me-262 s in the JV 44 . <S> Due to the low thrust at low speed it had a very long takeoff run, and to operate from short airfields designed for propeller aircraft and hastily repaired after attacks it needed to employ this technique. <S> Note on the picture below the small deflection angle, however: This only worked well when the takeoff run was made with zero flaps and then takeoff flaps (not full flaps!) were added shortly before rotation. <S> The downside was the risk of an overshoot in case the flaps failed to deploy. <S> If your airfield is long enough, it is certainly safer to set the flaps at the beginning of the takeoff run. <S> Me-262 <S> two-seater replica taking off (picture source )
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In most aircraft, using the smaller flap setting provides extra lift with only a bit of the drag.
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How long does it take to refuel a big jumbo jet? How long does it take to refuel a big jumbo jet? And what about a smaller A320. I'm talking in terms of time. <Q> This figure from the 737 Airport Planning document gives 9 minutes for the fueling time for a Boeing 737-600: <S> Image from B737 Airplane characteristics for Airport Planning <S> The following image shows the time taken for refueling a Boeing 747-8 Jumbo to be 44 minutes: Image from B747-8 Airplane Characteristics for Airport Planning <A> It depends on how many equipment are being used to refuel and how much fuel an aircraft needs. <S> But in general there are some ratings which manufacturers issue for handling and ground time. <S> For example, a B747-8 has (according to 747-8 Airplane Characteristics for Airport Planning ): <S> maximum usable fuel capacity of about 59,734 U.S. gallons or 226,113 liters 8 fueling nozzles max fueling rate of 500 US gpm (1,890 lpm) per nozzle total max fuel pressure 50 PSIG <S> Therefore, in theory it's possible to refuel an empty B747-8 to its maximum usable fuel capacity in 15 min with all 8 nozzles. <S> In normal refueling configuration two trucks (one truck each wing) being used which serves 4 pressure nozzle and takes 30 min to refuel 56,553 US gallons. <S> So standard fueling time for this aircraft estimated about 50 min. <S> For A320-200 <S> though these ratings are (according to Airbus A320 airplane characteristics for airport planning ): <S> maximum usable fuel capacity of 6,303 U.S. gallons or 23,859 liters <S> 6 fueling nozzles max fueling rate <S> 369.84 US gpm (1,400 lpm) per nozzle total max fuel pressure 50 PSIG <S> And the estimated fueling time is about 15 min refueling 6,303 U.S. gallons using one truck serving two nozzles. <A> I worked for a long haul airline with 744s departing South East Asia to Europe. <S> The airplane usually required 120-140 metric tonnes of fuel for the trip back. <S> There would usually be around 15-20 tonnes left from the previous sector and you would usually require around 30-40 minutes to fuel 100-120 tonnes. <S> This is using two pumps, one on each wing. <S> The problem was if you needed to fuel up to max which was around 170 tonnes (depending on the fuel density), the last 10-20 tonnes took longer to fuel. <S> This was rare though. <S> Since we only had slightly more than an hours ground time we had to board while fueling was in progress. <S> There is an SOP for this, basically a door had to be open at the rear and a set of steps positioned, we usually used door <S> 5L. <S> Also passengers were told not to fasten seat belts, crews were required to be at their stations and most importantly a firetruck had to be standing-by at the stand. <S> We had to pay for the firetruck call-out but on-time <S> departure was more important. <A> According to this article, it generally takes about 1-2 hours to fuel a large jumbo such as an A380. <S> As for smaller jets, the second answer to the Yahoo! <S> question says that Southwest Airlines claims to be able to turn a plane around in 20 minutes. <A> Most aircraft do not have empty tanks when being refuelled, and rarely fill their tanks to capacity. <S> Aircraft are fueled by flight parameters - so they need x gallons of fuel to reach their destination plus y gallons to reach a specified alternate in case of emergency plus a reserve of z gallons. <S> In this way, the plane weighs less on take off and the company saves money on fuel conservation.
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Given that the Southwest fleet is made up entirely of 737s, a jet such as the 737 or A320 should take about 15-20 minutes to refuel. It depends on a number of factors like: the aircraft size and variant the range required the aircraft load equipment available Ground crew proficiency ...among others things.
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Do large airliners have a short-field landing technique? Other than extra braking and reverse thrust, is there a specific short-field landing technique for large jet airliners? In discussions about the famous landings at St Maarten , it is sometimes said that part of the reason for the low passes is due to the relatively short runway, so the 747s try to land right on the numbers, rather than the usual technique of touching down within the first third of the runway. Such a procedure is fine in a Cessna, but in a large passenger jet? I have my doubts. <Q> Other than extra braking and reverse thrust, is there a specific short-field landing technique for large jet airliners? <S> Never heard of any. <S> The required landing distance is calculated so that the plane can reliably stop (even if reversers fail) and landing at shorter runway is not allowed. <S> so the 747s try to land right on the numbers, rather than the usual technique of touching down within the first third of the runway. <S> The usual technique is to aim for 1,000 ft down the runway and touch down with some flare somewhere around 1,500. <S> In discussions about the famous landings at St Maarten, it is sometimes said that part of the reason for the low passes is due to the relatively short runway, so the 747s try to land right on the numbers <S> Actually the TNCM runway 10 has PAPI and TDZ marking a little beyond the usual 1,000 ft mark at around 1,250 ft. <S> Ourairports says the threshold is displaced 162 ft (but it also says runway 9, so it is likely out of date), but according to the satellite images it is a bit over 300 ft plus some runway end safety area, placing the threshold around 500 ft past the fence and the touch-down zone around 1,750 ft past the fence. <S> Now the normal glide-slope is around 5%. <S> That means the aircraft is supposed to cross the fence at around 90 ft, on average . <S> That seems about right. <S> Of course you can't expect every aircraft to be positioned precisely within a few feet, so now <S> and then some crosses it at maybe 50 ft. <S> That is not intention, but simply a deviation. <S> But of course the photos of planes flying especially low are more likely to be picked for publishing. <S> Also, a short field landing normally calls for steep approach which make precise aim for landing spot easier. <S> That would actually place the aircraft higher over the beach. <S> But the glide-slope at TNCM is normal 3° (5%) one, so it is not a steep approach. <S> Such a procedure is fine in a Cessna, but in a large passenger jet? <S> I have my doubts. <S> In large jet it isn't. <S> Air transport has stricter regulations than general aviation because more is at stake and larger aircraft have stricter limits because the higher energies involved mean errors are harder to fix and have more serious consequences. <A> I'm not aware of any short field landing techniques for large commercial airliners. <S> But some of the do offer some modifications , that offer improved short field performance. <S> Most of these modifications are aimed at operating the airliners at the Santos Dumont airport, which has a short runway. <S> According to Boeing, The short-field design package is an option on the 737-600, -700 and -800 and is standard equipment for the new 737-900ER. <S> The enhancements increase payload capability for landing up to 8,000 pounds on the 737-800 and 737-900ER and up to 4,000 pounds on the 737-600 and 737-700. <S> This is mainly done using a few modifications, which can be factory ordered or retrofitted and include the following changes : Flight spoilers are capable of 60 degree deflection on touchdown by addition of increased stroke actuators. <S> Slats are sealed for take-off to flap position 15 (compared to the current 10) to allow the wing to generate more lift at lower rotation angles. <S> Autoslat function available from flap 1 to 25. <S> Flap load relief function active from flap 10 or greater. <S> Two-position tailskid that extends an extra 127mm (5ins) for landing protection. <S> This allows greater angles of attack to be safely flown thereby reducing Vref and hence landing distance. <S> among others. <S> Around 250 of these modified aircraft are in operations till date. <S> Not to be outdone, Airbus offers similar options in its A320neo . <A> They’re 150ft long. <S> Landing on the numbers in a transport category jet would fail any checkride. <A> I would argue there is nothing in the books specifically called ‘short landing technique’ as any landing in a jet is already designed to be as short as possible. <S> Then it becomes a ‘normal landing technique’. <S> Sure, if you have many 1000’s meters to spare, you might occasionally go for a greaser and land longer than usual. <S> Generally speaking though, the shorter your flare, the safer it is; more runway left to slow down, maybe reducing the need for reversers or easing up on the brakes so as not to heat them as much. <S> In that sense, a normal-SOP-landing on a transport jet is already a short-landing-technique.
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The short field technique in any jet is to perfectly hit the touchdown zone marker which is 1,000 feet down the runway.
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Why doesn't condensation form on the inside of airliner windows? If outside the aircraft is pretty cold and inside the cabin the air temperature is different, why don't the windows become fogged up on the inside? <Q> The humidity at the altitude airliners fly at is VERY low. <S> However, a tiny bit of moisture does build up - if you look closely you'll see little ice crystals on the window (it's also very cold up there - in the negative degrees F usually). <S> Also, if you look at the windows - they are often two or three layers with quite a bit of space separating the outside of the window from the inside (often multiple inches). <S> Some of this is for pressurization and some of this is for thermal insulation. <S> The VERY cold outdoor air is not in direct contact with the inside cabin pane. <A> Double glazing. <S> The gap in between the panes has very little moisture in it, so there is nothing to condense on the outside pane. <S> There is no condensation on the inside pane because of the temperature gradient between the panes. <A> Outer window panel is pneumatically isolated from the outsife, it is a pressure window , the second and third inboard windows are primarily there for thermal and acoustic insulation. <S> Condensation (frost) forms on the inside of the outer pressure window because there is a pneumatic pathway to the cabin and passenger breath contains water vapour which becomes attached to this surface during the flight.
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On top of that - airliners have multiple air conditioning "packs" that dehumidify the cabin air so there would be indeed by very little moisture to condense on the inside of the windows.
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What should I wash my plane with? What should I wash my airplane off with? As a new aircraft owner, any help would be appreciated. I am pretty sure using dish washing detergent is not the best here as we are told not to use the stuff on our cars. <Q> We could all offer opinions and product recommendations in response to this question. <S> However, the best answer is: in accordance with the manufacturer's instructions. <S> Since you ask the question generically, without any information on what aircraft you might have, I will answer generically. <S> Your manufacturer's instructions can generally be found in at least two places: the owner's manual/AFM and the maintenance manual. <S> For example, in the owners manual for a 1975 Cessna 172M, you will find Section V: Care of The Airplane containing instructions on how to wash painted surfaces, bare aluminum surfaces, interior surfaces, and the windscreen and windows. <S> The maintenance manual for the same aircraft contains nearly—if not exactly <S> —identical information in chapter 2. <S> Now, for that aircraft and others, Cessna recommends use of mild detergent in certain applications; you might not find that overly helpful in choosing what to use. <S> The airframe that I fly for work has tens of thousands of hours on it, and while I cannot vouch for how often it was washed in the past, I try to wash parts of it <S> a few times a week. <S> There is no apparent washing damage to the paint. <S> I will also highlight Cessna's instruction to use Stoddard solvent on areas of stubborn oil or grease; this can be especially helpful in cleaning the belly with it's typical collection of oil and dirt. <S> If the manufacturer's instructions are not clear, or are otherwise insufficient to answer your question regarding your specific aircraft, I would recommend asking your maintenance professional. <S> He or she should have both the knowledge and experience to steer you in the right direction. <S> For more insight into the world of aircraft cleaning, and especially for the specific product recommendations you want, you might take a look at this AvWeb article by Kim Santerre: Aircraft Cleaning . <A> Wash it just as you would your car. <S> Soap and water. <S> Of course, be sure not to clog up static ports with anything. <A> Water and with little soap mixed in. <S> Don't get crazy with cleaning solutions. <S> I think I used just a little bit of Dawn. <S> DO <S> NOT WASH YOUR PLANE TOO OFTEN AND AVOID PRESSURE WASHING!! <S> Too-frequent washing will cause water will to work its way into the wheel bearings and accelerate corrosion. <S> I washed mine a few times a year but dusted it frequently. <S> The only routine cleaning I did was bug removal. <S> I also gave the belly a once-over with Goop hand cleaner (no pumice, of course) and that worked magic on the exhaust, oil, grease, and hydraulic fluid stains. <S> I had to make a few passes but it was worth the effort. <S> The paint looked new! <S> Spot cleaning was simple after that. <S> Goop should be a staple on every hangar! <S> Use soap and water or plexiglass cleaner on windows and lense covers. <S> Never use windex or other harsh cleaners. <S> I used plexus to clean bugs from the wings as well.
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My practice is typically to wipe down the belly with solvent first, and then follow with a water and detergent wash. You should wash your aircraft in accordance with the manufacturer's instructions. Based on my research and experience, and time honored practice that I've observed, Dawn dish soap is widely used for cleaning painted Cessna aircraft with no apparent long term harmful effects.
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What are the pros/cons of ram air turbines? Commercial aircraft are equipped with ram air turbines that can be deploy to provide power in case all other sources of power are lost. Ram air turbines have the benefit of providing power as long as the aircraft is moving through the air. However, aircraft are almost always designed with internal generators, driven off of the engines. There is a limited case of adding generators to older aircraft . But they are also used to power large accessories, like the jamming pods on the EA-18 Growler . The EA-6B, which the Growler replaced, was also a modified attack aircraft using jamming pods with ram air turbines. Larger aircraft that are modified for the electronic warfare role don't seem to go this route though. Obviously the turbine will add drag, and it seems like internal generators are more efficient, since almost all aircraft are designed to generate power that way. So my question is: what are the benefits or drawbacks of using ram air turbines to generate power? While they are generally saved for emergencies, what makes them more useful in cases like jamming pods, compared to other options? <Q> You have kind of answered your own question. <S> The down side to ram air turbines is they cause drag. <S> The up side is that they provide power outside the internal generating capacity of the aircraft (e.g., in emergencies when there is no power). <S> In the case a of a jamming pod, having its own power source eliminates/reduces the need to rely on internal power. <S> That makes the pod modular. <S> If the pod did not generate its own power, there would need to be a generator inside that sits there regardless of whether the pod were attached. <A> I made a comment on TomMcW's answer , but I think it deserves to be an answer: <S> I think the answer lies in your question: The EA-6B , which <S> the Growler replaced, was also a modified attack aircraft using jamming pods with ram air turbines. <S> Emphasis and links mine If they were designing an electronic warfare aircraft from scratch, I'm sure that all the electronics would be powered by generators driven by the main engine(s). <S> These engines would be sized to provide appropriate thrust for the expected mission profile and have excess capacity to provide power for the electronics. <S> However, since they are modifying existing aircraft for a new role they've found there is not enough excess capacity in the existing engines for the expected flight regimes and electricity generation, so dealing with the extra drag from the RAT is a cheaper and more expedient alternative than re-engining the the <S> FA-18 (or the A-6 before it). <S> Also, the cables needed to bring the power from the generator to the wing station must be added, and in tightly packed combat aircraft the space might not be there to add the wiring later. <S> The RAT-driven pod only needs to be hooked up to a communication bus and brings its own power, so it can be designed once and used in a variety of aircraft. <S> Multi-function displays in the cockpit just need a software upgrade, and the aircraft can perform reasonably well in its new role. <S> Addressing the recently added text about larger aircraft not needing the RAT: The <S> E-3 Sentry (for example) is powered by the CFM56-2 producing 18,000-34,000 pounds of thrust while the 707 it was based on was powered by the P&W <S> JT3D-3B <S> produced only 18,000 pounds of thrust. <S> Per Wikipedia , the E-3 used CFM56-2A-2 version producing 24,000 pounds of thrust, thus it had the power for its normal flight regime plus power to spare for all the extra electrical demands of its electronic warfare role. <A>
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Another advantage to a RAT as opposed to using the engine powered generator is that it reduces the requirement for bleed air so the engines can be more efficient and responsive.
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Can the landing gear be pulled up while the plane is on the ground? If a pilot makes a mistake and inadvertently touches the gear up lever, will it actually activate while on the ground and make the plane drop onto its belly? I suppose that there would be some sensor to prevent this, but I would like clarification on that. <Q> This sensor prevents gear retraction while the plane is still on the ground. <S> Failure of this sensor would prevent gear retraction after takeoff. <S> If you note closely, the landing gears (even the non-retractable ones) are not connected using a simple metal pole; rather, there is an oleo strut which is compressed by the weight of the aircraft. <S> Besides airborne / ground detection, the struts absorb the vertical energy during touchdown. <S> I recall some decades ago engineers experimented obtaining the plane's gross weight by installing weight scales to each landing gear (as opposed to just an air/ground detection). <S> The readings were found to be inaccurate and they soon abandoned the idea. <S> Landing gear stories cannot be complete without mentioning this incident in 1990: <S> A training captain of a Saab 340 was betting with his students that the weight-on-gear mechanism would prevent gear retraction while on the ground. <S> On the accident airplane type, the mechanism would lock the gear handle, but the lock can be overridden if the pilot manually pull out and move the handle. <S> The instructor confidently pulled out the handle and to his surprise, the hydraulics started to move and the gears were retracted while the plane was still on the ground. <S> ( image source ) <S> The aircraft was written off. <S> This incompetent instructor pilot was killed 11 years later in another accident . <A> This incident was "half on ground" during takeoff: <S> Last year, the copilot of a Dash 8 applied erroneously the gear lever during takeoff as the rear gear had still ground contact. <S> This resulted in a tail strike. <S> The aircraft bounced back on runway 9 of Saarbrücken's airport, slipped some hundred meters and will be written off as well. <S> See the report of the German aviation authority , pages 60-76. <S> It turns out that the Dash 8 has a weight-on-wheels sensor only on the front gear. <S> The report says that the design responsible called this to "comply with the design logic". <S> Differently from the incident @kevin mentioned, the gear doors were already closed as the fuselage touched ground. <A> Safety standards have improved since the 1940s, but soon after a £1m restoration project on a WWII Spitfire, somebody blocked the runway at a local airport by demonstrating this design flaw. <S> Apparently the pilot got confused about which of two levers retracted the flaps, and which retracted the landing gear. <S> The accident happened just before sunset, so I don't think there are any good pictures available on the web that show the damage. <S> http://www.bbc.co.uk/news/uk-england-leicestershire-22474805 <S> https://assets.digital.cabinet-office.gov.uk/media/5422ed3640f0b6134200014f/Vickers_Supermarine_Spitfire_MK_XIX__G-RRGN_5-2013.pdf
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There is a weight sensor which senses if the plane is on the ground.
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What is the reference used when measuring flight speed? I'm a physicist who was amused by the argument in the comments of this question about gravity . The correct answer about the affect of the accelerating reference frame of the plane on the apparent gravity depends on how the airliner's speed is measured. I know very little about practical aviation. When I'm on a trans-Atlantic flight moving 900 km/hr, with respect to what am I moving? Is that my speed relative to the ground (which is also moving)? relative to the local atmosphere (which could be additionally moving due to wind)? relative to some imaginary, absolute grid hovering above the Earth's surface? relative to the "fixed stars"? This is probably a duplicate, but I can't seem to find the right search terms... <Q> Speed of a plane is actually measured in a number of different ways, and relative to different things. <S> Here is a summary of the different types: Indicated Airspeed (IAS). <S> This is the number shown on the instrument that measures airspeed, and isn't really relative to anything. <S> Rectified Airspeed (RAS) or Calibrated Air Speed (CAS) <S> This is IAS corrected for known errors in the instrument and the measurement system. <S> True Air Speed <S> This is the speed relative to the air around the aircraft; usually found by correcting the RAS for pressure and some other errors. <S> Ground Speed <S> This is the speed relative to the ground, or a fixed point on the earth ('imaginary grid). <S> Its the vector addition of the True Airspeed (and direction) plus the wind speed (and direction). <S> In olden days this was estimated from the Airspeed and the wind velocity, or through dead reckoning navigation, but now it is trivially found from GPS or other navigation aids. <S> Planes use different ones of these for different purposes. <S> Measurements relative to the fixed stars are not generally useful until you are in the realm of space travel. <A> There are multiple speeds referred to in aviation, some of which are not 'speed' in the traditional sense. <S> Indicated airspeed (IAS): <S> This is a measure of dynamic pressure and not actual speed, measured using the pitot-static system (i.e. difference of the total and static pressure). <S> It is a function of density and airspeed, not speed alone. <S> Usually, the critical speeds are given in terms of IAS as the aircraft behaves similarly in same IAS. <S> Calibrated Airpseed (CAS) <S> : This is nothing but the Indicated airspeed corrected for instrument and position errors- still not an actual speed. <S> True airspeed: <S> This gives the speed of the aircraft in relation to the sorrounding airmass. <S> This is the speed used in the flight planning (before taking into account wind, that is) and for measuring aircraft performance. <S> This is the speed with respect to the local atmosphere. <S> This cannot be measured without an external instrument and usually, measured with GPS. <S> As far as air travel is concerned, speeds relative to stars are not used, as there is no need for such complexity. <A> I will try to add some information to the previous questions, which are correct. <S> My intention is to provide you physical meaning, but previous answers are essentially correct. <S> When discussing reference frames where the speed is usually provided I will essentially summarize in 2: <S> The upstream speed is measure here (as the air approaches the airplane in this reference frame) and has been mentioned before as best approximation as " True Airspeed " (the other are measured and calibrated speeds). <S> Ground reference: is the reference located at the ground, usually located just below the airplane. <S> That's " Ground Speed ". <S> If you would like to know further about reference frames in the airplane, there are more reference frames (or variations of the previous one): <S> Body reference: just intermediate step to define other systems I am coming back to this one. <S> Is located in the center of gravity, the x axis goes along the fuselage from cockpit to tail, z axis along gravity. <S> Stability reference: is the body reference rotated along y axis to make the external air speed component in the z direction 0. <S> It is usually used to define angle of attack and compute stability of the trajectory. <S> Wind reference: is the stability reference rotated along z axis to make the air speed in this reference only in x direction. <S> Formally this is where lift and drag are defined. <S> (Notice that in body reference you are propulsed by aerodynamic force at the vertical tail plane. <S> :)) <S> Also, sideslip is defined as the rotation of axis system. <S> I have seen some literature defining lift and drag in stability reference. <S> I have seen in structural context to define another reference frame, <S> x as in body reference and y axis along the wing as in body reference. <S> This system is different to Body reference when turning, and used to compute the load factor. <S> It is very common to assume that the airplane is quasi-stationary, so <S> no acceleration assumed in the frame except for highly precise calculations (or the load factor).
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Ground speed: This is the speed of the aircraft with respect to the ground and as such akin to the speed of the car. Airplane reference (aka body axis): is the ideal reference frame attached to the airplane (not usually considering acceleration, but in practice should be done).
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If there was an engine malfunction, could we breathe contaminated air? If the engine on airliners has for example, an oil leak, can the oil or other substances contaminate the air on the passenger cabin? How would this situation be avoided? <Q> Yes, an malfunction in a jet engine can cause contaminated air to reach the passenger cabin. <S> It is a rare occurrence, but it does happen. <S> One of the most famous cases was British Midland Flight 92 on Jan 8th 1989 in Kegworth England. <S> Kegworth air disaster <S> "After taking off from Heathrow at 7:52 p.m., Flight BD 092 was climbing through 28,300 feet to reach its cruising altitude of 35,000 feet when a blade detached from the fan of the port (left) CFM International CFM56 engine. <S> While the pilots did not know the source of the problem, a pounding noise was suddenly heard, accompanied by severe vibrations. <S> In addition, smoke poured into the cabin through the ventilation system and a burning smell entered the plane ". <S> In addition to contamination from engine failures, there is a much more public debate over contamination due to perceived weaknesses in the design of the aircraft cabin air systems. <S> These weaknesses have not been positively identified but many believe it is due to faulty engine seals and/or air conditioning packs. <S> There are numerous reports of pilots, flight attendants, and passengers feeling ill from "toxic air" on aircraft. <S> The name "Aerotoxic Syndrome" is also used to describe the problem of bad air in aircraft. <S> More information here: Aerotoxic syndrome <S> Here is a website dedicated to Toxic Cabin Air. <S> Toxic Cabin Air <A> Jet engines on airliners take some relatively low pressure bleed air from the front stages of the compressor in order to feed compressed fresh air to the cabin and to power other items. <S> This air is as fresh as the outdoor air. <S> Note that when a commercial airline starts engines on the ground at an airport with a significant tailwind then the engine can ingest some of its own exhaust and <S> therefore upon occasion as a passenger you can smell the odor of kerosene. <S> If an engine is shut down in the air for some reason then no pressure is generated and other engines on the plane will supply the compressed air to the cabin. <A> The air pressurization is provided by the "packs" (air conditioners), which are in turn powered by the bleed air (hot air extracted from low stages of the turbine) of the engine: To avoid the problem, bleed air is shut when engine trouble is confirmed or suspected. <S> For example, the Engine Fire checklist for the Boeing 737 calls for: <S> [Autothrottle]... <S> Disengage <S> [Thrust lever]... <S> Confirm... <S> Close <S> [Engine start lever]... <S> Confirm... <S> CUTOFF ... <S> [ISOLATION VALVE]... <S> CLOSE [PACK switch]... <S> OFF <S> With one engine out, the cabin air is provided by the bleed air of the other good engine. <S> With a dual bleed shutoff (or failure), you better get down right away.
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Yes, it is possible for contaminated air to enter the cabin.
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Is it always advisable for passengers to wear seat belts when a 747 is on final approach? I noticed in this recent video that some of the passengers are not wearing their seat belts. I realize this is not a typical commercial flight, but is it advisable to wear seat belts when a 747 or similar aircraft is flying so close to the ground, (apparently) during a final approach? Or are the safety precautions here so thorough that it's not actually necessary in this case? <Q> This is especially true for aircraft on takeoff, landing, in low level flight, or in any other flight regimes that are especially prone to turbulence or other risk exposure. <S> A large, heavy aircraft—such as a B747 —will be less affected by wake or mechanical turbulence than would a smaller aircraft—such as a CRJ200 or a C172 . <S> However, even large, heavy aircraft can be subjected to severe turbulence that could result in injury or death if passengers are not restrained by appropriate safety belts. <S> Additionally, for flights conducted under 14 CFR 121 —which I am confident is a majority of the US operated passenger flights involving the B747 (though not, obviously, Air Force One pictured in the question <S> above)—passengers are generally required to: 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> Excerpted from 14 CFR 121.311 (b) <A> It is, of course, advisable to wear your seat belt, yes. <S> However, there appears to be somewhat of a tradition of not always wearing seat belts on Air Force One: Stanley B. Greenberg, Dispatches from the War Room: <S> In the Trenches with Five Extraordinary Leaders ( Google Books ): <S> Nobody wears seat belts and everyone uses their cell phones while the plane is taking off. <S> Presumably the crew would provide a special warning if they expected a rough ride. <A> Don't worry about what Obama does in particular . <S> It's always advised to wear seat belt whether you are in Boeing 747 or other small planes. <S> According to this Telegraph.co.uk article: "Seat belts are required and designed to ensure passenger safety and reduce the risk of injury, particularly during deceleration, turbulence and unplanned or difficult to predict events.” <S> And later on in the same article: <S> Last year, severe turbulence caused three EasyJet crew members to “hit the ceiling” over Italy, according to a passenger eye-witness, with one sustaining a hip injury. <S> Now all that can be said is if you don't want to be next victim <S> wear the seatbelts.
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Yes, it is always advisable for passengers to wear the provided safety belts in all phases of flight.
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What is the function of the lower vertical fin on a MIG-23? I would like to ask about the function of the lower vertical fin in Mig 23 . <Q> Directional stability at supersonic speed. <S> The air above the aircraft is less dense at supersonic speed, and elasticity reduces the effectivity of the fin - it bends and twists from the air loads. <S> Conversely, the lower fin operates in denser air and creates more side force per area. <S> Also, the lower fin shifts the aerodynamic center of the empennage downwards, which is improving the handling characteristics. <S> Adding area below the centerline helps to reduce the roll contribution of the vertical tail in a sideslip, which improves handling characteristics (more directional stability AND lower yaw-induced roll). <S> As long as the vertical tail surface sits above the centerline (more precisely the longitudinal axis of inertia - for now we can assume both fall together), any side force will also create a rolling moment. <S> This is undesirable because now a yaw command will not only create the intended yawing moment, but also a rolling moment. <S> If you want to yaw in order to turn, the vertical tail above the centerline will even roll the aircraft in the wrong direction, so you need more coordinated aileron command than with a symmetrical vertical tail. <S> The MiG-23 is not alone: Many supersonic combat aircraft use ventral fins. <S> See the picture below for an example where the effects of additional vertical tail area are compared to the effects of a ventral fin of the same area. <S> (Source: <S> Ray Whitford: Fundamentals of fighter design) <S> At supersonic speeds, the stiff, low aspect ratio ventral fin has a nearly constant contribution to directional stability, whereas the wing-like vertical tail loses effectivity in proportion to the Prandtl-Glauert factor $\frac{1}{\sqrt{Ma^2-1}}$ because it bends and twists more due to its higher aspect ratio. <S> The small ventral fin of the F-104 raised directional stability by 30% at Mach 2. <S> (Source: <S> Ray Whitford: Fundamentals of fighter design) <S> At high angles of attack, the vertical tail is in the wake of the fuselage which reduces local dynamic pressure and, consequently, effectivity. <S> The ventral fin then is in ideal flow conditions, so it can help to stabilize the aircraft at high angle of attack, just when the fuselage contribution to instability is largest. <A> It is called called a ventral fin and is used to provide improved stability. <S> A number of combat aircraft (like F-14, F-8, for example) have them. <S> the image below shows the ventral fin in F-8. <S> Image from <S> nasa.gov <S> This improves the handling qualities. <S> Another advantage is that they retain their effectiveness at high angles of attack, while the vertical fin may be blanked by the main wing. <S> The ventral fins in Mig 23 were quite big, which necessiated folding them when landing. <S> MiG-23 with wing flaps lowered, landing gear deployed, and ventral fin folded aside as it approaches to land ; image from aerospaceweb.org <S> This is not limited to Mig-23; <S> Vought XF8U-3 'Super Crusader' also had quite large ventral fins, which required folding. <A> That piece of tail under the belly made it easier for the MiG-23 to be stabilised in high speed conditions. <S> That part would be folded away for ground operations if you are also curious about that. <S> Source <A> Reduce the amount of the side sliping when jet bank. <S> F16 have that.
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Adding a ventral fin helps in increasing directional stability (especially at supersonic speeds) and reduces yaw induced roll (as the roll contribution of vertical fin is reduced in a sideslip).
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What is the relation between airspeed and rate of turn? I am reading about aircraft maneuvering and the end of section check contains this question: During a turn, if you reduce the airspeed and maintain the angle of bank, the result is a _____________ rate of turn. The correct answer is "higher" which is confusing me. If I reduce the airspeed, won't it take longer to complete the turn, thus "lower" rate of turn? I can understand that the turn might be smoother and more coordinated if I reduce the airspeed, but how can the rate of turn be higher? What am I missing here? <Q> Independent of airspeed, angle of bank gives you the "G" force in a level coordinated turn. <S> A 60 degree bank = 2 G's, at any speed. <S> At low speed, a given G force will give you a greater heading change than it would at a high speed. <S> Driving your car at 10 mph you can complete a U-turn, 180 degrees of heading change, in a couple seconds without pinning passengers against the door, but at highway speeds, even a hard turn that does impose big side-loads will take much longer to give you that much heading change. <S> Related to all this is turn radius : <S> at low speed, your turn radius for any given loading (bank angle) is smaller than it would be at a higher speed with that same loading/bank angle. <S> Thus, even though you're going slower, you have less distance (circumference of the circle) to cover, and so you are able to complete the circle (or one 360th of it) more quickly. <S> ((For the pedantic ones, everything here assumes level, coordinated turns. <S> Change those assumptions enough, things can be different, but those aren't particularly instructive cases until the base case is understood.)) <A> For an aircraft in a level, coordinated turn, the rate of turn is given by <S> $\mathrm{Rate\ of\ turn} = <S> \frac{1091 \tan\theta}{V}$ <S> where Rate of turn is in degrees per second, <S> $\theta$ is the bank angle in degrees, and $V$ is the TAS in knots. <S> So, as the airspeed decreases, the rate of turn increases and vice versa—as long as the angle of bank is kept constant. <S> Image from <S> cfinotebook.net <S> For an aircraft in a coordinated turn (i.e., no skidding or slipping), the vertical component of lift is equal to the weight, while the horizontal component is equal to the centrifugal force. <S> Forces in a turn, image from Instrument Flying Handbook <S> As the aircraft turns, if the airspeed increases with the bank angle held constant, the radius of turn increases with the square of the speed ($r = <S> \frac{V^{2}}{11.26 \tan\theta}\ \mathrm{ft}$). <S> Hence, the distance traveled during the turn increases as the square of the speed. <S> Even though the aircraft is flying faster, the distance to be flown increases faster than the speed. <S> As a result, the time taken to complete the turn is increased and the turn rate decreases. <A> Rate of turn means how quickly the plane's nose is changing direction, or how tight a circle its making, turn radius, like a car. <S> You can make a sharper turn at slower speed. <S> The airspeed will be slower as you travel through the air, but you'll change direction faster. <S> This also creates G-forces than can damage the wings etc. <S> so banking too much at high speed, you'll feel just like a car going to fast around a turn, and you'll naturally slow down a little.
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The rate of turn is inversely proportional to the (True) airspeed.
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Is it possible to sail a seaplane? Say a seaplane has ditched onto ocean or a very large lake due to engine failure. Is it possible to sail the plane to the shore using wind alone, similar to sailing a boat? <Q> You can sail a seaplane, but there are a lot of considerations. <S> For starters, it makes a big difference as to whether you're talking about a seaplane where the hull is in the water or a floatplane. <S> A floatplane sitting up on its pontoons (floats) is more up in the wind, but it's also more susceptible to rough water because of its higher center of gravity. <S> My personal experience with sailing a floatplane was with a J-3 cub with an 85 horse engine on rivers and lakes. <S> If we wanted to back onto the shore, we had to sail it since there was no reverse pitch propeller. <S> For purposes of explanation on how to do it, let's say that there's no wind, but we're on a river with enough current that the movement of the floatplane with the current when the engine is off gives the floatplane a wind relative to the water. <S> Further let's say the river is flowing from east to west, and we want to back onto a beach on the north shore. <S> We land and stop the engine upstream from the beach. <S> As the floatplane drifts it will weathervane into the wind. <S> Thus, with the controls neutralized, we'll be facing west and moving downstream in mid-river with the current, but not as fast the current because of the drag of the wind on the aircraft. <S> The rule of thumb is that you point the tail towards the shore you wish to get to. <S> We do that by applying left rudder and right aileron. <S> Thus we have increased the drag on the left wing, which will swing the nose left, and the left rudder will also swing the nose left. <S> Thus the nose is now pointed a few degrees toward the left shore (south), the tail toward the right shore (north). <S> The airplane will then sail to the right shore (north) relative to the direction the aircraft nose is pointing because the the aircraft is moving backwards relative to the water. <S> The trick in this instance is vary the control input to arrive at the downstream point you want. <S> For practice, I used to have students sail to alternate sides of the river on Oregon's Willamette River downstream from the city of Eugene. <A> It's been done at least once before. <S> In 1925 a US Navy PN-9 landed in the Pacific when it ran out of fuel on the way to Hawai'i. <S> The crew then rigged a sail from parts of the canvas wings and sailed their plane over 400 miles (in nine days) to reach the islands. <S> http://timeandnavigation.si.edu/multimedia-asset/naval-aircraft-factory-pn-9-116-scale <A> I know this is not what was asked, but I couldn't resist. <S> It was a curiosity and built only because none had been built before - or ever since. <S> DFS Seeadler floating on water <S> (picture source ). <S> First flight was in 1935, and the official reasoning was to create a modern sailplane for clubs without access to a good airfield, but a lake nearby. <S> But I guess the designer Hans Jacobs knew already how flimsy the official reasoning was: Below the keeled fuselage bottom was a wooden skid to allow landing on land.
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There was indeed a seaplane that could be sailed: A sailplane with a seaplane hull.
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How do I get attention on a busy radio channel? As I understand it (I'm not a pilot), radio communications are a more-or-less first come first served proposition. If I'm in busy airspace with near constant communication between ATC & aircraft, how do I break in to make contact with the ATC for whatever purpose necessary (establishing comms to enter airspace, or whatever the situation may be)? <Q> As Ron commented, the basic answer is that you try to anticipate when a short gap is going to be, and jump on before someone else does. <S> It sounds a bit daunting, but it actually works out pretty well in practice. <S> That being said, it's not exactly first come first serve. <S> ATC tends to prioritize talking to the aircraft which need the most immediate instructions. <S> So, an aircraft on final is going to get more priority than one which hasn't even entered the airspace yet. <S> Even if you manage to get your request in, if the controller has a more immediate issue to address, you may get completely ignored. <S> Sometimes they'll come back with "calling approach, say again" or sometimes you just have to try again later. <S> Either way, it's usually not too difficult to stay out of trouble long enough to get someone's attention. <S> If you're VFR and haven't made initial contact, you can probably just avoid the airspace for a few minutes. <A> Key up the mic and state: Who you're contacting (e.g. Seattle Approach) <S> Who you are (e.g. Skyhawk 1234) <S> Where you are (e.g. 5 west of Bremerton) <S> Your altitude (e.g. 5500) <S> Your request (e.g. VFR flight following to Renton) <S> If the frequency is really busy, some people will substitute #3, 4, 5 with "request" (e.g. "Seattle Approach, Skyhawk 1234, VFR request"). <S> Once the controller responds the remaining details can be filled in. <A> The first thing to get clear is: who are we talking to here? <S> a tower? <S> an ARTCC? <S> what? <S> In my experience the biggest problem can be trying to reach a busy tower for a small or medium-sized airport. <S> In other situations, usually ATC calls you, not the other way around. <S> For example, if you request vectoring, you only have to do it once; after that they call you. <S> If you are trying to reach a tower and they are tied up, it can be a real problem because as you get closer to the airport you need an answer. <S> In one or two cases I have actually had to circle to wait for some chat head to shut up <S> so I could talk to the tower and get instructions for an approach. <S> Commercial flights have this problem less because they are operating on filed flight plans, so the tower is ready and waiting for them. <S> Another serious problem is when you are in the pattern on downwind and the tower is too busy to give you a landing clearance. <S> In this situation all you can do is to keep flying downwind. <S> Sometimes it gets ridiculous. <S> I have flown literally miles downwind waiting for clearance to turn onto final, which then turns into this loooooong 5 mile final. <S> If you fly downwind too far, you might even have to leave the pattern completely and start the whole process all over again, although this has never happened to me.
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If you're IFR or have already made initial contact, you can probably just continue on your path and you'll eventually become a big enough priority for them that they'll call you if you still haven't a chance to get a word in.
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Is there a site that tracks all flights? Some of my flights are tracked on sites like Flightradar24 and others are not, regardless of flight plans being opened and closed. It would be nice to go to a website that tracks all flights, so I can review the flight dynamics after I land. I am interested in a website that provides this service, not an app (I have had limited success with these). <Q> <A> Tracking sites use FAA data for the most part, augmented by ADS-B data nowadays. <S> For FAA data, they use what's in the National system. <S> This is usually 99%+ of IFR flight plans, and some VFR flight following flight plans. <S> IFR flights plans that aren't included are those that are local area pop-up requests(staying with the same approach control with a pop-up IFR clearance). <S> For VFR flights, the only data in the NAS is what's input by controllers for flight following that leaves their airspace(leaving a TRACON headed to a center or another facility, usually; sometimes you can get a NAS code for just a local flight). <S> VFR flight plans sent to and activated by flight service are not sent to ATC, all they are is a tool for rescuers to search for you if you're late and never check in and a search needs to go find you. <A> The short answer to this question is to fly ADS-B. <S> If you use ADS-B, then in general, you will always be tracked unless you employ a specific blocking mechanism. <S> Other than that <S> your only recourse is to always fly under a IFR flight plan which should result in tracking 98% of the time. <S> If you are not getting tracked, it may be because you are using a VFR flight plan, or are flying in an area outside Europe or the United States.
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No, there will always be flights that are private, or for any other reason not traceable.
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Is a single engine failure on the HondaJet recoverable? Is it possible to recover from a single engine failure at cruising altitude on the HondaJet and safely land the aircraft? <Q> There would not be much point in having two engines if a single engine failure would be unrecoverable. <S> In fact, that would make the plane twice as likely to have an unrecoverable event! <S> If one engine has a 1/1million chance of failure, then the chance of failure of at least one of 2 engines is 2-in-a-million. <S> (technically, slightly less than 2-in-a-million... but close enough) <S> And if either engine failure is catastrophic, then you've doubled your chances of losing the plane. <S> I don't know about the HondaJet in particular, but by logic and statistics, I can say that a single engine failure must be recoverable. <A> The HondaJet is type certified by the FAA . <S> The type certificate says that it's certified in the normal category under 14 CFR 23 , which includes the requirements to be able to take off and climb on a single engine. <S> Simply put, the HondaJet has plenty of surplus thrust even on one engine <S> and there should be no problem at all landing it after a single engine failure, assuming no other complications. <A> While the others answers are completely correct regarding the ability of the Hondajet (and any other twin jet, for that matter) to safely fly after an engine failure (including during the takeoff roll past V1,) <S> it's probably also worth pointing out that you don't need any engines to safely land from cruising altitude . <S> Engines are generally needed to climb or maintain altitude, but you can glide with no engines at all. <S> According to Honda's website , the Hondajet has a maximum cruise altitude of 43,000 ft and has a cruise speed of 420 KTAS if cruising at 30,000 ft. <S> From 43,000 ft. <S> it would probably be well over 100 miles. <S> This would be true for almost any commercial or private jet aircraft.
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Even if you lost both engines at 30,000 ft., you'd almost certainly be able to glide around a hundred miles and still land safely.
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Why was the WWII RAF fighter joy stick loop design not used widely? WWII RAF fighters had a loop on top of the joy stick in case of hand loss or injury - Anyone know why the Allies didn't copy this very helpful idea? <Q> Generally only Hurricanes and Spitfires had them. <S> The cockpits on these aircraft were small and it was a problem for the control column to get full travel for roll control. <S> This was solved by making the control column rotate at about mid-stick instead of from the the floor. <S> Other aircraft didn't use them because the cockpits were large enough to accommodate a normal stick and still provide good leverage and side to side travel. <S> Pilots found them to be much more comfortable to hold and <S> loop style sticks did also get used some on larger aircraft with conventional floor mounted control sticks. <S> Full right aileron <A> Would Polikarpov R-5 / I-5 / I-15 / I-16 count? <S> I-16 panel. <S> Source . <S> Also photos of an earlier R-5 . <S> It didn't have that peculiar half-stick roll, but it did have the "loop". <S> I can't say it was "copied" from RAF; after all, R-5 was designed in 1928, which predates most if not all similar British designs. <S> Besides, Britain was not considered by the USSR an "ally" at that time (which didn't prevent them from using/licensing/copying British engines and perhaps other stuff). <S> Nor would I say it was done for the case of injury. <S> It was just hard to control these airplanes with one hand. <A> I believe the other consideration not mentioned here is that the spade design comes from earlier wwI British designs like the se5a. <S> So it was a carry over from those planes and the trainers like the tiger moth. <S> The spade facilitated two handed control. <S> Control surfaces were strictly operated by muscle with cables and the modest leverage of the control horns, pullies and assorted linkage. <S> In a dive or steep bank turn with g loads on the pilot it might take all you’ve got to pull back on the elevator. <S> Hence the observation made by another that heavier planes and multi engine (pilot co pilot) configurations get yolks in the American designs of the period. <S> The spade also allowed for easy switching of hands to access other levers, knobs etc mounted on either side of the cockpit without having to “let go” of the stick or pass it between your two hands as you would to get the same grip position on a straight stick. <S> By “allied” designs, I assume you mean American and many of our fighters except the earliest used hydraulics to control flight surfaces. <S> Oh and don’t forget that the Brits love to garden...so the spade was a familiar implement in their hands.
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The loop was there so a pilot could use both hands on the stick to get more lateral force since the effective length of the stick was now much less than a conventional floor mounted control stick. A control stick with a loop at the top was called a "Spade Stick". The early spits and hurricanes had no hydraulics (which were more costly to manufacture and viewed as vulnerable to failure from enemy flak and bullet damage).
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How is wind direction reported (blowing from or blowing to)? When the tower controller, the ATIS or a METAR says Wind 270, 15 knots does it mean the wind is blowing in the westward or in the eastward direction? Is there a single convention used to express the wind direction? <Q> As far as METARs are considered, the wind direction gives the direction from which the wind is coming. <S> From METAR definitions : Wind Direction. <S> The direction, in tens of degrees, from which the wind is blowing with reference to true north. <S> So, Wind 270 shows that the wind is coming from west. <S> The reporting in ATIS and tower is the same, only difference being that the reference is magnetic north, while it is true north for METAR. <A> Wind numbers say where the wind is coming from. <S> Wind 270 means that the wind is coming from the west, and blowing towards the east. <S> If you point west (270), you will have the wind in your face as a headwind. <S> If you point east (270 - 180 = 90), you will have a tailwind, or the wind at your back. <S> Another way to think about this is if you want to take off from runway 27, where you are pointing to 270, (pointing west), you want the wind coming from 270, so that you have a headwind. <S> It's easy to remember that when you are on runway 27 you are pointing to 270. <S> Just remember that a headwind aligned with the runway will have the same number, and you will remember that the wind direction is where it is coming from. <A> I always use the old saying; <S> The North wind doth blow, and we shall have snow... <S> Since this saying originated in England and in England it is colder to the North, we can conclude that a North wind blows from the North. <S> Incidentally, it is precisely the opposite with ocean currents. <S> The Gulf Stream is a North-Easterly current, because if you are floating in it, it will take you to the North-East. <A> As a pilot, you really want to know the wind direction on takeoff and landing. <S> A good rule of thumb is that if the direction is reported in writing (METAR) then the bearing is relative to true north; if by voice (ATIS) then relative to magnetic north. <S> This makes sense from the perspective that ATIS is related to a specific airfield, whose runway directions will be numbered according to the local magnetic variation. <S> At an untowered field, pick the runway numbered closest to the ATIS-reported direction.
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The reported direction will be where the wind is coming from , that is, opposite the direction the windsock is pointing.
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Where does the 35 feet screen height come from? When taking off, why are we required to climb at least 35 feet over the departure end of runway? Why not other numbers? This comes from the FAA regulations . I believe there must a clear explanation for this but can't find one. Is there any historical or mathematical reason? <Q> The best explanation I've seen for the logic behind the 35 foot crossing height requirement can be found in the FAA Instrument Procedures Handbook (IPH). <S> It's available from the FAA website at this link: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/instrument_procedures_handbook/ <S> In Chapter 1, Departure Procedures, under Design Criteria on page 1-16: "The aircraft climb path assumption provides a minimum of 35 feet of additional obstacle clearance above the required obstacle clearance (ROC), from the DER outward, to absorb variations ranging from the distance of the static source to the landing gear, to differences in establishing the minimum 200 FPNM climb gradient, etc." <S> So, the 35 feet is in place to account for a multitude of variables. <S> The phrase "differences in establishing the minimum 200 FPNM (Feet Per Nautical Mile) climb gradient" covers a whole host of potential errors such as variations in individual aircraft performance, early rotation, late rotation, under rotation, over rotation, poor airspeed control, etc. <S> This error proofing is important since the 35 foot requirement is used when building all performance data for go and no-go decisions. <S> That performance data is all based on set assumptions. <S> Reasonable deviations from the assumptions are mitigated (somewhat) by the 35 foot margin. <S> As with most safety margins, there isn't necessarily a precise reason for the size of the buffer. <S> However, even increasing the crossing height a slight amount, say to 50 feet can have significant effect on performance calculations. <S> At a minimum climb gradient of 200 FPNM, the difference between a screen height of 35 feet and 50 feet is just over 450 feet of required horizontal distance. <S> Of note, the regulation that created the 35 foot crossing height, SR422, came about in the late 50s during the beginning of jet-powered commercial aviation. <S> The aircraft being designed and fielded back then, the Boeing 707 for example, would have had a hard time making a higher restriction. <S> That likely had influence on the required crossing height. <A> Screen height is based on the height of a (London) "double decker bus, as used in the original trials at Croydon, where they hit one while taking off. <S> "Source <S> : <S> Phil Croucher (2019) <S> EASA Professional Pilot Studies, p.9-6 <A> As I understand it, from when I was attending flight engineer school with the Air Force, the screen height has to do with a 50' obstacle. <S> The 35' screen height for FAA TERPSd fields translates to being able to clear a 50' obstacle at 200ft/min providing you <S> are 35' AGL at brick last of the runway. <S> For Army TERPSd fields the screen height is typically 16' and for Air Force and Navy TERPSd fields the screen height is 0', meaning that if you maintain 200ft/min climb, you can rotate at brick last and then you will clear the 50' obstacle by the required minimum clearance. <S> The 35', 16' and 0' screen heights are assumed if no other screen height is given, and based upon who has evaluated the airport.
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In a tight performance situation such as high pressure elevation or short runways, a 50 foot crossing height could be too much for some large commercial aircraft.
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Is the landing gear controlled by the pilot or is it automatic? I have been watching a few aircraft landing videos in crosswind situations and I noticed that if the airliner missed the runway the landing gear would go back into the aircraft. So I'm wondering if this system is automatic after a takeoff or if it's controlled by the pilot manually? <Q> The extension and retraction, depend on the action from the pilot monitoring, on 2 pilots operation. <S> The pilot has a lever on their panel, on which they select the extension (down) and/or retraction (up).Some aircraft has a system to avoid extending them on high speed, to avoid some damage, and on the ground, avoiding retracting, for obvious reasons. <S> There are lights, green and red, indicating their position. <A> It's manual. <S> Once there is positive climb the pilot will retract the gear and flaps to minimize drag. <A> All landing gear that I know of are all controlled by the pilots. <S> I have never heard of an "automatic landing gear" as you describe it. <S> As some comments below say, there is one airplane that has/had an automatic gear (Piper Arrow) <S> but it was not really the brightest idea because it could cause in-flight problems if not handled properly. <A> As the other answers point out, it generally is operated by the pilots. <S> In the last project I have participated in, though, flap and gear control was performed by an automated system (see slide 17). <S> The control system was automatically deploying the flaps and gear at a specified location during the final approach, without any pilot intervention. <S> In the future there might be more aircraft that will use such automation, but not before the appropriate amendments will be done to the regulations and not before one such system will be succesfully certified. <A> As soon as there is a positive rate of climb, the gear is retracted because it is a large contributor to drag on the aircraft, effectively reducing its climb performance. <S> As a passenger you can feel this on some aircraft when the gear is deployed as you can feel the drag on the aircraft (and depending on where you are sitting, you may be able to hear the gear deploying). <S> Due to its large effect on the performance of the aircraft, in some aircraft the gear is also used as an impromptu air brake to reduce the speed of the aircraft - although in most modern aircraft, this function is taken care of by the air brake/spoilers. <S> Gear is retracted manually, usually by the pilot observing, and not by the pilot flying (PF). <S> Usually the pilot observing will say "positive rate, gear up" and then move the lever to retract the gear - this is what you are observing in those videos.
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The landing gear system is operated by the pilots.
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What is the difference between a high bypass turbofan and a low bypass turbofan? I see some questions on the site that talk about the relative positives and negatives of a high bypass turbofan (HB) vs a low bypass turbofan (LB). But I don't see anything explaining what actually makes a turbofan engine HB or LB? I assume it has to do with the ratio of air that is bypassing the compressor stages and just going through the fans. But what ratio makes an engine HB v. LB? And why was that ratio chosen? Please note: I am not looking for usage cases, I am looking for differences in design specifications. <Q> The first turbofan, the RR Conway , had just a bypass ratio of 0.25. <S> It was designed for installation into the wing root of airplanes like the HP Victor bomber or the Vickers <S> V-1000 transport project, so RR strived to keep the diameter small. <S> Of course, back then nobody distinguished low- and high-bypass engines. <S> The P&W JT-3D , which powered most of the second generation of jet airliners (Boeing 707 and DC-8), had a bypass ratio of less than 1.5. <S> But when the new generation of engines ( GE CF-6 , JT-9D ) with bypass ratios of around 5 were developed for the first generation of wide body jets, marketing needed a term to make clear that this was a new generation of engines, and the high-bypass ratio engine category was born. <S> Generally, the threshold is around 5, but note that some CF-6 versions have bypass ratios as low as 4.24 and still fall into the high bypass ratio category. <S> Therefore, Wikipedia sets the limit at a bypass ratio of 4. <S> There is no technical difference between a low- and a high-bypass engine, and the limit is arbitrary. <S> The jump in bypass ratio from 1.5 to 5 brought significant improvements in specific fuel consumption and noise reduction, but part of the technical progress was also from better materials and aerodynamics, which allowed higher compression ratios and turbine entry temperatures. <S> Now, almost 50 years later, we see the first engines with bypass ratios above 10 entering service. <S> Designs are being readied with bypass ratios of 12, so marketing will need a new word to describe those creations. <S> With "ultra high bypass" already taken by the unducted fan crowd, the search is on. <A> There is no particular ratio at which the engine becomes a 'high' bypass, though the it is generally taken to be around ~5:1. <S> The reasons are more historic than technical. <S> The first large scale development of the high-bypass turbofans was spurred by the USAF's CX-HLS competition, which lead to the C-5 Galaxy. <S> The requirements of the competition (range and fuel efficiency) lead to the development of a new generation of engine by GE and PW, which developed the TF39 and JTF14E respectively. <S> GE won the contract with the TF39 engine, which had a previously unheard of 8:1 bypass ratio. <S> PW figured out that it better develop a high bypass engine itself or lose the market and developed the JT9D, which had a 5:1 bypass ratio. <S> This engine was the first widely used engine with high bypass ratio (the previous engine had bypass ratios in the range of ~1 or so) and necessitated a special mention, which came to be called high-bypass engines, once it became widely used, especially in the Boeing 747 <S> (Ironically, it was the two losers of the CX-HLS competition PW and Boeing, which won the immediate race in civil aircraft). <S> Joe Sutter acknowledged the effect of the CX competition in the development of 747 : <S> I should add that fostering large high-bypass engines was all that the USAF C-5 competition contributed to the Boeing 747, as my new airplane would be called. <S> Not to be left behind, GE developed the CF6 series with bypass ratios of 6:1 and RR developed the RB211-22 which had a bypass ratio of ~5:1. <S> Due to these, the ratio of around 5:1 (or >4:1) is usually taken as the dividing line between the 'high' and 'low' bypass ratio turbofans. <A> "Bypass" in this context is how much air transits the actual fan stage and is used to directly generate thrust, vs. how much air transits the fan stage and moves into the compressor stage to be burned in the engine. <S> High-bypass turbofans route more air outside the combustion core, so the spinning fan generates most of the thrust (rather than the actual engine). <S> In this case, the turbojet core of the engine is used (mostly) to generate engine rotation, and the fans generate most of the thrust.
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Low-bypass turbofans don't use a lot of air for thrust; most of the air that transits the fan stage is routed into the engine, compressed, combusted, and exhausted like a standard turbojet.
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How is metal fatigue detected in an aircraft? There have been many accidents involving metal fatigue. How do the engineers, maintenance team, etc. know if an aircraft has metal fatigue? What is done to "minimize" metal fatigue or repair it? <Q> How do the engineers, maintenance team, etc know if an aircraft has metal fatigue? <S> First of all, is not an "aircraft" that has fatigue, but a component. <S> There are tools available to allow for early detection, my bachelor's thesis was about one of these: the photoelasticity of certain materials is used. <S> A light coat of one such material is applied on the new component and the photoelastic properties and exams done during the lifetime of the component tell the maintenance people what is the current status of the inner layers of the piece. <S> Another method uses electric resistance, as metal fatigue, by cracking the metal, increases the resistance. <S> Depending on the scenario, X-rays could also be used. <S> What do they do to "minimize" metal fatigue or repair it? <S> You cannot minimize fatigue, once it starts setting in, it is an irreversible process. <S> You can delay the likely catastrophic failure by applying strengthening elements around the affected one, but the safest course of action is to replace the component and recycle the old one. <A> Engineers have a variety of ways to detect metal fatigue in aircraft: <S> Visual inspection: sometimes cracks are visible to the naked eye, or can be seen under magnification Auditory inspection: sometimes a thump sounding wrong can give a clue that there's an issue. <S> It's not a primary means of checking for fatigue, but <S> something that may clue in an astute engineer that something needs to be looked into Ultrasound: Ultrasound uses very high pitched sound waves to image materials and can be used to find cracks inside materials <S> Radiology: <S> xrays and other types of radio imaging can be used to find sub-surface cracks <S> Visible dyes: <S> flourescent dyes in penetrating oils show up cracks which make it to the surface <S> Magnetic powders: these only work on iron-based parts which are rare on an aircraft but are used <S> Here's a good article that goes into some details on non-destructive fatigue testing. <A> Visual checks are no use for platform critical damage as by the time you see it <S> it is well into the failed zone which is why NDT techniques are used to detect an impending failure well before it causes a problem. <S> There are other techniques such as Dye Penetrant tests where a dye in a carrier fluid is painted into the surface and then wiped off. <S> The fluid is light enough to penetrate and 'wick' into any fine cracks and will highlight cracks that are invisible to the eye. <S> The dye is often fluorescent. <S> As for what can be done it very much depends in the extent and location of the cracking. <S> Extensive damage and/or damage to critical area will be repaired by replacement, minor damage can be gouged out and welded up. <S> The best method of minimising fatigue it to prevent it and so most manufacturers will feed back fatiguing data from surveys to the design sections who will design out the weak point if one exists. <S> Real life data trumps even the most extensive FEA predictions. <A> The pilot listens and notify the technicians that the plane is giving out strange noises. <S> And now seriously: For each plane type there are cards which parts need to be replaced or inspected after certain flight hours, start count or time. <S> Together with required quality control at production and maintenance it should prevent metal fatigue incidents as much as possible. <S> And for the rest - @AndyW already mentioned techniques used during the inspections
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Some metal fatigue can be spotted visually as an visible crack or as a collection of tiny cracks that can give the metal a 'frosty' look but most is done via non-visual non destructive testing techniques such as radiography (basically X-raying) or Ultrasonic testing to search for microfractures before they reach the problem stage. To the naked eye, there is no way to detect metal fatigue until it starts being too late: you can only see cracks that are already forming and/or propagating.
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What is an NTAP when referenced in a NOTAM? When reviewing notices to airmen (NOTAMs) for the KDNL airport today (08 April, 2016) there's a particular NOTAM that references an NTAP with a number. What's an NTAP? How does one go about looking one up? !DNL 03/008 KDNL SVC SPECIAL EVENT MASTER'S GOLF TOURNAMENT SEE NTAP 1604031100-1604112359 <Q> The Notice to Airmen Publication is an FAA publication, currently available in PDF or print form, published every 28 days. <S> As voretaq7 notes, this includes long term NOTAMs that a flight service brief won't include if you don't ask. <S> There is also a section with graphic notices, including general notices, special operations, airport and facility notices, and major sporting and entertainment events. <S> That last section is the one relevant for the NOTAM listed above. <S> This lists information and procedures for any airports affected by special events, which is nice to have in one place rather than looking up long and complicated NOTAMs for each airport. <S> For example, the Masters Golf Tournament referenced in the NOTAM above has a section in the NTAP, affecting airports AGS, AIK, DNL, and HQU. <S> The information includes preferred IFR arrival routings, potential for holds and VFR arrival delays, departure procedures, preferred IFR departure routes, IFR overflights, and VFR arrivals/departures to/from DNL. <S> There is also a special schedule for the tower at AGS, and a temporary tower at DNL. <A> NTAP is the Notice to Airmen Publication. <S> It is published every 28 days. <S> The electronic version can be found in the faa site . <A> Simply enough, it is the "Notices to Airmen publication", which has the full description of the NOTAM.
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The NTAP contains airway, airport, facility, procedural, general, and international NOTAMs.
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Are jet simulators a commercial business or are they owned by airlines? Are simulators owned by airline operators or are they property of private companies who are specialised in this business and offer the services on an outsourcing basis to airlines that require it? I'm talking about proper simulators like the Airbus or Boeing ones and not PC based ones. <Q> Both! <S> Some airlines operate simulator facilities. <S> For example, United has a training facility in Denver with a number of simulators. <S> In turn, they rent out training services to others who will pay to use the facilities ( more info on their offerings here ). <S> They can also provide trainers, cabin crew training, ground school training, and other such services. <S> Many airlines have similar programs. <S> They've even auctioned off simulator time to customers willing to bid frequent flyer miles for the privilege. <S> When an airline doesn't own and operate the necessary equipment itself (even an airline that runs its own simulators may not have a suitable quantity for every aircraft in its fleet), it can contract for such services from someone else. <S> That someone else might be another airline, a company that provides simulators ( example ) and may offer other training services like instructors, or a provider affiliated with the manufacturer ( example ). <A> In addition to the good information in @ZachLipton's answer, many aviation training companies offer simulator training for aircraft types other than those that most airlines fly, for example the Kodiak, Citation, or King Air. <S> This type of training is often used for training individuals flying their own advanced aircraft or for professional pilots. <S> Pilots flying for corporate or charter outfits will typically do initial and recurrent training with such aviation training facilities. <S> Examples of such training facilities would be the Spokane Turbine Center , Flight Safety International , SIMCOM Aviation Training , and many others. <S> In addition to these companies that specialize in aviation training for advanced aircraft, many flight schools that specialize in primary flight training also include training in high level FTDs —which have also been used by some airlines , at least in the past. <S> Examples of such schools would be MSU and UND , among many others. <A> Pan Am is one example. <S> Traditional airlines used to acquire their own simulators. <S> However for low cost airlines, pilot training is not core business and a simulator is not an automatic purchase. <S> There are more and more self funded students appearing in the aviation industry. <S> Pilot training is becoming an issue: there are over 500 new aircraft per year delivered of both B737 and A320. <S> More than 1 per day of each type! <S> Each additional aircraft delivered to an airline (so not a replacement) requires 4 - 5 flight crews. <S> 10 new pilots. <S> 5 captains and 5 F/Os, all trained in a simulator for captaincy and type rating. <S> To recap: A Level D full flight simulator for an airliner is a 10-20 million dollar device. <S> And there are private companies that arrange bank financing and then sell hours to airlines and self funded students, either with or without instructor services. <A> As mentioned earlier, most of the major airlines own their own full motion simulators. <S> In addition, major flight schools also have full motion sims as well as companies like Flight Safety International. <S> The OEMs also maintain full motion sims and can lease sim time to smaller carriers or flight crews attempting to become type rated in an aircraft which they sell.
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Yes there are private companies that operate Full Flight Simulators and sell simulator time to users, either airlines or self funded students.
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Can a helicopter really fly with rotors going this slow? I was watching this youtube video and I noticed that at 3:17 seconds they show a coast guard helicopter rescuing a man from a ship. Whats shocking about this is that the main rotor of the helicopter seem to be going incredibly slowly and the tail rotor has completely stopped. How was the helicopter able to stay flying with such a low rotational speed? Was this some optical illusion or was the rotor really spinning that slowly? Also, how was the helicopter not spinning? From what I understand the main purpose of the rear rotor is to counteract the rotational force of the main rotor. Since the rear rotor wasn't moving, shouldn't the helicopter developed a spin counter to the spin of the main rotor (even though it was slow)? <Q> It's an illusion that the blades appear to be going slowly. <S> It's actually a well known effect called the wagon wheel effect . <S> Essentially the rotor is spinning at close to an even multiple of the camera's framerate divided by the number of rotors. <S> This means that between frames the blades have moved a full quarter rotation (or a multiple of that). <S> Creating the illusion that the rotor is moving more slowly that it actually is. <A> Many things give similar effects. <S> Strobe lights are popular with dance and and other entertainment venues. <S> One game was to adjust the strobe timing so a spinning wheel would look like it was going backwards, then forwards, then standing still, and so on until you grew tired of the game. <S> Watch old movie westerns and the wheels sometimes look like they are going backwards. <S> In the days of old CRT monitors TV shows had to use special electronics with TVs filmed on show sets to avoid the video appearing to break up or doing other funny things. <S> You can get a simple strobe effect with many modern LED Christmas light strings. <S> Move your eyes rapidly so your vision crosses the lights and you may well see the lights appear to flash. <S> Actually, they are always flashing. <S> It is just that they are flashing faster than the eye can normally notice. <A> It so happens that when the video takes an individual frame, the rotor blades are at or near the same position, so the rotor appears to be turning very slowly or in some cases, to be stationary. <S> If you look up recent videos of large prop planes being started, you can often see the prop appear to become stationary (the prop blades also appear to be bending) as they rev the engine up... same basic effect. <S> You don't see this in old films, because the film was of such a slow speed with a long exposure time for each frame that a moving rotor would be blurred. <S> However... there was one helicopter whose main rotor ran at a very leisurely 88 rpm... <S> the Hughes <S> XH-17 . <S> It was cobbled together from a variety of sources, including a cockpit from a Waco CG4 glider, to test the feasibility of a very large helicopter with rotors driven by jets at the tip of the rotor blades. <S> Fuel was sprayed into the tip jets and ignited to provide rotor propulsion, hence the very small tail rotor - very little torque was produced by this system. <S> The two turbine engines are there only to supply compressed air to the jets at the ends of the rotors. <S> The XH17 has to date, the largest rotor blades ever fitted to a helicopter, with a 129 foot main rotor diameter.
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That's an illusion, the result of the frame rate of the video camera being a multiple of the rotor speed.
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What would the reason be for this helicopter maneuver? At 4:30 in this YouTube video, a Chinook traverses the runway on its rear wheels. The text on the video lists "Emergency landing and take-off". Is there any reason for the pilot to do this other than "because I can and it's an airshow"? The pilot then proceeds to back down the runway on the rear wheels, a maneuver that I can only imagine is showing off, but again, is there a legitimate flying need to do this? <Q> Ex-Royal Air Force helicopter force here, spent a lot of time around Chinooks. <S> I think the main answer is "because I can", but I can think of a legitimate combat use. <S> You are heavy, and forced to land downwind into a narrow strip because there is a hazard on the upwind side of the landing zone. <S> There is not enough room to turn around. <S> You could hover taxi backwards like this to pick up some inflow into the rotors from the relative airflow (and therefore increased lift), then climb away backwards until you do have enough room to transition into normal forward flight, more or less as shown in the video. <S> This is where team work kicks in - you've really got to trust your load master who is telling you exactly where you are. <S> Never seen it done though. <A> What you are seeing is whats called a Pinnacle Landing or Pinnacle Maneuver . <S> Why its practiced is much cleared from the below image. <A> It looks like it's done to showcase the impressive level of skill & control that the pilot is able to achieve w/ this aircraft. <S> Sort of like the Ken Block Gymkhana video series, where he's showing off amazing car control, but you would never want to drive like that except in a drifting contest. <S> Stretching the definition of 'practical', if you needed to tow something a short way & you had no pickup truck available, but somehow you did have a Chinook helicopter w/ a world-class pilot.... this would kind of be an option <S> Source: I just enjoyed the mental image of someone using a Chinook as a pickup truck <A> When our CH- 46 (PHROG) pilots are moving the aircraft on the runway they were directed by ground crew like myself, there are plenty of times we would taxi them forward and backward <S> so I don't believe it would be "just because" or "showing off". <A> My guess is that if you need to get into and out of a 'hot' strip this approach would minimise the time (and position in the sky) that you would be exposed to enemy fire. <S> Just the sort of flying that might be needed on special ops.
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It's part of every pilots training as is the rear wheel landing or "pinnacle landing" which is used to land on rooftops and mountain tops hence pinnacle. The Chinook has a large base that may prevent it from safely landing in circumstance that require an evacuation from a small raised area.
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Can commercial air traffic operate from uncontrolled airport, airspace? Are there any airports with scheduled services where big jets (say 737 or A320) or wide bodies regularly operate without control tower? Are there any rules (EASA FAA) for this? If controllers go on strike can commercial air transport continue to operate? <Q> I will answer your question with what we can see in Brazilian Airspace and its rules. <S> In Brazil, there are some airports - non towered, operated by radio stations - which give information such as wind direction/intensity and temperature and QNH. <S> Based on this information, the pilot decides on which runway they will land or take off, and relays this message to the radio operator. <S> The operator will only relay these pieces of information to pilots monitoring the radio frequency. <S> Those airports are not controlled, then, if there is any strike, flying visually, no control will be effective. <S> For example, ARU/SBAU is a non towered airport, and TAM Airlines operates the A320F there. <A> The Canadian Arctic has B737 scheduled airline operations to many uncontrolled airports that have no control tower. <A> American Airlines operates an A319 seasonally from DFW to Gunnison (KGUC), which is an uncontrolled airport . <S> There are probably many other similar examples. <S> An airline flight arriving at an uncontrolled field operates just like any other aircraft: it will almost certainly be IFR and fly an instrument approach, or a visual approach if conditions allow it. <S> Radio calls, pattern etc. <S> should be the same as for any other aircraft arriving IFR at an uncontrolled airport. <S> The airline's OpSpec might have some specific procedures for uncontrolled airports, but otherwise it's just another aircraft. <S> Controllers going on strike is a totally different scenario; you might want to ask about that separately. <A> There is no regulation saying that a 737 cannot land at a non-controlled airport. <S> All of the commercial pilots that have had their training in the private sector have had to land at non controlled airports. <S> I say all, but I'm sure there are some exceptions. <S> Let's just say most. <S> It is no big deal. <S> Here at our local airport, KLBX, there is no tower and there are four large jets that come and go every single day, even when the weather is IFR. <S> There is so little realistic understanding of aircraft and air travel due to the continued misrepresentation by the media and movies. <S> There was the incident of the control tower guy falling asleep and the commercial flight had to land without the tower control. <S> It was all over the news as though it was a miracle that the plane didn't just crash all over the place. <S> As though a pilot cannot land a plane without the tower saying "Cleared to land 13R. <S> " That's all they do anyway. <S> The pilot is still responsible for looking and seeing if the runway is really clear and ready to take the plane. <S> In IFR conditions there is still what's called the minimums. <S> If you can't see the runway when you reach the minimums you are not allowed to land there. <S> Again, there is an exception, but it won't be available at non-controlled airports because of the cost. <S> I don't know about Brazil or Japan or any other country. <S> I fly in the US only, and most of it in Texas. <S> You'd be surprised how many non-towered airports there are where you even have to turn on the runway lights from your plane at night. <A> Usually any airport with enough traffic that it would attract a big commercial jet will merit a tower. <S> However, there are a few weird exceptions here and there and some of the other answers have described these. <S> I think you may be thinking that a tower would be necessary somehow or that flying a heavy into an airport without a tower would be dangerous, and that is not necessarily true. <S> Pilots can self-organize and land themselves just fine without a tower. <S> The tower is mostly there to speed things up and enable large volumes of aircraft to land as quickly as possible. <S> If an airfield is busy and there is no tower, then the aircraft will tend to spread themselves out more, approach from longer distances and do things more slowly. <S> With the tower there it speeds everything up. <S> If an airport is out in the middle of nowhere and does not get any traffic, then there is no need for a tower <S> and it does not really matter whether the plane is big or small.
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Any plane can land at any airport as long as the runway is long enough.
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What does this statement about steep descent mean? Source: Wolfgang Langewiesche - Stick and Rudder; An Explanation of the Art of Flying In the first chapter the author mentions, in a glide, if you want to descend more steeply, you want to want to point your nose less steeply.And if you want descend less steeply you point your nose more steeply. What is the reason for this? <Q> The statement is only true if you fly at a speed below the best glide speed. <S> For simplicity, let's look at a glider: <S> Below you see the plot of the L/D ratio over speed of the DG-1000 two-seater glider : <S> Glide ratio over speed diagram for three different wing loadings ( source ). <S> If we just look at the lowest wing loading (leftmost curve), the best L/D can be achieved when flying at 95 km/h. <S> Minimum speed is around 62 km/h, so it is entirely possible to fly along at 80 km/h. <S> When the pilot reduces the angle of attack, the aircraft will pitch down and speed up. <S> If it now flies at 90 km/h, he has just improved his L/D from 43 to 46, so he will descend less steeply when dropping the nose. <S> Note that our flight path angle is now less steep, and the change in attitude is less than the commanded change in angle of attack. <S> Nevertheless, the pitch attitude is reduced and the pilot has the impression that he dropped the nose. <S> The same is true in reverse when slowing down. <S> When approaching the stall speed, large angle of attack changes will result in relatively small speed changes, so the effect of a steeper descent when pitching up becomes more pronounced as the airplane slows down. <S> Slowing down will increase drag, and more drag will result in a steeper descent. <S> As soon as he shifts his starting point to higher speeds, things reverse and the aircraft will descend more steeply when the nose is lowered. <S> Adding an engine will not fundamentally change this behavior. <S> It is only easier to explain when using gliders. <A> That comment by Wolfgang Langewiesche in his book "Stick and Rudder" has caused lots of discussion over the years. <S> Maybe that is what he intended when he worded it so ambiguously. <S> "By pointing the nose down less steeply, you descend more steeply. <S> By pointing the nose down more steeply, you can glide further" <S> This is really only true if you are flying just a little bit slower than best glide speed (best Lift /Drag ratio) or (best glide distance). <S> Also, that statement is really only true if you point the nose up or down just a little. <S> Best glide distance means the speed at which the most distance is traveled for the least amount of sink. <S> If you are flying slower than the best glide speed, putting the nose down and going faster, so that you are closer to the best glide speed, will allow you to cover more distance as the aircraft sinks. <S> If you are already flying at the best glide speed and point the nose down, you will no longer be at the beast lift to drag ratio. <S> You will increase the speed and distance traveled, but you will also increase the sink rate and drag from the higher airspeed. <S> That will result in a steeper descent because you are no longer at the best lift to drag ratio. <S> If you point the nose down to 60 degrees below the horizon I guarantee you will descend more steeply not less steeply and NOT glide farther as Langewiesche says in the book. <A> The key thing here is that he is referring to the ANGLE of descent, not the RATE of descent. <S> If you push the stick forwards the rate of descent will always increase, but the angle of descent may actually decrease. <S> This is because you go faster <S> so you generate more lift, thus your overall angle of descent will decrease. <S> A typical beginner's mistake some glider pilots make is that they get worried they are not descending fast enough when they are landing so they push the stick forwards to dive--a big mistake. <S> What happens is they go a lot faster, so they tend to overshoot even more. <S> Pulling back on the stick, slowing the aircraft down and flattening the pitch is what to do to steepen the angle of descent, just as Langewiesche says. <A> This is apparently talking about maneuver around the best glide speed. <S> The behavior of an airplane is counter-intuitive then. <S> Pushing the nose down, increases the speed and causes the angle of descent to decrease. <S> Pulling the nose up, decreases the speed and causes the angle of descent to increase.
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The underlying reason is the fact that drag will increase when the pilot moves away from the best L/D speed .
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What would happen if put a jet engine behind another jet engine? Just curious. Would it do nothing, would it generate a massive amount of thrust? Would it even work? <Q> There is an alternate way to answer your question, and it relates to thermodynamics. <S> Think about the purpose of a jet engine. <S> It exists to take uncompressed air, compress it, mix it with fuel, burn it efficiently and then expand it (hopefully adiabatically) to generate a larger volume of gas at higher pressure than the intake. <S> The work done by the engine is described by the Brayton cycle <S> (Figure 3.13 from http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node28.html ), and this cycle shows us where we can and can't hope to achieve theoretically efficient operation. <S> If you look at the chart of the cycle in the above reference, you'll note that the compression and exhaustion portions of the cycle are where inefficiency (in the form of entropy) creep in and prevent the cycle from being perfect. <S> As such, even if there were sufficient oxygen left to burn, putting two jet engines back to back would be horribly inefficient (because you are repeating the inefficient portions of each twice). <S> The better solution is to work towards improving compression ratios, and recovering more work from expansion. <S> Much of this has been done over the last 50 years, and is why Brayton efficiencies are in the 0.6 to 0.7 range for modern jet engines (ref same website, Figure 3.19). <S> EDIT: <S> Also, remember that jet engines are designed to work on air that is "cold" relative to their exhaust. <S> They don't compress hot gases efficiently. <S> You could certainly design a compressor to efficiently compress hot gases for combustion, but jet engine compressor sections are not designed for this, so the compression achieved by the second engine in your question would be MUCH lower than its design, which would further decrease it's contribution of additional thrust. <A> Engines need oxygen for fuel combustion. <S> Turbojet <S> After most of the oxygen has been extracted and used to oxidize / burn fuel in the first engine, air is no more useful. <S> In the second engine the core combustion wouldn't start, air would just turn the discs, but there would be no compression, so no additional thrust (discs would actually slow the flow). <S> Afterburners try to burn the remaining oxygen after the core combustion, but there is only the previously mentioned limited quantity to burn. <S> An afterburner is not a second engine, it has no rotating parts, only burners. <S> Turbofan <S> In addition of the core flow, a turbofan has a bypass flow. <S> The bypass flow is not used for combustion and still contains its oxygen. <S> However this flow generates most of the thrust by air compression / acceleration, so anything which slows the cold flow also degrades the engine efficiency. <S> There is a technique to burn the bypass flow: <S> The plenum chamber , but this requires something different and no rotors are involved. <A> Your question was inadvertently answered by Peter Kämpf when he provided this answer to another question. <S> One jet engine was placed in front of another in a test facility to test the high speed, high altitude performance of the trailing PW <S> J58 when it was chosen to power <S> the SR-71 . <S> Test details located here . <A> You would end up with an extremely inefficient setup, if it works at all. <S> It's not the lack of oxygen, because only 20-25% of the oxygen is begin burnt in the core jet engine, so there should be plenty of oxygen left for the second engine. <S> The high outlet temperature of the first engine would decrease the power of the second engine dramatically. <S> The exhaust velocity of ENG1 would be reduced by ENG2 as it wouldn't be able to process the incoming volume of air. <S> The turbulent flow will reduce the compressors efficiency as well.
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All in all, there would be no benefit to such a setup at all.
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What is the biggest airplane that does not need a paved runway? Since we don't need a control tower for instrument landings I was wondering what else that is thought to be needed could be skipped. I know some small general aviation is done on grass runways and I was wondering what is the biggest airplane that does not need a paved runway? Examples of manufacturer-approved usage or regular (e.g. daily or weekly) usage are preferred. <Q> Military transports are designed to be operated from unpaved runways- by extension, any of these converted to civilian use can operate from unpaved runways. <S> For example, the Antonov Airlines operates a number of Antonov An-124 'Ruslan' , which can and do operate from unpaved runways regularly. <S> The Volga-Dnepr group specifically states: <S> Multi-leg landing gears equipped with 24 wheels allow to operate the aircraft on unpaved runways ... <A> The H-4 Hercules (Spruce Goose) should easily win this contest. <S> That plane was ridiculously huge and, in fact, couldn't use a runway, rather it was a "flying boat" that took off from the the water. <S> So I'd say it's the one... <S> Granted, if you mean a grass or gravel strip aeroalias is probably correct. <S> The only other major planes that I know were designed to land on gravel were the early 737 and the 727 . <S> They both had special landing gear guards that keeps the front gear from kicking gravel into the engines and both have specific instructions for preparing the landing gear for touch down on gravel. <S> Here's the guard, if you were curious, on a 737: Source https://www.flickr.com/photos/capnmikesphotos/14891693505 , Author: Mike Pearson <A> It's not quite as big as the Antonov An-124, but honorable mention would have to go to the Lockheed <S> LC-130 . <S> It's designed to resupply scientific and military operations in polar regions, and so it has a dual wheel-and-ski landing gear setup that allows it to take off from and land on snow and ice. <S> (Image source: Wikimedia Commons) <A> These oldies seem worth mentioning... <S> that was in regular commercial service. <S> They landed in fields <S> They're more comparable in size to buildings or very large boats, rather than other airplanes <S> Hindenburg in green compared to Blue: <S> The Pentagon building, <S> Pink: <S> Queen Mary 2, ocean liner <S> Yellow: <S> USS Enterprise, supercarrier <S> Dark blue: <S> Yamato, WWII Japanese warship <S> Grey: <S> Empire State Building <S> Red: Mont, a supertanker <S> Compared to other airplanes (Hindenburg in orange): <S> Or the Spruce <S> Goose (* Not acutal Spruce) . <S> (Just noticed it mentioned in another answer, after posting this) <S> Originally designated HK-1 for the first aircraft built by Hughes-Kaiser, the giant was re-designated H-4 when Henry Kaiser withdrew from the project in 1944. <S> Nevertheless, the press insisted on calling it the “Spruce Goose” despite the fact that the plane is made almost entirely of birch. <S> Apparently it is <S> "the largest flying boat ever built and has the largest wingspan of any aircraft in history" at 320 ft 11 in (97.54 m). <S> Not strictly a "regularly used" airplane, but Hughes retained a full crew to maintain the mammoth plane in a climate-controlled hangar up until his death in 1976. <A> Going off on another direction if ice counts as "unpaved", a Boeing 757 was landed in Antarctica in November 2015, the first commercial airliner to do that. <S> Source is from the link above. <A> Another option might be the Soviet Ekranoplan: these are aircraft that use the ground effect to fly just off a surface of water. <S> For example we might have the Lun-class (73m) <S> : or the experimental Caspian Sea Monster (92m): <S> Sadly neither of these are flying any longer. <S> (source: <S> Wikipedia Ground effect vehicle and Lun-class ekranoplan )
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If you loosen your definition of "airplane" to " the longest class of flying machine and the largest airship by envelope volume " you could think of a Hindenburg-class airship
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What is the cause of tire marks at the extreme ends of runways? At LAX, planes (usually) take off from east to west. On the west end of the runways there are dark tire marks. What is the cause of thesey tire marks? Failed take offs? Late landings? Something else? See Google Maps of LAX <Q> The marks are left by the tires of landing planes when they touch down -- that is, ordinary routine landings. <S> The wheels of a landing aircraft do not start rotating before they hit the runway -- so right at the moment of touchdown, the wheels will at first skid along the runway surface until the friction between tires and runway has delivered enough angular momentum to the tire to spin it up so it matches the ground speed of the landing plane. <S> Once that happens, the wheel will roll normally. <S> This skidding causes the skid marks you have observed. <S> Even if the runway is usually used in the east-to-west direction, there are still enough days where landings are from the west that both ends of the runway will collect tire marks. <S> How many days that are doesn't really influence how black the runway gets, only how long it can go between having the rubber buildup cleaned off. <S> At the few airports that are really only used in one direction (such as the famous Princess Juliana Intl Airport at St. Maarten, which does not even have charted approaches from the east due to terrain obstacles) you will find the tire marks only at the touchdown end of the runway. <A> That would be caused by the tires which are not rolling start rubbing away on the runway on touchdown. <S> Since the tires are not moving, it is going to "scrape" on the runway and leave a mark. <S> This problem is addressed by this question . <S> It also produces some smoke as you can see in the image. <S> Image Source <S> Same thing happens when a car spins on the road. <S> I can't find the source for this. <A> The aiming point for landing is the 1,000' marker, the pair of solid white stripes. <S> This is where the ILS glideslope and visual landing aids are aligned. <S> Planes to float past the touchdown marker because of the flair at the end of landing so the densest tire marks tend to be at and just beyond the marker.
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The reason for the marks is that this is the touchdown zone of the runway.
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Can supersonic conditions be replicated on the ground? In a previous question the P&W J 58 engine for the SR-71 was discussed. The engine was a new and innovative design combining the characteristics of a turbojet and a ramjet. Before flying with such a new design I would think they would want to test it on the ground as much as possible to ensure the safety of the pilot and the aircraft. Otherwise you're sending a guy up with things that should work but so far only on paper. (I know that's what test pilots signed up for but they don't want to be reckless about it.) J-58 ground test. from Wikimedia commons From what I know a pure ramjet won't even operate at zero airspeed. What I'm wondering is how much can be learned from ground testing on such a radical new design, or any supersonic design for that matter? Can supersonic conditions be replicated on the ground? <Q> Arnold Engineering Development Complex (AEDC) <S> The U.S. Air Force and NASA both operate supersonic wind tunnels, as do Lockheed, P&W, and others. <S> The most advanced of these facilities are probably those at Arnold Engineering Development Complex on Arnold Air Force Base. <S> I won't mention any specific numbers from memory because they've likely changed since I worked there <S> and I can't remember exactly which ones were classified/FOUO/otherwise-not-public, but let's just say they're pretty good. <S> AEDC has test cells designed both for testing jet engines as well as for testing scale models of airframes (or full scale airframes if it's a small enough airframe, such as a missile.) <S> Additionally, it has facilities for testing upper-stage rocket motors. <S> Lower-stage rocket motors don't need the facilities at Arnold, as those are designed to operate in the atmosphere and can just be lit up out in a desert somewhere. <S> According to Wikipedia (which I believe is sourced from publically-available information,) Hypervelocity Wind Tunnel 9 can generate air flow of Mach 14 with simulated altitudes from sea level to 173,000 ft. <S> AEDC <S> Tunnel 9 (with test article) <S> Source: Wikipedia <S> In case that's not enough, G Range can fire projectiles at roughly the speed of low Earth orbit. <S> However, this one is kind of stretching the definition of "supersonic," since it's typically pumped down to such negligible air pressure that Mach number isn't really defined before a shot at that kind of velocity. <S> Still, as the wiki article indicates, it's capable of shots at up to 1.7 atmospheres, so it definitely counts as legitimately supersonic on those shots. <S> AEDC <S> Range G <S> Source: <S> Wikipedia Holloman Air Force Base <S> In addition to wind tunnels and other facilities at AEDC, the U.S. Air Force also occasionally uses rocket sleds , such as the one at Holloman Air Force Base , which currently holds the speed record for any type of non-air/space vehicle at 6,416 mph / 10,326 km/h (Mach 8.5.) <S> Holloman High Speed Test Track Source: Wikipedia Land Speed Record Rocket Sled at Holloman <S> Source: <S> Wikipedia <S> The "Speed Limit" at Holloman Air Force Base Source: some guy's website , which got them from publically-released images from Holloman AFB <A> It is a struggle, but it can be done. <S> For the J58, Pratt&Whitney had a test facility at West Palm Beach which would simulate conditions at speed and altitude. <S> From this site : <S> The picture actually shows test cell A-1 at Pratt and Whitney’s West Palm Beach facility. <S> […]. <S> This test cell was actually an altitude simulation cell used for testing purposes. <S> (We had a additional cell used for sea level runs for motors which were overhauled onsite also.) <S> It used a non-afterburning J-79 as a slave motor. <S> The exhaust of the slave was introduced to the inlet of the J-58 through a series of valves thereby simulating the speed, temperature, and density of the air at the inlet normally seen during flight. <S> In this particular picture the motor is running at sea level as indicated by the inlet screen. <A> As shown here , Lockheed Martin has a supersonic wind tunnel capable of generating wind speeds of up to mach 5. <S> A quick Internet search revealed an extensive list of other supersonic wind tunnels, indicating that such tech is fairly widespread. <S> In addition, as suggested by SMSvondertann, jet- and rocket powered cars such as the Thrust <S> SSC have attained supersonic speeds on land. <A> Not quite on the ground, but some organisations go to quite extreme lengths to simulate supersonic conditions. <S> Take NASA and their supersonic parachute intended for Martian atmospheric entry, also known as the Low-Density Supersonic Decelerator. <S> They recently tested this on a quite startling rig: <S> -The parachute was dropped from a helicopter -A 1km steel rope attached the chute to a winch via a pulley -The winch keeps the rope under tension... -...and is attached to the the star of the show - a 4-motor rocket sled, designed to accelerate the parachute to extreme speed before it hits the ground. <S> This rig is worth mentioning not least because the description conjures up an image of a pile of empty ACME boxes! <S> See here for further information
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Yes , supersonic conditions can indeed be replicated on the ground for purposes of airframe and engine testing.
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Can I bring a person with me while getting landing current if they're a licensed, current pilot? It's been over 90 days since I've been flying, but I have a biennial flight review coming up pretty soon and would like to prep for it. The regulations regarding this seem to be extremely vague, but is it legal for me to fly around, do my landings, log PIC time, and such with another licensed, current pilot in the plane with me? <Q> As long as you are not the legal pilot in command you can do what you want. <S> This means the other pilot has to be willing to act as the legal pilot in command on this flight. <S> 61.57 (a) General experience. <S> (1) Except as provided in paragraph (e) of this section, no person may act as a pilot in command of an aircraft carrying passengers or of an aircraft certificated for more than one pilot flight crewmember unless that person has made at least three takeoffs and three landings within the preceding 90 days, and— <S> (i) <S> The person acted as the sole manipulator of the flight controls; <S> The regulation is clearly required of the legal pilot in command. <S> Unfortunately, the other pilot is taking all the responsibility and gets none of the credit as they, under an airplane certificated for single pilot operations, cannot log any PIC time while you are getting current. <S> From LOGGING PILOT <S> IN COMMAND TIME (FAA) <S> : <S> However, two pilots may not simultaneously log PIC when one pilot is sole manipulator of the controls and the other is acting as pilot-in-command if the regulations governing the flight do not require more than one pilot. <S> If the other pilot is a CFI and it is a training flight <S> then no one has to be landing current as there are no passengers. <S> See the Kortokrax interpretation . <S> Relevant excerpt: <S> We agree that, for purposes of section 61.57(b), an authorized instructor providing instruction in an aircraft is not considered a passenger with respect to the person receiving instruction, even where the person receiving the instruction is acting as PIC. <S> (The instructor must be current, qualified to instruct, and hold a category, class and type rating in the aircraft, if a class and type rating is required.) <S> The instructor is not a passenger because he is present specifically to train the person receiving instruction. <S> Neither is the person receiving instruction a passenger with respect to the instructor. <S> This training may take place, even though neither pilot has met the 61.57(b) requirements. <A> I don't think it's that ambiguous. <S> The kicker in your requirementsis the "log PIC time" part... <S> CFR 61.57 <S> (a) General experience. <S> (1) Except as provided in paragraph (e) of this section, no person may act as a pilot in command of an aircraft carrying passengers or of an aircraft certificated for more than one pilot flight crewmember unless that person has made at least three takeoffs and three landings within the preceding 90 days, and— <S> (i) <S> The person acted as the sole manipulator of the flight controls ; <S> And this section: (2) <S> For the purpose of meeting the requirements of paragraph (a)(1) of this section, a person may act as a pilot in command of an aircraft under day VFR or day <S> IFR, provided no persons or property are carried on board the aircraft , other than those necessary for the conduct of the flight. <S> So I interpret that as no passengers. <S> If the other pilot is a CFI and giving instruction, then that would count but if they are just going for a ride, no its not "legal". <S> The take offs and landings have to be done either solo, not as PIC, or under instruction. <S> The other person may be a pilot, but unless they are performing pilot duties they are a passenger like any non pilot rated passenger. <S> By the way, the PIC does not have to sit on the left, you can still occupy the left seat as long as your pilot friend accepts PIC responsibilities as you complete your currency <S> then you can resume being PIC. <A> FWIW, I believe that wbeard52's answer is correct: 61.57 <S> says the acting PIC must be current to carry passengers; it doesn't say that the person at the controls must be current. <S> If you consider AOPA to be an authoritative source, their February 2011 Legal Briefing column discussed exactly this question: <S> Q: I’m out of currency to take passengers in my Cessna 172. <S> When I go flying to do my three bounces, I would prefer to have someone with me for an extra set of eyes and ears. <S> Does it have to be a CFI or can it be a private pilot, as long as he or she is current? <S> A: <S> [...] if the private pilot is current and is willing and qualified to act as PIC of the aircraft, that pilot may be on board the aircraft as PIC and you could be the sole manipulator of the controls in getting your three bounces. <S> I would make sure that both of you understand your roles in the aircraft before taking off, to avoid any misunderstandings.
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If your current passenger is willing to act and take responsibility for your flying as the legal pilot in command then it is allowable.
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What is the IATA code for the A320neo family? I was looking for A319neo, A320neo and A321neo IATA code all over the net but I could't find it, can someone help me with this. (As of 9 March, 2018, the answer with the highest up-vote count (from April 2016) states "will likely be the same as". A more definitive answer should be available now.) <Q> Unfortunately the IATA code list is copyrighted, and I can't find a public document that confirms it. <S> The more commonly used ICAO type designator, a four letter code can be found in ICAO doc 8643 . <S> It contains a list of all common aircraft and their codes. <S> The ICAO type designator for the neo will be the same as for the regular versions. <S> So A319, A320 and A321. <S> Only if the performance of the Neo aircraft significantly differs from the originals, then a dedicated designator will be created. <A> There are now ICAO designators for the A3XX Neo aircraft: A319 Neo: A19N <S> A320 <S> Neo: A20N <S> A321 Neo: A21N Source <A> As mentioned by @CrabLab: Reference: <S> A document by ICAO . <A> IATA and ICAO codes are not the same. <S> The requested IATA codes are used for ticketing and are not freely available. <S> A319neo: <S> Not yet in service <S> A320neo: <S> IATA code is 32V according to Lufthansa A321neo: 8 in service (still looking) <S> A321neoLR (aka A321LR): Not yet in service. <S> There is also a webpage for the Common IATA Aircraft Codes .
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The IATA three letter code for the Neo will likely be the same as for the regular model.
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Should head stay level or inclined in a bank? I just started to receive instructions to become a glider pilot, yay me! :)I (and my instructor) have noticed that I have the tendency to keep the head level (eye-line parallel to horizon) in turns and my instructor says that wouldn't be a good idea, because at some point I won't be able to keep the head level anymore, so I should practice with keeping my head level to the lateral axis of the plane, i.e. inclined together with the bank and eye-line parallel with the wings. What do professional or experienced glider pilots do? Is it maybe a matter of taste? Or should I let go of this tendency because at some point I just can't use horizon and gravity-sensation to orient myself (due to g-forces, spinning, etc.)? <Q> I am not a glider pilot, but the principle holds for flying any fixed wing aircraft 1 : you should keep your head level with the aircraft, as you described, not the horizon. <S> As your instructor explained, there may come—or will come—a time when you are not able to keep your head level with the horizon due to the nature of a particular maneuver or orientation, and that is a practical matter to consider. <S> It is certainly difficult to incline one's head 60° to the side in a steep turn. <S> From my perspective, however, the more important reason is that your frame of reference needs to be the aircraft . <S> You are used to viewing the world with the ground as your frame of reference; down is down, up is up. <S> As you learn to fly, however, you need to learn a new way to view three dimensional space, or—more specifically—the way you move through that space in the aircraft. <S> It might sound cheesy, but you really need to learn to become one with the aircraft and hold the same perspective regardless of the aircraft's orientation. <S> Now, that being said, as you gain experience and develop your skills, you may come to realize that this perspective shift does not always require that your head remain rigidly perpendicular to your shoulders. <S> Rather, it is a matter of perception which will eventually be independent of how your head is oriented relative to the aircraft. <S> At my first flying job I spent much of my time in maneuvering flight and my head was rarely still—much less level with the aircraft. <S> I spent a great deal of time with my head on a swivel, looking up and down, side to side, craning forward to clear into a turn, looking back into the cockpit, etc. <S> At this stage in your training, however, it is probably important to train to keep your head straight within the aircraft; certainly follow your instructor's instructions, and you should do well. <S> 1 <S> This probably holds true for rotorcraft as well, or any aircraft for that matter. <S> I am only sharing what I am familiar with. <A> I was taught (by multiple instructors) to keep head straight. <S> During my instrument training, I was told it helped w/spatial disorientation. <S> During my aerobatic training, my instructor sat behind me and would slap the back of my head if I did not keep it straight during maneuvers. <S> straight == not tilted, lean back and keep head firmly planted on headrest, do not compensate bank, etc. <A> Level with the wings. <S> If you keep level with the horizon then you are not maintaining an even lookout all round for a start and when you find yourself in a stack of other gliders in a thermal you need to keep a good lookout even with FLARM. <S> In addition what the head does the body tends to follow and so you may find yourself unintentionally decreasing the bank angle to match your head and then slipping out of the turn. <A> Until you learn this basic building block, other more advanced things will be difficult to grasp. <S> Airplane Flying Handbook, pg. <S> 3-11 <S> The pilot’s posture while seated in the airplane is very important, particularly during turns. <S> It will affect the interpretation of outside visual references. <S> At the beginning, the student may lean away from the turn in an attempt to remain upright in relation to the ground rather than ride with the airplane. <S> This should be corrected immediately if the student is to properly learn to use visual references. <S> [Figure 3-12] <A> As others have said, keep your head straight in reference to the aircraft. <S> To add to Ron's comment, head leaning can lead to coriolis illusion. <A> I find this an odd question. <S> When I am looking over the nose , my head is wings level. <S> But most of the time my head is moving around anyway, scanning for traffic and scanning instruments. <S> And especially when turning, I am looking through the turn which means <S> say 30 degrees to the side of the nose, and up and down over the horizon. <S> So I can't say how my head is oriented, except to say it's pointed at where I want to look.
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You need to keep your head level with reference to the airplane and not the horizon.
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Is it a flight violation to mishear ATC instructions for exiting the runway? I was on landing rollout and misheard a tower "turn off at xxx switch ground" call. We read back the incorrect taxi way and turned off there and switched to the ground frequency. After our incorrect read back we were not contacted again until ground told us to call tower. I was under the impression that the landing aircraft had the right of way over any traffic behind them, even on roll out. I was also under the impression that a tower cannot stop you from using the whole runway. Is missing a directed turn off a runway a flight violation? If so what FAR/AIM or regulation did it violate? Is the fault with us for mishearing or with the controller for not correcting us? Does this count as a runway incursion? Does the controller maintain responsibility for maintaining separation until we taxi clear? To answer a few of the questions from below:when we contacted the ground controller, they gave us a phone number to contact tower then gave us a taxi clearance. When they told us to call i became concerned with receiving a flight violation. We were not corrected to my knowledge, we only heard radio traffic once we had turned off the runway. This was also not a LAHS operation. another question: From the AIM 4-3-20 it says : "the following procedures must be followed..." "exit the runway without delay" " is that at the discretion of the pilot? also if tower gives you a taxiway instruction to leave the runway is that an instruction or a clearance? Is it a good idea to call the local FAA office and see if they have opened an investigation? <Q> I don't think you violated any regulations. <S> It was an ATC instruction, not an ATC clearance. <S> It was an instruction you were unable to comply with. <S> The instruction was badly timed and was obviously not clear since you did not correctly understand it. <S> In the busy time during the landing roll, you understood something different, and read back what you understood it to be. <S> The landing roll-out can be a busy time needing the attention of both pilots. <S> ATC issuing an instruction while you are basically still in the landing roll should not be expected to be complied with unless it is happens to be convenient for you to do so. <S> Many airlines SOP say that you do nothing until you are clear of the runway. <S> Both pilots remain heads up and don't touch anything. <S> The pilot in command alone will decide where it is safe to tun off the runway. <S> If ATC makes a "Request", and it can be safely complied with, then the PIC may decide to deviate from SOP and comply. <S> If you ran off the side of the runway trying to comply with an ATC "request", who do you think will be held responsible? <S> (I'll give you a hint, it won't be ATC) <S> This is a prime example of why ATC should not be doing this. <A> Mike has a good answer, but I thought it was worth while mentioning something you say in your question: ... <S> I was also under the impression that a tower cannot stop you from using the whole runway. <S> While in many cases this is true, there are some that it is not. <S> The main example of this is a Land and Hold Short Operation (LAHSO) . <S> If you accept a LAHSO then you are required to comply with the hold short point on the runway and not go beyond that. <S> (The only other one I can think of is when a crossing runway is closed). <S> So if you had accepted a LAHSO request (and its up to you as the pilot to accept or decline the request), and subsequently used more than the LAHSO permitted you to, this would be a violation. <S> Also, if you are a light plane and want more than your fair share of runway, its usually "polite" to tell the controller that you want "full length". <S> The controller is trying to space out landing aircraft and may assume that you don't need 8000+ feet of runway in your Cessna 172. <S> Legally unless you accept a LAHSO you are welcome to use all of it, but the controller will be a happier person if you tell them you need more. <S> I do this quite a bit when coming in on a certain runway that has the FBO at the opposite end, its better to land long than spend 10 minutes taxing. <S> The controller may request that you "make it short" for landing aircraft. <A> Exiting a runway is purely at the discretion of the PIC. <S> The tower-recommended exit is just that: a recommendation. <S> This is a safety issue.
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The pilot exits the runway where they and they alone decide it is safe to do so.
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When are pilots required to have approval to conduct practice approaches? I would like a clarification about requesting practice approaches. I have seen pilots at uncontrolled airports shoot practice approaches such as VOR, SDF, etc. without needing approval; obviously. Am I correct in thinking that a practice approach approval is only required to be explicitly requested when being controlled by ATC via flight following or approach/tower control? I know this may seem like a silly question, so I will describe a scenario so that readers understand the context of why I am asking a little bit better: A VFR flight passes through class C airspace, and contacts approach control prior to entering. On the other side of said class C airspace, a few miles out of the boundary line, there is a destination airport where the pilots would like to shoot a practice approach, which is a non-controlled airport outside of the boundaries of "ATC-contact-required" airspace. Do the pilots request a practice approach, or do they request to terminate radar service and then go ahead and shoot the approach? Maybe the answer lies in the content of the approach depending on whether or not initial fixes or a missed approach segment would lead a flight into "ATC-contact-required" airspace. <Q> Usually airports with approach controls will have it printed on the approach plate. <S> Take for example the non-towered field Menominee-Marinette Twin County: <S> The approach control frequency is highlighted in the chart. <S> This is who you receive approach clearance from. <S> KMNM is outside of KGRB (Green Bay) airspace by a good 40 miles, but KGRB approach control is responsible for the airport. <S> So the short answer is: Look at the approach plate for the responsible frequency/agency for the airport. <S> I think the other part of your question is more along the lines of "If I'm shooting an IFR approach, am I required to get clearance via ATC? <S> " <S> This I'm not 100% sure about <S> but I would guess that the answer is "yes" since you don't want to interfere with traffic shooting real approaches. <S> The Aeronautical Information Manual has advice for conducting practice approaches in section 4-3-21 <S> (Page 204): <S> (a) ... <S> Practice <S> instrument approaches are considered to be instrument approaches made by either a VFR aircraft not on an IFR flight plan or an aircraft on an IFR flight plan. <S> To achieve this and thereby enhance air safety, it is Air Traffic’s policy to provide for separation of such operations at locations where approach control facilities are located and, as resources permit, at certain other locations served by ARTCCs or parent approach control facilities. <S> (Emphasis mine) <S> Furthermore, it goes on to say... <S> (b) Before practicing an instrument approach, pilots should inform the approach control facility or the tower of the type of practice approach they desire to make and how they intend to terminate it, ... (c) <S> (e) <S> VFR aircraft practicing instrument approaches are not automatically authorized to execute the missed approach procedure. <S> But as I say in my comment, the AIM is a guideline, not a rule <S> and I don't think there is anybody stopping somebody from doing an instrument approach without controller notification, however because ATC isn't providing traffic separation at that point, it could be considered negligent of the pilot to not request ATC clearance. <S> Besides, a good portion of conducting practice approaches is talking to ATC. <A> After reading this thread I opted to call Seattle Approach control and spoke to the operations. <S> They told me, as long as you have a a transponder, have squawked VFR, and as long as you are staying in the vicinity of the airfield (10 miles) they can see you. <S> You don't have to contact them . <S> You are also required to transmit on the CTAF throughout your approach so the VFR traffic is aware of your whereabouts and intentions. <S> It might be different in your area, so <S> I recommend you contact your local approach control indicated on the approach plate to make sure they are ok with you shooting approaches under "VFR" conditions and that you will maintain a look out using a safety pilot. <A> You are not required to request a practice approach. <S> You are, on the other hand, required to follow the proper technique for flying in whatever airspace in which you happen to find yourself. <S> For instance: In Class E or G airspace with an operating control tower, you have to receive clearance to land. <S> In addition, if you have an operating radio, you must receive clearance to approach within 4 miles of the airport below 2500 feet AGL. <S> In Class A, B, C, or D airspace, you must maintain two-way radio communication with ATC and comply with ATC’s instructions and clearances. <S> If ATC authorizes you to self-vector for a straight in approach, you can maneuver <S> however you wish as long as it’s done safely. <S> Otherwise, you will have to request an approach (practice or not). <S> Also, requesting the practice approach will make ATC’s job of aircraft separation easier and safer. <S> They can anticipate your actions. <S> In Class E or G airspace without an operating control tower, you do not have to request a practice IAP approach. <S> On the other hand, you will have to request an actual approach if IMC conditions prevail unless you are NORDO. <S> When performing an IAP approach, you will have to make proper radio calls in a manner that a VFR pilot at a pilot-controlled airport would clearly understand. <S> Give your position as a distance and direction heading inbound (presumably) to the airport with an altitude. <S> Make your intentions of an approach and landing clear. <S> Many VFR pilots will not understand the verbiage and nomenclature used for IFR procedures and reporting points.
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At airports without a tower, pilots wishing to make practice instrument approaches should notify the facility having control jurisdiction of the desired approach as indicated on the approach chart.
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What distinct challenges are faced in taxi operations that aren't found in other phases of flight? The Federal Aviation Administration (FAA) made Runway Incursion Avoidance a special emphasis area and added it as a required task in several of the Practical Test Standards (PTS) documents. All the PTS documents have a bullet item that reads something like this: Distinct challenges and requirements during taxi operations not found in other phases of flight operations. I have reviewed the applicable sections of the Pilot's Handbook of Aeronautical Knowledge and AC 91-73B , but I haven't found a concrete answer on what exactly these challenges are. If an examiner asked me to explain these challenges I'd do my best, and I'm sure I could come up with some good arguments for my thoughts, but I like to know what the FAA is looking for when they ask a question and this one doesn't seem to have an exact reference. <Q> Well in air you don't have to worry about kangaroos in your path or a wheel falling off unnoticed , or people beside a taxiway mistakenly indicating you won't hit a golf cart . <S> Heaven forbid <S> you accidentally retract the landing gear . <S> Jokes aisde, taxiing can be a major challenge even for experienced pilots. <S> First off, your traditional warning systems don't work. <S> You can't check your route using a low or mid-range GPS because they don't have airport taxiway information. <S> You won't get a "terrain!" <S> warning when you're about to head off the end of a taxiway. <S> You don't use your ailerons or elevator to control your path; you use them to keep the wings from lifting and to keep you on the ground. <S> You use the rudder and steerable nose wheel/tail-wheel (if present) to keep you on the right path, with help from the brakes only when necessary. <S> Those brakes definitely will be necessary in a tail-wheel aircraft with a strong enough crosswind. <S> If you fail to control the ground path in a tail-wheel aircraft, an unstable and difficult ground loop can develop. <S> Did wbeard52 mention low visibility? <S> You can technically land a plane in zero visibility if your plane and the airport are properly equipped, but good luck naviagting the taxiways afterwards. <S> A pilot once remarked that "Taxiing at ORD the first time in low visibility conditions is impossible," and another remarked that he was so confused by low visibility he had to have a follow-me truck guide him. <S> [source] Taxiing can also be confusing in good weather, especially at night. <S> Sometimes the taxiway letters jump randomly around the alphabet, sometimes markings are obstructed, sometimes there's construction (you don't see construction much in the air!). <S> The FAA has an entire handbook appendix devoted to avoiding runway incursions that explains these navigational issues. <S> You also have to be vigilant for obstacles around you (like those kangaroos I mentioned earlier). <S> In a tail-wheel aircraft with a high nose, for example, it's recommended <S> to zig-zag <S> a little so you can see what's right in front of you. <S> In aircraft like the B777-300 <S> they actually have camera systems to augment visibility. <S> (see this question and the FAA's Airplane Flying Handbook ). <S> You can also look up a list of recent taxiing incidents here <A> There are quite a few challenges: Low visibility taxi <S> Did I mention complex taxi routes in low visibility Hot spots (which are designed to alert pilots to possible taxi operational challenges Runway incursion Winds and the possibility of the upwind wing rising unless compensated for. <S> Taxiing with your feet and staying on the yellow line Jet blast <S> Taxiing on a snow covered or icy taxiway <A> Challenges: <S> Your airplane is on ground, so the physics of ground play role. <S> Slipping, skidding, stopping, decelerating, pushback etc. <S> Visual outlook responsibility is both the pilot's and the tower's and any other traffic's. <S> A fuel truck or passenger bus or a follow me car can hit you any time. <S> Navigating on the airport can be stressful for a first comer pilot, especially if it's a crowded airport. <S> Whereas in air, most of the events are foreseen, and the autopilot handles most of the detailed tasks and creates the situational awareness to give time for the pilot to think carefully.
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Steering is difficult because the control surfaces are used differently on the ground, especially in a crosswind.
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Will having a history of depression prevent me from flying? The AOPA website lists four medications as acceptable treatments for depression. I was treated with one of them, but it ended up making things far worse, to the point where I had issues with suicidal ideation. I've since stopped taking it and, while I'm still somewhat depressed, no longer have those thoughts, and don't have any issues getting along with daily life. My depression is more along the melancholic lines, so I basically just don't find most things enjoyable. Being in the air is one of the few things that helps, so obviously I'm worried about not being able to do so. I don't have any of the symptoms that would seem to have an impact on actually flying, but I know having a history is a problem, so I've been trying to figure out how much this will affect things. Not sure if aircraft type matters for medical requirements, but I was hoping to either fly helicopters commercially, or in the very likely case that I can't find a helo school, I'd probably end up crop dusting. <Q> This is one of those questions where you really need to talk to an AME, preferably one who has significant experience working through these sorts of issues. <S> In order to get the Class II medical that you'll need to fly commercially, you'll end up needing to work through the process anyway, so you're probably better off starting with the expert, rather than with a message board like this one. <S> The only case where you'd save any money by starting here is if someone here were to accurately <S> tell you that there is no need to go to an AME as there is no way anything could possibly work. <S> I doubt you're going to get that sort of advice, because (a) we don't have any AME's that post here on av.se, as far as anybody has ever self-identified, at least, and (b) <S> this stuff is sufficiently complicated that you don't want to trust a layman's info or opinions, even one who "knew somebody who had a similar situation." <S> That said, I'd suspect that the chances are pretty good that you may well be able to get a medical certificate, so I would encourage you to pursue that path. <S> Let a good AME take a look at the specifics of what your history looks like, and listen to his/her advice about what would need to happen (maybe very little, maybe quite a bit) in order to satisfy the FAA. <S> This thread <S> deals with an entirely different medical condition, but the answers, and the logic behind them, apply here as well. <S> Be honest with the flight surgeon, and don't let random posters here talk you out of giving yourself every opportunity to pursue your dream of flying commercially. <S> Best of luck to you! <A> I have a history of depression and hold a 3rd class medical certificate. <S> In my case the depression is managed by medication so the certificate is issued under what is called a Special Issuance (SI). <S> Therefore I have personal experience with the extra "hoops" involved that others have mentioned. <S> You must start with a consultation with a HIMS (Human Intervention Motivation Study) AME. <S> These doctors have additional training and familiarity with the depression and anti-depressant SI protocol introduced in 2010. <S> The AME who moderates the AOPA medical issues forum is an excellent starting point (he helped write the protocol that the FAA adopted) and you can contact him directly for advice. <S> Alternatively you can find a HIMS AME in your local area by consulting the FAA's official list . <S> Good luck! <A> This is what the medical certification standards for third class say. <S> Second class's standards text in the "mental" section is verbatim to third class standards. <S> § 67.307 Mental. <S> Mental standards for a third-class airman medical certificate are: (a) <S> No established medical history or clinical diagnosis of any of the following: (1) <S> A personality disorder that is severe enough to have repeatedly manifested itself by overt acts. <S> (2) <S> A psychosis. <S> As used in this section, “psychosis” refers to a mental disorder in which— (i) <S> The individual has manifested delusions, hallucinations, grossly bizarreor disorganized behavior, or other commonly accepted symptoms of this condition; or (ii) <S> The individual may reasonably be expected to manifest delusions, hallucinations, grossly bizarre or disorganized behavior, or other commonly accepted symptoms of this condition. <S> (3) <S> A bipolar disorder. <S> ... <S> [stuff about drug and alcohol abuse truncated]... <S> (c) <S> No other personality disorder, neurosis, or other mental condition that the Federal Air Surgeon, based on the case history and appropriate, qualified medical judgment relating to the condition involved, finds— (1) Makes the person unable to safely perform the duties or exercise the privileges of the airman certificate applied for or held; or (2) May reasonably be expected, for the maximum duration of the airman medical certificate applied for or held, to make the person unable to perform those duties or exercise those privileges. <S> If a medical is denied the FAA can choose to make exceptions. <S> §67.315 <S> Discretionary issuance. <S> A person who does not meet the provisions of §§67.303 through 67.313 may apply for the discretionary issuance of a certificate under §67.401. <S> Here is a link to §67.401 <S> My personal opinion on the matter is that you will probably be able to get a medical and you may have a couple of extra hoops to jump through.
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I'd think the fact that you've proven to be stable and aren't on medication will help you.
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Why do the MiG-15 and MiG-17 have a split air intake in their noses? MiG-15 and MiG-17 both have a split air intake in their nose. However, they have only one jet engine . So why is the air intake split? Wouldn't it be a lot less drag to just let the intake flow cleanly into the engine? <Q> The advent of (turbo)jet engines resulted in an important change in design of aircraft- <S> the location of the engine, which can either be mounted on the fuselage or in the wings (as in Me 262). <S> Also, the engine was shifted from the front (as in the case of a majority of piston engined fighters) to the rear in jet aircraft (as the exhaust has to be routed below the fuselage otherwise). <S> In this case, the intakes can either be in the nose or in the sides (like in Hawker Hunter). <S> For the aircraft with nose intakes (a design which was eliminated by the ever increasing size of Radar equipment), the problem was how to get the air to the engine. <S> In case of Mig-15, the Russians split the air in a central splitter, which then passed through two narrow air ducts passing through either side of the cockpit, avionics bay, fuel tanks and the nose landing gear bay. <S> This inlet was quite complex, not to metion it made for a cramped cockpit, but on the other had, it was compact. <S> Similar air intakes were used in aircraft like the Mig-21. <S> Another method was to put to simply put the cockpit above the air inlet duct, like the F-86 Sabre, which resulted in the raised stance of the cockpit (and better visibility). <A> The intake is split in order to provide a place for the squishy human pilot to sit. <S> Sure, it would be less drag to have a straight pipe, but that would mean the pilot being subjected to the airflow. <S> If they wanted a straight airflow they would have had to move the pilot position or move the air intake. <A> The two air intake ducts of the MiG 15 pass either side of the nosewheel box and the cockpit. <S> Prototypes of the MiG 15 mounted guns in the space between the intake ducts, but this led to engine problems caused by ingestion of gun gas <S> and so the armament was relocated to under the nose.
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The alternative configuration of having a single duct passing underneath the cockpit, as used in the A7 Corsair II, necessitates the nosewheel being mounted further to the rear, which in the MiG 15 with it's short fuselage, would have made the wheelbase too short.
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Why don't Transport Category aircraft have a listed Vy? I was talking with a pilot about an inability to maintain the targeted climb rate in a particular situation and asked him what the Vy was for the jet. He curtly replied "Vy is only for Part 23 aircraft." (FYI for those outside the US: Part 25 aircraft are commerical planes, while Part 23 are usually general aviation planes. You can find more details here .) Yet, I know for a fact that there is a maximum excess thrust speed, because at a certain speed drag is at a minimum. This should be close to Vy. I also know that rate of climb is frequently listed for these aircraft. However, the optimal speed for gaining altitude isn't usually listed for commercial aircraft like it is for GA aircraft. In fact, many of the v-speeds like Vmca and Vdec are harder to find for larger aircraft. Why is this? I can think of several possibilities: Commercial aircraft speeds are defined by ATC and operating procedures, not by performance considerations Commercial aircraft have enough thrust that climb performance limits isn't an issue (which I doubt from my experience). Commercial aircraft use other parameters for similar purposes like rate of climb, v2, or long range cruise speed Jets don't list this speed but propeller planes do <Q> The crew can get a best rate or best angle of climb speed from the FMC (which "knows" the current weight of the aircraft, based on current fuel & an entered Zero Fuel Weight). <S> From an empty aircraft with minimum fuel to a loaded aircraft with max fuel, the weight probably won't quite double for most commercial jet aircraft, but the one might be 170% or more of the other. <S> With that much range, any single Vy you publish would be way far off in a lot of cases. <S> On a GA aircraft, without an FMC and operating in a much narrower weight range, publishing a single speed makes much more sense as the delta between published and actual becomes smaller and the consequence of being a couple knots off is probably slight. <A> Airplanes certificated under FAR Part 25 (Transport Category Airplanes) must meet far more complex and regulated takeoff performance criteria than can be reduced to a (light aircraft) <S> Vy or Vx (Vyse or Vxse) speed. <S> If you're taking off in a Cessna 310 and interested in gaining altitude as quickly as possible (rate) then having a published Vy speed (which can be adjusted for weight) is a benefit that the pilot may decide to take advantage of. <S> On the other hand, in a Transport Category Airplane a particular takeoff path (climb gradient) must be satisfied in accordance with FAR Part 25.111 <S> criteria, which are fundamentally and functionally irrelevant to the establishment of a "Vy" speed (this does not mean a Vy speed for a light aircraft is less important, just less relevant considering the certification regulations). <S> The issue can be complex, but generally speaking Part 25 airplanes must (depending on the operational regulations involved, e.g., part 121, part 135 ops, etc.) <S> takeoff and climb out using a profile (e.g. speeds, configuration, weight, thrust setting, procedures etc.) <S> that allows for the avoidance of obstacles during the climb. <S> see AC 120-129 <S> "Airport Obstacle Analysis" <S> For example, during normal Part 121 operations, more often than not, the the thrust setting used for takeoff is less (sometimes far less) than 100%. <S> The amount of thrust used is based on environmental/operational conditions (weight, runway, temp, obstacles, etc.) and computed so that the required climb gradient is achieved. <S> Performance engineers providing data to the carrier in textual form or programmed data (e.g. FMC) for <S> each airport/runway reduce the very complex amalgamation of regulatory requirements, necessary climb performance, <S> near/far obstacles in the area of consideration, etc. <S> into thrust/airspeed/configuration settings for the crew. <S> An excellent discussion of this entire issue can be found in this Aircraft Climb Performance NBAA article. <A> Well they do of sorts. <S> But your pilot friend is right <S> , they are not tabulated for a transport category aircraft like is done for a Part 23 aircraft. <S> Due to the large payloads, CG ranges and configurations, the best rate of climb speed must be computed for each situation. <S> There is no one published Vy for a large transport category airplane. <S> Incidentally the best rate of climb varies for any aircraft you fly, <S> it’s just that for smaller airplanes that range is quite small. <S> As an example, in a Cessna 172 the best rate of climb <S> Vy varies only a few knots between sea level and its service ceiling. <S> Larger, more powerful GA aircraft will have tables published in the performance and limitations sections of their AFM listing this. <S> Saying that any airplane has a single best rate of climb speed is a bit of a misnomer, similar to saying that an airplane has a ‘stall speed’, etc. <A> Actually modern jets in general do have massive excess thrust. <S> One big reason is due to safety requirements to handle engine loss. <S> Vy is a big issue while on a single engine or piston props. <S> With two turbofans/turboprops running and at low altitudes, they "climb like a rocket" compared with single piston and even twin pistons with big engines. <S> Additional reasons for the substantial thrust to weight is necessary acceleration for short runway takeoffs and just as importantly to still have excess thrust to climb way up there where the air is thin and high subsonic cruise can be achieved. <S> Up there the airframe and the engine are both more efficient, but due to lost thrust with altitude, you need big powerful engines. <S> Remember that for jets and high performance turboprops, 3000-4000fpm climbs are common. <S> It just doesn't take long until the terrain is no longer and issue and its more important to get to the destination faster and also save fuel. <S> Flying on Vy typically wastes fuel, because you are running the engine at max continuous power/thrust, while not getting neither the best forward nor the best vertical speeds. <S> Big jets prefer to climb at speeds above 250KIAS, so they hit the 250KIAS below 10000ft limit. <S> But strictly speaking, what would be used as Vy, to clear critical terrain right after takeoff, something in the V2+20 to V2+50 range would be used. <S> V2 might actually produce a better angle of climb, but its very uncomfortable to fly that close in case an engine quits. <S> Even then this is used for as short a period as possible. <S> V2+30 requires the aircraft has flaps deployed and is flying at half the speed it would like to go.
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Large commercial jets operate within a much wider range of weights than most GA aircraft do, and since Vy varies with weight, it wouldn't make sense to publish "a" single Vy speed for them.
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Do jet engine exhausts usually glow orange? In these two lovely images: Source: Wikimedia Commons Source: wvi.com The exhaust end of the engines are glowing bright orange from being so hot. Do they get that hot during normal flight operations, or are they hot because the engines are statically mounted for testing and have (relatively) minimal air flow to cool it? If it's normally this hot, what is the exhaust made of, and how is it insulated to keep it from melting the nacelle around it? <Q> Both images you posted are of Pratt&Whitney J58 <S> afterburning turbojet that was used on the Lockheed <S> A-12 <S> and Lockheed SR-71 aircraft. <S> That engine ran particularly hot. <S> The engine was designed for operation at Mach 3.2. <S> The efficiency of turbojet increases with speed, but only to a certain point and somewhere above Mach 2 it starts to decline. <S> However efficiency of afterburner continues to increase, so this engine was designed to operate continuously with afterburner and to generate higher fraction of power in the afterburner than other engines. <S> The afterburner combustor liner was able to withstand temperature up to 1,760°C (3,800°F). <S> The core of the flame was much hotter still, but a colder air was fed along the walls, like in all turbine engines, as explained here . <S> The engine was also cooled by incoming fuel similarly to how rocket engines are. <S> Additionally, at the top speed, the compression heating as the air was slowed to subsonic speed in the inlet heated it to over 400 <S> °C (800°F) at the compressor face already. <S> Since in the static test the air was not that hot, the engine might have actually ran a bit colder in the test than in normal operation. <S> This was however specific to this one engine. <S> The compression heating is negligible at subsonic speeds and grows faster at higher Mach numbers. <S> Most supersonic aircraft fly around Mach 2, where the effect is already noticeable, but not nearly as pronounced. <S> It just isn't as high as in this special case. <A> To supplement Jan Hudec's answer, you are also looking at the engine casing itself. <S> When the engine is installed in the aircraft there is additional nacelle material surrounding it so that even at full power the metal glowing will not be seen looking at it from the side. <S> (although in afterburner you will see the flame) <S> But the answer is yes, a typical jet engine will heat up enough to glow during normal flight operations. <S> However, is it much much dimmer than your photos, really just a dull orange. <S> And you usually only notice it if you are looking almost directly up the tailpipe at the turbine section. <A> Q1: <S> Yes the afterburner pipe and nozzle interiors can hit upwards of 1800-2000 <S> ° F during full throttle operations. <S> Q2: <S> In his book Sled Driver, Maj Brian Shul remarks about witnessing J58 engine test runs post maintenance out at Beale AFB, where the engines were brought up the maximum power for several minutes and then shut down. <S> He stated the engine jet pipes would glow orange hot during operations (and took the photos to prove it!), yet within a minute or so of shutdown the ceramic linings were cool enough to touch!
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Most engines have ceramic linings in the afterburner can and nozzle petals to protect the metallic parts from the high heat. For most engines, they run at roughly the same temperature in test as they do in normal operation.
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What lights does the Cessna 172 light rheostat control? I am part of a team developing a Cessna 172 P model for FlightGear, an open source free flight simulator. We are now programming how the panel and radio lightning rheostat should work, but we found a lot of unclear and/or contradictory information about it online. Our main problem is to understand how the radio light knob (labelled as RADIO LT) work in these older models of the 172. The POH from 1982 states the following: The engine instrument cluster (if post lights are installed), radio equipment, and magnetic compass have integral lightning and operate independently of post or flood lightning. The intensity of this lightning is controlled by the inner knob on the light dimming rheostat labelled RADIO LT; rotate the knob clockwise to obtain the desired light intensity. However, for daylight operation, the compass and engine instrument lights may be turned off while still maintaining maximum light intensity for the digital readouts in the radio equipment. This is accomplished by rotating the RADIO LT knob full counterclockwise. Check that the flood lights/post lights are turned off for daylight operation by rotating the PANEL LT knob full counterclockwise. This makes it look like the RADIO LT knob controls both the brightness of the radio digital readouts (i.e. the frequency digits) as well as other types of lights (radio cluster buttons and compass), but I found out that other renowned simulations of the 172 for other simulators do not dim the digital readouts with that knob. It also seems strange to me that one would be able to dim the radio digits under any condition, let alone turn them completely off. So does anyone here have experience with these models of the 172? Would anyone be able to describe how to best model the behaviour of the radio lights? <Q> This depends more on the radios installed than the plane its self, older era planes may have had King radios with analog numeric readouts. <S> These radios are generally back lit and controlled by what ever rheostat controls the panel those radios generally look like this ( source ) <S> later planes may have had digital readouts which in some cases had another control to dim the intensity. <S> This is often because in a sense the lights are always on you may need to control them with out turning on or dimming the panel. <S> As a matter of fact you generally want them to work opposite, during the day when the panel is dim or off you want the radio lights to be brightest they would then be dimmed in the evening as you bring the panel lights on. <S> Those radios often looked like this, ( source ) <S> The dim function may appear on units like the DME and Auto Pilot if they are similarly lit. <S> Its been a while since I have night flown with one <S> but if memory servers the newer GPS units like the GNS430/540 have backlit buttons that come on when the panel lights are activated. <S> These units also tend to have separate ways to control the screen brightness/contrast ( source ) <S> You may have more luck referencing the manuals for the radios them selves than the POH for the plane. <S> You should design for the types of radios you are putting in (looks wise) <A> The Bendix-King KX-155, KR-87, and KT-76C dim their digits based on built-in photosensitive resistors. <S> The faceplate backlighting and the illumination intensity of the NAV instruments is controlled by the radio dimmer button, which adjusts the voltage they receive via a voltage stabilizer circuit (LM350K). <S> Note; the lighting of the magnetic compass is controlled by the pedestal light dimmer! <A> The light rheostat is generally used to brighten or dim the overhead light used to shed some light on the control panel on older 172's (their all old). <S> It really is useless. <S> Newer ones have a few lights under the edge of the glare shield and the knob controls their intensity. <S> The post light is a light in the post between the glare shield and the cabin roof. <S> It's a white light and not something you want on at night. <S> If you are designing a simulator then make it real. <S> Make the panel almost impossible to see at night. <S> This way the player can get the feel of a real 172. <S> Check out Sporty's pilot shop. <S> That's why they sell lights you can strap to your head. <S> Or lights that clip somewhere <S> so you can see the instruments.
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The engine and flight instrument' lighting is controlled by another voltage stablizer adjusted by the instrument dimmer.
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Why is the Mooney's signature tail profile different from most planes? In another question, someone said everyone but Mooney has the vertical stabilizer on backward. (As a Cessna driver, this looks backwards to me). Is there an aerodynamic reason or some reason other than marketing? (Note the slants of the leading and trailing edges.) <Q> The best explanation I've heard is that at high angles of attack the rudder is nearly vertical providing the pilot better yaw authority. <S> I don't know whether this is true or not <S> but it makes for a good story, doesn't it? <S> Conversely, at high angles of attack a swept tail (and rudder) moves further away from a vertical position and is, in theory, less effective. <S> Some go on to speculate that the leading edge of the vertical stab, being un-swept, protrudes further into undisturbed airflow at high AOA/low airspeeds which may slightly enhance the pilot's ability to control yaw at the edge of a stall. <S> I've never spun a Mooney (I did complete my CFI in an M20F/201) <S> nor do I have a burning desire to do so. <S> I imagine that it's not a friendly spinner. <S> Catching the spin early would be critical in a slippery air frame like a Mooney. <S> Here is one discussion (of many) on a Mooney forum regarding the tail design: http://mooneyspace.com/topic/9905-mooney-tail-aerodynamics-not-backwards/ <S> I doubt very much that it's simply a marketing gimmick <S> (although, it could be as simple as that!). <S> I believe that the explanation I've relayed here is merely "somewhat plausible" as it was gleaned from hours of beer-fueled hangar talk and <S> some Google searching... <S> not exactly a scientifically rigorous method of research. <S> I have no credible references and, as far as I know, no data exists to back any of it up. <A> The tail only looks backward when people can usually see it: in the pattern, parked, or flying formation with a photographer in a slower aircraft. <S> Rather than using trim tabs to push control surfaces out of alignment ( which adds drag ), the entire empennage pivots for pitch trim adjustments. <S> To trim the nose up at low speed, the leading edge of the horizontal stabilizer tips down and the vertical stabilizer pivots forward. <S> For nose down trim at cruise, the horiz stab leading edge tips up and the vert stab leading edge pivots back. <S> My dad owned the 201 (M20J) <S> N58016 which had formerly been Roy LoPresti's "company car" and development mule for the 201, 231, and 252. <S> Dad and Mom went to some Mooney Homecomings in Kerrville, where Roy gave him a guided tour of the bits that made that airframe unique. <A> The 'reversed' tail has been the signature feature on many of Mooney's products, including the M18, M20, M22 and the new production M10 line of aircraft. <S> But not every Mooney did use the design; best example of that was the Mooney 301, which evolved into the Daher Socata TBM series of single engine turboprops. <S> I've heard a lot of the reasons for this design choice, including improved rudder authority at high AoA listed above. <S> Another is that a trapezoidal shaped planform is a more efficient lifting surface design for slow subsonic flight where compreesibile effects are trivial. <S> Of interest, this tail plane design employs one of the most unorthodox elevator trim arrangements in aviation. <S> Starting with the M20E, the entire empennage is a single assembly which attaches to the aft fuselage via a single hinge point. <S> Driven by a pilot controlled screw jack, the entire empennage would then rotate in the vertical plane, thus changing the AoA of the tail plane and providing longitudinal trim. <S> I'm not aware of any other aircraft which uses such a complicated elevator trim system including commercial aircraft which make use of an all moving tail plane box for this purpose. <A> I worked at Mooney for 11years, 6 as the Director of Engineering after Roy Lopresti left the company. <S> Art Mooney asked Al to design the wood spars so he could build them on a flat table. <S> This resulted in t iconic and characteristic "Mark" of the M20 Type. <A> The Mooney tail plane consists of three parts: vertical stab and L/R horizontal stab. <S> All three are interchanging.
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The story goes something like this: As the plane pitches up, the rudder, being slanted "forward," moves closer to a vertical position and provides better directional control at low speeds. A brief online search of Mooney tail lore yields everything from pure marketing to discussion of wetted area to better directional control during landing to spin recovery/prevention to "those swept tails provide no speed benefit and are simply designed to look good."
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What is the drag of helicopter rotor at jet speed? I wonder if a jet plane can have helicopter rotor for vertical take off and then, when moving forward just stops that rotor and uses lift from wings like normal plane. Since rotor blade seems thinner and smaller than wings, I guess when turned off, its drag should be much lower than wing. So why doesn't that type of hybrid plane exist? Or the drag of the rotor at the jet speed would be so high? If the drag is high, why is it high, since the rotor blade is also airfoil like wing? <Q> There were actually some experiments with stopped rotor . <S> Furthest with the actual implementation was probably the Boeing X50 Dragonfly : <S> By Source, Fair use of copyrighted material in the context of Boeing <S> X-50 Dragonfly <S> The main reasons I can think of why nothing like this reached production yet are: <S> When the rotor spins, the blade on one side moves aft and needs to have its leading edge face aft, but when the rotor is stopped, both sides need the leading edge facing forward. <S> So either the airfoil must be symmetric, but that has really poor efficiency, or some blades have to turn somehow, which is complicated. <S> To be light, rotor blades are normally very flexible and rely on the centrifugal force to keep them straight under load. <S> But when they stop, they won't have such force, so they must be much stiffer, which makes them bit too heavy to spin. <S> Having separate wings and rotor would add a lot of weight, especially since the rotor would still have to be made strong enough to resist the aerodynamic loads when stopped. <A> So why doesn't that type of hybrid plane exist? <S> This type of plane does not exist largely because there is a simpler way to go about this that has already been done with some success. <S> Planes like the Harrier are capable of VTOL by simply re-directing the exhaust of the jet. <S> ( source ) <S> In this case you reduce the amount of moving parts by not needing both a regular jet system and a helicopter mechanism (which requires a lot of up keep) instead its simply easier to have a directed nozzle ( source ) <S> This idea has been carried over into the prop world with Boeings <S> V-22 Osprey which has tilt control rotors that allow for VTOL but are also used for forward flight. <S> In this case ( source ) <S> To directly answer the drag question, yes the drag would be high (some one else may be able to provide a specific number or the math) but like anything else the design could be built it just would not be very efficient. <S> Since you can generally control the pitch of a helicopter rotor <S> you could potentially (on an even numbered rotor system) orient at least 2 of them to act like small wings and generate very limited lift to assist you even in their static situation. <S> Like most things in aviation planes are built for a given mission profile. <S> VTOL fits certain cases like anding on an aircraft carrier or in other hard to reach places but things like commercial planes already have a large runway based infrastructure to support them. <S> Any hard to reach place that you need to land at most likely also means your loads are small and a helicopter will suffice, you would need a large hard to reach place that had constantly large loads going in and out to justify a sizable commercial plane that had VTOL capability. <S> While there are some applications for this in the military space (carrier landings come to mind) there are other systems that have been found to be efficient to use. <S> Interestingly enough the directed exhaust from the new F-35's has caused issues on the deck of aircraft carriers. <A> Anything that uses a rotor to take-off vertically is most inefficent when lifting, hovering or moving slowly . <S> This is most obvious when a helicopter is at max weight or in "hot and heavy" conditions when it might not be possible to take-off vertically . <S> In order to lift vertically, thrust must be greater than weight. <S> This is not true for a "conventional" aircraft. <S> Maybe you could use the stopped rotor to generate some lift in a similar fashion to a conventional wing but as others have pointed out, to make a rotor blade which is rigid enough to act as a static wing and can still handle the forces generated when rotating is a serious engineering challenge that will add more weight and complexity (because the rotor hub must have hinges that can absorb the forces when rotating but keep the blade rigid when stationary). <S> You also need some complex, and therefore heavy, mechanism for tranisitioning the thrust from the rotor whilst lifting to whatever propulsion you use for forward flight. <S> More weight, more complexity, more maintenance, more cost, more to go wrong. <S> What's not to like? <S> ;) <S> The other answers also point out better solutions such as vectored thrust and using the same rotors to lift and to provide thrust in forward flight. <S> Add this all together <S> and you have a solution for a problem which doesn't exist.
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If you use a rotor only for lifting off, then that rotor becomes nothing but extra weight (and complexity) that you don't need.
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