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What is the difference between TAS and GS? I'm looking for an explanation of true airspeed and ground speed. <Q> TAS = <S> GS = <S> Groundspeed = <S> speed that you get on radar gun as airplane flies by, when radar gun is held by someone on ground. <S> As an example: TAS of 200 knots and a headwind of 20 knots gives a GS of 200-20=180 knots. <S> That is: the plane travels at 180 knots over ground but the air is flowing past the plane at 200 knots. <A> True air speed is the speed in relation to the mass of air you are moving in, and ground speed is the speed in relation to the ground. <A> Short answer. <S> TAS is GS without wind. <S> So, on a no wind day, TAS = GS
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True Airspeed = speed that you get on radar gun as airplane flies by, when radar gun is held by someone in gondola of balloon in same airmass (wind motion) as airplane. GS is TAS with wind factored in.
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What is the standard report when pilots exiting and clearing the runway Let us say I landed on runway 7 and will exit the runway thru taxiway Charlie, is that a standard report like "(Aircraft ID) taxing clear RW7 at Charlie"? <Q> Nitpick: that would be runway 07, not runway 7 <S> The phraseology is mostly standardised, and in general consists of notifying the relevant unit that you have vacated the runway. <S> At a small, GA airfield with AFIS in the UK the typical communication goes as follows. <S> ATCO: <S> G-ABCD Cleared to land Runway 07 <S> , wind 240 at 5 <S> G-ABCD: <S> Cleared to land, Runway 07. <S> G-ABCD ... <S> controlled crash .... <S> G-ABCD: <S> Runway vacated at Charlie <S> This becomes a bit more formal at controlled airfields. <S> In the UK, Cap 413 is the radio telephony communications bible. <S> Secion 4.89 "Runway Vacating and Communicating after Landing" is the part you'e interested in. <S> The communications would be more along the lines of (Note: CAP413 uses the name "Kennington" as a fictitious airport) <S> Kennington Tower: BIGJET 347, vacate left BIGJET 347: <S> Vacate left BIGJET 347 Kennington Tower: BIGJET 347, when vacated contact Ground 118.350 <S> BIGJET 347: <S> When vacated Ground 118.350, BIGJET 347 BIGJET 347: <S> Kennington Ground, BIGJET 347, runway vacated <S> Kennington Ground: BIGJET 347, Kennington Ground, taxi to Stand 27 via taxiway Alpha <A> In North America, it's "clear". <S> "Vacated" is used in UK and possibly other places that use UK CAA practices as a basis of their conventions and rules. <S> You will almost never use the phrase at a controlled airport; you pull off the active at the end of the landing roll, and when tower sees you are pulling off onto the taxiway, just tells you to contact ground with the frequency. <A> The FAA has published an Appendix to the Pilots Handbook of Aeronautical Knowledge that gives this example of exiting the runway. <S> Initial Contact After Landing and Clearing the Runway Pilot <S> : Lincoln ground, November 123QY, clear of Runway two at Bravo, taxi to the ramp. <S> Controller: November 123QY, Lincoln ground, taxi to the ramp via Bravo. <S> You still hear some pilots say “Clear of the active.” <S> but it’s mostly older pilots who were trained a long time ago and are set in their ways. <S> By saying who you are, what runway you just exited, and where you are, and (if it’s not obvious) where you want to go, ATC can more easily get you off of the movement areas and to your final destination. <S> It works at uncontrolled airports as well since landing traffic knows which runway you exited. <S> That’s especially useful if there are multiple runways in use. <S> It also helps taxiing aircraft because they where you are and where you are going <S> so they know if they need to hold for you to use the taxiway or if they can proceed to the runway.
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At uncontrolled airports in North America you will always hear "XXX is clear the active".
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What does 'laterally aligned' mean in this description? In the Airplane Flying Handbook there is a section on crosswind takeoffs that mostly makes sense. However, this paragraph confuses me. Takeoff Roll As the forward speed of the airplane increases, the pilot should only apply enough aileron pressure to keep the airplane laterally aligned with the runway centerline. The rudders keep the airplane pointed parallel with the runway centerline, while the ailerons keep the airplane laterally aligned with the centerline. Laterally is an adverb meaning 'Relating to the direction to the side.' Later on they use this image which shows the lateral axis. When I take off in a crosswind in an airplane with nose-wheel steering the rudder pedals are used to keep the plane on the centerline. The ailerons are deflected into the wind to keep the windward wing from rising. So what do they mean when they say that “the pilot should only apply enough aileron pressure to keep the airplane laterally aligned with the runway centerline”? Edit: I don’t think they are referring to keeping the wings level as some commenters say. This image from the same section somewhat exaggerates the effect but ailerons are used to keep the upwind wing down. <Q> The paragraph seems to be describing the following technique for lateral control during a crosswind takeoff: <S> Use the rudder to keep the heading (the direction the nose is pointing) parallel to the runway centerline. <S> Use the ailerons to control the bank angle so that the airplane stays approximately over the runway centerline. <S> The reason the Airplane Flying Handbook uses the word "laterally" here is that the ailerons are being used to control the airplane's lateral (left-to-right) motion. <S> Some comments speculate that the paragraph is really saying that the ailerons should be used to keep the wings level. <S> That doesn't make sense to me; in a crosswind, if you're using rudder to keep the nose parallel to the centerline, and you're keeping the wings level, then you'll drift downwind off the runway. <A> The lateral axis is the <S> left/right axis. <S> “Laterally aligned with the runway centerline” means: on top of the centerline. <S> Not a very clear way of phrasing, I agree. <A> This thing is horribly written. <S> I think Tanner is correct, in that the writer is referring to using ailerons to establish a bank angle to prevent lateral drift. <S> But while rolling, the bank angle you can create is limited to the compliance of the landing gear. <S> On an airplane with wide oleo gear, this is effectively zero. <S> So it's really about using rudder to keep alignment and using aileron to hold the wing down. <S> As you lift off, the into wind aileron will cause the downwind wing to liftoff slightly ahead of the other, putting you into a very brief cross-controlled wing down condition where you will be side slipping briefly; then for a brief moment, you are using aileron to maintain lateral position. <S> Which you immediately remove as you center the rudder and adjust the heading into wind as required, then level the wings to climb out (except on an IFR departure where you just maintain the runway heading). <S> Surprising to see something this poorly worded in an official FAA publication. <A> Can't always believe you read. <S> Notice <S> the rudder deflection is also incorrect in the third picture. <S> This is why finding a good instructor is so important. <S> A cross wind take-off is in many ways a mirror image of a cross wind landing: aileron into the wind, rudder away. <S> Yes, the downwind wing may rise first, and the plane is up on one wheel before lifting off, just as you would do in a cross wind landing. <S> No big deal. <S> Be on that rudder. <S> Some may choose to delay rotation a few knots, and then bring plane off the grounda bit more briskly, then transition into a crab. <S> Some may hold the side slip a little longer. <S> But airspeed is most important here. <S> Watch it and keep climbing safely. <S> Cross controlled slow flight practice should give you confidence in these situations. <S> Remember to stay at a safe margin above stall. <S> Best interpretation of "laterally aligned" would probably be the same as in the air: roll into the wind to keep from being pushed sideways. <S> So if your leeward wing comes up too much before rotation, simply ease off on the ailerons some.
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The only meaning that I can conceive of is that "laterally aligned with the centerline" is a fancy way of saying " on the centerline"—or, at least, keeping the distance from the centerline under control, so that you don't drift off of the runway.
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Why do shipping companies opt for the Boeing 747 instead of Antonov An-124? Both are quad-jets, but the Antonovs can carry up to 150 t of payload and are much cheaper (\$100M for the An-124 compared to \$238M for the Boeing 747-400F). I understand that MRO is quite an issue for Antonov, but we are talking about the freighting industry, which is less congested and less demanding than the commercial airliner industry. Is the skepticism of buying a SSSR-era product really founded, or is there in the West a lobbying trying to maintain the Airbus-Boeing duopoly and keeping foreign products out? <Q> This won’t be a real great answer, just major hurdles off the top of my head for wider AN-124 service. <S> Much shorter range. <S> At 80,000 kg the AN-124 gets 4500 nm. <S> 747-400 has a range of 7670 nm. <S> 1 747 is slightly faster, cruising at .855 Mach AN-124 is designed for a crew of 6; 747 has a crew of 3, or even 2 in the 747-8F <S> It would probably take Antonov a long time to catch up with Boeing’s production rates. <S> 747-8’s are being produced about one a month. <S> Back in the 70’s they were pumping out 80 or 90 of them per year. <S> I can’t find any numbers on fuel efficiency, but being that the Antonov was designed for military transport I would be very surprised if it could compete with the 747 in fuel usage. <S> 1 <S> I was not able to find good range numbers for the Antonov. <S> It’s hard to really pin down the numbers on the 747 also due to the number of variants. <S> The numbers here are taken from the Wikipedia page for each. <A> The An-124 is not available new: <S> Antonov stopped production in 2014 . <S> There are plans to restart production by the end of 2019 . <S> Existing aircraft are owned by the Russian air force and by a few specialized freight companies. <S> Neither are likely to sell their aircraft. <S> So the An-124 is not available. <S> If you really wanted to buy An-124s, you'd have to restart the production line. <S> In the past, Antonov tried to sell an An-124 version with Western avionics and engines, but the development cost required for those modifications was too high to make this an attractive offer. <S> Among Western companies, Russian aircraft are not popular. <S> See the absence of Russian airliners in Western fleets. <S> Antonov's attempt at a Westernized An-124 was intended to address Western mistrust in Russian engines and avionics. <S> The operating cost of an An-124 is probably higher than that of a B-747 (due to less efficient engines). <S> The extra internal volume might come in handy (IIRC cargo flights are often volume-limited) more than the extra payload capacity, but you'd have to find a way to utilize that volume using standard containers. <S> You don't want to repack all your cargo if it flies one leg of its route with an An-124. <S> Because much of the extra internal volume is in height, you might have to build a second floor, which complicates loading. <S> And IDK if the cargo hold is high enough to fit 2 layers of containers. <A> The Antonov 124 does not accept the standard ULDs and is very time-consuming to load and onload. <S> While the did have some form of pallets in the early days these were very heavy and added to the non-revenue weight. <S> The 747 freighter on the other hand will accept common commercial pallets/containers or commonly called ULDs (unit load device) and this cuts down tremendously on the loading time as well as the transloading of cargo. <S> A 74F can fly from Singapore to Dubai with a full load of 29 (30 for 744F) maindeck and 9 lower deck ULDS and these can be offloaded in Dubai and loaded onto another aircraft without dismantling. <S> This cuts down the handling time. <S> The AN-124 does have an in-plane handling system but its just an overhead crane where pieces of freight have to be hooked up and drawn into the plane. <S> Its not a user friendly system and thats why Antonovs usually have their own loading crews. <S> The 747F OTOH has a well-designed in-plane loading system which enables quick loading and offloading with minimal training required. <S> The systems are also common on all planes so anyone anywhere can load and unload the plane easily. <S> The low-purchase price is probably out of date and pretty meaningless. <S> Go try and buy one and see. <S> The supply chain for parts is also abysmal. <S> If the aircraft breaks and a part is needed it can take days. <S> The 747 was designed from the get go to only handle ULDs. <S> The cargo floors on these aircraft are only designed to take the weight on the aircraft frames, the floor panels are just composite fillers for the most part and in in fact Boeing left them out completely in the lower-deck holds, leaving the only the frame structure to support the pallets and some small pathways for the loaders.
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The forte of the AN-124 is in handling outsize/heavy cargo, the floor is suitably strengthened from the design stage to handle these items.
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Does flying an airplane upside down imply negative AoA? Why? I saw the statement below in this answer : Note that for normal level unaccelerated flight $C_L$ is always > 0. The minimum $C_L$ is a negative value for negative AoA, and would mean that the aeroplane is flying upside down. This would seem to me to imply that flying an airplane upside down implies a negative angle of attack. But the typical illustration and explanation of angle of attack is that it is the angle between the airstream and a reference line, the latter of which in airplanes is normally the wing chord. How can the two be reconciled? Alternatively, what am I missing? <Q> This is assuming the AoA is measured in the body frame of the aircraft, aligned with the chord line of the airfoil. <S> Also this assumes there is no thrust/drag or thrust/drag do not meaningfully contribute to vertical net forces. <A> It depends on what you are using for your coordinate system. <S> If you are using a coordinate system relative to the airfoil where the top of the airfoil points towards the postive y direction and the bottom of the airfoil points to the -y direction, then inverting the airplane will cause a negative AOA since the airfoil would be fixed in this coordinate system. <S> In this case the negative AOA would cause negative lift as defined in this coordinate system. <S> However, if I defined the coordinate system relative to the ground where -y points towards the ground and postive y points towards the sky, then the AOA would remain the same in both normal and inverted flight and the AOA would be positive with positive lift in both cases. <A> We could pick the system of co-ordinates where AoA does not depend on which side of the plane is the "upper side": the side facing the sky could be the upper side, regardless if that side has landing gear on it or not. <S> This would look more intuitive for human to understand. <S> However various algorithms of computer simulation would have difficulties at the 90 degrees roll. <S> At this angle the AoA would reverse the sign, because the "upper side" is now the opposite. <S> Such changes make tasks like calculating derivatives over this point awkward. <S> The math is much easier without the badly-behaving points. <S> This is generic everywhere in mathematical modelling. <A> "The minimum Clift is a negative AOA value" means that positive lift is still being generated at a negative angle of attack. <S> Go to Airfoil Tools on the net and study the graphs. <S> Many cambered airfoils do this down to a few degrees negative AOA. <S> For aerobatic planes, symmetrical airfoils are used to get similar lifting properties when trying for sustained inverted flight. <S> They will generally will have 0 lift at 0 angle of attack. <S> So "negative" or "positive" lift really depends on which direction you want the WING to generate lifting force. <S> For example, if you enter a loop, you may be inverted but pulling back on your stick to complete the loop. <S> AOA is still positive. <S> However, if you do a half loop and wish to fly straight away inverted, you now push your stick forward, to negative AOA, creating lifting force towards the bottom of your wing (which is now "up"). <S> When you half roll back to upright, then pull the stick back for positive lift. <S> This is the "Immelmann" maneuver, from early in the last century.
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Level flight (no change in altitude) upside down, with an airfoil with a zero-lift AoA of less than or equal to zero degrees, requires a negative AoA to get upwards lift.
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Why do fighter pilots use night vision goggles rather than normal light inside the cockpit? I've seen military personnel using night vision goggles (NVGs). With their flight altitude, I don't think the enemy can notice them. I thought it may be due to eye strain, but other units use red lights during long jobs that need looking at a screen. Also, you should consider some fighter pilots have short missions and their eyes won't get tired from light. I wonder why they don't use normal light. Normal light versus red light versus night vision. I never used night vision, but I don't think it's comfortable to use. <Q> former F-18 pilot here <S> , it's my first post here <S> so be kind :) <S> NVG's are not for domestic use, they are entirely tactical. <S> Here are some uses; Night formation (Defensive/Offensive counter air missions), such that formation members can fly lights off or in night mode (which we did all the time). <S> Most fighters have external NVG lighting that can't be seen with the naked eye. <S> Target acquisition (Offensive Strike/CAS etc) in low/no light environments (permits visual rules of engagement upgrades etc Laser ID. <S> Laser range finders and target acquisition pod lasers can be seen through NVG's, we can conduct visual 'hand-over' procedures using lasers to talk on a wingman to a target. <S> Lasers are weapons and have their own master arm switch, just like the gun, bombs and missiles. <S> With NVG's, I can see formation members with <S> low/no light dozens of miles away, which can't even be done during the day. <S> This brings enormous tactical advantage in air-air scenarios. <S> NVG's are not used to see inside the cockpit. <S> Hope that answers your question! <A> Fighter jets do have a normal cockpit lighting in them. <S> Occasionally crews do use night vision goggles, not for viewing instruments, but visual refer nice outside the jet, and cockpit lighting can be adjusted for NVS systems. <S> But it is not recommended for all applications to use night vision goggles only, so standard carpet lighting is provided. <A> The major issue for any combat pilot isn't to see what's going on inside the aircraft, but rather what is going on outside. <S> Wikipedia has some more information on the effects of using red light, but the short version is that the red light preserves night vision while at the same time making it possible to read instruments and labels. <S> For a combat pilot who might need to watch for other aircraft, fly in formation or close to terrain at night preserving the normal night vision is essential. <S> Night-vision-goggles also helps, but these work primarily by amplifying existing visible light. <S> Adding additional light sources inside the cockpit would have the same effect as if you didn't wear them and turned up all the lights; you'd have no problem seeing inside, but wouldn't see anything outside due to the contrast.
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In addition normal cockpit lighting is so low that it’s virtually impossible to see an illuminated cockpit from a distance.
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How do slats reduce stall speed? I've read in PHAK that slats reduce stall speed, but in what way? Is it because of the increase in surface area? <Q> It's because leading edge devices allow a higher Angle of Attack. <S> The four types of leading edge devices work by pointing the nose of the wing downwards so that at higher AoA there is no flow separation at the upper surface near the nose. <S> Deflecting the slats does not increase $C_L$ , the aeroplane must increase AoA to do that. <S> Lower stall speed comes with the higher $C_{Lmax}$ From this answer, which also contains a graph showing that flaps increase $C_L$ at constant AoA. <A> Slats increase the camber of the wing, which increases the coefficient of lift. <S> When you deploy slats, the AOA is actually lowered for that part of the wing. <S> This is the same washout principle Dunne ingeniously applied to the D.8 swept wing bi-plane in 1912! <S> You now have a more heavily cambered wing at a lower angle of attack, so more lift is to be had by increasing pitch more. <S> Since the Clift is higher, one can generate the same amount of lift at a lower speed. <S> Airflow underneath the wing and its contribution to lift may be worth further study. <S> The action of the air curling around the wing leading edge and impacting the "underside" in an upwards and forward manner (Eye of Jupiter?) or a bit of compression may help explain why they work so well (in addition to the benefits of lift creation by increasing camber on the upper part of the wing). <S> You can now pitch up a little more, but be careful. <A> The two main leading edge devices are leading edge slots and leading edge flaps: Slots energize the boundary layer to delay stall by allowing higher pressure air from below to "leak" in a controlled way to the upper surface. <S> The slot is effectively a convergent duct, large at the bottom and small at the top, so the air is slightly accelerated as it flows through the outlet at the top, more or less parallel to the skin surface. <S> Because the air is slightly accelerated relative to the freestream just above it, being squeezed through a convergent duct in effect, Coanda effect enhances its ability to follow the upper surface contour and help the freestream stay attached. <S> Leading edge flaps, basically drooping leading edges, increase wing camber the same way that a trailing edge flap does, increasing Clmax somewhat at a given angle of attack. <S> If I combine the leading edge SL o T and fl A p together, I get a SLAT. <S> The slat extends its nose down and forward from the normal LE position, increasing camber somewhat, like a LE flap. <S> The slot created when the slat extends energizes the boundary layer and delays separation, allowing the wing to generate lift into the mid 20 degree range. <S> So you get a little bit higher CLmax for a given AOA <S> and it can operate to a much higher AOA, giving you the highest possible CLmax and lowest stall speed. <S> Fixed slots were all the rage in the 30s and 40s to control flow separation forward of the ailerons on airplanes like the Globe Swift , negating the need for wing washout, but these didn't really reduce stall speed, just kept the ailerons working in the stall. <S> They fell out of favour because the drag penalty of the always open slot was worse then the efficiency loss of washout.
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Slats are greatly helpful in reducing the AOA and increasing the Coefficient of Lift of part, or all, of the wing.
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Can you feel passing through the sound barrier in an F-16? Is it possible for the pilot to feel passing through the sound barrier in an F-16? What about other modern aircraft, will you feel anything? Do you need to go back to really dated designs before you can notice this, is it a problem of the past, or did the documentaries I watched which discussed this problem grossly exaggerate it? <Q> At least, that was my experience in the T-38, and according to every account I've read. <S> If the aircraft is NOT designed to go supersonic, then the experience can be quite different, although that mostly comes from loss of control at high Mach numbers (starting in the 0.9X range, as best I recall), rather than anything that occurs right at Mach 1.00. <A> You can watch for yourself 4 minutes in on this video. <S> Can't tell at all, so much so that they have to let people know with a big sign. <S> Once the issues of buffeting during the transition were fixed in the design of supersonic aircraft, pretty anticlimactic. <A> In the F-18, you experienced a very slight "tuck", which was basically the nose of the aircraft pitching around the horizontal axis very slightly. <S> But , it was extremely minor, and in order to notice it you needed to be in smooth air, and paying close attention. <S> In 99% of transitions through "the number", you were so focused on other stuff you noticed nothing.
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In an aircraft designed to go supersonic, it's an absolute non-event, and one is only aware of it by observing the instruments, and noting diminished control authority-- slower roll rate, etc.
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Where is the compression on a compression strut in a tube and fabric airplane coming from? I understand the functions of every part of a tube and fabric (two spar) ultralight wings and the loads they carry but what keeps puzzling me is the compression strut of a two spar wing as seen above.My question is where is this compression on a compression strut between the main and rear spar coming from? Is it from the drag and anti wires, the spars itself, where and how do you calculate this conpression force? <Q> You want a nice, taut fabric cover on this wing, don't you? <S> The main function of the compression struts is to keep both spar tubes from being pulled closer by the fabric cover. <S> Of course, Niels is right, aerodynamic forces come on top of this and will also pull on the tubes in the wing's plane. <S> In order to calculate those forces, integrate the tension in the fabric over wingspan when loaded by maximum lift forces. <S> Below I have sketched those lift forces – they want to pull the fabric up, increasing tension within it <S> and so the compression forces on the struts. <S> I hope I got the basic structure about right. <S> Please correct me where needed. <A> During flight, a forward-pointing force must be applied to the leading edge of a wing in order to push it through the air against the drag force that the air is applying to the wing, and to prevent the force of the onrushing air from crumpling the leading edge backwards. <S> The purpose of the compression strut is to convey that force from the main spar to the front edge of the wing, which appears as compressive stress in that strut. <A> The cross wires are the clue: they are under tension, and the compression bar neutralises the pre-tension forces. <S> This arrangement transforms the construction into a geometrically defined structural shape that can absorb the bending moment of the wing. <A> They are called compression tubes because they are under compressive load at all times in the wire braced ladder truss formed by the spars, compression tubes and cross bracing, whereas other members can be under tension, or compression, or unloaded, depending on whether the drag loads are from the front or the back (anti-drag) <S> (back mostly in the theoretical sense, although you could have reverse loading in the right flight conditions - <S> and the drag wires need the anti-drag wires there to absorb their pre-tension to hold everything square when it's sitting on the ground). <S> In flight, they are also in compression, transferring the drag loads from the first bay's drag wire to the next bay's drag wire. <S> I've tried to colour code the loads in the diagram. <S> The green wires are called drag wires, the red wires are called anti-drag wires. <S> In forward flight, the green wires will be in tension and the red wires unloaded, and the compression tubes in compression. <S> In "backward flight" <S> (say in a tail slide), the red anti-drag wires will be in tension and the green wires unloaded. <S> At rest, the wires are equally loaded with a pre-tension to keep everything square. <S> But in the drag, anti-drag, or at-rest case, the compression tube sees only compression load. <S> Theoretically, you could attach the compression tube to the front and rear spar with just a locating pin sticking out the ends that fit in holes in the spars, because the tube connections to the spars never get "pulled on"; they are always being pushed. <S> On some fabric airplanes the connection is not much more than that; maybe just a threaded pin that goes through the spar with a nut on the other side to hold it in place before the wires are tensioned.
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The compression tubes are under compression by the tension of the cross bracing wires when at rest.
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Was the Boeing 2707 design flawed? The mach 2.7 capable Boeing 2707 has an interesting design. I'm curious if there has been any studies done that concluded that this aircraft would simply not have worked, given the way it was initially designed, even if sufficient funding existed. If so, what was the problem with the design? By problems, I don't mean it being financially feasible or sustainable, I mean technical limitations and restrictions imposed by physics. Could this sort of aircraft ever have achieved a sustained mach 2.7, and carry 277 passengers? I'm personally inclined to believe it might have worked, considering other notable aircraft of the time, such as the military planes; the XB-70, the SR-71, or the civilian Concorde, and Tu-144. The civilian planes mentioned here are somewhat slower, but the military planes are somewhat faster, and puts the 2707 right in the middle. However, it would be nice to see an actual evaluation of its design, if such a thing exists. <Q> The three competing supersonic designs are discussed in this video – The Forgotten American Concordes. <S> Two competing designs from the USA were proposed to the US government, which was going to fund 75% of the development cost: one from Lockheed, and the B2707 from Boeing which was the winning design. <S> The B2707 was meant to be bigger and faster than Concorde, and this was one of the three issues that eventually saw the project being cancelled: Concorde flew at Mach 2, heating up the nose to 127 °C and the wing leading edges to 100 °C. <S> The whole plane was considerably longer at cruise than it was on the runway due to heating up from the supersonic flow, but at this speed aluminium could still be used as the main construction material for most of aeroplane. <S> The B2707 would be heating up much more, ruling out aluminium and having to use titanium, skyrocketing the construction price per aeroplane. <S> The oil crisis of the early 70s raised fuel prices a lot, with unfavourable consequences for the operating costs. <S> It was thought that since the travel time is shorter there could be more daily flights, but: protests about supersonic booms prohibited supersonic flights over most land, meaning that the only viable market was the US east coast to the European west coast. <S> If so, what was the problem with the design? <S> By problems, I don't mean it being financially feasible or sustainable, I mean technical limitations and restrictions imposed by physics. <S> Could this sort of aircraft ever have achieved a sustained mach 2.7, and carry 277 passengers? <S> Image source <S> It might have, there were military aeroplanes flying at M 2.7 or faster at the time like the <S> XB-70 Valkyrie built out of stainless steel, but the technology was still immature. <S> Passenger transport implies high reliability and long testing times to verify if the safety requirements can be met, and this was a major issue to be crossed out at the time of cancellation. <S> So the question: "Could this sort of aircraft ever have achieved a sustained mach 2.7" at the required reliability rate was never tested. <A> The 2707 started with a variable sweep, but it was too heavy to be feasible <S> Here's a mockup of the 2707 with its variable sweep <S> And here's a video of Boeing's mockup But variable sweep mechanisms add a lot of weight . <S> And, being a civilian airliner, there would likely have to be all sorts of safety backups, adding more weight. <S> As the video notes, the 2707 could cross the Atlantic, but without passengers <S> And Wikipedia notes this quote <S> Boeing also faced insurmountable weight problems due to the swing-wing mechanism (a titanium pivot section having been fabricated with a weight of 4,600 pounds and measuring eleven feet long and 2.5 feet thick)[15] and the design could not achieve sufficient range. <S> The redesigned 2707 went with a delta wing like the Concorde, but by then other cost factors caused the US government and Boeing to cancel the project <A> It certainly would have worked, as there weren't really any technical obstacles, only financial. <S> The real issue is, was it possible to build it and put it into service with un-subsidized ticket prices that would fill seats AND make it possible to make a profit on its operation? <S> It's important to note that the Concorde was only feasible because British and French government direct operating subsidies made it possible to charge only astronomical prices for tickets, vs down-a-black-hole prices that would have been required without subsidies (even with subsidies, traveling on Concorde was about as expensive as traveling to Europe on a Clipper flying boat in the late 30s. <S> The British and French governments were basically subsidizing, or giving away money to, rich folks for national pride reasons). <S> Even allowing for the fact that Boeing benefits from de-facto subsidies in the form of military development contracts for designs with ultimate civilian use, and assuming such had been available for the 2707 (a military related development program to get it off the ground that is), the direct operating costs would have made it unfeasible in a non-subsidized airline environment (if the KC135/707 wasn't able to make money in 1958 at the airline operating level, it wouldn't have worked either). <A> I know the airplane was re-designed during development due to weight and complexity issues associated with the swing wing design. <S> Variable geometry was the rage in the sixties and Boeing felt that, from initial studies of the problem, that is could make use of the swing wing design for improved low speed flight. <S> A delta wing configuration was selected in later iterations of the 2707 design. <S> This, combined with the unprofitably, environmental issues, heat control, drove the company to cancel the nearest thing America ever got to an SST.
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It turned out that even with a titanium wing box, the airplane was just too heavy to carry the proposed passenger load. Bottom line: the operating numbers simply didn't work out, except as a "national pride" sort of project, like Concorde, and outside of military applications, that sort of thing doesn't happen very often in the US.
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Why was this commercial plane highly delayed mid-flight? What could be the main reasons for a short-haul flight to be delayed over an hour in-flight? Recent Lufthansa LH 2227 CDG-MUC flight took off only half an hour after scheduled time, but landed at destination delayed nearly an hour and a half. Meaning (if I am reading these stats correctly) that this particular flight spend an hour extra in the air over scheduled time. I begin to question if there is enough fuel for the plane to stay that long extra? I flew the very same flight few days ago and that flight also took of half an hours after schedule and landed fifteen minutes after schedule. Meaning that a plane manage to "work out" half of its delay en route. This particular, pictured flight not only didn't work out its initial delay, but also added another hour to it while being in air. I was always told (and saw that in my small commercial flying experience) that short- or middle-haul flights delayed 15-30 minutes on take-off, long-haul flight delayed 60-90 minutes on take-off, are nearly always able to land on-time, effectively "working out" their initial delay during flight, by flying faster etc. What happened or could happen here? <Q> If you look at the details, you’ll see the aircraft left the gate at 9:37, but only took off at 10:47. <S> They probably received notice of the issue in MUC pointed out by Machavity while taxiing to the runway (and then asked to park somewhere waiting for the airport to be ready for them). <S> No sense returning to the gate for a delay like this which is expected to be relatively short. <S> A possible alternative (though probably not here) is they they had an issue right after gate departure which triggered a maintenance request. <S> It happened to me once on some regional airliner which had an issue just when they spooled up the engines (or just after a few meters, don’t remember). <S> Immediately powered down and had some part of the engine changed (or maybe just a filter or something similar) while we were waiting, took about an hour or so. <A> Munich was closed for a short time due to a security breach <S> The airport tweeted: “According to the information currently available, a person has probably entered the clean area of Terminal 2 through an emergency exit door from the unclean area. <S> “As a result, police measures are currently in progress.” <S> Terminal 2 is the home of Lufthansa, which operates hundreds of flights through Munich each day. <S> And this is likely the main kicker for this flight <S> While arriving flights are currently being allowed to land, the airfield is filling quickly and diversions may soon begin. <S> The plane probably circled as long as fuel margins would allow, rather than sit on the ground in a long line. <A> re 'working out delays' <S> The flight uses an operational flight plan which shows the routes (waypoints), speed, altitudes. <S> There are usually some compromises made, a shorter route may cost more (overflight fees) and a cheaper route may take longer. <S> The company will usually select what is best ie more economical with flight time acceptable. <S> This is usually easier to do on longer flights of course, on shorter routes there may not be much choice.
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In exceptional cases like longer delays, the ops dept may choose a higher cost route to minimise the impact (more direct route or higher cruise speed).
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Was a six-engine 747 ever seriously considered by Boeing? The Boeing 747 can carry a fifth engine on the side. As the airframe looks quite symmetric, I think that it would not be big work to hang a sixth engine on the side as well. From here, we seem to be quite near to the six-engine aircraft - a few extra pipes and wires are probably all we need to get these engines turning. Was a six-engine 747 present at some time of its development history? I think this could be, assuming: less powerful engines than eventually were available maybe it could take off with less runway some special uses with very heavy payload. There are no six-engine variants mentioned, built or proposed, on Wikipedia. The expected answer would mention some sources relevant to the design decisions through the history of this aircraft. <Q> The "fifth engine mount" option on the 747 is not designed to handle a running engine. <S> It was an option used only by Qantas as a means of ferrying spare engines to remote locations, where flying a plane for a long distance to a maintenance facility on three engines was not possible. <S> Only four of the Qantas fleet of 747s (totalling more than 60 aircraft) had this fifth engine option. <S> The mount for the fifth engine was not designed to transmit any thrust the engine would have delivered if it was running, and it fact the engine is partially disassembled by removing the fan to reduce drag (which reduced the loads on the 5th engine mount, as well as drag on the plane as a whole). <S> Some pictures and videos here: <S> https://www.flightradar24.com/blog/how-qantas-ferried-an-engine-on-the-wing-of-a-747/ <S> To convert this into "a 5 or 6 engined plane" would require a lot more than just "a few pipes and wires". <S> The wing structure would have to be redesigned to handle an extra 50,000 pounds (or more) thrust from each extra engine, plus the extra weight of a proper pylon and nacelle structure. <A> No, it wasn't considered during the development. <S> ( Bowman ) <S> The 747 came from Boeing's studies for the USAF CX-Heavy Logistics System program, which was won by the Lockheed C-5 Galaxy. <S> See: What was Boeing's competitor to the C-5? <S> That project called for four engines, and an engine was designed for that purpose. <S> See: <S> How was the high-bypass concept invented? <S> So the powerful engine was available. <S> Regarding requiring less runway, it would have been a bad product. <S> Airplanes are sized according to both takeoff and cruise: <S> Y-axis is takeoff thrust/max takeoff weight and X-axis <S> is max takeoff mass/wing area ( Preliminary Sizing - HAW Hamburg ) <S> Shortening the takeoff by adding more engines, or overly powerful engines (a lot more than cruise requires), would lead to poorer cruise economy due to the increased drag (if two additional engines or bigger engines are used) and higher fuel rate per thrust unit – gas turbines get better fuel rate per thrust unit if they're running near their design limit , that won't be the case if there's a lot more power than needed in cruise. <A> [This answer refers to the original version of the question before it was edited.] <S> Literally speaking, yes. <S> At least you have thought about it. <S> Seriously, the target is not to fit as many engines as possible, but how to fulfill the performance and safety requirements with as few engines as possible. <S> More engines means more power and redundancy, but fewer engines means less cost, complexity, weight, higher fuel efficiency, and a lower probability of a single engine failure. <S> The big four engine aircraft are currently losing market share, and we can observe a transition to two engine aircraft. <S> There are many studies and articles on this topic, for instance "Size matters for aircraft fuel efficiency. <S> Just not in the way that you think" by Dan Rutherford on the ICCT blog.
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Considering the aerodynamic wing flutter problems with the initial 747 design, sticking another two engines on the wing would most likely have required a complete redesign of the wing.
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What is the maximal acceptable delay between pilot's input and flight control surface actuation? While I was watching a cockpit video of an A330 landing in which the pilot was frenetically moving its sidestick, I wander what was the reaction time of this flight by wire system. Indeed, the time for transmiting the signal from the sidestick to flight computer, the time for computer to interpret all its inputs (pilot's input, probes,...) and to decide to act on flight control surfaces, the aircraft's reaction is not instantaneous. Then, I realize that whatever the transmission system, there are delay between pilot's input and air control surfaces movement (material's elasticity, time for hydraulic fluid to transmit pressure, other mechanism I can't imagine). Thus my question is: is there a maximal delay between pilot's input and flight control surface deflection to certify an aircraft? If needed, for the FBW system, a direct law can be considered (no complex computation as flight control surface movement is proportional to input) If needed, the question can be restricted to airliners flying under FAA and EASA jurisdictions. EDIT : given the first feedback (comments, edits, answer), I want to highlight this question is not restricted to fly-by-wire (transmitting pilot's input through mechanical links may also induce delay) EDIT : I think I didn't emphasize enough that this question is only about delay between pilot's input and control surface reaction. I understand that this delay is negligible compared to all other delay, but this is the one the question focus on. <Q> Excessive phase lag is a direct contributor to Type I Pilot-Induced Oscillation (PIO). <S> Phase lag comes from: Rigid body dynamics of the aircraft (e.g. delay between elevator surface and pitch rate response) Actuators (finite acceleration time between input and desired surface angle) Structural compliance (e.g. cable friction) <S> Transport delay in signals Finite computational bandwidth ( <S> e.g. loop closure bandwidth) <S> From NASA Report 4683 , PIO susceptibility can be expressed assuming the pilot is compensatory ; that is, the pilot input and the aircraft response would be exactly in phase, except for a constant time delay (across frequencies). <S> This model is expressed as: $$G(s)=\frac{K}{s}e^{-\tau_e s}$$ <S> where $\tau_e$ is the effective time delay, or equivalently, phase rate as a function of frequency From its research, it found that an effective time delay larger than 0.3 sec leads to PIO issues. <S> Given a typical pilot time delay of 0.2 sec, this would imply an upper bound aircraft effective time delay of 0.1 sec at higher frequency (around 5 rad/s), end to end. <A> This is a classic problem in control system theory . <S> The condition to be avoided at all costs is the case where the pilot's control actions get out of phase with the movements of the plane, so the sidestick-action makes the oscillations worse instead of damping them out. <S> The two ways that could happen are 1) if there are significant processing time delays in the control system connected to the sidestick and 2) <S> if there are significant delays in the pilot's reactions. <S> As pointed out above, the control system time lags are tiny compared to the time constants of the plane's responses to aileron movement, etc. <S> and the significant time lag in the overall system consisting of plane + pilot + computer control system is in the PILOT, not the control system. <S> This gives rise to something called PIO or pilot-induced oscillation , where the response time lag of the pilot pushes the whole system into divergent oscillation- <S> as for example in the case of a pilot porpoising a plane down the runway after bouncing off the runway on his or her initial touchdown. <S> I do not know if computerized flight control systems contain subroutines that prevent PIO but perhaps Peter Kaempf knows! <A> There is quite some experience in this in Level D simulators, which have computer generated responses that must match those of the original aircraft, within tight tolerances. <S> A couple of decades ago, the gold standard for Unix real time host computers was 30 Hz. <S> So 30 times per second, all of the following was computed: Surface deflection from stick input, including cable stretch, oil flow simulation etc. <S> Aerodynamic hinge moments on the surface. <S> Hydraulic hinge moments exerted by the actuators. <S> Aerodynamic forces amd moments on the aeroplane. <S> Inertial response of the aeroplane. <S> Visual system response. <S> Motion system response. <S> All other system states and responses. <S> With an update rate of 30 Hz the standard was deemed acceptable for Level D zero flight time training, which implies a time delay of 1 frame = 0.0333 sec. <S> So we know that this is fast enough: frequency rate 30 Hz, time delay 0.0333 sec. <S> As an aside, for present day computers this iteration rate is something to smile at, the code that ran @ <S> 30Hz on a state of the art realtime unix machine runs @ 3000Hz <S> on a Macbook Pro now. <A> Is there a maximal delay between pilot's input and flight control surface deflection to certify an aircraft? <S> Literally, no. <S> The FAA's only pronouncements about latency are about ADS-B . <S> To measure what you're asking about, a temporal delay is too simplistic. <S> You need something like the system's band-limited impulse response, or its temporal equivalent of a modulation transfer function. <S> And not just from stick deflection to surface deflection, but all the way to rate of change of (say) roll rate. <S> FAA doesn't even try to enforce numbers on the output of that process, never mind the intricacies leading up to it. <S> If an aircraft's control latency in some respect was dangerously large, the test pilots (or the flight simulators!) would notice it well before certification forms were sent to the FAA. <A> For civilian certification there are no specific requirements for certification in the FAA Part 23/25 or in the EASA CS 23/25. <S> But obviously they require aircraft not to be prone to PIOs, even though there is no specific section addressing the issue. <S> As @Jimmy mentioned above time delays in the control system are the main reason for type <S> I PIOs. <S> So designers’ objective should be minimize those time delays as much as possible. <S> On the other hand military requirements goes a little bit more in detail in terms of certification requirements. <S> Aircrafts are rated as Level 1, 2, and 3 based on the time delays of 0.1, 0.2, and 0.25 seconds in the control system. <S> Obviously, Level 1 being the best. <S> There is also a requirement in the same manual (Flying Qualities of Piloted Aircrafts) to define time delay in terms of phase lag. <S> And it classifies it according to flight phases, such as takeoff and landing, cruise etc. <A> The technical term used is latency <S> i.e. the propagation (or transport) delay between the input (pilot control) and the output (control surface movement). <S> The aircraft designer (or Original Equipment Manufacturer) determines the acceptable latency. <S> For airlines like Airbus (A330), or Boeing (B787), the latency between the pilot control inputs and the flight control surface actuation usually ranges between 50 to 100 msec.
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The acceptable latency depends on the type of aircraft i.e. Airlines, General Aviation, or Hobby aircraft, flight control dynamics of the particular aircraft, the systems through which the resultant signal is produced (Pilot Control Sensors -> Flight Control Computer/Mechanical Linkages -> Actuation Unit -> Surface movement), and the critically of the signal (ex: control surface actuation). It starts from 15 degrees and goes up to 60 degrees of phase lag for Level 1, 2, and 3 requirements.
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How does speed affect lift? I understand the lift coefficient shown above. But does lift increase with speed, and how? I understand I can't apply this to the graph as it is a coefficient, but if I had an angle of attack of 10 degrees and a speed of 0 knots, we would obviously have no lift assuming there isn't any wind, but if we increased our thrust and speed, we would gain more lift, and if we increase AOA even more, we get even more lift and the same with thrust. But what about 0 degrees with symmetrical airfoils, does lift also increase with speed, and does it work similar? <Q> The lift equation is $$L = \frac{1}{2} C_L · v^2 · S · \rho$$ where <S> $S$ is wing area, $C_L$ coefficient of lift, $\rho$ air density, and $v$ airspeed. <S> Using units of measure $\text{m}^2 <S> $ <S> for $S$ , $\text{m}/\text{s}$ for $\text{v}$ , and $\text{kg}/\text{m}^3 <S> $ for $\rho$ <S> , the result is lift in $\text{N}$ (newtons). <S> Concerning symmetrical airfoils, they work quite well too, and the equation given above is perfectly valid for them. <S> If it’s true that at zero degrees their $C_L$ is zero, they give zero lift regardless of the speed (zero times anything is zero). <A> If you have a fixed aerofoil in a wind tunnel, lift increases with the square of the air speed. <S> However a real aircraft usually only needs enough lift to balance its weight, so as it flies faster it will also decrease the angle of attack to keep the lift constant. <S> Conversely, if a pilot wants more lift in order to make a tight turn, he will usually increase the angle of attack rather than increase speed. <S> Lift also increases with air density and wing area (as per xxavier's answer), but those are usually outside the control of the pilot! <A> It's difficult (impossible, really) to predict what happens based solely on air speed. <S> To get a meaningful result, you need to go by Reynolds number. <S> Normally, you'll have a completely separate graph for each tested Reynolds number. <S> At a different Reynolds number, not only with the lift change, but the basic shape of the Cl/alpha line is likely to change (e.g., as the Reynolds number drops, it's pretty routine to get a much "sharper" stall-- <S> that is, where your graph shows a nice, smooth roll off in lift as the AoA increases, at a lower Reynolds number, it might easily have only minimal loss of lift, then drop much more quickly. <S> For example, here's a Cl/AoA graph for a NACA 6409 airfoil: <S> The gold line is at Re=1,000,000, the teal at Re=50,000. <S> These are both quite low, but at least give the general idea. <S> Note in particular that the curves have substantially different shapes. <S> At Re=1M, the lift increases almost linearly with AoA, right up until it approaches stall (at which point it rolls off quite smoothly). <S> At Re=50K, the increase is much less linear, and Cl increases sharply shortly before stall, then drops like a rock, with almost no warning at all. <S> But also note that it's all about Reynolds number. <S> Low air speed with a large chord acts much the same as a much higher air speed with a much smaller chord. <S> For a concrete example, the airfoils used in the impellers of a jet engine operate at high air speeds, but have extremely small chords. <S> This gives a very low Reynolds number despite the high air speed. <S> Even for a supersonic jet, the impellers are often operating at a lower Reynolds number than the main wing of something like a Piper Cub or a Cessna 172. <A> Welcome to Aviation Stack Exchange James! <S> A simplified answer would be: Lift is produced by airflow around the wing (expression for this is given in xxavier's answer). <S> Given everything else stays constant, you will get more lift. <S> (IRL the consequences of increased speed and lift are numerous, but beyond the scope of this question) <S> For a symmetric airfoil at zero AoA the Cl would be 0, and speed would have no effect on lift: regardless of speed, lift would be zero.
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If you increase the speed, you will increase the airflow around the wing.
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Do any aircraft carry boats? A small boat could be part of general cargo, but that would typically just mean it's unloaded at an airport and transported to the nearest body of water by land infrastructure. This is not what I'm looking for. Instead, is there any aircraft that can directly deploy a boat to (or retrieve one from) water? I would imagine there are cases when moving a boat by plane could be useful, especially when there's little or no infrastructure available on land. Does such an aircraft exist? <Q> Yes. <S> During and after WW2 several aircraft were converted to serve as "Dumbo" aircraft, dropping boats or rafts near people in distress. <S> Other models were used as well, but the B-17 were among the most prominent. <S> Most were retired when the helicopter gradually took over rescue operations. <A> <A> Large enough helicopters do it. <S> Above example is a Boeing CH-47 Chinook ( businessinsider.com ) <S> But since you have tagged it seaplane , not to my knowledge. <S> It's often the other way around, seaplane tenders tending to seaplanes (or used to). <S> (I take it by boat <S> you don't mean the inflatable and/or small type, as those are not hard to transport.) <S> Catalina launching beaching gear ( pinterest.com ) <A> I would like to suggest the "Landseaire" flying yacht which carried boats under the wings as per this question. <A> It was one of the main roles for the Vickers <S> Warwick in WWII. <S> From Wikipedia: <S> From 1943, Warwicks were loaded with the 1,700 lb (770 kg) <S> Mk IA airborne lifeboat and used for air-sea rescue. <S> The lifeboat, designed by yachtsman Uffa Fox, laden with supplies and powered by two 4 hp (3.0 kW) motors, was aimed with a bombsight near to ditched air crew and dropped by parachute into the sea from an altitude of about 700 ft (210 m).[36] <S> Warwicks were credited with rescuing crews from Halifaxes, Lancasters, Wellingtons and B-17 Flying Fortress, and during Operation Market Garden, from Hamilcar gliders, all of which ditched in the English Channel or North Sea.[37] <S> More on airborne lifeboats... <S> (also source for image above) <S> Of course, many WWII bombers carried inflatable dinghies, but I think the answer is looking for something more substantial. <A> The Fernic T-9 of 1929 was prepared for an Atlantic crossing and as a precaution had removable upper engine nacelles which could double as a life raft, including an outboard engine. <S> A less planned use of an airplane part as a boat occurred when in 1932 <S> the Junkers <S> W-33 of Hans Bertram and Adolf Klausmann crashed in a remote part of Western Australia. <S> They removed one of the floats and made it into a boat for fishing and excursions. <A> Took me a while to find this photo, from my personal archive from the East Fortune Airshow 2015 of a Royal Norwegian Airforce Lockheed Orion. <S> As I recall, the commentator stated that the orange object visible in the 'bomb bay' is an air-droppable lifeboat, for their search-and-rescue missions. <A> The Boeing C-17 <S> Globemaster III can deploy boats. <S> There are some videos on YouTube ( example ) that show the process:
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It is quite common for float planes to carry canoes & kayaks, e.g.
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Why are planes allowed to fly with just one pilot? I chanced on this article which raises the titled question: Why aren't two pilots mandated for all planes esp. military? What happens if the lone pilot becomes incapacitated, esp. if the plane has passengers who aren't pilots? Two captains of Cathay Pacific Airways lost sight during two separate flights, according to the Hong Kong Civil Aviation Department. In both cases, the first officer managed to land the aircraft safely. [...] On January 28, 2016, a pilot of the British Royal Air Force had lost sight during a training flight in a Hawk jet in North Yorkshire. Another jet had been scrambled with an instructor on board that helped the impaired pilot to land at RAF Leeming air base. Sources quoted by the Telegraph had said at the time that his vision was affected by the sudden deterioration of an eye infection. <Q> Well I guess there are multiple angles to this. <S> Perhaps someone can chime in with reference to regulations, but I can offer a more pragmatic answer. <S> Like it or not, aviation, like many other things, is a trade-off between risk and cost <S> and I think that's what it boils down to. <S> So what is the risk of single-pilot incapacitation and what is the potential consequences versus what is the cost to have all aircraft have <S> at least two pilots aboard (not withstanding the impracticability of fitting two people in most single-seater aircraft. <S> So, I guess, we as a society have accepted the risk of single-pilot incapacitation and it seems that mostly the consequences are acceptable compared to the cost. <S> It would be unlikely that we would mandate against single-pilot cockpits, but where to draw the line between single-pilot and multi-crew aircraft is certainly an on-going and active regulatory discourse. <S> In the end, I could ask you why don't we mandate two people with two steering wheels in cars? <S> It would certainly prevent some accidents (hell, maybe many!), but it could also cause some too. <S> And, practically, it just isn't going to happen is it? <A> Why isn't a second driver (and dual controls) required for automobiles, or commercial vehicles like trucks and buses? <S> There are far more auto crashes caused by incapacitated drivers than there are plane crashes caused by incapacitated pilots. <S> Additionally, 1) <S> 2) <S> For military fighters, having two crew adds weight, which decreases performance. <S> 3) <S> For general aviation, imagine the hassle if every time you wanted to take your Cessna or Piper up for a spin*, you'd have to find a second pilot to ride with you. <S> Not to mention what it does to the idea of soloing. <S> * <S> Well, perhaps not the most felicitous choice of word there :-) <A> As others have said, it's about risk vs cost. <S> More specifically, the requirement for two (or more) pilots is roughly linked to the size (i.e. number of seats) on an aircraft, which balances the cost of a second pilot (which has to be paid by the passengers) with the number of passengers at risk. <S> Light aircraft are frequently flown with zero passengers, so it just doesn't make sense to require a second pilot. <S> And some very light planes only have one seat anyway!
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Most (maybe all) commercial passenger flights DO require two pilots.
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How are aircraft depainted? There are several questions about livery changes and livery in general on this website. Yet, I fail to find information about paint removal. As a routine maintenance for an airframe that can live for up to 30 years, livery is redone several time as explained here . When changing painting, it should be preferable to remove the old one (I'm mostly thinking about weight as a big airliners has a lot a surface to paint). Moreover, I imagine that for military aircraft changing their operation theater, paint must be redone to adapt camouflage, and thus accumulating many layers of paint may have consequences. Given material and other aviation-specific constraints, I also imagine there are special techniques to handle any intervention on the airframe. Is this paint removal done and if so, how? <Q> Paint stripper. <S> Lots of paint stripper. <S> (originally I said thinner, but I have been corrected, it's more accurately called stripper) <S> Seriously though, it's actually not too different to other things that you paint. <S> You need to spray on paint stripper. <S> But, just like when painting the aircraft, it's imperative that you cover up all the delicate systems on the aircraft fuselage. <S> See here: Also, I think it would be rare to paint a new livery over and existing one without first removing the old paint (maybe only if you were just changing small details), because covering an aircraft in paint weighs A LOT. <S> For a 747 or 777 sized aircraft the paint job can weigh over 1000lbs Carrying that around costs fuel and fuel costs a lot! <A> In addition to the chemical method in Simon's answer , there are mechanical methods, like bead blasting . <S> This method was introduced in the 80s by airforces concerned with the volume of chemical waste generated by their maintenance facilities. <S> It essentially consists of using compressed air to project fine plastic particles against the painted part at high speed. <S> These abrade the paint away mechanically and can be recycled a few times before they break down too much and become ineffective. <S> Glass particles can also be used for more heavy duty blasting, but these need more careful procedures to avoid damaging the substrate, since they are much harder than plastic. <S> Whether it has any advantages over chemical stripping, depends on the specific case. <S> Industry regulations change across time and space, and waste plastic dust might be more problematic than waste chemicals in some places, but not others. <S> Also, the size of the parts to be stripped and the kind of training required for the operators play a significant role in choosing one method over another. <A> Not to be a smart-ass, but I think the correct answer is "in accordance with the airframe manufacturer's instructions." <S> Aircraft are generally given a corrosion protective layer (or passivated) at the time of manufacture that usually gives them a green color before they are painted. <S> For this reason, unpainted planes are sometimes called "green" planes. <S> Historically the treatment was usually a zinc chromate primer, but that is highly toxic <S> and I doubt anybody still uses it on new planes. <S> I suspect some of the more modern treatments add green pigments just to give the green planes the expected look, but I don't actually know that. <S> Following manufacturer instruction on whether and how to use chemical strippers or mechanical removal of paint is important to not damage the protective layer in ways not expected by the manufacturer. <S> Some treatments require parts to be dipped in a chemical bath before assembly, so if you remove or damage that treatment layer, you're not likely to be able to restore the corrosion protection to an as-new status. <S> If you remove the protection and replace it with your own in a way not specifically approved by the manufacturer, your plane no longer is in full compliance with the type certificate and you've become something of a test pilot. <S> TL;DR: Don't do stuff to planes that isn't approved by the manufacturer or a supplemental type certificate applicable to your specific plane. <A> There are other methods in addition to the chemical and mechanical ones already mentioned in other answers. <S> In some cases, paint is removed from aircraft using a laser. <S> Here's a video I found from the US Air Force that demonstrates the process:
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Abrasive blasting not only removes paint, but also dirt, corrosion and even anodic coatings, with enough passes.
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Is it possible to build 'Contra-rotating' EDF? Is it possible to design an EDF (Electric Ducted Fan), with two counterrotating blades, that will have more thrust than two separate EDFs with the same blades? <Q> The primary reasons you'd want contra-rotating pairs with conventional (unducted) propellers are cancellation of torque/P-factor, and delivering more power with a limitation on diameter (tip speed, usually, or landing gear height). <S> Neither of these really applies to ducted fans; it's easy to null out the slipstream rotation with fixed vanes in the duct, and flow is always perfectly axial <S> so there's no P-factor to worry about. <S> Further, pitch can be built high enough to absorb the needed power without supersonic blade tips, and generally is. <S> Bottom line <S> , there's nothing to be gained from the extra weight and complexity of contrarotating fans in a duct compared to just using a slightly larger fan and motor to deliver the increased thrust you're chasing. <A> Probably not. <S> (Peter Kaempf can tell you the exact number). <S> This is true regardless of whether the props are turned by electricity or gasoline. <A> Inline, contra-rotating EDF do exist in the RC community but they are very hard to get right. <S> What does not exist are inline EDF configurations that produce more thrust than the two EDF units mounted separately. <S> There have been many failed attempts to get inline EDF to produce more thrust than a single EDF <S> but there have been several successful attempts. <S> In case the above statement escaped your notice let me rephrase it: a lot of attempts putting two EDF units inline fail to produce significantly more thrust than a single EDF . <S> My own attempts got me around 0% to 10% more thrust while using around twice the current. <S> It's hard to get it right. <S> But some people have managed to get more than that. <S> Of those who've successfully flown twin inline EDF units the advantage seems to be not extra thrust but higher overall efflux speed. <S> Generally the rear EDF would have a higher pitch fan so it can accelerate the output of the first EDF without slowing it down. <S> You will end up with a heavier plane with almost no gain in thrust <S> but hopefully a higher top speed. <S> The main problem is if you get the pitch of the rear EDF wrong then it will simply act as an airbrake instead of an accelerator (you will sometimes notice this phenomena with pattern planes and motor gliders - non EDF - <S> where diving with the prop spinning is slower than with the prop stopped). <S> The following are some of the more successful discussions/articles from various RC forums over the years. <S> Unfortunately a lot of original content on the results of some of the projects are no longer online but the forum thread is still there: https://www.rcgroups.com/forums/showthread.php?262808-Electric-Ducted-Fans-November-2000 <S> https://www.rcgroups.com/forums/showthread.php?83207-Multi-stage-EDF <S> https://www.wattflyer.com/forums/showthread.php?t=67783 <S> https://www.rcgroups.com/forums/showthread.php?1674106-Two-edf-units-in-the-same-duct <S> Non-inline staged EDF There is one interesting experiment that used two regular EDF fans one behind the other but is not inline. <S> Instead the first EDF is installed in a cheater hole that blows additional air into the intake from above the plane. <S> This also did not get twice the thrust but got more than the usual amount of almost nothing. <S> You can see the video of it here:
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In general, a stacked pair of contra-rotating propellers produces somewhere around 70%-80% the thrust of the same two props if mounted separately
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What are the advantages and disadvantages of tail wheels that cause modern airplanes to not use them? Photos' source: Cessna 140 and Cessna 150 . According to Wikipedia here , the Cessna 150 is successor of Cessna 140. Both have two-seat capacity and a single engine. Why was the Cessna 150 changed to tricycle landing gear from the "old school" tail wheel? If we consider that the two airplane models have the same weight and capacity, then what are the advantages/disadvantages of tail wheels vs. tricycle landing gear? Why are so few new tailwheel aircraft produced? Note: I mentioned the Cessnas here solely because I knew their story better, so I can more easily compare them. This question should not be considered specific to only Cessna's products. <Q> A tailwheel is a good choice for operation on unprepared surfaces with aircraft that have low wing loading and need to be as light as possible. <S> Two main wheels and a small tail wheel weigh less and cause less drag than a tricycle gear, especially if they cannot be retracted. <S> On the Bo-209 Monsun <S> only the nose gear was made retractable because, being positioned right behind the prop, it caused 40% of gear drag all by itself. <S> On the other hand, high wing loading aircraft with their high landing speed would need very long landing runs due to their inability to brake hard. <S> A rejected take-off close to the decision speed would be impossible without crashing through the airfield perimeter. <S> Braking too hard with a tailwheel configuration will cause a headstand . <S> To summarise the reasons given in this answer : <S> A tricycle gear offers better visibility on the ground. <S> A tricycle gear allows full brake application. <S> A tricycle gear has less drag during the initial stage of a take-off run. <S> Cessna simply shifted priorities between the 140 and the 150. <A> A tailwheel aircraft is particularly susceptible to a dynamic instability during landing which causes the plane to violently spin around, point backwards, and skid off the runway. <S> This is called a ground loop and is one of the leading causes of landing accidents in tailwheel aircraft. <S> Avoiding ground loops requires good reflexes, good training, and lots of practice. <S> A tricycle gear aircraft is immune to ground looping, making it easier to handle on the runway during landings. <S> Because the tailwheel aircraft has no nose gear, it will weigh less and experience less drag during flight than the same airframe with a nose wheel, so it can fly a little faster and a little farther on the same fuel. <S> However, the cost to insure the tailwheel aircraft against landing accidents is greater than the cost to insure the tricycle-gear plane, which wipes out any savings on fuel burn. <A> Already some excellent answers here, but to add to Peter's response, in spite of the challenges, some folks prefer tail wheel planes because they are better for back country type flying - landing on unpaved surfaces, etc. <S> If you take a look at any of the short take off and landing (STOL) contests around the country, you see almost exclusively tail wheel planes competing. <S> AOPA article on STOL contests <A> Why was the Cessna 150 changed to tricycle landing gear from the "old school" tail wheel? <S> According to my old-time teacher, the accident rate in flying school changed dramatically when changing to tricycle gear. <S> Ground loops used to be common and potentially expensive with tail-wheels. <S> That seems to be enough of reason for a flight school to stop buying tail wheel planes. <S> ( The 150 I believe, was mainly targeted at schools ). <S> For specialized uses with trained and experienced pilots, tail-wheels are still in use.
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A tricycle gear makes loading and unloading easier because the fuselage is horizontal.
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What is this WWII four-engine plane on skis? I've seen this plane but I don't know its name: <Q> According to Wikipedia, this four-engine all steel(!) <S> heavy bomber first flew in 1930 and was the world's first cantilever aircraft in this class. <S> The skis do not appear to have pertained exclusively to any specific variant, given that the first flight already used them. <S> It was used up to and including the Second World War, and a number of experimental variants were developed from it. <S> One of the most interesting was the Zveno project , an experiment with parasite fighters. <S> Here you can see the Zveno-SPB variant of the TB-3 with two I-16 fighters under the wings: <S> The Zveno-SPB saw operational usage and even success in raids against the Romanian oilfields during WW2. <A> As yury10578 and AEhere correctly pointed out it's ANT-6A "Aviaarctica", polar version of TB-3 heavy bomber. <S> (The plane's name is written on its body) <S> Its drawing in that exact livery: ANT-6A with ski-only landing gear: <A> That must be one of the civil variants of TB-3 as other guys already said. <S> Went under designations ANT-6A and/or G-2, I'd have to dig out a book to tell more precisely. <S> Interestingly, Wikipedia tells almost nothing about it -- and this plane (well, planes -- there were a small series) <S> was quite a hero of Artic flights, if I recall my reading right. <S> ADDED: <S> Well, it was (a hero etc.). <S> On May 21, 1937 ANT-6A commanded by <S> M.V.Vodopyanov (aircraft register number N-170) made ice landing in the North pole region, the first in history. <S> Later, flight of 4 ANT-6A's landed the "North pole-1" polar expedition and their supplies. <S> The ANT-6A <S> (actually, ANT-6 "Aviaarktika") modifications included a drag chute, which allowed to reduce a landing run by 35-50%. <S> These aircraft could have either wheeled or ski landing gear. <S> The cargo weight was up to 2500 kg, while the total load could reach almost 50% of takeoff weight. <S> G-2, however, and here I was wrong, was essentially TB-3 without the armament and with added cargo securing equipment and some "passenger carrying equipment"--hard seats (up to 4000 kg load or up to 50 passengers). <S> Some of those registered thousands of flight hours.
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Looks like a TB-3 or a variant thereof.
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Why would a fighter use the afterburner and air brakes at the same time? I was looking for air brake pictures on different fighters, and then I saw a Tornado using afterburner and air brake at the same time! Air brake duty is to reduce speed, isn't it? So why would a fighter burn so much fuel to increase thrust and then use speed brakes simultaneously? <Q> The first photo is from the Tornado Role Demonstration Team's display at RAF Leuchars in September 2012 ( source ). <S> That Sep '12 show or its preparation is on YouTube. <S> Most of the instances of the air brakes as seen from the cockpit (looking behind) are followed by the swing-wing extending and the afterburner turning off (you can tell from the sound of the variable nozzle actuators ). <S> While the photos are cool, I'd say it's just perfect timing before the pilot turned off the afterburner while slowing down. <S> Such example (above) can be seen after 7:40 in this video . <S> Notice the wing position, and from the video notice the aforementioned sound once the wing is extended. <S> Another possible reason is slowing down for the spectators to see and hear the afterburner. <S> That can also coincide with the fake bomb drop – a pyrotechnic wall of fire, the smoke of which can be seen in the first photo in the question (example below). <S> An RAF Tornado GR4 carries out a mock bombing run ( BBC ) <A> However using afterburner causes aircraft to go supersonic very quickly. <S> So they use speed brakes to stay subsonic. <A> While the pictures above are most likely a result of the reason posited by ymb1 (showing off max blast while staying subsonic for the crowd), using afterburner with speedbrakes to reduce weight is a known practice in the fighter community, in line with Kolom's answer. <S> Even if an aircraft is equipped with a fuel dump system, environmental restrictions and standard operating procedures limit the altitude at which fuel may be dumped; if already below that floor, using afterburner with speedbrakes extended is a practical way to reduce landing weight. <S> I don't have any specific sources to cite, just drawing on my experience as a naval aviator.
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Most jets with afterburner don’t have a fuel dumping system so when they need to reduce weight in a short time they use afterburner to attain a permissible landing weight.
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What would the altimeter indication be through a cold front? Cold air is heavier than hot air because of its greater density, so the QNH of an airport inside a cold front would be higher. Flying towards the cold front would be, "low to high, hello sky". But I also know that for altimetry, cold air generates lower pressure inside the pitot-static system than warm air, and it would increase the altimeter reading, so "hot to cold, look out below". I'm confused because of the 2 contradictory factors. If we fly towards a cold front without adjusting the altimeter setting, would there be an increase or a decrease in the indicated altitude? There's an ATP question: Event after an aircraft passes through a front into the colder air. Answer: Atmospheric pressure increases. Well, yes, that's why QNH would be higher, but our altimeter would sense the temperature and "feel" a decrease in atmospheric pressure. So, what would be the real indication of the altimeter in this situation? <Q> There are two altimeter reading questions here, what happens when: flying towards the cold front (third paragraph) flying into the cold front (headline) <S> According to this University of Illinois web article following things happen: Flying towards a cold front (or in the article the front is approaching you, but it makes no difference): pressure drops steadily <S> temperature is steady Passing through the front : <S> pressure reaches minimum, then rises sharply temperature drops suddenly. <S> So, to answer both questions, assuming you are flying at relatively low altitude and maintaining it in reference to your altimeter <S> and you do not adjust QNH: <S> Approaching the cold front you would steadily drift downwards: from high to low, look out below! <S> Passing through the front you would need to climb to maintain steady altimeter reading: low to high, hello sky! <S> You see, the question is about what happens to altimeter reading, but since the vertical position of the aircraft is maintained in reference to the altimeter reading, whether it's you or the autopilot flying, the altimeter reading would not change. <S> The vertical position of the aircraft would be instinctively or algorithmically adjusted to keep the reading at a selected value. <S> What happens at altitude, is (for now) somewhat beyond me (pressure gradients and stuff), so <S> I dare not answer that scenario here yet. <S> P.S. <S> a private pilot should not fly through a cold front: it's not a good place for small planes to be in... <A> Well, I think you have a wrong point of view. <S> It indicates pressure altitude <S> so it does not matter what the density of the surrounding air is. <S> Your reference is the assigned pressure altitude and that is remains constant. <S> But the thing is that the cold air is more dense than warm so, as you suggested, your true altitude is lower in the cold air mass. <S> Should there be any obstacles you should increase your indicated altitude so that acceptable obstacle clearance remains. <S> If we turn the situation around and you actually would maintain your true, physical altitude constant some how, the indicated pressure altitude would be higher in the cold air mass. <S> The QNH is not directly affected by the cold air. <S> The QNH is always referenced to airport altitude so on the ground altimeter always displays airport elevation regardless of the air temperature. <S> Another question is the weather phenomena that cause extremely cold temperatures. <S> When temperatures go below -20C it is often caused by local high pressure accompanied by arctic air mass from the polar region. <S> I’ve seen QNH over 1050 with very cold temperatures. <A> "For altimetry, colder air generates lower pressure inside the pitot-static system than warm air" may be the source of your confusion. <S> We are taught the gas law PV= nRT. <S> The application that lower temperature lowers pressure is valid for a CLOSED container, not for the atmosphere we fly in. <S> If you reduce the temperature (as weather over a region), you increase the air density, all other things (such as altitude) being equal. <S> This results in a lower altimeter reading for the same altitude when passing INTO a cold front. <S> A study of barometer trends as cold fronts pass at the same altitude <S> (the ground you are standing on) should confirm these thoughts. <S> Regarding the reverse case, flying into warmer air, it's "high to low, look out below!". <S> That is the one we need to look out for (gives higher altitude reading than where the aircraft actually is). <S> This is why it is never a bad idea to radio in for the barometric pressure at your landing site if weather changes significantly. <A> The truth of it is always the simplest..... <S> Since you are flying and registering your height by your Altimeter there will be no change in your altitude at all. <S> However, if you wish to know if your height above the ground after flying through a cold front that too could be a poser.... <S> You would need to know how you are crossing the isobars.... <S> Put it most simply <S> then pressure generally would increase along the flight path unless you were flying on a course towards the low centre ( in this regard you would need to draw a hypothetical set of isobars and plot a hypothetical course across the cold front ). <S> You will see that you can maintain the similar pressure or also actually have it decrease or increase depending on your track. <S> Flying from high to lower pressure whilst maintaining altimeter reading and local altimeter setting would result in a descending path... <S> Mnemonic.... <S> High to Low.... <S> Look out BELOW.... <S> Ouch..... <A> The altimeter reading is closer based on pressure than temperature. <S> A cold front is a low pressure system and will affect your altimeter. <S> If you reduce the pressure on your altimeter your altitude indication will decrease. <S> If you are flying at 500 ft with a setting of 29.92 and fly into a cold front that has a pressure of 29.00 you will show an increase in altitude on your altimeter even flying straight and level. <S> But once you call the nearest airport and get the local pressure and set to the new local pressure your indicated altitude will return to 500 ft(ish). <A> From a practical sense, remember: From high to low, look out below. <S> If your barometric pressure and/or your temperature goes down (either/or), your altimeter will read a higher indicate value than the actual MSL true value. <S> You will be at a lower altitude than you think. <S> Ex. <S> Check the Pressure and Density Altitudes at an airport reporting METARs over time. <S> The reporting equipments actual elevation never changes (or <S> at least it shouldn’t). <S> Yet the Density Altitude will change even in conditions of similar barometric pressures.
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If you fly from warm air mass into colder air your altimeter will read the same.
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Do contra-rotating propellers have the same RPM? Image source Here is a contra-rotating propeller. The front propeller rotates counterclockwise while the back propeller rotates clockwise. My questions are: Do they rotate at the same speed (RPM)? If not, which one is rotate faster, and why? <Q> This is done so that as well as allowing effective conversion of very high power into thrust, torque and P-factor are cancelled, making the aircraft easier to fly (especially in a single-engine or two-into-one installation). <S> This is why you see the same diameter propeller in front as in the rear -- <S> if they were turning at different rates, the slower one could be larger diameter <S> (a limitation on diameter is transonic conditions at the tips) -- but you always see the same diameter on front and rear. <A> It depends on the power source. <S> a single piston engine driving both props (as shown in the image in the question): they're geared together <S> so rpm will be the same. <S> two turbines driving one prop each (e.g. Double Mamba ): <S> no coupling between the engines, so prop speeds may be different. <S> You could even shut down one engine in flight (for low-speed, fuel-efficient cruise). <S> The speed of each prop depends on the throttle setting of each engine, so the pilot can run either the front or rear prop faster, or have them both at approximately the same rpm. <S> Compound engine driving both props: the Napier Nomad drove one prop from the crankshaft, and the other from a turbine. <S> While RPM would be related, they wouldn't necessarily be identical. <A> No, not all contra-rotating propellers turn at the same rpm. <S> Take two russian (very famous) examples, the Tupolev TU-95 Bear, and Antonov AN-22 Cock (go figure...). <S> Both use versions of NK-12 turboprop engine, and as can easily be seen in many videos available on the internet, their propellers are not geared in a way that would make them turn in equal rpm. <S> TU-95 propellers turning ratio is such, that for each full turn of the front propeller, the one behind turns a little more than half a turn: TU-95 engine start on Youtube . <S> For AN-22 <S> the ratio is one full turn for front prop, and about 3/4 for the rear one: AN-22 engine start on Youtube . <S> As for the reason of this, I have no knowledge about that. <S> My more or less civilized guess would be that it has to do with load distribution between propellers, and maybe something to do with vibrations and resonances of the powertrain. <S> The aforementioned ratios can be seen during engine startups, but if the propellers are geared together, the ration will of course be fixed througout the rpm range. <S> There has been speculation that the props on NK-12 are driven by separate turbine shafts (not making their rpm's physically connected at all), but I have not been unable to <S> prove this wrong or right. <A> For the aircraft in the picture ie a heavily modified P-51 unlimited racer driving a Rotol Contra Rotating propeller, the answer is yes. <S> Both propellers are geared off the same crankshaft and turn at the same speed. <S> All contra rotating propellers turn at the same speeds during operation. <S> If not, it would negate the purpose of the setup, that is to eliminate a net P-Factor, spiral slipstream and engine torque effects. <S> They would also cause nauseating pulsing noises in the cabin which become very uncomfortable after long periods.
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Most if not all contra-rotating propeller systems are geared together so that both sections turn at the same speed.
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Why there so many pitch control surfaces on the Piaggio P180 Avanti? Picture source . I have seen that there is kind of sonic aircraft like B-1B Lancer that used elevator and canard or fins at the same time for pitch control. That quite understandable because it is fighter jet that required high precision control. There are another airplane that used canard but not elevator, like Tupelov Tu-144 . But this Piaggio P180 Avanti is quite strange for me. It is equipped with elevator, canard, and also another additional device. I am not sure that propeller airplane needs what needed by the above B-1B Lancer. Then my question are, what is that device (number 2 in the picture), what is that name, and what is that for? Are device number 2 and number 3 controllable? <Q> Surface 1 is a horizontal stabilizer with elevator, just the same as on any other aircraft with a T tail arrangement. <S> Surface 2 is called a rear strake or a tail fin. <S> There is one on each side of the fuselage. <S> They are not movable. <S> Surface 3 is a canard, providing extra lift. <S> The canards on P.180 have a trailing edge flap. <S> The flap is necessary to counteract the nose down trim of the flaps in the main wing. <S> Without the canard flaps the elevator would not have sufficient authority to maintain adequate pitch control when full flaps are deployed on main wings. <S> Surfaces 1 and 3 have movable parts, but surface 1 is the only surface connected to pitch axis control of P.180. <S> Piaggio P.180 article on Flying magazine explaining design features (and a lot more). <S> Rear strakes- <S> tail fins on Wikipedia <A> Why there so many pitch control surfaces on the Piaggio P180 Avanti? <S> You mark 3 surfaces, but only one is movable, i.e. there is only one pitch control surface on the P180, not "so many". <S> what is that device (number 2 in the picture), what is that name, and what is that for? <S> Don't know the name myself, but it is there to guide the airflow around the back of he fuselage. <S> Are device number 2 and number 3 controllable? <S> not for continuous pitch control, see above and Jpe61's answer <A> No. 2 is a ventral strake and No. <S> 3 is a canard. <S> Neither have actuated control surfaces on the P.180. <S> The ventral strakes are there to provide additional directional stability and the canards provide a more direct longitudinal balance and control, alleviating tailplane loads, and improving low speed handling. <S> The Avanti was built for speed (400 KTAS in a turboprop!) <S> and quite a bit was sacrificed for that. <S> Note the thin, high aspect ratio wings and lifting body fuselage.
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They provide extra stability during operation at high angles of attack when the fuselage is disturbing the airflow to the vertical tail.
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Is it safe to fly with a B737-800? Is it different from a B737 Max 8? I'm flying from Costa Rica to Chile in November with a B737-800 plane. I'm wondering if this is a different aircraft than the B737 Max 8 or if it's the same? <Q> All B737 Max, as of today 19-Sept-2019, are still grounded and will be for the foreseeable future. <S> So if you are flying in an aircraft, you are guaranteed that it will not be one of those. <S> As for the underlying question "is it safe to fly in airplane model "X"? <A> Yes, it is a different generation of the 737. <S> The Boeing 737 currently exists in its 4th generation: <S> Original Series: <S> The first generation first flew in 1967 and consists of the 737-100 and 737-200 models, which differ in fuselage length. <S> Classic Series: <S> The Classic first flew in 1984 and the main difference is the use of high bypass turbofan engines. <S> It consists of 3 different length variants: 737-300/-400/-500. <S> Next Generation (NG) Series: <S> The NG first flew in 1997 and consists of 4 different length variants: 737-600/-700/-800/-900. <S> The aircraft you will fly on is from this series, as are most 737s, which are still in use today. <S> MAX Series: <S> The MAX first flew in 2016 and also consists of 4 different length variants: 737 MAX 7, MAX 8, MAX 9 and MAX 10. <S> As Federico said, all variants of this series are currently grounded because of problems with the newly introduced MCAS . <A> The 737-800 is not affected by the issues grounding the 737 MAX because the incriminated system (MCAS) does not exist on it. <S> The 737-800 is part of Boeing's "Next Generation" series .
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The 737 Max is much more recent. " the answer always is that if authorities are allowing it to fly, it is safe to the best of our knowledge.
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What is lifting force of V-22 Osprey? Is any other than the two rotors? Picture is from here . Is any other force to lift the V22 other than its rotors? Is any possibility that the power plants their self are not generating thrust? I was just wondered that such short propellers can lift (especially when VTOL) the aircraft even with additional heavy humvee. <Q> The rotors are powered by Rolls-Royce T406 engines, which are turbo shafts : all useful generated turbine power is converted into shaft power for the rotors. <S> Note that turbo props do convert some of the exhaust energy directly into propulsion thrust, turbo shafts do not. <S> All helicopters can provide enough rotor thrust to lift their own weight plus that of (internal or external) payload. <S> Wikipedia lists the max. <S> VTOL weight as 23,859 kg, about the same as the CH-47 Chinook double rotor helicopter at 22,680 kg. <S> The Chinook rotors are indeed longer and therefore require less power to generate the same amount of thrust: 4,590 kW for the V-22, 3,529 kW for the Chinook. <A> As in all turboprops, some thrust is derived from the turbine exhaust, but it's very little, compared with the big thrust of those enormous propellers... <A> Most of the energy from the turbine engine is harvested to turn the propeller as explained on NASA website (for example): <S> NASA: <S> Turboprop Thrust <S> The exhaust of Osprey engine has actually proven to be quite problematic, as it damages the take-off platform: <S> Wikipedia: Bell Boeing V-22 Osprey (see design section, last paragraph)
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The lift is provided by the rotors only. The engines do create some thrust (exhaust gasses), but it is of little significance.
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Why are the wings of some modern gliders tadpole shaped? Why are the wings of some modern gliders tadpole shaped, rather than teardrop shaped? An example is the Schleicher ASG 29. Or did they just add a flat plate at the trailing edge for the flaps and ailerons? Source: flickr.com <Q> The flaps and ailerons are "reflexed" on this glider. <S> They have been raised to a setting above the normal zero position, above the airfoil's normal chord line. <S> A number of flapped gliders have this feature. <S> Two main benefits are a reduction in pitching moment as the pressure distribution on the wing is moved forward, so less downforce work for the tail, reducing trim drag, and lower induced drag because with the trailing edge partially unloaded <S> it has an effect like reducing wing area and moves the best L/D speed up a bit. <S> So overall, best glide angle is a bit better, and the speed it's achieved is a bit higher. <S> You use reflex for "penetration", going as flat as possible as fast as possible, for whatever reason, like getting through an area of sink in a hurry. <A> You can position the flaps/ailerons on the ASG 29 not only downwards but also upwards. <S> The flap/aileron is triangle shaped as you can (barely) see on this photo of an ASG 29 wing joint: <A> Flapped airfoils will have a suction peak once the flap is deflected away from its zero deflection position. <S> This means more load on the boundary layer and earlier flow separation at the same lift coefficient. <S> In order to avoid this suction peak over a range of flap angles, the airfoil contour is optimized on the top side for a small positive deflection and on the lower side for a small negative deflection. <S> Now you get that "tadpole" shape between those two flap deflections, but also more flap effectivity and lower drag. <S> This effect is increased on the upper side for negative flap deflections . <S> They are standard on gliders in order to shift the laminar bucket of the airfoil to the actual lift coefficient. <S> I bet the lower side contour of the wing in the photo is smooth across the flap hinge line. <A> The upward flexure of the trailing edge of the airfoil does two things: <S> It maintains attachment of the flow boundary layer across the airfoil surface and decreases drag. <S> Separation of the boundary layer would increase pressure drag and, essentially, momentum of the separated flow that is now being carried by the aircraft. <S> This would decrease penetration and adversely affect airspeed and lift-drag ratio. <S> For a sailplane within its maximum flight performance envelope, it decreases the forward pitching moment of the wing. <S> Nose-down pitching would increase airspeed and sink-rate, thereby requiring up-trim of the tail-plane to counter the nose-down tendency. <S> This up-trim also increases drag, thereby adversely affecting the lift-drag ratio. <S> Up-trim can also be maintained by shifting the center of gravity aft by moving trim ballast aft. <S> Nevertheless, the best flight characteristics for maximum lift-drag ratio of a high-performance sailplane are maintained through neutral trim settings producing no essential drag (an aerodynamically balanced aircraft), and a clean wing flying within its best performance range at the given altitude and airspeed (that is, wing Reynolds number and angle of attack). <A> Effectively the raised flap lowers the angle of attack by virtue of the variation of the chord line. <S> Less drag, higher speeds for, as has been said, penetration.
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Basically you can reduce the lift (and therefore drag) of the wing by moving the flaps/ailerons upwards, extracting better speed from the wing.
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What is the meaning of first flight and introduction in aircraft production? They are info from wikipedia ( here and here ). I don't know many about the B-52 Stratofortress, but I'll take another case. The N-250 I remember its first flight which was performed with large scale, watched by Indonesian's former President and many other high rank officers. I remember the date, or at least the exact year. It was 1995. Then my question is, if 10-Aug-1995 was its first flight which was performed with great fully, then what is the meaning of introduction (15 June 1997 in this case)?. If it was widely open to public when performing first flight, then why does an airplane needed to be introduced? <Q> If the testing goes smoothly, it might be that no more changes are necessary and the aircraft can be delivered to customers as it is. <S> But if problems show up during these test flights, changes might be necessary before finishing the final design. <S> The introduction refers to the first flight by a customer (an airline for commercial airliners or a military unit for military aircraft). <S> This is also referred to as entering service . <S> This could happen in the same year as the first flight (e.g. Boeing 737 Classic series in 1984) or many years later (e.g. Concorde in 1976, 7 years after the first flight in 1969). <S> Another term commonly used is the launch of an aircraft type, which refers to the start of the development program. <S> The IPTN N-250 <S> you mentioned was never introduced into service. <S> Wikipedia claims the 15 June 1997 as introduction date, but on this day the aircraft was shown at the Paris Air Show: (image source: airliners.net , taken by Peter Vercruijsse in Paris - Le Bourget on June 15, 1997) <S> The image description says: "Gatotkoco", the prototype N-250 returning from a demonstration flight at the Paris Air Show. <S> The N-250 programme is currently (early 2000) on hold due to a lack of finance. <S> This does not count as introduction and is therefore a mistake in the Wikipedia article. <A> Typically, introduction means introduction into service. <S> For passenger aircraft this means the first delivery to the customer and/or first revenue flight. <S> For military aircraft this means the first date that an aircraft is declared operationally ready to perform (part of) the intended tasks. <S> This usually occurs some time after the first flight because the test program has to be concluded. <S> Depending on whether it is a modification of an earlier certified model or a totally new aircraft, the time between first flight and introduction into service can range from several months to several years. <A> Between those two events are 2 major steps: Flight testing by the company that builds the aircraft. <S> This is a series of test flights in which the aircraft is tested under all circumstances it will be expected to operate in. <S> The first few flights are just to make sure all the aircraft systems work as expected in flight <S> Then there are flights to explore the performance envelope (flying at different altitudes and speeds) <S> , this is done in incremental steps (slowly increasing flight speeds, G-loads etc.). <S> Then there are environmental tests (flying in cold/hot weather) <S> When the test flights are concluded to satisfaction, and any modifications have been tested as well <S> , it's time for certification: <S> basically, another series of test flights, this time they are monitored by the certification agency. <S> They also dictate which tests have to be done. <S> First flight may be a public event, but the aircraft is far from ready for commercial use. <S> First flight is a PR exercise, with the company showing their new project in a working state for the first time.
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The first flight of a new aircraft type refers to the first time the aircraft is flying during the development and testing phase.
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Do jackscrews suffer from blowdown? With hydraulic control surfaces, at high airspeeds, there is a point where aerodynamic loads exceed the capability of the actuators. This limits control authority and can result in the control surface not being in the position commanded by the pilot. Jackscrews are commonly used for horizontal stabilizer control. I know they can jam and be difficult to move under high loads, but can they be blown back from their set position or do they stay put? <Q> Acme screw type screw jacks with the square threads, as used in stab trim systems (as opposed to a recirculating ball screw), are usually inherently irreversible because of the higher friction of the direct sliding contact of the square sided threads vs a rolling ball interface (as a sliding interface, it's totally dependent on the grease to keep friction in check). <S> This is why the trim screw <S> jack of the 737 becomes extremely difficult to move manually when the jack is heavily loaded, even though the movement input is coming from input side that is supposed to be the low effort side, requiring a technique of unloading it with elevator inputs to manually trim when the airplane's actual speed and trim speed are far apart. <S> Ballscrew type jacks however, typically used for flap actuators, have very low internal friction and very high efficiency thanks to the ball interface between the "nut" and screw (rolling, not sliding). <S> As a result they can be back-driven more easily; how easily depends on the gear reduction within the worm drive gearbox. <S> Ballscrew operated flap systems typically require friction brakes in the drive line, or anti-backdrive devices incorporated internally in each actuator (basically a clutch device that is disengaged only when the torque is coming from the input side), to prevent a flap surface that is disconnected from its drive motor from creeping up from air loads. <S> Acme screw actuators also have internal brakes but these mainly function to lock an inoperative motor when there are dual motors, so that the live motor can't backdrive the dead one instead of the downstream gear train. <S> They also serve to lock the acme screw when both motors are off, but this isn't as critical with an acme screw. <A> Screws can be either self-locking or overhauling. <S> Jackscrews used for stabilizer control are designed to be self-locking, since their purpose is to make the stabilizer adjustable, but prevent it from moving by itself. <S> A jackscrew (or screw jack) is pretty much by definition a self-locking screw. <S> It should be noted that vibrations can induce travel in screws, even those that are self -locking under static load by desing. <S> I was, however, unable to find a study regarding such scenarios in jackscrews applied in aircrafts. <S> It is reasonable to assume that jackscrews used to adjust the stabilizers are designed in such a way, that the trim system as a whole is not prone to moving on its own in any foreseeable scenario. <S> Wikipedia: Screws - self-locking property <A> Limited control authority can be a design feature. <S> Full surface deflection at high airspeed may impose high load factors which exceed the structural design strength of the airframe, in which case the control surface authority can be limited by the maximum actuator force. <S> Reversibility of the load is a function of: Backdrive load. <S> Thread friction. <S> Screw thread pitch. <S> There is a self-locking pitch limit: between zero and this limit, the screw is irreversible (self locking). <S> The best known example of this is found in nuts and bolts, which have the cross sectional triangular thread shape resulting in the highest friction. <S> Note that: The bolt becomes more difficult to turn with increasing tension: the friction is still a function of the back load. <S> All bolts in aircraft must have a locking feature to prevent unlocking due to vibrational friction fluctuations, as mentioned in a comment from @BrockAdams. <S> Drive screws are mostly not designed to be irreversible, most threads for drive shafts have a rectangular thread and high pitch in order to minimise friction and maximise efficiency. <S> The stabiliser pitch screw in an aircraft is subject to varying loads, both in a positive and a negative direction, and can therefore not be designed such that it is self locking due to load and friction. <S> If that feature must be designed in, a separate lock must be manufactured, with redundancy features to prevent uncommanded lock in undesired situations.
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Jackscrew actuators can be designed such that they are back driven.
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What is the first fighter jet which was built with twin engine and tail configuration? What is the very first fighter jet that pioneers the twin engine and twin vertical stabilizers over the engine just before the exhaust (like the F-14, F-15, F-22, Su-35, etc)? <Q> One of the first was probably the unconventional XP-79. <S> https://en.wikipedia.org/wiki/Northrop_XP-79 <S> It never entered service of course, but does meet your criteria. <S> Twin tails and twin rear mounted engines though the tails were in separate tail booms outboard of the engines, a similar configuration to that of the DH Sea Vixen and Venom of roughly the same period. <S> These did enter service. <S> Then there is the XF-90 <S> which has twin rear mounted engines with a single vertical stabiliser over them. <S> The Soviet La250 and Tu28 had similar configuration but came later. <S> This also did not enter service. <A> Probably the MiG-25. <S> Near as I know, it was the first to use the ‘four poster’ layout. <A> Prototype only: the YF-12A. <S> This was an A-12 <S> derived fighter plane. <S> The A-12 is better known for its other derivative, the SR-71 Blackbird. <S> Both the A-12 and the SR-71 were intended for reconnaissance tasks, but the YF-12 would have been a fighter. <S> With a first flight in 1963, it beats the Mig-25 by a year.
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Something that kinda meets your criteria would be the F7U Cutlass .
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Are there any privately owned large commercial airports? Do any large, commercial airports exist that aren’t owned and run by the city government they exist in/near? To provide context, I’m talking major airports that handle commercial airline volume. Do any (hub or regional) airports exist that are fully owned and operated by private companies vs government authorities? Or is this a total fallacy? I could understand companies big enough to have their own corporate fleet/airstrip, but I’m talking a full-scale airport with airlines the public can use. <Q> Building an airport is a very expensive endeavor and usually involves government subsidies or is completely done by the local government. <S> In recent decades, most government owned airports in Europe have however been transformed into companies that both own and operate the airport, usually with the government as initial owner of this company. <S> Since this privatization, some governments have sold their shares of the company resulting in completely privately owned airports. <S> Going through the 20 busiest airports in Europe from Wikipedia's list , the following airports are completely or by majority privately owned : London Heathrow Airport owned by Heathrow Airport Holdings <S> London <S> Rome <S> Leonardo <S> da Vinci-Fiumicino owned by Aeroporti di Roma (3.8% government owned) <S> Zürich Airport owned by Flughafen Zürich AG (38.38% government owned) <S> Copenhagen Airport owned by Københavns Lufthavne (39.2% government owned) <S> Lisbon Airport owned by Vinci SA , although operated by the government The following airports are run by a private company, but they are majority government owned : Paris Charles de Gaulle Airport and <S> Orly Airport owned by Groupe ADP (50.6% state owned) <S> Amsterdam Airport Schiphol owned by Royal Schiphol Group (92% government owned) <S> Frankfurt Airport owned by Fraport (51.47% government owned) <S> Madrid-Barajas , <S> Barcelona-El Prat and Palma de Majorca owned by Aena S.A. <S> (51% owned by ENAIRE , which is a public corporate entity) <S> Munich Airport owned by Flughafen München GmbH (100% government owned) <S> Manchester Airport owned by Manchester Airport Holdings (64.5% government owned) <S> The following airports are directly owned by the local governments : <S> Istanbul Atatürk Airport Dublin Airport <S> I am not sure who exactly owns Sheremetyevo and Domodedovo in Moscow. <A> London Heathrow (LHR) is owned by a private company, Heathrow Airport Holdings . <S> I'm sure there are many other examples around the world. <A> The major Australian airports were all privatized from the late 1990's. <S> Smaller regional airports are still usually council-owned and operated. <A> In New Zealand both Auckland and Wellington airports are privately owned. <S> In both cases the local government have a non-majority shareholding which provides a fig leaf of representation but in reality nothing other than sincecures for local politicians . <S> They are de-facto monopolies for the region they serve and manifest the types of behaviour you would expect from that situation. <S> In theory their profits are limited by a formula which is overseen by national government <S> but this just has the effect that they squeeze every last cent out of activities which fall outside of the formula but which they still have a monopoly over. <A> Don't forget Punta Cana Airport , Dominican Republic. <S> It was one of the first privately owned airports in the world. <A> Speaking of Sheremetyevo to continue @Bianfable answer, as of 23 April 2019: 66% are held by Sheremetyevo Holding which it turn is owned by an offshore cypriot TPS Avia Holding. <S> TPS Avia Holding in turn: 65,22% are held by trust of Ponomaryenko abd Skorobogatko families and 34,78% Arkadiy Rotenberg. <S> While that seems to be private owners, they are tightly connected to the Russian government and especially Vladimir Putin. <S> 30,43% are off to Federal Property Management Agency Minorities are Aeroflot Airlines and VEB Capital (bank). <S> Both of those companies are controlled and owned by the Russian government <S> So on paper Sheremetyevo is a privately owned company, but in fact it is controlled by Russian gov't. <S> Source in russian: vedomosti.ru <A> In the United States, there is only one privately owned and operated airport with scheduled commercial service: Branson, MO , which only has seasonal service to three other destinations. <S> The vast majority of airports in the United States are at least publicly owned, and many (the majority, I believe) are publicly operated as well. <S> The fact that airports in the United States have largely not been privatized while many airports in Europe have been privatized is perhaps a bit surprising, given both the USA's and Europe's relative views on private vs. public enterprise. <S> The Government Accounting Office actually produced a report on why airport privatization hadn't taken off (so to speak.)
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Gatwick Airport with a majority ownership by GIP Oslo Gardermoen owned by Avinor (100% state owned)
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What powers an aircraft prior to the APU being switched on? I know that APUs are power plants for non-propulsion related purposes and that they are turned on before takeoff. What powers an airplane prior to the APU being turned on? <Q> Other than the APU, there are multiple ways to provide electrical power to an aircraft: <S> Battery: <S> Running only on battery power will however deplete the battery quickly. <S> The battery can also be used to start the APU. <S> Ground Power: <S> Most (maybe all) airliners can accept a connection to a Ground Power Unit (GPU) , which will supply AC electrical power to run all aircraft systems on the ground. <S> These can be either mobile units (typically powered by Diesel): ( source ) or direct cable connections to the airport power grid: (taken from this question ) <S> Engine: This would be the method of last resort, but you can run an engine to provide electrical power via its generator. <S> Note <S> however that starting a jet engine would typically require bleed air from the APU or an Air Start Unit (ASU) . <S> Some turboprops can run an engine with a stopped propeller to provide power ( Hotel mode ). <S> The engines also provide all electrical power during the flight, which is also used to re-charge the battery. <S> Running an APU on the apron is typically discouraged or restricted 1 by the airport because of the noise and pollution. <S> It does however provide one advantage over ground power: the APU also supplies bleed air to the air conditioning systems. <S> Without it, air conditioning is only possible via a Pre-Conditioned Air (PCA) hose. <S> See What is this tube connected to a 757 for? for details. <S> The APU is usually switched off after starting the main engines. <S> It can however be used in the air on some aircraft. <S> See In what conditions is the APU used in midair? <S> for details. <S> 1 <S> Some airports have restrictions on when an aircraft is allowed to run the APU, e.g. Amsterdam: <S> The use of aircraft APU is forbidden in these stands in the period between 2 minutes after blocks for the arrivals and 5 minutes before off blocks for departure. <S> The APU will still be used to start the main engines during push-back. <A> Onboard batteries for DC and a ground power supply for AC. <S> The ground supply can come either from an airport vehicle or from the stand itself. <S> Since the standard AC in aviation is 115V and 400Hz, the usual ground power supply needs to be converted to a higher frequency. <S> This used to be done with a rotating converter, i.e. a motor (at 110V and 60Hz or 220V and 50Hz) driving a generator (at 115V and 400Hz), but can probably be done with solid state electronics these days. <S> As for why the 400Hz, there is a good answer here <S> but it boils down to: higher frequencies can work with lighter transformers, but also radiate more, so 400Hz was chosen as a compromise. <S> Of course, on more advanced aircraft with weight to spare, one can find ways to convert DC into AC and viceversa. <S> DC can be converted to AC using an inverter, while the oppoosite is achieved through a rectifier (typically the rectifier is only one component in something more elaborate like a switched-mode power supply, since by itself it would give a pretty choppy "DC") <A> Worked at an airport for 3 years. <S> Aircraft were either powered by battery, GPU, jet bridge, or engines. <S> But being powered by engines presented a problem, in that all the blast zones would be deadly and severely limit what work can be done on the aircraft, if any. <S> Generally the procedure was to get the ground power connected as soon as the aircraft was parked. <S> Alternatively, the pilots could use their APU, but that costs them fuel, and it's less expensive for them to have us use our fuel (though I'm sure that cost is passed into the parking fee the airline pays for each gate.) <S> Also, working on an aircraft that had an APU running was extra loud, even with hearing protection.
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The battery is typically the first thing you would turn on and it usually provides DC power to emergency systems only (at least on an airliner, smaller aircraft are fully powered by the battery).
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Does a left spin differ from a right spin for a single-engine propeller aircraft, in terms of spin characteristics & ease of recovery? Given a single-engine propeller aircraft with its nose-mounted propeller rotating on the right-hand side when viewed from the cockpit, and given the typical effects like P-factor, prop-wash and gyroscopic forces associated with the propeller - Would there be any differences between left-hand and right-hand spin modes? (Differences both from the physics perspective as well as perceptional difference from the pilot's point of view. For example, the differences could be there from a theoretical perspective but minor enough that the pilots can ignore them in real life). If the answer is yes for Q1, which side, in this particular case, would have a more severe spin in terms of spin rate, loss of altitude and so on? If the answer is yes for Q1, which side, in this particular case, would have a harder recovery compared to the other side? To reduce variables, let's assume there are no asymmetries in the aerodynamic configuration which may make the aircraft favor one direction over the other for spin and we are only considering the effect of propeller-rotation-direction-related effects on the spin. <Q> Chipmunk, left-handed engine: Spinning to the left, recovery takes 3/4 turn, spinning to the right, recovery takes 1/4 turn. <S> In either case, descent rate is 6000ft/min, so not affected by the airflow direction. <A> It differs but not as much as it does for jet aircraft. <S> This may seem counter-intuitive, but in spin, inertia and gyroscopic effects play major role. <S> On propeller aircraft, the most practical difference must be with inadvertent entering spin, where power (and the associated asymmetry) is significant. <S> But after entering spin, the first thing one does is reducing power to idle. <S> This makes aerodynamic asymmetry ('P-factor' etc.) <S> negligible (unless the tail is deliberately offset, as is done on many single-prop aircraft), and the prop gyroscopic effect is rather small. <S> Jets, while looking perfectly symmetric, still have engine(s) rotating one way (with a few notable exceptions), and their gyroscopic moment is very significant, even at idle. <S> (The rotor is much heavier and spins much faster). <S> If the gyroscopic moment tries to raise the nose in a given spin rotation, the spin will usually be unstable. <S> For example, MiG-15/17, with its left-rotating engine, had a very unstable right spin, which tended to change to left over time. <A> A well known spin recovery technique is PARE. <S> Power to idle, Ailerons neutral, <S> Rudder Away from spin, Elevator nose down. <S> Power to idle is critical to avoid complications in spin recovery. <S> Now, aerodynamicly, spin behavior recovery is much more similar left or right, with the right being slightly easier to recover from. <S> If your plane is stable, and CG is set right, it should not spin unless it is forced to. <S> Rudder control remains effective through stall, and is your best friend to avoid, or stop, a spin before it becomes fully established or flat. <A> Two things have to happen simultaneously to cause a spin: stall and large enough yaw rate. <S> To recover from a spin you need to stop both of those. <S> Therefore anything that increases the intensity of either a stall or yaw rate will hinder you recovery. <S> Specifically talking about the propeller contribution: let’s say we have a clockwise prop, which produces left turning/yawing tendencies. <S> Because there will be more yawing moment that we need to overcome. <S> However whether the difference would be perceivable or not by the pilot would really be depended on the aircraft, power setting, idle power/torque, size of the prop, aircraft’s inertial characteristics etc.
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Most jet fighters have very asymmetric spin characteristics, to the point that one spin may be stable and difficult to recover while the opposite spin be unstable and difficult to enter. Since it creates left yawing motion; left turning spins will be easier to enter and harder to recover from than the right spins.
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Why increase or decrease rudder when using elevator in turns? In normal 30 degree bank level turns, instructors teach students that if you are to correct your altitude you also need to change your rudder input. Why is that? For example if you are descending in your turn you are to pull the elevator and also lessen your rudder input. And if you are climbing in your turn you are to push the elevator and push more rudder. Is this because of you are tightening your turn when pulling elevator and therefore you are starting to skid and therefore you need to lessen your rudder to compensate. And if you are pushing the elevator you are doint the opposite starting to slip and therefore you need more rudder. Or is there some other explaination to why you need to do this? EDIT: Hi, no I think you have misunderstood the question. They do not teach to use the rudder to compensate for pitch/altitude. They teach properly to use the elevator. But they say that when you make a change with elevator to a higher nose you don't need that much of rudder than before. And when you use the elevator to push nose down there is more need of rudder. The rudder change is just to compensate the need due to change in configuration. Not to use it to change the altitude. <Q> Instructors that teach that to students are fools. <S> You should be using rudder only as required to keep the ball centered - period. <S> If you are applying rudder to influence the pitch attitude, to "help hold the nose up", this is very very bad, and leads to stall/spin accidents. <S> But in any case it is strictly used to keep the tail lined up behind the nose in the airstream. <S> Anything else and you are skidding or slipping in the turn. <S> If you are in a 30 deg banked turn, and are descending, the total lift from the wings is insufficient; you need more elevator input, NOT top rudder, which creates a slipping turn, which will make the airplane flick over the top into a spin if you stall while doing it. <S> Don't overthink it. <S> Ailerons to keep the bank angle, elevator/power to control the pitch and altitude/speed, rudder to center the ball; just do whatever it takes. <A> With 30 degree bank from the ailerons, your wings create a centripetal force to make a turn. <S> Now pitch and power are increased because the vertical component of lift is reduced, and the rudder makes the turn coordinated. <S> Adding elevator will not only lift the nose, but also add yaw - the same sine & cosine are at work. <S> You reduce rudder to keep the yawing force constant. <S> Yes, that is the whole explanation. <S> Just imagine a turn with 60 degree bank, or even knife-edge flight. <S> Or look how a V-tail works on the early Beech Bonanza. <S> It is all about splitting and combining force vectors. <A> @Michael Hall. <S> Elevator use changes the aircraft pitch angle to the relative air flow, and hence the amount of P-factor experienced by the aircraft will change. <S> Since this is manifest as a yaw, an appropriate rudder change is necessary. <S> John K. is correct—-this <S> is not the way to teach turns.
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Rudder is mostly being used to counteract adverse yaw from the aileron inputs, and to some degree to correct for yawing motions caused by power changes.
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Can airflow reverse over the flight surfaces of a uav in high wind conditions Can airflow reverse over the wing of a uav in high tail winds and low forward airspeed i.e 25knt fwd airspeed in a 35 knt tailwind? What would be the overall effect on the elevator and rudder? I suspect the rudder would be remain the same but operate at a reduced efficiency however, wouldn't the function of the elevator reverse and/or become ineffective, especially at high angles of attack? As a point of note, this uav does not have ailerons, I believe the roll effect is achieved as a combination of pitch and yaw. <Q> It is possible, but only if there were a very sudden and dramatic change that the aircraft was unable to overcome. <S> However, it would be only temporary. <S> If the airflow direction was actually reversed the control surfaces would likely be blown to a full deflection position one way or the other depending on which side of neutral they were. <S> Otherwise, the aircraft would still move forward at 25kts relative to the moving airmass, with the additive effect of the wind giving it 60kts of ground speed. <A> If you're taking about a steady 35kt tailwind it would make no difference. <S> The surfaces only react in relation to the air mass whether that air mass is moving or not. <A> No, at least, not in the way you seem to think. <S> When any aircraft flies, it does so relative to the air , not the ground. <S> So, when you're watching from the ground, the air acts like a treadmill. <S> So, if you've got a 35kt South* wind, and a UAV that's flying North at 25kts, then, from the perspective of the ground, it will be traveling North at 60kts. <S> It will still have 25kts of wind over its control surfaces, which will perform as normal. <S> If this UAV then turns around, it will appear from the ground to be flying backward, going North at 10kts even though it's facing south. <S> But it will still have 25kts of wind across its control surfaces, which will perform as normal. <S> There are two ways to actually have a reverse airflow across its wings. <S> You can reverse the thrust of the engine, or the wind can suddenly switch directions (as detailed in other answers). <S> In either case, all control surfaces would function in reverse (assuming, of course, that whatever servo system moves the control surfaces is strong enough to fight the tailwind and actually move them). <S> *Remember, when discussing wind direction, you specify the direction that the wind is coming from . <S> So a "South wind" would be blowing out of the South, toward the North. <A> You can test this with a simple balsa model and a desk fan. <S> In the air, this has actually been seen with a model plane at around 15 mph hit with a strong gust from behind. <S> The elevator, pulled up to create downforce on the tail (to pitch the nose up), reversed, sharply pitching the nose down. <S> Needless to say, the wing lost lift as well. <S> A complete reversal in airflow in flight is extremely rare, requiring a huge gust. <S> Keep in mind the plane moves with the air mass in a constant wind. <S> But a gust need not drop your airspeed to negative numbers to cause a dangerous loss in altitude, as can happen in a microburst. <S> The remedy is to pitch down immediately and add power to regain airspeed. <S> Close to the ground, recovery may not always be possible. <S> But there is one practical application to your thoughts, positioning of ailerons while taxiing. <S> Is wind is quartering from behind, you want that aileron DOWN to help hold the wing tip down. <S> As you turn into the wind, having the aileron UP pushes the wing down (as in normal flight). <S> Same story with the elevator. <S> And a crossing wind can certainly prompt a rudder input. <S> Far more likely to experience these issues on the ground, and maybe not a good day to fly if they are happening in the air.
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Reversing airflow on both rudder and elevator will reverse the direction of their torquing force.
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Is aerodynamics study compulsory for building a plane? I want to make a plane like a trike. I have a design and some knowledge about plane requirements. <Q> You don't need to know much aerodynamics to build a plane if you follow plans for an existing design that somebody else has engineered and validated, and you don't make any modifications. <S> If you are trying to design and build something new, even if superficially similar to existing aircraft, then yes you will need to study aerodynamics and other aspects of aeronautical engineering. <S> This doesn't necessarily need to be formal academic study but there is a substantial body of knowledge that you will have to learn in order for your project to be safe and successful. <A> It's not compulsory as in there's no law requiring you to have studied aerodynamics in order to design an aircraft. <S> It is however exceedingly hard to design an efficient and safe (and able to fly at all) aircraft without a thorough understanding of aerodynamics, so studying the field is a very good idea. <S> What set the Wright brothers apart from many others who were trying to design and build flying machines around that time is that they went through the effort of studying and analysing other flying things, like birds, and also looked at the partially successful attempts by people like Otto Lilienthal and learned from what worked for those machines and what didn't. <S> Only when they had what they considered an understanding of how things worked did they set out to build their own models, gliders, and eventually powered aircraft. <S> Had they just set down behind their workbenches and start churning out parts to put together with little thought as to their correct shape, size, and such, they'd have failed like so many before (and since). <A> Some aircraft have been built by thousands of people, none of whom were asked for their diplomas. <S> But if you want to legally fly what you've build, in USA airspace, then you must choose which category it falls into and what laws apply to it. <S> https://www.eaa.org/eaa/aircraft-building/building-your-aircraft/getting-started/selection-articles/faa-51-rule
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No, aerodynamics study is not compulsory for building an aircraft, or parts of it.
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Is it allowed to let the engine of an aircraft idle without a pilot in the plane. (For both helicopters and aeroplanes) Is it allowed to let the engine of an aircraft idle without a pilot in the plane. (For both helicopters and aircr). Would there be a difference between a C172 and a 737? <Q> You won't see it done in the fixed wing world unless the aircraft is tied down or otherwise securely restrained (like when you tie off the tail to something when hand starting your no-starter taildragger; some pilots just use chocks or parking brakes to hand bomb their airplane, but it's a terrible idea). <S> However, it's common in the helicopter world especially in bush operations. <S> With the collective and cyclic friction locks tightened down and the engine in ground idle, it can't really go anywhere and a pilot who lands in a remote area without assistance to hook up a sling load or lug something on board will often do it without shutting down. <A> I'd say no, you're likely to be busted under 91.13... <S> 14 CFR § <S> 91.13 - Careless or reckless operation <S> (a)Aircraft operations for the purpose of air navigation. <S> No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another. <S> Having had a parking brake slip on a small GA aircraft once or twice myself, I can say its generally a bad idea regardless of regulations. <A> It would be very difficult for a lone pilot to <S> hand prop start an aircraft without this occurring for some span of time, which would lead me to conclude that it is not forbidden. <A> Generally speaking, no. <S> To add some detail, in the Navy we would "hot switch" pilots occasionally in the EA-6B - shutting down the left engine on the pilot side, but leaving the right one running. <S> In these cases the plane was chocked, (chained when shipboard) and there was always an NFO in the right seat to monitor the engine and shut down if needed during the minute <S> or so it would take the next pilot to climb in. <S> Otherwise the only other time you would not have a pilot in the plane <S> is when a turn qualified engine mechanic was there instead, supporting maintenance. <S> I would imagine similar policies are in effect at the airlines.
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Legal or not, it is a very bad idea.
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What is the difference between experimental and amateur built aircraft in the US? What is the difference between experimental amateur and amateur built aircraft in the US, or are they the same? If not, is there a difference re specifications, inspections, engines, passengers, etc.? <Q> The FAA provides pretty clear definitions and/or explanations: <S> Amateur built: Title 14, Code of Federal Regulations (14 CFR), part 21, section 21.191(g), defines an amateur-built aircraft as an aircraft "the major portion of which has been fabricated and assembled by person(s) who undertook the construction project solely for their own education or recreation." <S> They define Experimental as a category , since it has to do with how the airworthiness cert is issued: A special airworthiness certificate in the experimental category is issued to operate an aircraft that does not have a type certificate or does not conform to its type certificate and is in a condition for safe operation. <S> Additionally, this certificate is issued to operate a primary category kit-built aircraft that was assembled without the supervision and quality control of the production certificate holder. <S> And further Special airworthiness certificates may be issued in the experimental category for: Operating amateur-built aircraft: to operate an amateur-built aircraft in which the major portion has been fabricated and assembled by persons for their own recreation or education. <S> Operating kit-built aircraft: to operate a primary category aircraft that was assembled by a person from a kit manufactured by the holder of a production certificate for that kit, without the supervision and quality control of the production certificate holder. <S> So... <A> "Experimental" was originally applied to development test aircraft only. <S> The application of the term to amateur builts is an artifact of the early days of homebuilding in the early 50s, when the Civil Aviation Authority (FAA's predecessor) was persuaded to create a formal licensing structure for amateur built airplanes created for personal use, and they decided to piggyback on the existing Experimental category normally used for test aircraft, as the path of least bureaucratic effort. <S> So you have a somewhat odd categorization, done nowhere else, where airplanes NOT created for development and testing, but just built for people to have fun and fly, still have EXPERIMENTAL plastered on the side. <S> In Canada the homebuilt category was originally called "Ultralight", but then in the 70s actual ultralights appeared on the scene and the name wasn't really suited to 180 mph airplanes like Thorp T-18s, so a new Amateur Built catagory was created to cover traditional homebuilts, with ultralights just ultralights. <A> As I understand it (I am not a pilot, nor do I live in the US) in the US: <S> "amateur built" is a subset of "experimental". <S> "experimental" aircraft are assesed and issued with airworthyness certificates on an individual basis under requirements less rigorous than the normal type-certification process. <S> However the FAA doesn't want manufacturers using experimental certification as a way to do an end-run round the normal certification process, so they put limits on what aircraft can be registered as "experimental". <S> "amateur built" is a subset of experimental for aircraft that are more than 51% built by amateurs and is one of the least restrictive experimental categories. <S> Another subcategory of experimental that the aviation hobbyist may run into is "experimental exhibition", this category is often used for ex-warbirds and is also sometimes used as a means to heavily customize aircraft. <S> The downside as I understand <S> it is you have to convince the FAA that you will genuinely be using the aircraft for exhibition purposes. <S> Regarding passengers as I understand it <S> no experimental aircraft is allowed to carry passengers for hire and some are not allowed to carry passengers at all. <S> As I understand it amateur builts are allowed to carry passengers not for hire after passing some additional testing/proving. <S> I don't know if the rules on carrying passengers are different for other types of experimental.
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All amateur built aircraft are experimental (flown under an experimental airworthy type certificate) but not all experimental's are amateur built, for example a pre-production aircraft may need to be registered as an experimental for test flights before a type certificate is received.
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Could the principle of owls' silent flight be used for stealth aircraft? I was wondering about the ability of owls to fly so silently. Is it because they flap gently, they flap less often or do is their structure responsible? I was thinking their principle of stalking can be applied to stealth aircraft. Is it possible? <Q> Their primary wing feathers have an unusual structure incorporating a fringed, comblike leading-edge, which reduces wind noise. <S> The wing feathers also have an overall softness or flexibility. <S> The trailing-edge of the wing is also dominated by soft, fringed edges. <S> Even the underwing lining (covert) feathers have an unusual softness that plays a role in sound suppression. <S> See for example -- https://www.owlpages.com/owls/articles.php?a=7n , https://animals.howstuffworks.com/birds/owl-fly-silently1.htm .Google "owl feather structure" for more. <S> I'll leave it mostly unsaid, as to whether any of these features are worth incorporating into a jet-powered aircraft. <S> Maybe some of these features might be applied to the intake or exhaust areas, in a more rigid metallic form? <A> In addition to quiet flyer's excellent answer: Owls have large wings in relation to their body size and weight. <S> One might think that no, their bodies are quite large, but actually owls are kind of fluffy flying feather balls: what you percieve as their bodies, is mostly air. <S> This leads to two things: Low wing loading. <S> Their large wings do not need to create as much lift per area unit as, say, with pigeons. <S> This leads to less turbulence, which in turn means less sound. <S> The fluffyness (for lack of a better word) suppresses turbulence in wing - body attachment area, and any other turbulence around owl body. <S> This means, of course, less sound. <S> When combined with wing structure described in q f's answer, all these factors create a pretty much absolutely silent flight. <S> Check out <S> this excellent BBC Earth clip comparing the sound different birds make when they fly, and why so. <S> As for the aplicability of these features in stealth aircraft, not likely, athough I strongly second PerlDuck's vote for fur covered wings on aircraft. <S> The fact is, however, that there is no sense in making the wings or the airframe more silent, when the sound of the propulsion is orders of magnitude louder than any other part of the aircraft. <S> P.S. <S> It's actually quite eery to encounter an owl in flight when it's dark. <S> You can hear other birds when they fly in your vicinity, but owls, no, they just blast right by you totally silently, without a warning. <S> They've scared me sh__less a couple of times out in the wild, and I'm pretty sure they enjoy it... <A> Stealth aircraft are built to reduce their observability in 3 main areas, with the goal of reducing the warning time an enemy has: radar optical and IR sound <S> This is in order of detection range: Radar can find an aircraft potentially at hundreds of km, optical systems go to a few tens of km, and sound becomes a factor only when the aircraft is very near (at low altitude and high speed, you can get within 100 m of the target before you become audible). <S> The detection range also gives you the order of importance. <S> Radar takes priority. <S> The sound produced by an aircraft is dominated by its engine noise. <S> The air rushing over the skin makes some noise, but that's generally only audible when the engines are shut off. <S> This means there's no benefit to reducing skin noise. <S> In addition: a fringed, comblike leading-edge This is a nightmare for radar stealth. <S> You want the structure to be as simple and smooth as possible, because when you have a large number of surfaces in many directions, you get many radar returns. <S> Improving audio stealth would compromise radar stealth. <A> Owls' bodies are optimised for silent unpowered flight; even when owl flight is powered flight, it's powered by wing flapping (rather than jet engines or turboprops). <S> At most I suspect you'll be able to help silence the noise from a body passing through the air; as gliders are rather quieter than light aircraft, I suspect this is the minority of the sound, at least until speeds get very fast where the aerodynamic and acoustic models will be very different anyway. <S> However, as "aircraft" is widely defined, perhaps they would be useful for a drone that for portions of its flight mostly glides silently at low-ish (owl-like) speeds, for covert photography, covert small payload delivery, or some other likely nefarious purpose. <S> Heck, it could actually be disguised visually as an owl. <A> If the other excellent answers roll off you like water off a duck 's back, this may convince you: What owls had to give up in exchange for quieter (not silent!) <S> flight, is fast flying and flying on rainy days. <S> Their feathers miss (most of) the oils that make other flying birds able to take quite a drenching without much trouble (and water birds even more so). <S> Planes crashing because of wet wings would be frowned upon, of course --- but the fixed wings would not have that problem; however any moisture would defeat this noise reduction. <S> Only during landing & take-off noise reduction is really wanted (cruising altitude is too high to care); the added drag throughout the flight is (and added weight+drag when wet during takeoff+landing) will surely rule it out. <S> However, you can consider applications where it would be justified : If there's a large premium for silence, no need for high speed? <S> Sounds like e.g. a specialized drone for observations to me. <S> Then: If it's raining, take out the regular spy-drone (as the rain covers the drone noise); if it's dry, your special 'owl-drone' goes out... <S> This more or less doubles your cost-of-ownership as you need two not one drone.
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Because of low wing loading they also can fly with very little wing movement, also leading to less sound generation.
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Why does the SR-71 Blackbird sometimes have dents in the nose? On many pictures (maybe on most of the pictures) part of nose looks hammered or slightly smashed, or bent.Please note these 2 symmetric dents just behind nose spike: source source On other pictures these dents are missing: source Why? Is this a feature or damage? <Q> The SR-71 had a detachable nose (photo #2), and could change between three different nose cones depending on the mission. <S> I haven't found a lot of information on the three, other than what this site and this site mentions: <S> Training nose with dead weights <S> Radar nose containing a Side Looking Radar. <S> This is probably the bulge you saw on the photos. <S> Photo nose containing the optical bar camera, taking very wide photos of the ground. <A> Got it. <S> Those indents are cut-outs for the "DEF A2" radar warning and ECM system. <S> Relevant quote: <S> The receive antennas are located aft of cut-outs on the left and right nose chines. <S> The transmit antennas may also be visible in the OP's picture on the underside of the A/C, but hard to say. <S> This manual is linked from the wikipedia article on the SR-71 as refs 72-75. <S> Direct link to the imaged page from the manual: <S> https://www.sr-71.org/blackbird/manual/4/4-124.php <S> Note that the manual is silent on rear-facing sensors. <S> This is consistent with the SR-71's primary defense characteristic, that being speed to outrun all threats. <S> To the SR-71, a threat not already in the forward cone is simply not a threat. <S> Also alluded to in this article about a one-off SR-71 development for countering an eventual hole in the defense strategy: <S> There's an illustration without explanation on a reddit thread : <S> The picture there is not attributed, and at any rate, is too large to upload here. <S> As mentioned in the reddit thread, the SR-71 itself did not carry the large radar illustrated -- the picture is actually of a YF-12, but close enough for our purposes here, as the other element in the picture is clearly identifiable as lying within the cut-out, and consistent with the manual's description of the DEF A2 system receive antenna. <S> It shows the fairing removed from the area in question, revealing a light/off-white/silvery disc positioned at the aft end of the cutout. <A> The bulges are a key component of the (for that time) very sophisticated radar imaging system, ASARS-1. <S> There's more information here . <A> Ferry noses had no need for DEF systems and so didn't have the bulges. <S> If you look carefully at the noses you will see that there is a band just aft of the pitot mast that is all composite <S> and it was called an isolation something or other. <S> There were several noses. <S> OBC is optical bar camera and could take a horizon to horizon panoramic picture like every second - in stereo if you wanted to use twice as much film. <S> The SLR or side looking radar, which was replaced by the ASARS advanced synthetic aperture radar. <S> The Asars nose looks pregnant and is quite distinct. <S> Those are the operational noses of which I know. <S> There may have been others before my time. <S> There was a capre nose, but I don't know what CAPRE stands for or if that nose is distinct from the ferry nose. <S> The SR was originally intended to have not only swappable noses but also swappable forebodies and they would latch them at the fs 715 break. <S> you would have an interceptor forebody, a penetrating bomber forebody, a recon forebody, which are way cheaper than the whole proulsion system, which would be swapped out according to mission requirementsI <S> was on the project in Burbank from 1987 to 1990 <A> When looking at a picture of a Blackbird, you might be looking at either of 2 different aircraft - the YF12 and the SR71. <S> One of the differences between them is the nose - the SR71 has a smooth continuous chine, whereas the YF12 has the indentations that you've spotted but with usually a forward-looking sensor there (possibly IR?). <S> So it depends which aircraft you're looking at.
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Bjelleklang is right, the nose is detachable and would be switched out according to the mission's needs. There was also the possible threat that future ground defenses would someday have the ability to reach the SR-71 from behind since it carried no aft facing defensive countermeasures. The dents are there to provide a proper thickness window for DEF systems.
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Why is thrust available constant with speed for turbojet engines, when it varies with speed for turboprop engines? Similarly, why is power available (nearly) constant with speed for a propeller engine, while it varies for a jet engine? <Q> Turboprops and turbojets - or, more broadly, jets - produce thrust in somewhat different ways. <S> First of all, let's address the way thrust is produced. <S> Per Newton's 2nd and 3rd laws, force equals acceleration times mass, and an action (accelerating the air) produces an opposite reaction. <S> After canceling out the variables (the math is easy to find), thrust is proportional to T=v*m' (m'=mass flow rate), and power transferred to the air <S> is proportional to P=v^2*m'/2. <S> All velocities are in the airplane's frame of reference. <S> Now let's go to how engines produce this thrust. <S> A jet engine first decelerates the incoming air to a near-zero velocity, generating drag, then accelerates it to a constant velocity, higher than the initial one, producing thrust. <S> Both v and m' for a jet engine vary across the envelope, but they change much slower than the plane's speed. <S> The engine spends roughly the same amount of power per unit thrust at any velocity. <S> A propeller doesn't decelerate the air at all. <S> It only accelerates the incoming air by some amount. <S> This converts power P into velocity <S> v. <S> Now, per above, P~v^2. <S> If you encounter air moving at 0 m/s, you need 5 kJ/kg to accelerate it to 100 m/s. <S> If the air is already moving at 100 m/s, you need 15 kJ/kg to get it to 200 m/s. <S> The result is that propellers encounter less resistance at low airspeed, so they get more thrust per horsepower the slower the plane is. <S> This allows them to push more air or push it faster, producing more thrust. <S> For fixed-pitch propellers, this works by producing more air delta-V and less drag. <S> Turbofans, combining a fixed-pitch ducted propeller with a turbojet core, are somewhat in between. <S> They lose some efficiency and some thrust as they gain more speed, like propellers, but their curve is much smoother and closer to turbojets in this regard. <S> The above is an extreme simplification (as is the jet's thrust curve in the question), just enough to get the idea across. <S> The jet's actual thrust is also non-linear, which has been addressed in another question: How (and why) does engine thrust changes with airspeed? <A> Assuming that the net thrust of a turbojet is constant is not correct. <S> It is assumed to be constant (for simplicity by the aircraft performance engineers and usually valid for low subsonic speeds), but in reality, the performance is not constant, and it also varies with altitude. <S> This is best shown by a simple simulation of a turbojet engine. <S> The following graph shows the net thrust as function of the Mach number. <S> It clearly shows that the net thrust is not constant with speed: <S> The inlet of the turbojet slows the flow down and creates the optimal conditions for producing the exhaust jet. <S> A turboprop relies on adding energy to the freestream air, as the speed of the airframe increases, there is less energy can be added to accelerate the flow. <A> There are several effects which in combination make constant thrust a good approximation at subsonic speed. <S> Thrust is created by accelerating a working mass in opposite direction. <S> Net thrust is the difference between the impulse of the air flowing towards the engine and the combined impulse of burnt fuel and the air exiting the engine (and propeller, if one is fitted), derived after the time. <S> Since that impulse is the product of mass and speed, you can either accelerate a large mass by a small speed difference, like a propeller does, or a small mass by a large speed difference, like a turbojet does. <S> When flying faster, the entry impulse of a propeller quickly grows large relative to the exit impulse, so thrust <S> goes down with the inverse of speed . <S> On the other hand, the high exit speed of a turbojet results only in a small increase of the entry impulse relative to the exit impulse while speed increases. <S> But if that were all, even the thrust of a turbojet engine would drop when speed increases. <S> But there is a second effect which helps to let thrust grow with speed. <S> With the square of speed, to be precise. <S> That is the ram effect which helps to precompress the air entering the engine. <S> At subsonic speed, this just about compensates for the loss of thrust: At low speed, the growing entry impulse lets thrust drop a bit but at higher subsonic speed the ram effect becomes larger and raises thrust again, such that a constant thrust becomes a good approximation. <S> However, at supersonic speed the ram effect becomes dominant and thrust grows with speed squared – until the absolute internal pressure becomes too high so the engine must be throttled (or the aircraft needs to fly higher ) or the shock losses in the intake become too large and thrust drops again.
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High-performance turboprops tend to have variable pitch propellers, which will be adjusted to push more air (slower) at low airspeed, or less (but faster) at high airspeed.
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Are there any real life instances of aircraft aborting a takeoff or landing to avoid a vehicle? I came across a fake video of an A380 closely avoiding a fuel truck. More details at Snopes including a link to the YouTube video. While this video is not real, I'm interested in finding out if it's a realistic situation and if there are any real instances where accidents have been avoided because crew decided to abort takeoff or landing as a result of an unexpected runway intrusion as seen in the video. <Q> This is formally called a "runway incursion" and it does happen like 2005 Logan Airport runway incursion or the B733 / vehicle, Amsterdam Netherlands, 2010 . <S> Skybrary has a full list you can find here which is quite lengthy and includes a full section for Vehicle Incursion . <A> In 1978 a B737 aborted a landing due to a snow plow on the runway. <S> The aircraft crashed during the go around because one thrust reverser did not stow properly. <S> https://en.wikipedia.org/wiki/Pacific_Western_Airlines_Flight_314 <A> Yes. <S> I was on final once when a taildragger in front of suddenly turned around to backtaxi and turn off on the taxiway he had just passed, thinking to do me a favor and get off the runway quicker. <S> Unfortunately, I had been catching up to him on final anyway, so I just powered up and went around. <A> If you don't quite abort... <S> Plane Collides with SUV While Landing at (Texas) <S> Northwest Regional Airport (52F) <A> I can remember one evening quite some years ago when there was a sudden extremely loud noise. <S> Not quite an explosion -- much too protracted and no shock, but you get the general idea. <S> Since there was no flying debris, no visible columns of smoke, no sign of anything else out of the ordinary, I ignored it apart from paying more attention to the news that evening. <S> This required afterburners! <S> The emergency services lines closer to Heathrow were jammed for quite some time, with people trying to report the "explosion". <A> I personally witnessed one at EWR (Newark International). <S> The runways in EWR run parallel to New Jersey Turnpike, only meters away. <S> I was driving on NJ Turnpike northbound when a flight (looked like a B737, but I'm not sure) <S> touched down parallel to the I-95 just at my level and moments later powered up and went around. <S> A few more moments later I noticed another, much smaller, plane further along the same runway. <S> This was in 1998 or 1999. <A> I am but a meager low time private pilot, but I'm sure this happens all the time as it has happened to me. <S> Before I got my certificate, I departed my home (towered) airport solo planning to buzz over to a nearby very small uncontrolled airport and practice some landings. <S> When I arrived, the city mower was working around the runway, apparently not listening to CTAF. <S> I aborted the first landing as he crossed the runway just in front of me. <S> Fortunately, he was just finishing the area around the runway <S> and I was able to continue practicing without any further issue. <S> From a safety standpoint, it was never a big deal. <S> I saw the mower, was aware of his location, and watched to see if he would depart the area before I got close to the ground. <S> He didn't, so I performed a go around. <S> I was surprised that he seemed not to notice me, but it was more inconvenient than unsafe. <A> On my first flight I flew into LAX and we were coming into land and suddenly went up again. <S> Looking out of the window and there was another plane on the runway. <S> The captain confirmed over the intercom that was the reason for the aborted landing. <S> I would guess this was in 1977.
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Not only is it possible but it happens. The news reported that Concorde had aborted a landing at Heathrow because somebody had strayed onto its runway.
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Why don't combat aircraft have rear-facing *laser* weapons? This question is similar, but only talks about guns. I don't mean a laser that is going to destroy the plane, but why aren't rear-mounted, rear-firing lasers that can blind a pilot a thing? Most of the concerns about weight and relative velocities from the other question disappear with a lighter-weight laser that is firing light. <Q> Such weapons are not used by countries that abide by the Geneva Convention : <S> It is prohibited to employ laser weapons specifically designed, as their sole combat function or as one of their combat functions, to cause permanent blindness to unenhanced vision, that is to the naked eye or to the eye with corrective eyesight devices. <S> For the U.S.A., page 45 of Navy Shipboard Lasers for Surface, Air, and Missile Defense says: <A> Besides the other answers, international law and the technical complexity of putting a laser on an airframe, lasers have interesting limitations as weapons. <S> Lasers do not deal well with cloud cover. <S> Hundreds of meters of cloud cover between two planes flying on instruments disrupts a laser's coherency, but not a guided missile's accuracy. <S> You can imagine how unappealing spending money on a weapons system that is made useless by clouds is. <S> Another factor is that modern air combat is rarely 1 plane vs 1 plane. <S> Ground radar, AWACS planes, satellites, and allied aircraft all work together. <S> It does you no good to blind a single opponent if ground radar has locked on to you, because modern systems can pass that lock to missile launchers and other aircraft. <S> Now anyone in range can launch a guided missile at you, a guided missile you can't blind. <S> As more airplanes become drone piloted, blinding the drone's cameras will not stop the operator from retaliating against you, because the drone's radar and other instruments are still functional. <S> So why spend money to solve a problem that is only tangentially related to your real problem? <S> The problem is not that another pilot is in the sky. <S> The problem is them being able to lock on to you with guided missiles, or even know you are around. <S> If you have technology that prevents their missiles from acquiring an accurate lock, launching missiles is just a waste of money. <A> The Geneva Convention only addresses permanent blinding. <S> Temporary blinding is all it would take to render an enemy pilot unable to react for at least long enough for you to employ evasive maneuvers and/or come around for an offensive. <S> That said, one wouldn't even need a laser. <S> Any sufficiently bright LED array would do the job. <S> Of course, this assumes the enemy pilot isn't equipped with any kind of eye protection. <A> In addition to the already mentioned Geneva convention, there is also the power requirements issue. <S> Lasers powerful enough for combat weapons require more electrical power than can be generated by a fighter (one reason why the YAL-1 was based on a Boeing 747). <S> Also, high power lasers generate a lot of heat. <S> Heat dispersal in a small airframe is difficult, especially if you want to minimize your IR signature. <A> Because weapons of mass destruction are maintained and developed, the Geneva Convention might not be respected much during wartime. <S> Also, F-35s <S> and F-22s have been mentioned in articles proposing laser weapons systems: https://nationalinterest.org/blog/buzz/f-35s-and-f-22s-could-soon-fire-laser-weapons-think-laser-dogfights-83586 <S> https://www.militaryaerospace.com/power/article/14034450/laser-weapons-jet-fighters-unlimited-magazines <S> If ignoring the Geneva Convention, I'm not sure how effective such a weapons system would be. <S> Wouldn't it be rather trivial to mitigate most or all of the damage by the enemy pilot, once such an imagined laser system is known to be used? <S> The pilot would merely need to wear protective laser goggles or use other means of limiting the amount of light that enters the eye. <S> The cost of developing the laser weapons system, compared with cost of the protection against it (laser goggles) doesn't seem to add up. <S> Also, an aircraft that sends out a continuous hundreds-of-kilowatt laser beam towards your own sensors provides an attractive target for your own missile. <S> You might impair the other pilot's visual flight when the beam is on, but looking down at the instruments to fire a missile should be possible when sufficient eye laser protection is worn.
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After passing through a significant amount of cloud vapor, the laser will not have enough energy to damage the target or blind the pilot.
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Why don't nonrigid airships have multiple gas cells? Nonrigid airships (blimps) differ from rigids and most semirigids in having the entire envelope form a single large gas chamber, rather than dividing the lifting gas among several redundant gas cells. Having only one compartment for the entirety of the airship's lifting gas raises the specter of an envelope rupture causing the loss of the airship's entire gas load, 1 resulting in ungood things happening to the airship and its occupants. In contrast, having multiple discrete gas cells (either by using a number of separate internal gasbags contained within the outer envelope, or else by dividing the envelope itself into compartments using gastight septae), in the fashion of all rigids and almost all semirigids, would allow the airship to remain airborne even if one or two 2 of the gas cells were ruptured and completely deflated, 3 and would allow gas cells of uncertain structural integrity to be filled only partially (to reduce the stress on the cell walls, and, thus, the likelihood of a complete rupture) while still maintaining full inflation on the known-good cells. In addition to the obvious safety benefits, the use of multiple gas cells would also allow better control of the envelope's shape (by allowing different gas cells to be inflated to different pressures to - for instance - stiffen the parts of the envelope experiencing the greatest loads), and would allow minor to moderate maintenance and repair work to be done on the envelope and/or individual gas cells without having to deflate the entire airship. So why don't nonrigids have multiple discrete gas cells, rather than a single, undivided envelope? 1 : This would be exacerbated by a nonrigid airship's need to maintain a considerable positive internal gauge pressure in order to prevent the aerodynamic forces on the airship from distorting its envelope; this positive internal pressure would greatly accelerate the escape of gas from the envelope, and the tension forces on the envelope resulting from said positive internal pressure would tend to produce severe tearing emanating from the site of any rupture (think of what happens when you pop a party balloon). 2 : Or, potentially, more, depending on the size of the airship and the number of gas cells contained therein. 3 : Note that this does not necessarily mean that the airship will remain capable of forward flight (although, depending on the circumstances [primarily which gas cell(s) lose pressure, and where within the envelope they happen to be located], it very well may ), only that it won't be in danger of plummeting to the ground in the event of a rupture. If a gas cell near the middle of the airship were to lose pressure, this would likely cause the envelope to distort to such a degree as to render controlled forward flight impossible, as @A.I.Breveleri correctly points out - but the key is that the airship would still have one or more intact gas cells providing a considerable amount of residual lift, allowing a controlled forced landing . 4 4 : This would be an especially great advantage in the case of a major rupture occurring at altitude (where the undivided envelope of a typical nonrigid could easily lose its entire gas load during the time needed to descend to ground level), and even more so if the temperature gradient of the ambient air is greater-than-adiabatic ( in which case you lose lift as you descend even if you aren't progressively losing gas ). <Q> With the loss of one cell you also lose the same fraction of lift. <S> Unless you can drop an equal amount of ballast quickly, having some more gas cells isn't much of an advantage – the ship still falls out of the sky. <S> The Zeppelins could lift up to three times their empty weight simply because they became more efficient by growing larger. <S> Blimps are small, so their lifting capacity is restricted. <S> Carrying so much ballast would require a much bigger blimp. <A> It is not at all clear how the partition between adjacent cells would be constructed, or what shape it would assume if one abutting cell lost pressure. <S> The complete distortion of the airship's shape would be as much a disaster as the partial loss of lift. <A> Non-rigid airships are structurally supported by the above-ambient air pressure inside the envelope. <S> If a cell at the edge is punctured, the rest can maintain some structure. <S> If it's a cell in the middle, everything to the outside of it will collapse. <S> Either way, the remainder of the blimp will only be good enough to gently land for repairs. <S> Gently landing for repairs is something punctured airships are already able to do - the gas doesn't escape instantly. <S> And as an airship is getting down, the gas inside expands (provided the air ballast bags are emptied), refilling the volume for a while longer. <S> So, this design decision would add weight, but not any extra capability or safety. <S> The only way to keep the airship structurally sound with some of its cells punctured is to add some sort of rigid structure - which would make it a rigid or at least a semi-rigid. <A> One other possibility: the loss of one cell while the remaining cells were inflated, especially losing one in the center, would likely deform the entire airbag to such a state that the rest could be torn open by the stress. <S> In which case, a minor leak could become loss of all buoyancy, very quickly.
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It is difficult to have a non-rigid airship airworthy with one cell punctured and emptied and the rest intact.
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What is an airliner pilot's first go-to if he or she doesn’t have a positive climb rate immediately after take off? Assuming a typical transport-class aircraft, what would the pilot do if the aircraft does not have a positive rate of climb immediately after takeoff? Would the pilot just lower the nose to pick up airspeed, then raise it back up once they’re satisfied? Or maybe retract the flaps a bit? Assuming the throttle is at 94% N1, would applying full throttle at that point even stop the decline in speed? <Q> The first thing I would do is advance thrust to maximum available thrust, make sure both engines are indeed operating. <S> Next I'd check is if the speedbrake is stowed. <S> I would not consider retracting flaps because when you are too slow to climb you are definitely too slow to retract flaps... could be deadly. <S> Normally this kind of situation can't happen unless you have at least one engine failure and the remaining engine not working at full thrust or the wings are contaminated with ice or snow. <S> The aircraft is perfectly capable of climbing on one engine, so if you have two engines on max takeoff power and are still not climbing then something is seriously wrong. <S> In case of ice/snow on the wings, well there is not much you can do about that in the air, put on wing anti ice and hope that it is quick enough to clear the wings of any contamination, this comes at a penalty of losing precious thrust because of the bleed air extraction. <S> This situation is usually avoided by removing snow and ice from the wings whilst still on the ground - before taking off. <A> This sort of scenario happens from time to time. <S> Before a flight the crew will calculate the flap setting and speed at which the aircraft rotates based on aircraft weight, the weather conditions, and runway length. <S> If any of these are entered incorrectly, the aircraft could rotate too soon and not lift off when expected. <S> To decrease wear on the engines, modern jet airliners will often use less than full takeoff thrust. <S> If the crew finds the aircraft is not accelerating or lifting off as expected, they can increase the thrust to the full takeoff setting. <S> This is probably the first thing to check as it's a quick and easy step that would help get the aircraft up to the necessary speed and in the air faster. <S> There have been several crashes where insufficient flaps were suspected as a contributing factor, causing the airplane to not lift off as expected and making it more difficult to control at low speeds. <S> The crew might actually increase flaps to lower the speed needed to lift off. <S> The crew may also decide to to reject the takeoff. <S> By the time an aircraft is rotating, there may not be enough runway left to stop safely, so the crew must make a quick decision as to what the safest option is. <A> First I would check on PM for pilot incapacitation as it might be the first cause. <S> Then, if the plane is indeed not climbing if because something was totally wrong. <S> Even with one engine failure you are supposed to have a positive rate of climb on the 1st segment and 2.4% on the 2nd segment. <S> Make sure the trust setting is correct. <S> Retracting the flaps would cause you to sink at this moment.
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It's very unlikely that a crew would decrease flaps in this situation, as this would decrease the lift , and thus take even longer for the aircraft to lift off.
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Can an F-16 land on an aircraft carrier, at all? Looking at the F-16 again, I noticed the tailhook which it seems to have. I know the F-16 is not designed to land on any aircraft carrier, however, if it was between ditching in the ocean and attempting to land on a carrier. During wartime or any emergency; if the F-16 found itself over an ocean and needed to land, and there was a friendly carrier nearby. Could it be done? For this we assume an unmodified F-16, any of the F-16 variants are candidates for this thought experiment. However, I assume the lighter F-16A (I assume they all have the hook, even the early block A variants?) is better, since it has less mass which needs to come to a full stop? I understand that this will probably be speculation at best, I'm just curious. Forgive me. If someone happens to know the figures of maximum load on the F-16 tail hook versus what would roughly be required, that would be awesome. However, I'm also taking just educated guesses. My own layman efforts towards an answer, limited to mostly just identifying some obvious issues: Is the F-16 tail hook even compatible with the arrest system an aircraft carrier uses? Perhaps it wouldn't catch the arrestor cable at all. If it does catch it, perhaps it is not designed for that kind of abuse, and would tear straight off the airframe if this was attempted. For carrier landings, the aircraft will typically from what I understand not flare and make hard landings which really beats the undercarriage. I'm not so concerned with the undercarriage breaking, it would be better to recover an F-16 with broken undercarriage than losing it to the ocean. However, if the undercarriage does break, it might prevent the hook from catching the cable at the correct angle. Even if it does grab the cable, perhaps the aircraft with broken undercarriage would risk sliding off the side of the deck. From what I understand, there are no barriers on modern Nimitz carriers any longer. Hence they will not be considered as an option. Perhaps a barrier could catch an F-16 but I'm more curious about the properties of the hook, undercarriage, and other issues with landing on a carrier. I know landing on a carrier is hard, so what is it that makes it so hard for an F-16? <Q> The hook is for emergency use at airports that have Runway Arrestor Systems . <S> Lots of non-naval fighters have arrestor hooks for that purpose. <S> Now, there is nothing stopping someone from landing an F-16 or any other fighter on a carrier deck and using its arrestor system, which works the same way. <S> The main issues are the proficiency required to do it and the ability of the airframe to take it. <S> A carrier landing isn't really a landing; you more or less descend into the ocean and the deck gets in the way. <S> So the airplane needs a pilot trained to do that sort of thing, and an airframe that can do it repeatedly, that is, land with a descent rate of >500 fpm, a "hard landing" for a normal airplane, without developing cracks here and there and everywhere after a few dozen times. <S> No doubt that in theory, you could take a carrier qualified pilot, check him/her out in the F-16, and that pilot could shoot traps onto a deck with the F-16 using the hook (launching it is another matter in the absence of catapult link). <S> But they wouldn't be able to do a lot of them before the airframe would be toast. <A> I am only assuming this, but I believe the net as shown in the picture could catch several non-naval aircraft including a F-16. <A> No, the F-16 cannot "carrier land", even with the tail hook. <S> The Air Force jets (aside from any that are shared with the Navy) have tail hooks only for emergency purposes during landing, or securing the aircraft during engine run-up testing. <S> The tail hooks are not designed to arrest an aircraft like it would for a carrier landing, the land-based arresting systems are much gentler on the airframe. <S> The scenario you present is almost impossible. <S> The jet would have to fly quite some ways out to find a carrier and the carrier would certainly deny landing clearance. <S> They would tell the pilot to eject near the carrier and they would go pluck them out of the water. <S> If ejecting wasn't an option, they would ask them to ditch near the carrier so they could recover them quickly. <S> They could just as easily find a place to land on solid ground for the distance they would have to go. <S> The issue with landing on the carrier is not just the skill, but all the equipment that is on the deck. <S> If they allowed that to happen, they'd have to clear the deck and the only way to do that quickly is to push the aircraft over the side. <S> As far as I can tell, that has only happened once in history . <A> Something not yet mentioned is that the vertical speed typical of carrier operations is way higher than that for typical F-16 (or any non-naval type) landings. <S> The landing gear of the F-16 is not designed to handle the resulting loads and would be liable to collapse, it's simply not strong enough. <S> You can see this easily by comparing the landing gear of an F-16 with that of the similar class F/A-18. <S> Notice how flimsy the F-16's legs look in comparison to those of its naval brother? <S> And how the Hornet has far stronger shock absorbers built into its landing gear than does the F-16? <S> There was an idea to adapt the F-16 to carrier operations at one point, which would have included a stronger landing gear, stronger main fuselage spar, and other modifications for carrier operations, but the Navy decided the resulting aircraft didn't meet their performance specifications (range, payload, etc.) and opted for the F/A-18 instead. <S> Some links about the plan: https://en.wikipedia.org/wiki/Vought_Model_1600 <S> https://www.defensemedianetwork.com/stories/v-1600-the-carrier-capable-f-16-that-wasnt/ <A> During wartime or any emergency; if the F-16 found itself over an ocean and needed to land, and there was a friendly carrier nearby. <S> Could it be done? <S> I'd say yes, using the barricade, one time in extremis . <S> The pilot would have to fly a really flat pass to not knock off the landing gear, but a really good pilot highly motivated to not die flying a good aircraft on a day with a steady deck could do it. <S> He could a few practice runs at it while burning off the rest of his gas. <S> I'm not sure the carrier Skipper wouldn't recommend he jump out next to the boat, though.
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Yes the F-16 would be able to land on a carrier however it would most likely break/damage the landing gear and other components because it's not built for it. The tail hook would get ripped off by the carrier system.
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Is a turbocharged piston aircraft the same thing as turboprop? Simple question, and I've always assumed that they are the same thing, but I'd like feedback from someone who knows more than me :) <Q> They are both internal combustion engines that have a turbine in their exhaust that is used to power a compressor to pressurize the air before it is used for combustion. <S> In the turboprop, the turbine also powers the prop. <S> In between the compressor and turbine, the fuel/air mixture is burnt without significant moving parts. <S> Without the turbine and compressor, a turbine engine is essentially a tube with heating element in it. <S> In a turbocharged piston engine, you have an otherwise normal piston engine which turns the prop. <S> The turbine is in the exhaust from the piston engine and powers the compressor pushing air into the piston engine. <S> The turbine and compressor are not connected to the prop though. <S> Here they are as diagrams along with some other types of engine. <A> No, a turboprop is more like a jet engine with a propeller in the front instead of a fan: <S> Source: <S> Wikimedia <S> In its simplest form a turboprop consists of an intake, compressor, combustor, turbine, and a propelling nozzle. <S> Air is drawn into the intake and compressed by the compressor. <S> Many turbo props have a gear box (as shown in the image above, the black part to the left) which drives the prop from the engine. <S> Whereas a turbo piston is simply a normal piston engine with a turbo charger attached: <S> Source: <S> BoldMethod <S> You can learn more about how a turbo piston works on BoldMethod: How a turbocharger system works . <S> The basics is that it uses the exhaust gases from the engine to drive a compressor which increases the pressure (and oxygen content) going into the intake. <S> More oxygen (and fuel) means more power. <S> For turbo-pistons it also means that you can get sea-level performance at altitude. <S> As far as fuel is concerned, a turboprop runs off of Jet-A (Kerosene) fuels and (most) turbo charged pistons run on av-gas. <S> Some diesel turbo pistons also run off of Jet-A and it is very important that you don't put Jet-A in an av-gas piston or av-gas in a turbo prop. <A> A turbocharged engine is a common gas engine with pistons <S> The limiting factor on a gas engine is how much air can get into the pistons. <S> It is supercharged - that is, an air pump forces more air into the engine than it would draw naturally. <S> The mechanically driven variety is seen on Mad Max . <S> If you use exhaust flow to spin the pump, it is turbo supercharged. <S> People shorten "turbosupercharge" to "turbocharge". <S> A turboprop engine is a jet engine. <S> Fullstop. <S> The jet engine makes lots of thrust. <S> They stuck some extra turbine blades in the jet blast, which spin another shaft. <S> That makes it a "turboshaft engine" because it makes rotation instead of thrust. <S> You put something useful on that shaft, like a generator , helicopter rotor , naval screw , air compressor , fan , propfan , or in this case, a prop. <S> That's a turboprop! <S> The advantage of a jet-based instead of piston-based engine is power-to-weight - after all you have nominally 2 moving parts, the spindle of the jet engine <S> proper and the added turboshaft, and nothing reciprocates. <A> They are completely different things, a turboprop is similar to a jet engine as it has compressors, the main difference is that there's a shaft that spins a propeller instead of turning a fan. <S> It's the same technology used on car diesel and gasoline engines, and it works the same way. <S> There are vanes that can be adjusted to manage the boost level, on cars these are computer controlled but in many airplanes turbo speeds are have to be manually adjusted by adjusting boost pressure in the exhaust (keyword: wastegate). <S> Recent aero-diesels have modern computer controls though. <S> Turbos on piston aero engines can either be turbochargers, in which case they add extra power to an engine by increasing the compression in the cylinders, or they can be turbo-normalizers, which maintain sea level air pressure to the engine even at higher altitudes. <S> There are superchargers as well, these are also compressors for piston engines <S> the difference is they use engine power directly to compress the air rather than exhaust pressure. <A> No, one is https://en.wikipedia.org/wiki/Otto_cycle <S> one is https://en.wikipedia.org/wiki/Brayton_cycle , thermodynamicly extremely different
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A turbocharger is device for piston engines, it uses pressure coming from the exhaust manifold of a piston engine to compress air going into the intake manifold.
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Why was the Vulcan bomber used for the Falklands raid? There is a lot of information about this complex operation. But can anybody explain why they chose to use an aircraft? They could easily shoot cruise missiles from a ship or ballistic missiles from a nuclear submarine. The easiest and quickest option would be just to shoot an ICBM directly from the UK using a conventional warhead. Just put the coordinates in and task done. No risk to anyone! I think the UK had all the needed technology by that time. <Q> This is borderline as an aviation question <S> but I will answer it anyway. <S> They didn't use those weapons because they did not have them at the time: Conventional cruise missiles did exist but most were nuclear, and the UK didn't possess any conventional ones. <S> ICBMs with conventional warheads did not and probably still do not exist because they are not a good idea: <S> Their capacity is low: <S> A sub launched <S> ICBM has somewhere around 2.5 to 3 metric tons' throw weight, much of that would be taken up by warhead guidance, thermal protection and other necessities <S> so your actual warhead would be maybe 1000kg, or 2200lb. <S> That's not that big a conventional bomb, and it could only launch one. <S> A fighter bomber could drop 2 of those. <S> The Vulcan bombers on the raid carried 21 1000 pound bombs. <S> They aren't accurate enough: a nuclear weapon can be a bit off and still destroy its target utterly, a conventional weapon needs a great deal of precision. <S> The Polaris missile had an accuracy of 3000ft (900m). <S> That's okay for a nuke, it' still ruin someone's day, but completely inadequate for a 2000lb bomb. <S> More modern ICMBs have more like a 100 meter accuracy, which is a lot closer but still not good enough for a conventional bomb <S> They are expensive: that's a lot of cash for a 2000lb bomb that probably will miss <S> Launching one could start WW3 : If you launch an ICBM someone is going to see it <S> and if they think it might be directed at them a retaliatory strike could be the answer. <S> The world has come perilously close to this more than once, it simply isn't worth the risk! <A> Because all of Britain's adversaries were either nearby (Warsaw Pact) or too far to economically fight (China). <S> Since Britain's weapons only needed to reach the Caucasus, they simply never developed ultra-long-range assets like the Tu-95 Bear or B-52 Stratofortress. <S> Unfortunately no-one was willing to provide any of those under Lend-Lease. <S> Nor would they have any reason to need ICBMs with the range to hit Falklands from the UK (they wouldn't have ICBMs in Ascension, <S> who would they nuke? <S> The Congo? <S> Guyana?) <S> Again the enemy is in Europe, so everything is sized and positioned to go just that far. <S> Your question takes for granted the pre-existence of weapons systems like the "down a chimney" Tomahawk. <S> Honestly, the British inability to do anything but have their SSN crews shake their fists at the islands, was a major impetus in developing those new families of weapons. <S> Every major force watched with keen interest and thought "Gosh, what if we had to deal with one of these?" <S> However, they certainly did have relevant weapons: Aircraft carriers. <S> This type of mission is the reason carriers exist. <S> They could project power from the Spratleys to, indeed, the Falklands. <S> Further, there'd be little point to using cruise missiles or ICBMs before <S> the main force was in position to make good on the advantage. <S> And once the main force was in place, they could strike from there, and did not need long-range weapons. <A> An attack by carrier airplanes wouldn't work because the carriers, and the accompanying task force, would also be in range of the Argentine planes based in Port Stanley. <S> Using nukes against the airport at Port Stanley would have destroyed Port Stanley and all the UK citizens there. <A> This hasn't been explicitly said, <S> so: The UK didn't have cruise missiles or ICBMs with conventional warheads at the time. <S> The Trident II D5, the UK's only ever ICBM, entered service in 1994: BBC . <S> As for cruise missiles, the BGM-109 Tomahawk has been introduced in 1983 (US) and 1998 (UK): Royal Navy . <A> Someone mentioned the harrier wasn't able to carry a bomb heavy enough to crater the runway. <S> The Vulcan's dropped 21x1000lb bombs on the Falklands. <S> The Harriers in the Falklands dropped 1000lb paveways (Laser guided). <S> They could carry 2 normally perhaps even up to 4. <S> So they could and did drop the same size of bomb, probably more accurately. <S> Though there was radar controlled guns and SAM that would have been made it very hazadous for low flying aircraft. <S> Though the harriers did raid the airport on occasion. <S> Some of have suggested there was inter service political rivalry. <S> The Vulcan raid was a another means for the RAF to contribute to the war. <S> Though the Harrier GR3 pilots were RAF. <S> It was probably a combination of a lot of these factors.
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The UK needed a surgical strike to neutralize the Port Stanley airport in the Falklands so that Argentine airplanes based there couldn't attack the coming UK convoy or the impending UK ground attack. Honestly, even if the British had appropriate cruise missiles (they did not), they would have no reason to own ones with the range to hit the Falklands from Ascension.
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Keeping the engine under the wings, doesn't hurt the lift as the airflow speed is higher under the wings? To create a lift, the airflow speed on top of the wings should be higher than the airflow speed on the bottom of the wings. But when you keep the engine on the bottom of the wings, wouldn't it hurt the lift as air flows faster on the bottom of the wings? <Q> To create a lift, the airflow speed on top of the wings should be higher than the airflow speed on the bottom of the wings. <S> No, that's not true. <S> In order to create lift, the pressure on top of the wings must be lower than the pressure on the bottom of the wings. <S> The airflow speed doesn't matter. <S> I'm guessing your thought process is something like this: To create lift, the pressure on top of the wings must be lower and the pressure on the bottom must be higher. <S> According to Bernoulli's principle, faster moving air has lower pressure and slower moving air has higher pressure. <S> Therefore, to create lift, the air speed on top must be faster and the air speed on the bottom must be slower. <S> However, point 2 here is wrong. <S> Bernoulli's principle does not say that faster moving air has lower pressure. <S> What Bernoulli's principle says is that given two points a and b , if the fluid flow is steady, and the fluid flow is incompressible, and viscosity is negligible, and gravity is negligible, and the points a and b are on the same streamline , and the fluid is moving faster at <S> a <S> than at b , <S> then the fluid has a lower pressure at <S> a than at b . <S> Since the air above the wing and the air below the wing are not on the same streamline, Bernoulli's principle doesn't tell you anything about the speed of the air going above and below. <A> You're going by an old outdated lift theory, still taught in a lot of places. <S> The wing induces a very large package of air to move down as it's going along, and this newtonian action/reaction of this package of air being induced to move down is most of "lift". <S> The Bernoulli part is important, because the pressure differential is a factor and it also is part of what encourages the air above the wing to move. <S> Anyway, most of the air mass that is motivated to move downward is above the wing. <S> You can put stuff under the wing and it has little effect on this, but put stuff above the wing and the whole process of making a large package of air extending half a span above the wing to move down is disrupted. <S> This is why you see airplanes like Skyraiders completely festooned with junk underneath the wing, but which has little effect on the wing's lifting ability. <S> Put all that stuff above the wing, and it'd never get off the ground. <S> Same deal with engines. <A> No, because the air is still turning the same way. <S> It might even help a little bit, depending on the wing shape. <S> To create lift you need lower pressure above the wing than below, but the difference in speed is the effect, not cause of this. <S> The cause is that the air would like to continue moving straight due to inertia, and the pressure decreases above until it can pull the air down along the surface, while it increases below until it can push the air out of its way. <S> The air behind the engine does not have lower pressure. <S> Remember that the Bernoulli's equation is just formulation of conservation of energy for fluids. <S> So it applies when the flow is accelerated without adding energy . <S> Then the pressure decreases to compensate. <S> But adding energy is exactly what the engine does. <S> So in this case the increased kinetic energy of the flow is added by the engine, and the pressure does not decrease (well, it might, depending on the nozzle design and operating conditions, but the goal is that it does not, because that way the engine is most efficient). <A> To create a lift, the airflow speed on top of the wings should be higher than the airflow speed on the bottom of the wings. <S> That is correct. <S> Lift is the result of a pressure difference between upper and lower side, and pressure is proportional to the inverse of speed squared if no energy is added. <S> But when you keep the engine on the bottom of the wings, wouldn't it hurt the lift as air flows faster on the bottom of the wings? <S> Note the point about adding energy in the paragraph above. <S> As @JanHudec correctly points out, speed in the engine exhaust stream does not indicate suction. <S> The pressure in the exhaust stream is still higher than on the upper side of the wing and lift is not diminished. <S> But friction drag is proportional to speed, so the higher speed on the upper side will cause more friction drag from the engine mount and nacelle. <S> Also, the engine intake will slow down the air ahead of it (ram effect) and since the air that flows around the intake ends up on the lower side, this blocking effect of the engine intake causes less de- and acceleration of air, lowering losses. <S> Adding the greatly increased volume stream of the hot exhaust gasses also keeps pressure up since all the volume behind the nacelle can be filled with exhaust gas. <S> Adding the engine, therefore, slightly increases lift. <S> But the most important reason is maintenance and accessibility. <S> The low-hanging engine is easy to reach and to inspect. <S> That is a major reason why the "classic" layout that started with the Me-262 and was carried over to the passenger jets is still preferred. <S> There have been designs with their engines mounted above the wing (for noise abatement), but that never caught on. <S> The next reason is cabin noise. <S> By shielding the loud exhaust stream from the cabin by placing the wing between both, passenger comfort is significantly improved. <S> This was especially important for the early jets with their high exhaust speeds .
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Placing the engine on the lower side puts it into a comparatively slow airstream.
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Why do airports in the UK have so few runways? Almost all of the major airports in the United Kingdom are single-runway (or functionally-single-runway ) installations, with only two of the very busiest (Heathrow and Manchester) having as many as two runways (although Heathrow has a third under construction). (In addition, even for the three major UK airports that have two runways, the two runways are always a parallel set, with no provision made for crosswind operations.) This is - with few exceptions - far fewer runways than would be normal for airports of their size. Taking the seven airports in the UK with more than ten megaemplanements in 2018 and comparing them to similarly-sized airports elsewhere: Heathrow (two runways, with a third under construction) v. O'Hare (seven runways, with an eighth under construction) Gatwick (two [ functionally one ] runways) v. Newark (three runways) Manchester (two runways) v. la Guardia (okay, two runways) Stansted (one runway) v. Baltimore-Washington (two air carrier runways 1 ) Luton (one runway) v. Calgary (four runways) Edinburgh (one runway) v. Norman Mineta (two runways) Birmingham (one runway) v. Raleigh-Durham (two air carrier runways 1 ) Having so few runways not only increases congestion and severely limits the number of flights that can use the airport without infringing on safe separation distances between aircraft, but also poses the risk, for the four single-runway airports, 2 of an unserviceable runway (for instance, due to snowplows, potholes, trespassers, flocks of birds, wayward deer, or a disabled aircraft) shutting down the entire airport, potentially for a prolonged period of time. Why do the UK's major airports have so few runways compared to the norms for airports of their sizes? 1 : Plus one general-aviation runway each for Baltimore-Washington and Raleigh-Durham. 2 : And, to a lesser degree, for functionally-single-runway Gatwick, as its emergency backup runway is close enough to the main runway for a single debris event to potentially affect both . <Q> There are perhaps 101 non aviation-related reasons why the UK does not have larger airports, such as space consideration (we're only a small island!) <S> , politics (NIMBY!), civil engineering (Airports are commonly near urban centres and are often surrounded). <S> If you look at most large airports in the UK their runway(s) are east-west(ish). <S> The reason for this is over 70% of the prevailing wind direction in the UK is West or SouthWest. <S> In addition, we rarely have extremes of wind - those exceeding the crosswind capabilities of common commercial airliners. <S> Heavy snow is even rarer. <S> I can probably count the number of times a runway at a large airport has been closed due to any of the reasons you mention in the last 20 years on two hands. <S> Bottom line; it's just not necessary. <S> There is no socio/political/weather climate to warrant it. <A> It's ALL about land use. <S> Look at Mirabel, Denver's new airport, or Dulles (at the time it was built). <S> They basically razed some farmland. <S> America had the opportunity to do a whole lot of that. <S> Whereas in the UK, you have an ancient civilization dotted with villages, the entire system of landed [owns land] gentry (as seen on Downton Abbey ; Highclere Castle has been in the same family for 300 years), and the social systems involved the land itself: the land was owned by the lords (literally "land lords"), and leased to the occupants; that's where for instance Mr. Darcy's "income exceeding ten thousand per year" came from. <S> And the House of Lords is still a political force. <S> In the UK, airport sites aren't selected, so much as gouged out of history . <S> So it is not lightly that they expand an airport. <S> Personally, I think in this kind of situation, the entire exercise is folly; they should site airports on land that could not possibly have been developed except with modern methods, such as the proposal to put London's airport in the Thames estuary . <S> Oh wait <S> , there's history there too . <A> When Heathrow was opened as a commercial site it had THREE different runways in a triangle and by 1955 it had SIX runways <S> - You can see them here: <S> Wikipedia commons - arranged to allow parallel operation on any 2 runways no matter what the wind direction was. <S> But with the coming of larger transport aircraft having higher landing speeds and greater crosswind tolerances, the need for the extra runways was diminished - and by the end of the 1950s only the east/west runways were being used - they got extended into the 2 runways in use today, whilst the other runways were closed - they're used as taxiways today. <S> Heathrow is adding a third runway - east/west for capacity. <S> Most other airports are single runway or "functionally single runway" - which means that only one runway is ever in use at a time because that's all they need to be, or because that's what they've been limited to by planning restrictions. <S> Gatwick is in the middle of trying to open up its second runway for parallel operations - this was part of the original plan when it was opened, but is being fought hard by locals on noise grounds. <S> In other areas one of the ways to quell opposition has been for airports to quietly buy up land under the approach paths for 15-20 miles in each direction and ensure it stays as farmland. <S> This is not economically possible in the UK - and even if a brand new airport was to be opened away from a major city and rail/road links magicked into place for it (which have proven very hard to get established - even a decent north/south rail link into Heathrow is near-impossible), the odds of being able to acquire affected land at any price are slim to negligable. <A> The wind in the UK is fairly constant east-west, thus there is no need to construct runways in other directions. <S> The only reason to construct extra runways, is for the case where the capacity of the current runway system is insufficient. <S> LHR shows that you can handle a large number of yearly flights with just two runways. <S> LHR is currently operating at max capacity, thus there are plans for a third runway. <S> The other airports you are mentioning are not even seeing half the traffic of LHR and are thus fine with using just one runway. <S> If you are currently running an operation with just one runway, your capacity can more than double if you construct another runway, since you can then use one for take-off and one for landing. <S> LHR has some graphs indicating how the wind influences the operation: <S> https://www.heathrow.com/noise/heathrow-operations/wind-direction <S> Airports closer to the ocean, such as Aberdeen, have more runways since the wind direction is less constant. <S> TLDR; dominant wind direction dictates the orientation of the runways and the number of yearly flights dictate the number of runways. <S> This is all within political/environmental/spatial limits.
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However, the most aviation-related related reason I can think is that we just simply rarely need cross runways.
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What kind of motion will an airplane enter into when disturbed? When an airplane is disturbed from a longitudinal equilibrium position, what sort of motion will the aircraft experience? Will it be a phugoid or a short period motion? Or will it be both? <Q> The separation into short-period and phugoid motion is somewhat artificial. <S> There is just motion. <S> It just happens that when you fly a 'real' airplane (or solve its equations of motions), you'll have quite different timescales for angular motion (isolated pitch; low seconds) and linear motion (changes of altitude and speed; tens of seconds and even minutes). <S> Broadly speaking, heavier and faster <S> airplanes with swept wings demonstrate more of this separation. <S> At the other end of the spectrum, smaller airplane models have similar timescales for both the short- and long-period motion, and for them the separation is not meaningful (which makes it more difficult for analysis!) <S> So, to answer the question, both will usually occur. <S> In some cases, depending on the airplane and your point of interest, you can ignore one or the other. <S> On airplanes where separation is significant and motion is stable and well damped, it may also be possible to produce a disturbance that results in (practically) <S> one kind of motion: either short-period (e.g. a small elevator impulse) or long-period (e.g. a brief application of pitch-neutral air brakes). <A> This is the result of careful design and testing, plenty of prototypes weren't that forgiving. <A> The answer depends on whether the plane is designed for quick responsiveness to control inputs or hands-off stability. <S> Hands-off stability requires the plane to exhibit critical damping in its responses to perturbations whereas quick responsiveness requires something closer to underdamped response, in which control inputs from the pilot are required to prevent oscillation or divergence.
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Wikipedia suggests that both happen, and that short period motion should be damped out in a second or so for an aircraft to be certified, and that phugoid motion should be gentle enough that a pilot corrects it almost without thinking.
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Do modern jet engines need igniters? I've read that modern aircraft don't need spark plugs like conventional aircraft do, as the jet fuel autoignites once it's mixed with the hot air exiting from the compressors. Then why do aircraft like the Airbus A320 still have 2 igniters in the combustion chamber, to ignite the air fuel mixture? <Q> Jet fuel will not self-ignite when starting a modern turbine engine. <S> This article from the WingMag Aviation Magazine says: As the temperature isn’t quite sufficient to initiate self-ignition (the autoignition temperature of aviation fuel is around 220 degrees Celsius), spark plugs are arranged around the combustion chamber. <S> They generate a spark that ignites <S> the air-fuel mixture and the turbine now drives the fan and compressor through a shaft, as described above. <S> The exhaust gas temperatures begin to rise and the engine will now keep “running” as long as there is a supply of aviation fuel. <S> Once the engine is running at a sufficiently high speed, the autoignition temperature can be sustained (same article): [The fuel] is injected into the combustion chamber through several “fuel nozzles” where it can self-ignite and continue to run if the temperatures are sufficiently high. <S> See also <S> How is combustion flame maintained in the combustion chamber after igniters are switched off? <S> Igniters are not only needed for a cold start. <S> They are also used in case of an engine flameout. <S> From the Boeing 747-8 FCOM (7.20.8 - Engine System Description, emphasis mine): <S> Auto-Relight <S> An auto-relight capability is provided for flameout and rollback protection. <S> Whenever the EEC detects an engine flamout or rollback, both igniters areactivated . <S> A flameout is detected when a rapid decrease in N2 occurs. <S> A rollbackis detected when N2 falls below idle RPM or compressor pressure falls below idleminimums. <S> Note that this is for a modern jet engine, the General Electric GEnx . <A> The autoignition temperature of kerosene is 428F. <S> The temperature coming out of the last stage is usually above that at moderate power settings, up to 7-800 F or more at takeoff thrust. <S> However the temperature has dropped somewhat by the time the air gets to the fuel nozzle, and in heavy rain there may be superheated water cooling things down some more, and also when the engine flames out it cools off rapidly as the compressor rpm decays. <S> And during start the discharge temperature doesn't get hot enough until after it's running. <S> So for starting at any temperature you need the igniters, and for relights if there has been any time to cool down you need the igniters. <S> Theoretically, at moderate to high power settings, if the flame went out it would auto-relight immediately if the fuel was still there or was immediately restored (you'd get a big ITT/TIT spike), but what normally happens is it flames out, say due to rain or something, and things cool off enough that the igniters are needed to get it going again. <S> Or at least there is a high probability that the igniters will be needed to light off. <S> So pretty much all modern engines have igniters that come on automatically following a flameout, and if not, you are supposed to operate with continuous ignition in heavy rain and extreme turbulence. <A> those are to help the fuel ignite during a cold start , when all the components in the hot section are at ambient temperature and there exist no flames in the burner cans. <S> And as pointed out by Jan Hudec, the start motor (if the engine has one) or the APU (if it does not) cannot spin the compressor fast enough to heat the air to the point where the injected fuel will autoignite. <A> The easiest way to understand this is by comparison to a piston 4 cycle engine: <S> In the piston engine the 4 cycles occur in the same location, but at different times. <S> I.e. the combustion cycle gives way to the exhaust cycle as the fuel is burned up and pushed out the exhaust valve. <S> On each subsequent cycle the fuel air mixture must be ignited again. <S> Contrast this with a turbine engine where each of the 4 cycles occurs simultaneously, but at different locations in the engine. <S> In other words, the burner section is burning continuously and the igniters are only needed to light it at the start, or to relight if the flame blows out. <S> Think of it like a propane or natural gas stove or torch: <S> You need a spark to light the flame initially, but the need for a spark goes away as long as the flame stays burning.
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The igniters are switched off by the FADEC once the exhaust gas reaches a certain temperature because they are no longer needed.
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Is "wingman" strictly a military term? Does it have to be a potential combat situation for a pilot flying on another's wing to be called a wingman. If two aircraft are being flown in formation to a destination simply for the purpose of transportation, would the term wingman be used? Is wingman used in civilian aviation? <Q> And unless there is a better term, it would be logical to extend the use to civilian formations also. <A> A wingman is used in a combat situation, the function of the wingman is to protect the aircraft it is assigned to. <S> example: <S> Aircraft A is tasked with a reconnaissance mission to take photographs in hostile airspace. <S> Aircraft B is assigned to A as it's wingman. <S> If during the mission an enemy plane is spotted, the wingman (B) will do whatever it's takes to protect the mission of A. For formation flying, there is a leader of the formation but to my knowledge there are no special word describing the roles of each aircraft in the formation. <A> While the terms originated with the military, they are used in the civilian world when flying in formation. <S> Formation flying does require training to be performed safely. <S> As formation flying is not mainstream, getting the necessary training can be problematic. <S> One source is the organizations associated with Formation and Safety Team (FAST) . <S> They are "a worldwide, educational organization dedicated to teaching safe formation flying in restored, vintage military aircraft and civilian aircraft. <S> " <S> Their training protocols are pretty much the standard for formation flying in the civilian world. <S> On their website they provide training and reference material. <S> In all formation flying, there is a "Lead" and there is one or more "Wingman" or just "Wing". <S> So, yes, the term wingman is used outside the military.
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While the combat military role of a wingman is established, the term is entirely appropriate and is used for non-combat formation flying as well.
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How much of an airplane's forward energy is lost to lift? An airplane needs to move forward to generate lift, and because energy isn't created from nothing, all the kinetic energy of lift comes in the form of drag, where air (air resistance) turns forward motion into upward motion. Some of the drag on an airplane is therefore "productive" in that it produces lift, and some is "unproductive" in that it takes forward motion from the plane without providing lift. What percentage of an airplane's forward kinetic energy loss due to drag is productive as opposed to unproductive? <Q> In the most simple model for subsonic aerodynamics, drag is split into two components: Zero-lift drag, that is all the drag created when the airplane produces no net lift. <S> This kind of drag has again two components: Friction and pressure drag <S> , that is the aerodynamic drag parallel and perpendicular to the local surface. <S> This drag would dominate in a vertical dive or a zero-g parabola . <S> Drag created due to lift. <S> Since that was explained mathematically first by using the Biot-Savart law for electromagnetic induction, this is called induced drag. <S> The simplest explanation is: Lift is created by bending the oncoming air slightly downwards, and the reaction force is perpendicular to the mean angle of that airstream. <S> Induced drag is the force component parallel to the initial direction of motion of the air relative to the airplane, and lift is the perpendicular component of that force. <S> Thus, induced drag is lift times half the tangent of the bending angle . <S> While zero-lift drag in creases with dynamic pressure, i.e. with the square of airspeed times density, induced drag de creases with dynamic pressure. <S> Like this: Drag components over speed for a typical glider (own work). <S> The nonlinearity at the lowest speed is due to flow separation when the lift-creating limits of the aircraft are approached. <S> The physics for large aircraft are the same, only the numbers will be larger. <S> Due to the dependency on the square of airspeed, the sum of both components has a minimum when they are of equal magnitude. <S> However, given enough thrust, a motorized aircraft can sustain level flight at the far right end of that diagram when lift-dependent drag almost vanishes . <A> When flying at the airspeed that yields the maximum L/D ratio, which is also the airspeed that yields the lowest total drag force, <S> 50% of the total drag is "induced drag", i.e. drag due to the creation of lift. <S> At higher airspeeds, a lower % of the total drag is "induced drag". <S> At lower airspeeds, a higher % of the total drag is "induced drag". <A> No energy is 'lost' to lift.
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All the energy delivered by the engine is spent, directly or indirectly, in accelerating air downwards in order to produce lift...
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What makes airplanes pitch up during landing? So what exactly pitches the plane upward with the rear end down? Do flaps help lower the nose when deployed 80%-100% down with such low speeds? <Q> From the Boeing 737 NG FCTM (6.10 Landing): When the threshold passes under the airplane nose and out of sight, shift the visual sighting point to the far end of the runway. <S> Shifting the visual sighting point assists in controlling the pitch attitude during the flare. <S> Maintaining a constant airspeed and descent rate assists in determining the flare point. <S> Initiate the flare when the main gear is approximately 20 feet above the runway by increasing pitch attitude approximately 2° - 3°. <S> This slows the rate of descent. <S> After the flare is initiated, smoothly retard the thrust levers to idle, and make small pitch attitude adjustments to maintain the desired descent rate to the runway. <S> Ideally, main gear touchdown should occur simultaneously with thrust levers <S> reaching idle. <S> A smooth thrust reduction to idle also assists in controlling the natural nose-down pitch change associated with thrust reduction. <S> Hold sufficient back pressure on the control column to keep the pitch attitude constant. <S> A touchdown attitude as depicted in the figure below is normal with an airspeed of approximately VREF plus any gust correction. <S> The flaps are set much earlier during the approach phase. <S> They are not changed any more during the landing phase. <A> Flaps help to increase the lift at low speed, allowing the aircraft to fly at a lower than cruise speed speed. <S> The pitch up is caused by the elevator on the rear wing. <A> For landing an airplane has to slow down. <S> When looking at the lift equation, $$ <S> L=\frac{1}{2}c_L(\alpha)\rho v^2A$$ <S> We find that, to get constant lift <S> $L$ with lower speed $v$ <S> we need to increase either $c_L(\alpha)$ or wing surface area <S> $A$ <S> (we can't change the air density $\rho$ ). <S> Note the explicit dependency of the lift coefficient on the angle of attack $\alpha$ . <S> We can increase the angle of attack by pitching up, which is why planes generally have a nose high attitude on landing. <S> Flaps change either the lift coefficient for constant $\alpha$ , the wing surface area, or both. <S> This helps to reduce the required angle of attack, so the the pitch attitude may be reduced as well. <A> I don't know if your question relates to the approach phase or the flare. <S> The later as explained above has to do with the elevator, the former i.e for the approach phase you will notice that airliners and even more so fighter jets come on the approach indeed with a high noze up attitude. <S> That has to do with swept wings. <S> Swept wings allow an aircraft to fly faster by retarding the speed at wich the wings will become supersonic. <S> That's all fine, but the problem with that is (amongst other ones): it will reduce the lift generated by the wing therefore forcing the aircraft to fly at a higher angle of attack during the approach. <S> Hence the noze up attitude of the plane during that phase.
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The change in pitch during the landing is called the flare and it is controlled by the pilot (or autopilot for an autoland) using the elevators (i.e. pulling on the yoke).
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If Space Shuttle flies "like a brick", why does it need the wings? I have seen the Shuttle named a "flying brick" multiple times. However a brick, as understood in the building industry, is a simple rectangular shape without wings and without any adaptation of the form. If the Shuttle was only capable of that much, why could not it be a lifting body like Martin Aircraft X-24? <Q> Without the wings it would fly like a stone. <S> Seriously, you are taking the expression too literally. <S> The Space Shuttle is landing like a glider plane with a (not so good) glide ratio of about 4.5:1 (see <S> What was the Space Shuttle's glide ratio? ). <S> No brick would be able to achieve that. <S> Designing the Space Shuttle as a lifting body ( ≠ brick) was actually considered. <S> It appears that a lifting body design was not able to comply with the flight envelope requirements. <A> As everyone has pointed out, it's a joke. <S> Others have answered the lifting-body question (it didn't meet design requirements), so I just wanted to expand some thoughts on the spirit of the "flying brick" nickname. <S> I suspect whoever came up with the term didn't spend a lot of time analyzing it. <S> However, I think it's significant that the nickname is flying brick - not falling brick. <S> It doesn't imply that the shuttle doesn't have wings or can't fly. <S> Instead, it implies that the vehicle has blunt and non-smooth surfaces which creates tremendous drag (like a brick) and limits its glide ratio. <S> For my talk on how to land the space shuttle, I created this visual, which I think captures the spirit of the nickname: <S> Unfortunately, even though I think you knew this was a joke, a lot of people take jokes and analogies too seriously and turn them into conspiracy theories. <S> I get lots of comments on my talk from people who think that, if the shuttle flies like a brick, it can't possibly be a glider and therefore... <S> space is fake. <S> ♂️ (/facepalm) <S> So... I don't think having serious answers to a question like this is a bad thing. <A> The Space Shuttle's heat shield was made out of LI-900 Silica tiles that strongly resemble bricks and thus the shuttle was sometimes called the "Flying Brickyard" . <S> If you would like to know why NASA chose a wing design over another capsule or lifting body <S> they actually published an explanation here as to their choices. <S> In short it was a mix of socio-political pressures and old school "airplane" mentality where many of the engineers came from, a large chunk of Air Force requirements driving the original designs and hard engineering reasons that lead to the Delta Wing vehicle that was ultimately built. <S> In response to the other portion of your question, A lifting body could be used and that is basically the design of Sierra Nevada Corporation's new Dream Chaser . <A> "Flies like a brick" is merely a figure of speech. <S> It comes from personal feelings of the pilot when comparing it to an actual plane. <S> It's just like the saying that someone is "dumb as a rock". <S> Obviously, even the most stupid person (or even animal) is much smarter than rock. <S> The saying merely expresses the frustration of the speaker when dealing with a person that stupid. <S> "Flies like a brick" was coined most likely because of combination of its abysmal glide ratio (1:1 at its worst, 4.5:1 at <S> it's best) with simultaneous (and counter-intuitive) reliance on it. <S> Compare it to a 747 which has quite poor glide ratio of 17:1 <S> and it's not supposed to glide. <S> Sailplanes have over 50:1, so that's the kind of performance a sane person would expect from a vehicle that's meant to do nothing but glide. <S> An actual brick has glide ratio of about 1:10. <S> In fact, the Space Shuttle flies more like the best sailplanes (11× difference) than like a brick (45× difference). <S> Surprisingly, it's marginally better than Concorde at take-off (4:1), but not at speed (12:1). <S> I couldn't find the glide ratio of an X-24, but it must have been considerably better than 1:1 (to be considered flying instead of falling), so that's still more than 10× better than a brick. <A> Adding to other answers, yes space shuttle is a brick that flying not just a brick. <S> Body-lifting can not be disregarded in hypersonic flight during the reentry, it is not just the wing creating the lift, it is the whole bottom section hitting the atmosphere. <S> Looking at another famous spacecraft, Appollo, it doesn't have any conventional wings but NASA uses only CG shift and altitude control to achieve atmosphere skipping because the body lifting from its bottom side. <S> This documentary explains how it is done: <S> The wing also gives the shuttle huge landing flexibility, or what called the "cross-range" which brings to my third point. <S> Changing direction in orbit takes a crazy amount of energy and in orbit, you are on "rail" sort of speak. <S> The Earth rotates below you and to return you have to wait until you got a close passage across your landing site. <S> However, with Shuttle's relative big wings, it has a huge of cross-range(it is actually a design goal originally from the Air Force), the shuttle can make big direction change during reentry just like a normal airplane. <S> It has about 1100 nautical miles in cross-range, which means the closest approach to Cape Canaveral could be as far out as in the middle of the Atlantic Ocean and still be able to glide back.
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In addition to its poor glide ratio the shuttles name also stems from the materials its made from as much as it does its poor glide performance. The small wings make it fly like a brick.
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How do flaps help an aircraft take off at a lower speed, yet cause drag at the same time? Wouldn’t the drag caused by the flaps just decrease the acceleration, so, although they can lift off at a lower speed, wouldn’t it be faster to just use no flaps and rotate at the higher speed that is required? <Q> Increasing the flaps does increase the drag, but not by that much initially. <S> For the first stages of flaps you gain more by reducing required takeoff speed. <S> If you would increase the flaps more and more, eventually the drag would become too much and you would lose takeoff distance again. <S> Flap setting has an affect on the wing’s lift coefficient and on the aerodynamic drag. <S> This reduces the takeoff distance. <S> In the same time increased flap angle increases drag, reduces acceleration, and increases the takeoff distance. <S> The net effect is that takeoff distance will decrease with increase of flap angle initially, but above a certain flap angle the takeoff distance will increase again. <S> An optimum takeoff setting can be determined for each type of aircraft and any deviation from this setting will give an increase in the takeoff distance. <S> The flap setting also affects the climb gradient. <S> Increasing the flap angle increases the drag, and so reduces the climb gradient for a given aircraft mass. <S> If there are obstacles to be considered in the takeoff flight path, the flap setting that gives the shortest takeoff distance may not give the required climb gradient for obstacle clearance. <S> ( skybrary.aero ) <S> Note that the climb gradient is also affected: <S> More flaps allows taking off from shorter runways, but reduces obstacle clearance capabilities. <A> Because without flaps extended there is less safety margin for stalling in the landing. <S> Picture above from <S> this answer shows the lift coefficient as function of the angle of attack. <S> With flaps extended, a certain amount of lift is reached at a lower AoA than without flaps. <S> It is a safety feature during landing, when speed needs to be reduced as much as possible. <S> Not so much during take-off, and TO flaps setting is often not fully deployed. <S> But deploying them does reduce TO distance since the same lift can be reached at a lower speed. <A> Wouldn't it be better to use no flaps, and rotate at the higher speed that is required? <S> Well, now we are talking about a short field take off. <S> If you ever watched Lindbergh's takeoff the day of the famous journey across the Atlantic non-stop flight, barely clearing a power line on climb out, or even actually done one off a muddy or snowy runway, you know the answer to this question. <S> Many take-offs are done with flaps up because an aircraft will produce more lift per given amount of thrust (drag) " clean ". <S> Key to this is reaching the speed where the wing can be set to its optimal Lift to Drag ratio AOA and also be going fast enough to produce adequate lift. <S> Cambering up a wing makes it a better lifter, giving the ability to get the plane off the ground at a lower speed, but at the expense of more drag (read thrust and drag interchangably). <S> Notice the same effect can be achieved by increasing the coefficient of lift of an unflapped wing by raising the AOA past optimal L/D ratio, but the risk is, especially with wings that stall at a lower AOA, the power on stall! <S> So if the runway is covered with take-off roll drag producing items such as mud or snow, or simply is not long enough to reach flaps up takeoff speed, we use some flaps and slats to get airborne and climbing as soon as possible. <S> Once airborne, it is generally best to retract flaps and climb out Vy, unless that obstacle needs to be cleared, then we use the less efficient Vx. <S> Increasing camber (and AOA) does increase amount of lift at a given speed, but will require a proportionally greater amount of thrust. <S> A bigger or turbocharged engine helps here, along with careful monitoring of airspeed.
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Increasing flap angle increases the lift coefficient, and therefore reduces stalling speed and the required takeoff speed (the same lift will be created at smaller air speed due to greater lift coefficient).
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Why are the first sounds of an approaching enroute airliner low frequency, booming ones? Often I will hear an intermittent, low frequency, powerful, booming sound that resolves into that of an airliner flying enroute high (FL 300+) overhead. So the first sounds that an airliner flying overhead to be heard are those. Why? I assume it has to do with the atmospheric conditions and how sound waves of different frequencies propagate forward.. <Q> The air attenuates high frequencies more than it does low . <S> Thus, lower frequency sounds travel farther, so you hear them first. <S> Also, longer wavelengths will appear to "bend" around obstacles more than ones with shorter wavelengths, so buildings around you will in many cases develop acoustic "shadow" zones for higher frequencies as those buildings' dimensions are significantly larger than their wavelengths. <A> The lower frequencies, even from the music from a dance hall or band, or that car near you playing loud music will be heard first. <S> It may be all you hear!It is also common that as we get older, and especially those in aviation, we become high tone deaf!! <A> If you live in the approach path to a big airport, then there will be thumps and muffled booms as the landing gear is extended. <S> It could be this that you are hearing.
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Low frequencies are attenuated less over distance and by obstacles.
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How to start up a Lockwood-Hiller Valveless Pulse Jet? So me and my group mates in university got a lockwood hiller valveless pulsejet manufactured, and there was one error in manufacture. We are having trouble with trying to start the engine as demonstrated in the attached link. Is there an error in the engine you can see? One manufacturing error we identified is that the exhaust cone is slightly at an angle and is not exactly parallel to the combustion chamber+intake which looks something like the attached. Could making it parallel solve it?Also, would putting the gas cylinder upside down solve it? <Q> The key to the operation of a valveless pulse jet is the oscillating shock wave created by repeated explosions in the combustion chamber. <S> In this video <S> they talk about using a spark plug to trigger these explosions initially, and once the engine is running the process is self sustaining. <S> Looking at your video <S> I don't see any connections to the engine except the fuel pipe, and you seem to be attempting to start the engine by pushing some burning material into the combustion chamber. <S> This will not create an explosion, so the shock wave that keeps the engine running won't be created either. <A> To my eye, comparing with memory of many YouTube videos, the conical ends of the combustion chamber are too short and the bends in the exhaust pipe are both too small radius and the pipe is slightly flattened at those bends. <S> The angle of the exhaust pipe shouldn't matter -- I've seen these build completely straight and gotten to run -- but the sharp bends will produce out of phase shock wave reflections, and the too-short ends on the combustion chamber may also have a negative effect on the resulting gas compression. <A> This "university" project may have made an old mistake of scaling up before the design parameters were properly set. <S> A pulse jet, theoretically, is a truly amazing engine that uses an invisible piston to compress the next batch of air and fuel, a resonant shock wave. <S> So you may wish to start with a smaller, more reliable r/c model pulse jet as a demonstrator, rather than trying to get that monster to run. <S> Once experience is gained, move on to scale, keeping in mind the risk factors. <S> Tuned pipes also have application in increasing the output of 2 cycle engines by reducing losses of fuel and air out the exhaust port as the cylinder recharges for the next power stroke. <A> Just to answer my own question and not waste anybody’s time, all I needed to do was to invert the cylinder to get Liquid Gas to flow out. <S> It worked! <S> Here:
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A properly shaped "tuned pipe" must be made or it simply will not run effectively.
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What makes an airport "international"? What are the requirements for an airport to be designated as an international airport in the US? Is there a minimum runway size or required customs office? <Q> There is no US regulation about whether an airport can be called "international." <S> The Secretary of the Treasury designates the official list of international airports of entry . <S> But not all airports on this list are even called international, and it does not include all airports with international flights. <S> There are even some airports called "international" with no customs facilities or plans to have them in the near future. <S> The airport name is determined by the airport owner. <A> It is defined by the ICAO in <S> this glossary : International airport. <A> "International" is supposed to be a code word to inform pilots and ATC that the Border Guards have a presence, and can admit you into the country: stamping passports, collecting duties, all that stuff. <S> What you shouldn't do, say, is fly from Canada into Oswego County Airport, rent a car and drive over to Syracuse Hancock <S> International to clear Customs/Immigration. <S> You are to land at Hancock International, clear Immigration, then if needed fly onward to Oswego County. <S> The only exception I can think is if you have an emergency, such as weather unexpectedly closes in and no international airports are viable . <S> Aviation authorities will be sympathetic; they want you safe. <S> The border guards will be less amused. <S> They will suspect a setup and that you are up to no good. <S> From their POV, if conditions were marginal, you shouldn't have attempted the trip. <S> You wouldn't want to make a habit of it.
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Any airport designated by an ICAO Contracting State in whose territory it is situated as an airport of entry and departure for international air traffic, where the formalities such as customs, immigration, public health, agricultural quarantine and similar procedures are carried out.
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Where can I find current downloadable tower, ground and approach frequencies for USA airports? I have searched the FAA site and cannot find a spreadsheet with current freqs for airports, only incomplete lists. Online flight planning tools must get query-able current freqs on a monthly basis, but I sure couldn't find them. I'm looking for what Airnav, the Chart Supp US, AOPA flight planner all provide if you search on a specific airport, but in a format I can query from a personal spreadsheet. <Q> I have found something that will work. <S> It is not pretty and <S> I swear I can still smell the punch cards that produced the text files, but here it is: https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/NASR_Subscription <S> It is free, it appears to be updated by the FAA, (I verified it has the current frequency for my local VOR that I know changed 2 months ago) <S> and it is searchable. <S> Download the current zip file, use the .txt data layout files to determine where in the fixed length record of whatever file your desired data resides in is located. <S> I did a quick import into Excel and am able to strip the information that I need out based on position in the field. <S> Not the pretty spreadsheet <S> I was hoping for, <S> but ... <S> Thanks for the suggestions, everyone. <S> If anyone knows any standard software for the NASR subscription (or what the !@ <S> *# NASR stands for), I'd be interested. <A> That information can be found on FAA.gov <S> However, updated PDF copies of all of the chart supplements are hosted by the FAA here . <A> There are subscription based services by companies like Jeppesen and Lufthansa that provide such data, at a price. <S> Free data is only available in more cumbersome formats like PDF documents and websites. <S> Handy for looking up individual airports for your trip planning but not for automated data mining.
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You can use the FAA's search tool rather than manually look in a copy of the chart supplement.
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Are there advantages to slotted wingtips? Are there advantages to the way some birds' wingtips end in separate feathers instead of a more solid shape? As an example, separate-feathered wingtips: more solid wingtip: <Q> Slotted wingtips provide torsional flexibility. <S> A bird’s wingtip feathers must twist in one direction during the upstroke of the wings and in the other direction during the downstroke to keep the local wind striking the wing at an appropriate angle to generate lift and thrust... <S> The turning could be done at the base, with a completely inflexible feather; the aerodynamics are improved and material saved if the local flow forces twist the feather by just the right amount. <S> -- S. Vogel, Comparative biomechanics: life's physical world, p. 382, 2003. <S> They also reduce drag. <S> The minimum drag of a Harris' hawk gliding freely in a wind tunnel was measured before and after removing the slots by clipping the tip feathers. <S> ... <S> the feathers that form the slotted tips reduce induced drag by acting as winglets that make the wings non-planar and spread vorticity both horizontally and vertically. <S> -- V. Tucker, Drag reduction by wing tip slots in a gliding Harris' hawk, Parabuteo unicinctus, J Exp Biol 198:775-81, 1995. <S> They are effective while flapping, not just while gliding. <S> We used particle image velocimetry to measure the airflow around the slotted wing tip of a jackdaw (Corvus monedula) as well as in its wake during unrestrained flight in a wind tunnel. <S> -- <S> KleinHeerenbrink et al, Multi-cored vortices support function of slotted wing tips of birds in gliding and flapping flight, J R Soc Interface 14(130):20170099, 2017. <A> They function like an array of winglets. <S> Each feather is aligned to optimize its angle of attack in the local flow, which is circulating from the bottom to the top around the tip, to extract energy from the circulating flow, weakening the circulation (by redirecting it the other way - a wing deflects air to make lift) and providing a beneficial lift/thrust component ("thrust" to the extent that the airfoil is angled nose down to achieve an optimal AOA, and lift being 90 deg to AOA). <S> The result is a wing with very low aspect ratio that regains a bit of the efficiency lost with a low aspect ratio wing, where the benefits of low aspect ratio are important for the bird (maneuverability and ability to fight). <S> I'm sure that these benefits are magnified at the very low Reynolds Numbers that bird wings operate at (to the bird, the air is way more viscous than to the airliner, and to the bee, the air is like motor oil). <A> Birds with wingtips like this tend to be thermal soarers, so they probably help the bird detect air currents. <S> When circling in a thermal, you need to know where the air is rising most strongly so you can avoid flying out of the lift. <S> Glider pilots feel one wing rising or falling, but a bird with delicate feathers could feel the differences between the actual airflow at each tip and respond faster. <S> The swift in your second photo is not a soarer. <S> It requires agility to catch insects mid-air. <S> Some birds (like an Albatross) are extremely efficient gliders with a solid wing tip. <S> They glide on much faster moving air that must be easier to feel, so they're shaped for efficiency rather than sensing.
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The separated primary feathers produce individual wakes, confirming a multi-slotted function, in both gliding and flapping flight.
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Why are early wing planforms mostly rectangular? I am looking at the history of wing planforms, and I am having trouble finding reasons for why the wright flier and other early aircraft were built with rectangular wings. I thought it was due to being more structurally secure, but I can't find any sources that explicitly say that, or describe the thought process of early designers. Is my reasoning correct, and are there any other reasons for the decision to use a rectangular wing (vs a tapered wing)? <Q> The benefit of tapered wing lies in its proximity to the elliptical lift distribution while retaining much of the structural benefit of a rectangular wing. <S> But we owe this knowledge to a few things: The Kutta-Joukowski Theorem : published in 1906 by Nikolai Y. Joukowski and influenced a great deal by Martin W. Kutta. <S> The Lifting Line Theory : published in 1919 by Ludwig Prandtl and inspired by the work of Frederick Lanchester. <S> The term induced drag was coined by Max Munk, a colleague of Prandtl in 1918. <S> Although Lanchester had published some results on aspect ratio and finite-wing aerodynamics as early as 1907, they weren't taken seriously by his compatriots and had very little impact as a result. <S> The Wright Flyer flew in 1903. <S> By all accounts, the Wright brothers designed it through trial and error. <S> As a result, the insight of tapered wing couldn't have been known to them during the Flyer's design and through much of the First World War. <S> In any case, most of the early airplanes were bi/triplanes with external struts being their structural members. <S> The drag from the struts would've overwhelmed any benefit gained from tapered wings. <A> The rectangular "Hershey Bar" is a safe reliable, and yes, easier to build design. <S> But if you look more carefully at the Wright Flyer wings, you can see they were already rounding off the trailing edges to decrease drag. <S> Tapering to a point serves the same function, and also enables one to build a bit more lightly due to reduced torque stress from the end of the wing. <S> Same reason a prop is usually tapered. <S> It evens the load along the wing. <S> The common sea gull is a good example of tapering done nearly to perfection. <S> But aircraft mimicking this design lack the fine control gulls have of their wings and trade decreased drag for increased probability of often fatal "tip stalling". <S> "Washing out" (reducing) <S> the wing tip angle of attack helps remedy tip stalling, as well as deploying slats at lower speeds. <S> The rectangular wing is fine for many recreational aircraft. <S> Another drag saving device that can be used is the Hoerner wing tip. <S> Tapering can be seen on gliders, and even on the Cessna 172, but it is not absolutely required in aircraft design if fuel savings or optimal glide range is not an issue. <A> the simple cross braced ladder structure is easy to make. <S> There are some (Fokker DVIII springs to mind), but overall you don't see many tapered wings prior to the 1920s. <S> The Wrights weren't engineers, just bicycle mechanics, but they really were geniuses. <S> They taught themselves all the math required. <S> They weren't really building on the work of others; they started out using Lillienthal's theoretical framework during their glider experiments, discovered that it was deeply flawed so as to be unusable, and built their own wind tunnel to work out their own numbers, to develop their wing from scratch. <S> On top of that, they designed and built their engine from scratch because nobody made one light enough. <S> Pretty amazing. <A> Wing ribs are usually made with the aid of a template or tool. <S> For metal wings, it could be the male and female parts of a mould used in a press. <S> For wooden wings it's a board with blocks of wood that hold all the pieces in place while the glue dries. <S> Either way, a rectangular wing only needs one tool for each rib, while a tapered wing needs a different tool for every two ribs (assuming you can reuse it for port and starboard wings) <S> In these days of CAD and CNC machining, it's easy to forget how much effort it took to scale drawings by hand, and build tools and templates that accurately matched those drawings.
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A rectangle gives the maximum area for a given span, and for something like the Flyer, running on 12 hp, they needed all the wing area they could get in the lightest possible package, so rectangular it is. Basicly, it angles the bottom of the wing to more of a point when it meets the top, helping push the downflow of the vortex away from the top of the wing. Plus it's the easiest structure to build with minimum weight, since all the joints are simple 90 deg ones and
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Is a 40-year-old person too old to start an ATC career? My wife: is 40 years old is a mother of two (able to do five things simultaneously / in the same time) has been working as an English and French teacher for her whole career (19+ last years) has very little to do with airline industry (being a passenger and low-level enthusiast) I think that this is enough (especially point 2. and 3.) and I'd like her to at least try to become an ATC (i.e. enroll for a preliminary English test). She is reluctant saying that she: is too old have very little or no technical background / education / experience to pass even first tests, not mentioning becoming a professional ATC. Can anyone judge which one of us is right or at least provide some source of information, based on which such judgement can be done? I.e. to formulate an answer (similar to this one ) on unique challenges and limitations for starting a career as an ATC at 40 years old? It is possible in the country where we live (Poland). The original limitation (26 years old) was raised to 35 years old some 10-15 years ago and then 40 years at most. And now the age barrier is lifted completely. <Q> Some years ago (in the 80s) I tried out for ATC in Canada and took the preliminary screening test, which was a series of 25 diagrams representing radar displays with targets moving around different airways, crisscrossing each other in various directions, and you had to answer 2 questions for each diagram, whether or not targets at different speeds and <S> altitudes would conflict with each other (there was a table with all the targets' speeds, tracks and altitudes). <S> It was a timed test <S> and I wasn't paying attention <S> so I was at question 45 when time was called <S> and you had to drop your pencil right away. <S> So I didn't answer the last 5. <S> I got one or two wrong, giving me a score of 43, a "pass" for the test, but there so many applicants they were only taking candidates with scores over 45 for the next stage. <S> Probably would have made it if I'd just answered the remaining 5 at random. <S> Anyway, actual background is not that important. <S> They are looking for a very special set of mental skills, and someone has them or they don't. <S> Mainly, a very high cognitive and spatial IQ, and a very powerful memory. <S> To the extent that educational background matters, it would mostly be as a sign of intelligence. <S> I used to know a centre controller who told me that once trained and experienced, and having the required mental abilities in the first place, and the fact that the high stress periods don't last an entire shift (there are "rush hours" where things are intense, then relatively quiet) <S> the job wasn't nearly as tough as the public perception. <S> She should just go ahead and apply and start the screening process, as I don't believe there are any specific professional or educational prerequisites, and there is no harm in trying. <S> She will probably find out pretty quickly whether there is a chance. <S> One thing going for her is the overall personnel supply situation which is affecting ATC to some degree as much as other parts of aviation (shortages of applicants with what it takes). <A> It is country specific <S> In the US, as well as I can translate the legalese to English, your application must be accepted by the FAA before you turn 30 . <S> (I considered it myself, about a decade too late.) <S> In Canada, you must be at least 18 years of age , but I couldn't find any readily available maximum. <S> As another answer indicates, there may not be one. <S> In Denmark <S> (per a comment by J. Hougaard), there used to be a maximum age for applicants, but it was removed a few years ago because it is against EU Law to discriminate based on age. <S> He assumes the same applies in other EU countries, including Poland. <S> That said, in Poland, PANSA appears to be the agency involved. <S> I can't translate any of it, so you're on your own there. <A> I think that a lit bit technical knowledge is required to at least think of being an ATC because imagine a “mayday” situation. <S> The ATC has to plan everything according to it and this is the point where technical knowledge comes really handy. <S> Also,Age won’t be a limiting factor <S> but maybe you should think about your kids as well,being an ATC would require lots of training hours and after that maybe 6-8 hours of shifts per day that would stress her out mentally and physically which may have some effects on the upbringing of your kids. <S> If you think that her job is necessary for your financial requirements then you could try but let it not affect your kids(that is the worst thing specially if they are about to be teenagers). <A> It's listed as the very first sentence on their website about how to get a job as a controller. <S> There are also strict medical requirements basically the same as those for a PPL class medical. <S> This is in no small part because there's a 5+ year paid for education prior to becoming a controller and the agency of course wants to get their investment back. <S> And if you're much older you're likely to not be able to work the high stress job long enough for that to happen, it's that simple (as was explained to me by a recruiter when I asked about the age restrictions years ago).
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in the Netherlands, LVNL will not hire anyone over the age of 30 (this used to be 25 until some years ago). Secondly it isn’t necessary that doing five tasks together at the same time makes you suitable for an ATC because there can be no room for error and being one is not as easy as one may think.
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What instructions should I give to an untrained passenger for Hand propping Cessna 172N as a pilot? Does anybody know what is the most effective way of hand propping a Cessna 172N, with a passenger who is not mechanically inclined. So you need to give them the most easy to follow and simple instructions. Like after pulling the hand brake, and priming and opening the throttle 1/4 inch what do you tell them to do? I would push the throttle gently in after I'd hear the engine coughing to power when hand propped, while keeping my feet on the brakes, till engine's smooth revving and maintaining power. But to a person that has no familiarity with the noise of the engine and does not know what to expect, what should I say. Edit I thought I should elaborate a bit to shed some light on what happened. We had come back from a half a day of hiking around the hills of Santa Ynez in the afternoon with my hiker friend. After trying to crank the ignition a couple of times, it just moaned jerking half way through a hesitant arc. We looked around for something to use as chocks, found two rocks like 8-10inched and kind of heavy and pushed them to a locking position in front of the tires. I set the throttle; told him not to touch it before I jump back after cranking and wave him all clear. Then he pushes the throttle by half an inch while pushing the breaks. We brought the engine back to life after a few tries. After I felt we have a enough of prop rotation inertia I got on to the right seat and brought the RPM down. He got out and removed the rocks. Got back in and we flew back to Van Nuys. <Q> That is crazy. <S> DON'T just rely on an person who's new to airplanes and only training is 5 minutes of showing them what to do, who may or may not react correctly when it springs to life, as the only thing preventing the plane from heading off somewhere while you try to dive clear. <S> Don't. <S> Do. <S> It. <S> Tie the tail. <S> To something. <S> Anything. <S> Use the passenger and show them what to do and give them a careful briefing, but tie the tail down anyway. <S> You don't know how the passenger is going to react if things go off kilter. <S> And if tying the tail is simply not an option, and you have no choice because you have to leave because zombies are approaching <S> , at least point the airplane toward some obstacle just beyond the normal turning radius, like a wire fence, for it to run into when it takes off with your passenger confused and frightened because they pushed the throttle in too much and let off the brakes when the thing jerked forward on them, with you diving for your life. <S> Once it's running at idle and everything is kosher, set the parking brake <S> and you can walk back to untie it with your passenger ready to switch the ignition off if it starts to roll away. <S> And make sure to use the correct terminology with your assistant. <S> Don't say "switch on/switch off". <S> It's "Switch off" for ignition off, and "Contact" for ignition on (it's old fashioned sounding, but it works). <S> I have been personally burned by a guy who did things the usual way, when I said "switch off", then repeated "switch off" to make sure he heard it. <S> He thought I'd said "Switch off" then <S> "Switch on" when I'd just said switch off twice. <S> I neglected to brief him on the use of the word "contact" <S> so it was my fault in the end. <S> Anyway, I got a nice noisy surprise when I turned the prop over thinking ignition was off. <S> Hand propping is quite a dangerous operation, especially on tri-gear airplanes where you have to lean forward to do it. <S> I trust you yourself have been properly trained, and know things like not to hook your fingers over the blade so you don't get pulled into it if it kicks back, that sort of thing. <A> I’ll second John K’s answer. <S> It is a real easy way to get seriously injured or killed, as this idiot almost found out. <S> It should also involve two competently trained people, one to do the hand propping, and the other at the controls of the airplane during the process to control fuel, ignition and throttle throughout. <A> If the person operating the throttle has to react within a fraction of a second to a changing sound that's unfamiliar to them, they're doomed. <S> So play them a few videos of good and bad starts to make the sounds familiar. <S> Tell them what to do in reaction to the changes. <S> Quiz them a few times to ensure they understand. <S> This might take ten minutes, but then they'll be happy to have mastered a new skill, and you'll have gained a second pair of ears listening carefully during the flight itself. <A> A c172 is hard to prop safely, most trigear aircraft are. <S> Do not let any non-pilot get near any prop! <S> In an emergency, say your stranded on a Baja desert strip with a dead battery, tie down the tail, work all controls yourself,ie switch's,mixtures,throtles etc. <S> If I think well of my passenger I might place his hand on the throttle to pull back on my signal,and prop it yourself, if you've been trained, If not? <S> activate your ELT and pray for a helicopter.
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Do not attempt to hand prop an airplane without receiving professional instruction on how to do it safely.
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When can a taxi clearance allow me to cross multiple runways? I was just reading the FAA instrument procedures handbook and saw the paragraph below in Ch 1 . I'm puzzled by this, because I routinely get "Cross runways XX right and XX left on Alpha" as part of my taxi clearance. How do I square that with the statement here? Instructions to cross a runway are issued one at a time. Instructions to cross multiple runways are not issued. An aircraft or vehicle must have crossed the previous runway before another runway crossing is issued. This applies to any runway, including inactive or closed runways. (Top of 1-8.) <Q> However, waivers are available to airports with parallel runways close enough to make it impractical or even hazardous for aircraft to stop in between them and wait for a second instruction. <S> They are essentially treating such a pair as a single runway for the purposes of this rule. <S> I'm not aware of any list of airports with such waivers or notification to pilots. <S> However, one could predict whether it is likely by looking at airport diagrams. <S> Consider the example of SFO/KSFO, which has such a waiver on both pairs; even a quick glance reveals why it's needed. <S> Also, I suspect the main concern behind the general rule is pilots misremembering which runway(s) <S> they were cleared to cross when there is a substantial distance between them. <S> The case of two very close parallels, along with the unusual (and thus memorable) multiple crossing instruction, does not seem to have the same safety concern. <A> @StephenS is right about San Francisco being an example that is exempt from the 2010 rule . <S> The FAA ATC Job Order discusses this point in § 3-7: <S> At those airports where the taxi distance between runway centerlines is less than 1,000 feet, multiple runway crossings may be issued with a single clearance. <S> The air traffic manager must submit a request to the appropriate Terminal Services Director of Operations for approval before authorizing multiple runway crossings. <S> (Emphasis mine.) <S> The paragraph references JO 7210.3AA - Facility Operation and Administration , which actually mentions 1,300 feet. <S> An example for such an instruction I remember hearing on LiveATC is "cross the ones", meaning 1L and 1R. <A> Based on the FAA Safety Alert posted below, since June 2010 controllers were no longer allowed to give multiple runway crossings at the same time: Instructions to cross a runway will be issued one at a time. <S> Instructions to cross multiple runways will not be issued. <S> An aircraft or vehicle must have crossed the previous runway before another runway crossing is issued. <S> https://www.faasafety.gov/files/notices/2010/Jun/Runway_Crossing_Procedural_Change_FAAST_Blast.pdf
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The general FAA rule is indeed that ATC cannot issue a clearance to cross multiple runways.
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Can i create a home built aircraft with this engine? http://www.chiefaircraft.com/da-100.html Would this engine work for a homebuilt ultralight aircraft? I am still in the research phase, so i don't know what the weight of the aircraft will be, but I would like to know what a good prop size and max weight that it will be able to fly. <Q> It's a 100cc engine, and it's in the Radio Control section of that web site. <S> It's an engine for model aircraft. <S> I suppose, technically, that's a home-built aircraft, but you're not going to sit in it! <A> A 10 hp RC engine that runs at 8000 rpm? <S> Even if you were building a single seat ultralight, in most cases you'd need at least 3 to 4 of them to have any kind of decent performance, if you could stand the racket they make. <S> For something that can carry two people, 5 or 6 at least. <S> You'd have a pretty cool looking bank of throttles to control all those motors though! <S> That being said, I can think of one practical application; a Lazair ultralight has probably one of the lowest power requirements in the ultralight business and got by on two 10hp 2stroke forestry water pump motors, so two of those RC motors on a Lazair, of which used ones are easy to find, should work. <A> Scale up to the DA-150L, https://www.desertaircraft.com/products/da150l . <S> It's more mature and widely available. <S> With a 32x12" prop it gives 82 pounds of thrust at 5400 RPM. <S> It puts out 16 hp. <S> The "original ultralight" Easy Riser flew with just 11 hp. <S> So it's possible. <S> Here's some broader discussion of more than just the powerplant: Can an ultralight aircraft fly with a 18hp engine? <A> Desert Air makes R/C aircraft engines. <S> The 200 cc DA-200 puts out around 19 hp. <S> I would go with 3 DA-100, two on the wing, one on the nose, giving it the Ford Trimotor look. <S> But these engines run around $ 1000.00 US dollars each, and are NOT designed for human flight. <S> It may be possible to time share a safer aircraft such as a Cessna 152 at a local airport for that kind of money. <S> But if you wish to proceed, the single cylinder 2 cycle 313 cc 28 hp Hirth F-33 is specifically designed for ultralights, yet would pass for an R/C engine any day. <S> And please do not believe the Wright Brothers got by on 12 hp. <S> That version barely got off the ground. <S> Weight reduction, however, is helpful.
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You can use any engine in a homebuilt or ultralight, including one from a Model A Ford if you want.
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Why aren't flights continued after losing a tire on rotation? I have read about a lot of incidents where airplanes lose one of the tires on rotation, yet they cancel the flights and go back for an emergency landing at the departure airport, risking overweight landing or burn fuel for 2 hours until they are within the MLM. My question is why don't they choose to continue the flight to the destination since they already airborne? Fixing tire out of station seems much cheaper than burning or dumping fuel to me. <Q> Blown tire - can't raise gear, shredded tire will not fit in the bay. <S> -> <S> Gear down - much lower maximum speed and lots of additional drag -> <S> Both of those mean very poor fuel economy -> <S> Very poor fuel economy means not enough fuel to reach destination <S> So that's off the table. <S> Given that, there's no question that it's better to follow the safest course... <S> And you had an extremely high pressure tire <S> just explode, a couple feet away from the airplane's skin. <S> Especially when that brings you back to a field that is in fact an operating base for that airline, and is likely to have inspection and repair services, and may have a spare airplane. <S> I could see a Southwest flight out of SJC diverting to nearby OAK, since OAK is a main operating base for Southwest and will have an easier time fixing or replacing the aircraft. <A> That kind of thing would be a judgment call on the part of the crew (ultimately the capt) and would come down to what is the safest action based on the circumstances, with logistical/convenience considerations being a distant second. <S> When you have a blown tire you will want to avoid raising the gear, because they can catch fire <S> and you don't want to retract the fire into the fuselage (and <S> your own fire detection system won't tell you this until it's retracted, so you really won't know until it's too late). <S> On top of that, you may have engine damage, especially if they are tail mounted, and/or flap damage. <S> So the imperative is to get the hell back down post-haste. <S> However, the airport is also a consideration. <S> Most of the time the departure airport has long runways and good emergency services, so the crew will elect to do a turnback even if fuel dumping is necessary. <S> Individual airlines may have specific policies on this as well, and a capt at one airline may have more discretion on what to do than another. <A> Because an emergency landing is preferred to gambling the airplane and the lives of everyone on board just to save a few bucks. <S> One of the fundamental rules of professional flying: Never attempt normal operations or try tricks with a compromised airplane. <S> You might get away with it once, but sooner or later it will get you and, with a $300 million airplane and 270 souls aboard, there will be hell to pay. <S> Blown tires, with the kinds of tire pressures used, are dangerous. <S> Depending on what caused the tire to fail, there can be additional damage to the aircraft. <S> An emergency cannot be treated casually under any circumstance. <S> In the wake of the Concorde accident in 2000, flight crews don’t take risks with that. <S> Your best policy with a tire failure post V1 is 1) get airborne 2) <S> assess the situation and contact ATC for additional help from the ground 3) <S> select the best airfield nearby or within flying distance for a emergency landing 4) <S> dump fuel for the minimum aboard needed to attempt the landing and 5) conduct an emergency landing with crash and fire crews waiting.
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And let’s not forget that you will have to land with a failed tire which has serious damage and fire risks associated with it as well. In other circumstances, say if the departure airport is remote and has short runways with minimal emergency facilities, the crew may elect to divert to the nearest airport with suitable facilities, and will likely do the diversion leaving the gear down.
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Is an afterburner louder than the same jet engine without it? I would speculate that an afterburner increases the noise because it is nearer to the exhaust. But it certainly causes so many changes in the exhaust flow that it could be less loud as well. It may also depend on the shape of the nozzle. That an afterburner increases the spacial volume of exhaust gases does not necessarily mean that the sound volume increases as well, because it strongly depends on the level of turbulence. Does activating an afterburner make a jet engine louder? And why? <Q> This PDF indicates an increase by ~10 dB for an F-8K in afterburner versus the same aircraft in 100% dry thrust. <S> This PDF indicates smaller increases: +5 <S> dB for an F-15 <S> +4 dB for <S> F-22 and F-35 <A> It has been around 20 years since I've been on a carrier deck, but I recall that it wasn't as dramatic of an increase as you might think. <S> It may have gotten a little bit louder, but what I remember more is that the tone changed. <S> The sound was more "full" when the afterburner was engaged. <S> I realize this is a rather subjective answer. <A> and it's obvious to anyone who attended enough military airshows. <S> Watch an F-16 depart with reheat on, then reduce thrust to military power (max thrust with reheat off) on the climb out, and it almost sounds like the engine flamed out. <S> The flow out the nozzle may be just over mach at military power, but will be well over Mach 2 with reheat on. <S> The nozzle changes shape with afterburner to manage all the extra energy and pressure, from a straight convergent duct to a convergent/divergent duct, like a rocket exhaust bell. <S> Although he doesn't cover the noise issue, this video explains why the nozzle has to change shape to control the mass flow through the engine because of all the heat energy added (math warning to those put in a catatonic state by arcane formulae). <S> The extra sound that results is a given. <A> To explain if the afterburner makes the engine louder, you must understand what the afterburner does. <S> In the afterburner, the exhaust gases are re-heated by injecting fuel in the afterburner duct. <S> The left oxygen is used to burn the fuel, which results in an increased exhaust gas flow. <S> Note that the engine itself will not spool up faster: this is done by opening the exhaust nozzle; without opening the nozzle, the pressure would be too high and the fan would stall. <S> The extra gases leaving the engine produce a higher velocity jet stream; more mass and more velocity will yield more thrust, which is the purpose of afterburning fuel. <S> If you look at jet noise modelling , you will find that the formula to calculate the jet noise includes the exhaust velocity (to the power of 8), so increasing the fuel flow and increasing the velocity will also increase the noise production. <S> The referenced model has been implemented in our gas turbine simulation program and verified against the noise measurements of a fighter aircraft to find that this model perfectly agrees with the measurements. <A> From an energy standpoint, the engine produces heat, thrust, and less significantly, sound. <S> Ignore the afterburner for a second and just consider throttling up, whether a jet or your car. <S> The engine gets louder. <S> That's not a law of physics <S> , that's just what happens. <S> There's no theoretical reason why the extra waste energy can't go 101% into heat, and -1% into sound (think of noise-cancelling headphones) or into sound at frequencies inaudible to the human ear. <S> But practical combustion engines get louder (both overall and to the human ear) as they burn fuel faster. <S> You would be surprised if throttling up made your engine quieter. <S> The same goes for increasing fuel burn via afterburner, only more so. <S> For one thing the afterburner is inefficient, so there is a higher proportion of waste energy to dissipate. <S> For another the afterburner noise happens later and is less controllable, even if there was any desire to do so.
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I would say definitely yes, because of all the extra energy added to the exhaust flow
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Do afterburners use excessive amounts of fuel? The purpose of an afterburner is to provide additional thrust, and it is obvious that more fuel is needed for that. But that is to be expected independent of an afterburner. That more thrust needs more than a proportional increase of fuel may be the case because the thrust increase needed per speed difference is not linear¹. The reason to build afterburners may be that stronger jet engines can not be build with the same mass or volume. Or that a stronger jet engine is not useful in standard use, for example because the fuselage would overheat. Doubling the speed increases the fuel usage by more than double I would expect, purely based on aerodynamics, independent of the engine. Is the fuel usage for increasing speed greater with an afterburner than with a stronger jet engine? How much? Why? ¹ For spaceflight, that is true according to special relativity. <Q> This is because the fuel is being added to a part of the engine where the air is less compressed, so the energy conversion is a lot less efficient. <S> The bright orange flame coming out the tail pipe when in reheat is pretty much all that un-oxidized carbon fluorescing - wasted energy. <S> See this article. <S> Fighters use reheat because all that extra power is available with minimal extra weight (the weight of the burner and additional fuel), but they can only exploit that power for short periods if they want to have decent range or endurance, so they are generally used for dashing somewhere, or to assist with maneuvering, or taking off with a heavy load. <A> If you look at it in terms of thrust vs fuel flow, then yes, they're very inefficient. <S> However, if you just look at the amount of fuel burnt to get an interceptor from the runway to 30,000ft, then they can be more efficient. <S> Without afterburners the same climb would take significantly longer and could use more fuel. <S> Without afterburners, you'd need much larger, heavier engines to reach mach2 <S> and it might not even be possible to get to the same height and speed in the same time , which after all, is the point of an interceptor. <S> Think of it <S> this way - if minimum fuel was the only criteria, we'd send the pilot by train. <A> Yes they do use a lot of extra fuel, but the amount is depending on the operating conditions (Mach flight speed and altitude)! <S> Comparing MIL (military) power setting ( <S> maximum power without reheat) to MAX power setting (engine will be in MIL power, but the reheat will be scheduled and the exhaust nozzle opened) <S> you can see that it is not uncommon to have 3 to 6 times as more fuel flow depending on Mach and altitude and the gas turbine. <S> Note that burning fuel at a low pressure is not very effective in terms of efficiency, but in power output it is very large. <S> Again, depending on the operating conditions it is not uncommon to double the amount of thrust. <S> The questions you ask about using a bigger engine is not easy to answer, increasing the engine (for a design, you cannot increase the engine simply for an existing airframe) would also increase the frontal area and as such more drag. <S> Such questions could be answered with a gas turbine simulation program in combination or coupled with an aircraft flight model.
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Yes the specific fuel consumption of the afterburner, lbs of fuel used per lb of thrust, is much higher than the core engine.
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Why does a turn and slip indicator matter? I'm studying the principles of flight, and I'm having some unanswered questions in my mind regarding the turn and slip indicator. I'm reading that a turn and slip indicator displays the slip or skid of the turn. It probably has something to do with directional stability. But the questions I'm having are: Why does it matter if the airplane is in a skidding or slipping turn? What are the consequences of skidding or slipping turn? Is it dangerous to be in a skid or slip? Why would a pilot would like and/or not like to be in a skid or slip? <Q> When you slip it means one wing is more directly pointed into the airflow, which increases lift for that wing in comparison to the other. <S> When done deliberately it's an aerobatic maneuver called a snap roll, when it's not deliberate <S> it's a major cause of stall-spin accidents on take-off and approach. <S> So slip is dangerous in some situations. <S> In level flight slip creates drag, so it's worth keeping the ball in the middle when safety is not a concern as well. <S> As for deliberate slip as I said before slip can be induced for aerobatic maneuvers like snap rolls and spins, slip can also be used for non-aerobatic maneuvers like side-slips, where you put the airplane out of balance to increase drag, allowing more rapid descents without increasing airspeed. <A> The "slip" part of the Turn and Slip Indicator (T/S) measures the lateral (transverse) acceleration of the airplane. <S> When the slip indicator is centered, the pilot and passengers will feel gravity directly in-line with the seats ; otherwise, they will feel a lateral sway, which doesn't provide the best ride experience, especially if martini spill is involved. <S> Obviously, this is important whether you are in a turn or simply flying level. <S> In symmetric flight with multiple engines providing the same thrust, a zero lateral acceleration is very close to having zero aerodynamic sideslip. <S> Achieving flight with minimal sideslip improves the fuel economy since sideslip introduces unnecessary drag for symmetric flight. <S> In practice, however, non-zero sideslip may develop because of minor aerodynamic asymmetry, prop wash, and especially if you have one engine inoperative (even with T/S centered). <S> Having non-zero slip indication in itself is not dangerous. <S> All Part 23 and 25 aircraft certify by performing steady-heading sideslip up to maximum rudder pedal or the limit of their lateral control. <S> When you decrab in a crosswind, you will intentionally generate sideslip. <S> However, an excessive slip coupled with high angle of attack is dangerous as it can lead to potentially irrecoverable spin-stall . <A> In a small aircraft, the turn indicator (and the slightly better turn coordinator) is usually electrically powered, while the attitude indicator is vacuum powered. <S> If the attitude indicator fails, either mechanically or do to vacuum fail, the turn indicator can assist with keeping the wings level in instrument conditions. <S> The slip indicator is merely a ball in a fluid and is not subject to any electric or vacuum failure, and can be a backup for an electronic flight display's slip-skid indicator. <S> In attempting a coordinated turn, the ball can be "stepped on" via the rudder to prevent undesirable yaw. <S> In some aircraft, rudder isn't necessary in a turn or initial bank as yaw is negligible. <S> Under Instrument Meteorological Conditions (IMC), a skid at or near stall speed indicates a spin (usually undesirable), and the instrument can assist with recovery. <S> A slip at speeds well above stall with rapidly increasing airspeed indicates a spiral. <S> The spiral may be due to misleading attitude indicator, and the indicator and ball can assist in recovery from a spiral. <S> In a multi-engine aircraft under instrument conditions, yaw (and heading change) is one of the first indications of an engine failure of some sort due to asymmetric thrust, and "stepping on the ball" and raising the wing of the dead engine can restore stable flight.
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At a high angle of attack, for instance a climb and close to stall speed, a slip can put one wing into a stall, causing the non-stalled wing to flip the airplane. The turn and slip instruments are combined for convenience and by convention more than anything else, slip is important whether you are in a turn or not.
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Do any companies offer 'ejection' experiences? Most airlines now offer fear of flying courses, most airports provide flying lessons and some specialist companies offer zero-gravity flight experiences. Are there any companies that provide 'ejection' experiences, where you can fly an aircraft and eject from it at a pre-determined location? Please note, I'm not talking about sky-diving. I want to actually use an ejection seat. <Q> No, there are no companies offering ejection seat experiences, for many reasons: <S> Cost: <S> Ejection seats are expensive, base costs are somewhere around $100,000 per seat. <S> Seats can't generally be re-used, therefore the cost of an experience is going to be well over that No platform: There are airplanes that are designed to eject someone and keep flying safely, they are used exclusively for seat testing and not open to the public. <S> Someone would have to develop and build an airplane designed to give a "fighter plane ejection" experience Ejection is incredibly dangerous: the chances of injury or death are very high. <S> Ejection seat companies have used test dummies instead of humans for decades for this reason Ejection can lead to life changing health issues: the G forces on a modern seat are at least 12G, and go up from there <S> - they can't be any less or you won't clear the airplane. <S> This compresses the spine and can lead to debilitating, life lasting injury. <S> If your ejection position isn't right you can break or lose a limb Ejection isn't fun : there's not a pilot or crew member in existence who has used an ejection seat and said "Whoopee! <S> Let's do that again!" <S> Instead they say, if they are capable of speech, "Ow!" <S> or "Please get me clean underwear." <S> So a company would have to spend tens of millions to develop a system that only rich people would be able to use, still less would want to, and a very precious few would be crazy enough to try. <A> Ejection seat training is as close as you'll get to "actually using an ejection seat" <S> barring an actual use that is not for fun. <S> Here are some companies that provide said training <S> and you'll get to feel the 10 G. <S> Though if you are not fit <S> I doubt they will offer their services. <S> Spinal injury is not fun. <S> https://www.amst.co.at/en/aerospace-medicine/training-simulation-products/basic-and-advanced-ejection-seat-trainer/ <S> https://www.etcaircrewtraining.com/ejectionseat/ <S> https://www.nastarcenter.com/about-us/our-equipment/ejection-seat-trainer <A> Yes, there is. <S> Since ejecting from an aircraft destroys the aircraft, you'll just have to buy one with an ejection seat. <S> I'd recommend an L-39 or a Dassault Alpha Jet. <S> They can be had for about \$1.5-$4 million. <S> After that you can pretty much do whatever you want. <S> Head out over the ocean, pull the ejector handle, wait for the Coast Guard. <S> Seriously though, no. <S> The chances of serious injury or death, especially for somebody who does not have the years physical training required of fighter pilots is almost sure to result in your own permanent injury or death. <S> Ejecting from an aircraft destroys the aircraft, so nobody is offering a "fly and eject" experience package. <S> Might as well take the "Russian Roulette" experience with it, you're chances are probably better with that game.
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Certain civilian/aerobatic planes come with ejection seats, and that requires training.
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Is there any obvious warning when auto-pilot is disengaged or when the mode changes? Under the investigation section of the First Air Flight 6560 incident, it describes the catalyst for the accident: The approach was entirely flown on autopilot, which was correctly set to capture the localizer signal and track along the runway centreline (VOR/LOC capture mode). However, an inadvertent movement of the control column by the captain during the turn onto the final approach track caused the autopilot to disengage from VOR/LOC mode and revert to maintaining the current heading, resulting in the aircraft rolling out to the right (east) of the runway centreline. My question: Is there any obvious warning (on common commercial aircraft, i.e. 737, A320) when auto-pilot is disengaged or when the mode changes? I would have expected there to be an audible notification, some flashing light or something to make it as apparent as possible that something has changed, if it's as easy to change as 'nudging the stick'. <Q> The Boeing 737 allows a mode called control wheel steering (CWS). <S> The A320 doesn't. <S> For what is CWS, see: Is it possible to disengage only one axis of a two-axis autopilot? <S> The wording on Wikipedia doesn't emphasize this point; however, the final report does. <S> The pilots may also manually control the aircraft in a normal manner with the control wheel and column (control wheel steering [CWS]) without disengaging the pitch or roll axes of the autopilot system. <S> Pilots can then assist the autopilot system in flying to a selected heading or course. <S> Use of CWS does not disengage either channel of the autopilot system. <S> The autopilot system was modified from the original design to allow for the use of GPS guidance for the course signals to the autopilot (section 1.6.10). <S> Note that Wikipedia says "( <S> ...) disengage from VOR/LOC mode (...) <S> ". <S> Therefore, for First Air Flight 6560, the autopilot was not disengaged. <S> Switching to CWS is not aurally annunciated. <S> See also: Why are callouts of changes in the Flight Mode Annunciator not automated? <S> Autopilot disengagement is accompanied with aural and visual warnings. <S> See: <S> Why is an auditory alarm necessary when the autopilot disengages? <S> (All bold emphasis mine.) <A> You asked about commercial aircraft in general, so I will give an answer from that point of view. <S> Is there any obvious warning when auto-pilot is disengaged ? <S> Yes, both visually as flashing lights, and aurally. <S> Furthermore, the lights and tone does not go away until a second confirmation is received from the pilot. <S> For example, pushing the button on the yoke / stick once will disengage the autopilot but trigger the warning. <S> A second click is needed to silence it. <S> Is there any obvious warning when mode changes ? <S> It is not a warning, as mode changes are explicitly made by the pilot. <S> I'd still consider it "obvious" because the active mode is shown right on top of the Primary Flight Display (the instrument you should spend most of the time on). <S> Picture: A/P disengage button on yoke, A/P disengage warning light and A/P mode indicator circled in red. <S> Image source <S> https://www.team-bhp.com/forum/attachments/commercial-vehicles/1506426d1463061690-boeing-777-pilots-review-boeing777cockpit.jpg <S> So what happened on First Air Flight 6560? <S> In this particular instance though, there are a few factors (in my opinion) that contributed to the crew not noticing the autopilot state: <S> The 737-200 is a rather old design. <S> Compared to a modern cockpit where things are seen "at a glance", it requires more concentration to fly. <S> The 737 series have a rather unpopular feature called Control Wheel Steering (CWS). <S> It allows the pilot to partially disengage one axis (pitch / roll) of the autopilot by moving the yoke in that axis only. <S> On newer models, this feature is removed since very few pilots actually use it. <S> On the Boeing 777 for example, such yoke movement would result in A/P disengagement and the trigger of the warnings I described. <S> Note that this incident is quite similar to the crash of Eastern Air Lines Flight 401 , where the captain accidentally bumped the yoke, causing the autopilot to switch from altitude hold mode to CWS mode in pitch. <S> The pilots failed to notice the change in time to avoid the crash. <A> As to changing autopilot modes, there a visual cues for this on autopilot units, flight displays and separate autopilot mode displays to allow a flight crew to visually verify when an autopilot is engaged.
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Most autopilots feature both an aural warning siren or similar aural cue as well as visual cues on both autopilot units as well as cockpit displays, so there is a means to alert a flight crew of an autopilot disengagement.
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Does the power behind the engine make any difference to how strong the thrust is? What difference does horsepower make? If the engine can spin the propeller fast enough, why does it need power behind it? <Q> You ask: If the engine can spin the propeller fast enough, why does it need power behind it? <S> Good question. <S> However, the answer is in the if of your question. <S> A propellor does work - it pulls (or sometimes pushes) <S> the aircraft through the air. <S> In order to move the aircraft at a useful speed (or even at all) it has to spin pretty fast. <S> The faster it spins, the more work it has to do. <S> That work requires power. <S> If the engine doesn't have enough power, it can't spin the propellor fast enough. <S> So yes, though the power and the speed of the spin are not the same thing, you won't get the spin without the power. <S> If you consider a car, the engine has to spin the wheels fast enough to move it along at the desired speed. <S> And what makes it possible for it to spin the wheels fast enough is power. <S> Otherwise, the wheels won't turn fast enough (or at all), and the car won't move fast enough (or at all). <S> It's the same in the case of an aeroplane. <A> Most propeller-driven airplanes use constant-speed props. <S> That means they use a governor to vary blade pitch (and thus resistance) so the engine always spins at the selected speed. <S> The main exception are very low-powered aircraft, such as used in primary flight training, which can barely keep the prop spinning at a decent speed even at a very low, fixed blade pitch. <A> A prop is just a wing going in a circle. <S> If you have a wing going straight through the air, you need force propelling it along, a thrust source, and that force is used to make the wing redirect air down by operating at an angle of attack, creating lift, which is vertically oriented thrust. <S> It takes energy to do this. <S> In a single engine airplane the wing is being driven forward in a straight line by a thrust source on the fuselage. <S> Unless it's going downhill, it has to have the thrust source. <S> A prop, or helicopter rotor, is the same wing being driven around a central axis instead of linearly. <S> Being driven around an axis, instead of linear force being applied to the wing, it's rotational force, or torque, which comes directly from the engine. <S> In the end, it's still force applied to generate aerodynamic thrust forces, but in the prop's case the output is horizontal thrust instead of a vertical thrust force (lift). <S> So in an airplane, the stronger the thrust force pushing or pulling the plane along <S> , the higher angle of attack the wing can operate at for a given speed, driving air down harder, and more lift (vertical thrust) is created. <S> Or it can stay at the same angle of attack and just get pushed through the air faster. <S> With the propeller, the stronger the rotational force, the higher the propeller blade's AOA can be <S> and/or the faster it can go, driving air aft harder, and more thrust (horizontal lift) is created. <S> So the more propeller thrust you want to make, <S> the more horsepower (torque x velocity) is required. <A> Because spinning the propeller to make thrust creates friction and drag. <S> Using a piston engine as an example, when we start the motor and add fuel, the motor will spin the propeller faster and faster until the friction of the pistons moving, plus the energy required to move fuel/air mixture in and exhaust out, plus the friction of the bearings, plus the drag of the propeller through the air, equals the expansion force released by the fuel burning in the cylinders. <S> Once maximum rpm is reached, this is called "steady state". <S> The average force of the fuel being burned and pushing the pistons is equal to all friction and drag forces. <S> If you designed your engine well and it does not overheat, you get maximum THRUST until it runs out of fuel. <S> So for a given prop, the more horsepower you have the more rpms you get. <S> Sizing props with engines can take some time to learn, but it is generally better not to overspeed the engine by trying for very high rpms and risk overheating it. <S> A larger prop swung more slowly will be more efficient, but you still need to burn enough fuel per unit time to get it going. <A> Newton famously (is quoted as saying) "For every action there is an equal and opposite reaction. <S> Propellors propell by forcing air in one direction (action) and in turn generate a force against the propellor (reaction) which drives the air forward. <S> The classic drag equation Force <S> = 0.5 <S> x Air_density <S> x Cd <S> x A <S> x <S> V^2 ... <S> (i)& the related Power = <S> Force x V ... <S> (ii) 0 <S> < Cd <= 1 is the drag coefficient. <S> Cd=1 is the best case in this application. <S> A = area (of prop circle in this case), V = velocity of air through prop, when analysed these equations are found to link the thrust, and the power imparted to the air which passes through the propellor. <S> ie <S> to get air of a certain velocity, or a certain amount of thrust you need to 'plug in' appropriate figures into the above equation. <S> As soon as the propellor starts moving air it will generate thrust and thrust is linked to the power consumed (or delivered) by the 2nd equation.
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The more power you have turning the prop, the higher the blade pitch will go, biting deeper into the air and thus generating more thrust, and therefore the faster the plane will travel.
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Does auto pilot take into consideration the altitude, speed, and the difference in heading change, to calculate the degree of bank? Or is there a “standard” that the auto pilot follows at all times? By “standard” I mean the aircraft will bank at x amount of degrees each time regardless of the following mentioned? The more you bank, the sharper the turn is, correct? <Q> If your talking about standard rate turns, those are not really practical in large commuter aircraft. <S> As true airspeed increases the maximum turn rate decreases when the bank angle is limited to a comfortable level of less than 30 degrees of bank. <S> So please make this question more specific, which airplane category are you talking about? <S> Usually the autopilot uses the difference between the target heading and the current heading to generate a bank angle target, often just proportional by a linear factor but limited to <S> , e.g. 25 degrees of bank or the minimum of a 30 degree bank turn and a standard rate turn bank angle or even manually selected like in the Boeing aircraft. <S> The autopilot then calculates the difference between the target bank angle and the actual bank angle and generates a roll rate target. <S> Based on the roll rate target and current roll rate the autopilot computes a roll acceleration target and finally an aileron deflection target, which could, for example, just be a factor times the roll rate deviation. <S> The computation from the deviation of any of these parameters to the next lower level control loop target can consider the true airspeed and altitude, yes. <S> But this can't be said for all types of autopilots that ever existed and is too broad of a question. <S> For certification of an autopilot system it has to be demonstrated that the autopilot remains within a safe enveloped, as specified in the requirements. <S> This could limit the roll acceleration, roll rate, maximum bank angle or demand a response within a certain time frame or a maximum deviation for any of these values, transient allowed overshoots, etc. <S> Since the autopilot has to work throughout the flight envelope the parameters used in the computation of the bank angle, roll rate, roll acceleration, aileron deflection, etc. may require a look-up table for each airspeed and altitude to ensure a stable and safe operation. <S> This can differ between aircraft types, e.g. a large passenger aircraft should fly less aggressive roll maneuvers because the people sitting on the outside far away from the center are being subjected to major g-forces as the aircraft rolls, which is uncomfortable and potentially hazardous. <A> The amount of bank is that which is required to achieve the standard "Rate 1" or 2 Minute turn, being 3 degrees heading change per second, which takes you in a full circle in 2 minutes. <S> This is a universal protocol for turns in the IFR world. <S> This varies with true airspeed (the faster you're going the higher the bank angle required to turn at 3 deg/sec) <S> but you get a good ballpark number by dividing TAS by 10 and adding 7 (so at 180 kt, it's 18 + 7, or 25 degrees bank). <S> The pilot of a transport aircraft has the Flight Director to tell him/her the precise bank angle target required. <S> (If the turn rate indication or Flight Director indication was not available, that's when the 10% of TAS + 7 formula comes in handy.) <S> The autopilot does the same thing. <S> It uses whatever bank angle it needs to to achieve Rate 1, and it'll be programed to use a certain roll rate and roll out lead heading angle (normally quite gentle - several seconds to roll into a 25 deg banked turn). <S> It'll start to roll out of the turn about 15 degrees of heading before the target and reduce the roll rate as it gets close to creep the last few degrees to avoid overshooting. <S> The amount of heading change doesn't really come into it, unless the heading change is so small that it's time to start rolling out before the turn rate even gets to Rate 1. <A> In all the jets I fly, the autopilot will always bank at 25 degrees. <S> It doesn't worry about standard rate turns. <S> As others have pointed out or alluded to; a standard rate turn with airspeed above 180 KTAS requires larger than comfortable bank angles. <S> The autopilots also have a half bank feature to limit banks to 13 degrees. <S> Most often pilots will use that feature on a single engine climb at V2. <S> Some FMS installations will also limit its bank angle above a certain altitude to half bank to limit the chance of an acceleration stall. <S> The autopilot must be in NAV mode for that to work.
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The pilot hand flying a light aircraft has the Turn and Bank or Turn coordinator to determine when the bank angle is correct for Rate 1 and flies whatever bank angle gets the indicator showing the correct rate.
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Does a pilot need clearance to enter the traffic pattern? In one video, I saw a Cessna that got its instructions to enter the pattern along with landing clearance, but I saw another where the pilot just flew in and got clearance somewhere around late-downwind. Edit: Still confused here, if you need a landing clearance to enter traffic, then why do diagrams like this exist: (Figure 4 indicating the recommended area landing clearance should be given) And why do you see so many videos on youtube of late landing clearances? And why do I see people get cleared to land when they're on downwind abeam to the numbers if they already have clearance? <Q> The US AIM (Aeronautical Information Manual) says: <S> When necessary, the tower controller will issue clearances or other information for aircraft to generally follow the desired flight path (traffic patterns) when flying in Class B, Class C, and Class D surface areas and the proper taxi routes when operating on the ground. <S> If not otherwise authorized or directed by the tower, pilots of fixed-wing aircraft approaching to land must circle the airport to the left. <S> Pilots approaching to land in a helicopter must avoid the flow of fixed-wing traffic. <S> However, in all instances, an appropriate clearance must be received from the tower before landing. <S> ( AIM 4-3-2-b.) <S> ( AIM Fig 4-3-1) <S> So it is mandatory to receive a landing clearance, but if traffic flow doesn’t demand it, there is no need to fly the traffic pattern. <S> The controller basically has a lot of freedom here, but the standard is to get instruction to join it, even if this means to join a long final. <A> At a controlled airport, you need a clearance to land, and sometimes to enter its airspace (varies by class of airspace and country). <S> How to enter the pattern is not a clearance, at least if you're VFR. <S> Depending on other traffic in the area, ATC may give explicit instructions on how to enter the traffic pattern. <S> If there's no other traffic present (or at least none near enough to cause a conflict), though, ATC may not care how you do it. <S> Their job is to ensure a "safe, orderly and expeditious flow of traffic," not to dictate every single thing a pilot does. <S> The diagram you cite shows the standard traffic pattern, which is what pilots use at uncontrolled fields, or at controlled fields if ATC doesn't specifically instruct us to do something different. <S> Even when ATC does give instructions, it is usually based on the names of the pattern legs, e.g. telling you to enter on base or long final (because that makes the most sense given your position and that of other traffic) rather than on the downwind as usual. <A> The difference will be controlled and non controlled airspace. <S> In uncontrolled airspace you will transmit on guard or airport freq. <S> your position and type aircraft and state your intentions. <A> Note: This answer assumes that you are in FAA airspace. <S> There are two aspects about entering a terminal area to land. <S> First, there is clearance into the terminal area, and secondly, there is clearance to land. <S> Let's look at them separately. <S> The clearance into the terminal area is dependent on airspace and your flight flan. <S> You do not need a landing clearance to enter the traffic pattern. <S> This is clearance to fly a path in the sky, but is not a clearance to touch anything on the ground. <S> If your terminal area is controlled, you will need to work with ATC to arrange your entry into the traffic pattern. <S> Depending on your entry geometry, this could be a full rectangular left hand pattern as you depicted, they could just give you a long final, or anything in between. <S> For further reading about FAA classes of airspace, this is a good reference . <S> Where clearance into the traffic pattern permits a flight path, landing clearance allows the airplane to touch the ground, but does not provide any clearance for path of flight. <S> Thus, if the airfield is controlled, you need to receive a landing clearance before wheels touch the ground. <S> Situationally dependent, you will typically receive landing clearance about when you turn base. <S> It is controller technique to give you an earlier or later landing clearance. <S> You may fly a full traffic pattern expecting to receive clearance, and when on short final it is not received, you have to execute a go around.
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When in controlled airspace you will receive clearance to enter the pattern and proceed to landing.
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How to glide in a circular pattern? I was just curious as to how you would make a glider glide in a circular pattern ( or helical ). Will there be a large difference when considering a conventional glider vs a delta wing glider? <Q> Maintain coordinated flight ( no skidding, no slipping ). <S> There is no difference in turn dynamics between a conventional glider vs a delta wing glider. <A> A conventional 360 turn can be flown the same way in a powered airplane and glider: a gentle bank towards the turn, using rudder to maintain coordinated flight. <S> However, the purpose of a glider circling is often to catch a thermal (i.e. lifting air). <S> In order to maximize the lifting force, a glider pilot might keep the wings level and use rudder to turn, a technique that is unique to gliders. <A> Delta gliders have a unique way of turning amazingly similar to the wing warping technique attempted in the early days of flight, using DRAG differential to yaw the aircraft. <S> This is the result of the differential of sweep angle with a change in relative wind, between the inside and outside wing. <S> Elevons are used to roll the plane to its bank angle. <S> The resultant sideways motion creates more drag on the inside wing, more than the "adverse yaw" created by the elevon deflection. <S> The plane will turn without a rudder. <S> Examples of rudderless deltas include hang gliders (weight shift) and flying wings (elevons). <S> Straight winged gliders do not create sufficient yaw drag differential when rolled, in fact, the ailerons will tend to yaw it in the opposite direction, hence the need for rudder input. <S> Conceptually, the rudder is the inside wing for a delta, and the tail for a straight winged aircraft, with many possibilities, including spoilers, in between, depending on your design style. <S> The large trailing portion of the delta also contributes to the turn.
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Assuming there is no wind, a circular pattern is most easily achieved by flying a constant speed and a constant bank angle.
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Why did my LGA-ORD flight make an S-shaped turn round the time it was passing a storm? On a recent United UA1709 flight into Chicago (hit by a heavy storm at the time), I felt a noticeable descent, combined with two wide banks around 1 hour before landing. Looking at the flight path, I see an S shape that deviates from the original flight path. Looking at the altitude readings here , the plane registered a descent of around 3000 fpm around the time of the turns from a cruising height of 30000 ft to 21000 ft. This descent took the plane under cloud cover and into the storm, so I am certainly confused as what motivated this flight path. Given that the flight was an hour away from landing, I find it hard to believe that this was a holding pattern of some sort. Some more things that I noticed during this flight (not sure if relevant) was that a few minutes after this, I noticed lights indicating a plane flying directly above (hard to estimate distance given bad visibility). Furthermore, in-flight WiFi briefly cut out for a few minutes. Can anyone explain what happened here? <Q> I find it hard to believe that this was a holding pattern of some sort. <S> Believe it. <S> An hour before landing would be about the point at which the aircraft will start its descent to its destination. <S> Almost certainly, air traffic control were delaying your flight for a few moments to ease insertion into the landing pattern at Chicago. <S> Doing this at altitude burns less fuel than waiting until the aircraft is lower down. <S> The storms were incidental. <S> Had the pilots been avoiding the weather they'd have diverted north or south and then resumed their route. <S> A large S-bend wouldn't be necessary. <A> Based on your provided flight info, I looked up the track history on flightradar and did see some potential traffic conflict that might have tempted the controller to route your plane that way. <S> The first turn to the South appears to be a conflict with AAL 91, who was coming in from the North, also descending. <S> AAL 91 executed a 90 right turn, while UAL 1709 turned left. <S> Now your flight is heading South. <S> The controller had to turn you back at some point; if you keep going that direction you're going nowhere. <S> That explains the second turn. <S> The traffic above seems to be AAL 436, who was in an climb towards the West. <S> It appears there were 3000 ~ 4000 ft of vertical separation when you pass each other. <S> The controller eventually sent your plane into the queue of planes landing at Chicago. <S> (For anyone interested, the area of interest is to the ENE of ORD, just near the shoreline. <S> UTC time is 20191127 00:45) <S> Was this normal? <S> Yes. <S> Once a flight leaves cruise altitude, it is subject to "vectoring" (given headings to fly) by ATC. <S> During ascent (from around 10,000 feet up to cruise altitude) and descent (from cruise altitude to Initial Approach Fix), it is common for ATC to route planes around to ensure they're safely separated. <S> The exact traffic you encounter varies with traffic to/from other nearby airports, as well as weather (as you've noticed), so it is always a bit unpredictable. <A> Storms have nothing to do with this. <S> I'm a pilot who routinely flies into both Chicago O'Hare and La Guardia. <S> ATC normally tries to change speed of incoming aircraft but sometimes it's not enough and delay turns are required to ensure adequate separation. <S> If they get really backed up due to bad weather or switching active runways, then holding may be required. <A> Since you mentioned storms I would imagine the pilots had requested a deviation from track/altitude to avoid bad weather. <S> The storm you felt was problem the fringe of a bigger storm system and they would have been given/or requested a path/level where the storm activity was reduced. <S> Wi-fi also suffers in storms. <A> the flight plan movements look very similar to the shape of the storm. <S> So this could just be a visualization issue.
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The S-turns are because of flow control into busy airports.
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What is the reason for this engine oil service procedure on a Bombardier CRJ? Someone told me that servicing the engine oil on a Bombardier CRJ900 aircraft with the APU on could lead to the particular engine being overserviced. He then advised that the engine-oil service be done within 20 minutes of aircraft shutdown. What's the reason for this? <Q> For the CF34-3B engine on a Challenger 605, checking must be done between 15 minutes and 2 hours following shutdown. <S> If done outside of this window, the engine must be dry-motored (cranked without introducing fuel) for at least 30 seconds. <S> Otherwise the oil level may (incorrectly) show too-low (the oil tank is not at the bottom of the engine), which could lead to overfilling. <S> Overfilling is said to be worse for jet engines than operating them with slightly too-low oil levels. <A> When the engine is running, it sucks up the oil from the reservoir and puts it in all the galleries, ie the oil's all in the right places to lubricate the engine. <S> When you shut the engine down, the oil starts returning to the reservoir by gravity. <S> So there's a gentle drip-feed back into the reservoir, which means that the apparent oil quantity measured at the reservoir is increasing. <S> So the problem is WHEN should you measure the oil quantity - when just before the oil starts returning to the reservoir, or after that process has completed? <S> Well, it can take a while, so the general convention is to read the oil quantity, and to add oil as necessary, before the oil has gone back to the reservoir. <S> (Don't know why the APU has anything to do with this.) <A> I don't know the specifics for that plane, but in general you do oil changes with the oil warm so that it is less viscous, so there's a minimum amount of dirty, old oil left inside the engine ( <S> and so you don't have to wait hours for it to drain). <S> However it's generally a bad idea to do it while the engine is still at operating temperature, because then the oil will be hot enough to cause serious burns as you remove the drain plug.
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The Aircraft Flight Manual or Flight Crew Operating Manual will specify the timeframe during which engine oil may be checked after engine shutdown.
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Why does the faster-moving air over the static port not result in a lower static pressure? I understand the concept that the static port is measuring "static" pressure, meaning the pressure the air is exerting on its surroundings. However, there is also Bernoulli's principle, which, put simply, states that as the velocity of air increases, the pressure it exerts on its surroundings decreases. We see this in effect in venturis, of course, but it seems to me that Bernoulli's principle would also imply that the pressure observed from the static port would similarly decrease as the aircraft accelerates . Obviously this doesn't happen however, since the altimeter is unaffected by acceleration. Thus my question: why does the faster-moving air over the static port not lower the pressure it exerts? Here is a video explanation of Bernoulli's principle being used in pitot-static systems, which seems to suggest the static port would indeed observe a pressure decrease (I've labeled the part I think the narrator is using as the static port): <Q> It's not that simple. <S> Aircraft are complicated shapes. <S> The fuselage is composed of all sorts of angles of attack, things sticking out into the airflow, and the pressure distribution of air across it is very uneven, just like that of a wing is. <S> Take a look at this diagram from an FAA mechanics publication. <S> There are zones (like points 2,3, and 5 in the diagram) where the static pressure deviation is zero. <S> This is where the engineers put the static ports. <S> Another way to think about this is that you're right that the airflow over the static ports should make the pressure lower--- <S> but the question is: lower than what? <S> The answer is: lower than the airflow's stagnation pressure, when the outside airflow is at rest (relative to the aircraft). <S> Which happens at the nosecone, or the leading edge of the wing... or at the pitot tube. <S> It's lower than that by the same amount that the pitot pressure is higher than ambient, making the pressure at the static port exactly ambient outside pressure. <S> Which should make sense, because in the reference frame of the air, that static air isn't doing anything but sitting around waiting for an airplane to come by. <S> The Bernoulli effect does, however, have an overall average result: the cabin pressure in the airplane is lower than static, because the angle of attack of the various surfaces of the fuselage generates suction, pulling a small amount of air out of the cabin, just as it does for the wing if there are little holes in the wing. <S> Which is why you get the little blip when you pull the Alternate Static open. <A> However, there is also Bernoulli's principle, which, put simply, states that as the velocity of air increases, the pressure it exerts on its surroundings decreases. <S> I think that's accurate. <S> So let's suppose you're flying at 120 knots. <S> The air ahead of the aircraft is moving at 120 knots (in the aircraft's frame of reference). <S> The air immediately outside the static port is also moving at 120 knots. <S> The air behind the aircraft is, of course, also moving at 120 knots. <S> Since the speed of the air is the same in all three locations, according to Bernoulli's principle, the pressure should be the same in all three locations, too. <S> So, we've established that the air pressure immediately outside the static port is about the same as the air pressure several feet away from the aircraft. <S> Can we conclude that the air pressure inside the static port is also the same? <S> Bernoulli's principle doesn't tell us the answer. <S> The main reason is that Bernoulli's principle only applies along a streamline , and the air outside and inside a static port are not on the same streamline. <S> But in any case, Bernoulli's principle doesn't give us any reason to think that the air pressure in a static port should be lower than in the surrounding air. <A> As pointed out by JScarry, the position and shape of the static port opening on the airframe are carefully chosen to minimize any ram air or suction effect and thereby sense the static pressure as accurately as possible. <S> In homebuilts, the static port location has to be determined by experiment, and if your experiments are sloppy, you'll find it possible to fly 250 MPH on a 65 HP engine (I'm exaggerating a bit here; I knew someone who built a kitplane with a homebrew static port and attributed its impossibly good top speed to his superior construction technique ;-))
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Bernoulli's principle would also imply that the pressure observed from the static port would similarly decrease as the aircraft accelerates.
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How can I get a ride in the jump seat as a non-professional pilot? A couple of years ago, I had a strong fear of flying. Now, I really enjoy it. In fact, it is a dream of mine to sit in the jumpseat of an A320 during takeoff. I've had a handful of flying lessons. If I took my logbook and explained my interest to the captain, is there any chance this could happen? If not, how could I make it happen? <Q> It's hugely unlikely. <S> Almost vanishingly unlikely, with few exceptions perhaps for something a little smaller than a passenger-carrying A380 (like a private jet on a repositioning flight where you know the captain well) <S> You used to be able to go up and see the captain on the flight deck <S> - I did it a few times as a kid. <S> Even then asking to sit in the jump seat was usually met with a smirk. <S> And then 9-11 happened. <S> With effect from 1 November 2003, ICAO Annex 6 was amended so that under Chapter 13.2.2 “all passenger-carrying aeroplanes of a maximum certificated take-off mass in excess of 45 500 kg or with a passenger seating capacity greater than 60 shall be equipped with an approved flight crew compartment door that is designed to resist penetration by small arms fire and grenade shrapnel, and to resist forcible intrusions by unauthorised persons. <S> This door shall be capable of being locked and unlocked from either pilot’s station”. <S> And with that came locking of the cockpit door, and no more visits to the cockpit during flight <S> (incidentally, if you ask nicely, the captain will often let kids take a peek when they're deplaning the passengers) <S> And then germanwings happened, and they had a rethink. <S> But still no visits to the cockpit during flight at all for the average Joe. <A> As a non-professional pilot, to get a ride in the cockpit jumpseat, you'd have to meet at least three conditions: company policy must allow passenger in jumpseat PIC must allow passenger in jumpseat <S> you'd have to be well known and trusted person to either SIC or PIC (preferrably PIC) <S> If you fail to meet any of those, no jumpseat ride for you. <S> So, very slim chances, but not impossible. <S> The aforementioned is based on personal experience, multiple occasions, and applies to a major intercontinental airline which I will not name. <A> I regrettably inform you that your chances are very slim, outside of actually completing the training required to fly the aircraft. <S> To the captain, the stranger is simply someone claiming to have flight experience. <S> To the stranger, it may be an experience; to the captain, it is a routine, daily job, with schedules, policies and regulations to follow. <S> In my airline, this would be strictly against policy. <S> Even if we were to jumpseat a flight attendant, there has to a necessity to do so (e.g. no rooms in the cabin / broken seat etc.) <S> There are companies that provide simulator rides to the general public. <S> There are none that provide a jump seat ride as far as I've heard. <S> Disclaimer: I am not affiliated with the linked company. <A> I would suggest to purchase a training session for A320 in a certified flight simulator like this one , for instance. <S> I understand this is not a real flight, but these simulators feature full scale cockpits with all controls, and the realistic algorithms to simulate the flight itself. <S> A after the instructor giving you an introduction, you will be able to take the controls yourself during take off. <S> This may work pretty well as a counter-measure against the fear of flying. <A> This is not really direct answer to the question 'as-is'. <S> It's more answer to 'how can a Non-Pilot' fly regularly in the jumpseat. <S> Just become Flight Dispatcher. <S> In many airlines that gives you 'Known Crew' badge. <S> And with it and PIC permission you can fly in the cockpit as much as you wish. <S> Dispatchers even trump flight attendands in that regard. <S> Regular jumpsitting is part of the work actually. <S> Some FDs just use it as a meaning of commute - in the US per ALPAs rules AFAIK. <S> The catch - in the EU <S> the training is 2000 EUR, the course requires you to pass 14 exams - the very same as for ATPL :D <S> &
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In this world where aircraft terrorism is always a concern, you would have to have a very good reason to convince the captain why he has to put a complete stranger in the cockpit.
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If you were to fly an ILS in a knife edge would you receve GS and LOC be flipped? because LOC and GS work the same way, if you were to fly one at 90 degrees bank would your information be displayed on the wrong indicators? <Q> No, the directional part of ILS is located at the ground. <S> (Ground) transmitter creates lobes with specified frequency and modulation to mark the high, low, right and left areas. <S> LOC and GS signals are distinguished by the carrier frequency, deviation from the optimal approach by relative intensity of 90 Hz and 150 Hz modulation in the signal. <S> These signals provides information about position relative to the airport regardless of airplane attitude. <S> So flying knife-edge LOC axis of the instrument still shows (correct) horizontal deviation and G/S axis correct vertical deviation. <S> Of course, display of the instrument is turned 90° together with the whole airplane, so its G/S axis now lines up with the green-blue boundary you see behind your windows (I hope you are not flying such maneuvers in IFR conditions :) ) <S> but it is still the G/S axis and it shows vertical deviation from the optimal glideslope. <S> Only difference would be that airplane antenna won't match the transmitter polarization (ILS transmitters transmit in horizontal polarization and receiver is likely polarized in the same plane), so you loose some signal intensity and receiver <S> can be more sensitive to reflected signals, therefore reducing maximal working range and possibly increasing probability of spurious signal detection. <A> The indications on the GS and LOC will stay centered. <S> If you deviate from the GS or LOC the deviations will be shown on the respective instruments. <S> The instruments don’t know or don’t care what the aircraft attitude is. <S> The instruments only care about the deviation. <A> LOC and GS work the same way <S> They work on the same principle, but they each have their own radio signal. <S> The localizer is on the frequency tuned in the radio (in range 108.10 MHz to 111.95 MHz), the glide-slope is on an associated frequency from the 329.15 MHz to 335.00 MHz (the mapping is not sequential for some reason). <S> So the localizer needle will still show the deviation from the localizer signal and the glideslope needle will show the glideslope signal. <S> They just won't be aligned with the directions to steer any more. <S> Neither also knows anything about direction. <S> Each carrier has two tones broadcast on it (90 Hz and 150 Hz) that indicate left and right on the localizer frequency and high and low on the glideslope frequency. <S> So when you are to the left of centreline, the receiver will sense more 90 Hz on the localizer and the localizer needle will move to the right relative to dashboard, no matter how your plane is oriented. <S> Also due to the nature of phase-shift directional antennas, there are other maxima around besides the main ones just around the intended flight path. <S> One especially has to be careful about the false glide-slopes at 6° and 9°. <S> The 6° has reverse sensing, that is above it the needle will direct you to the 9° one, below to the correct 3° one. <S> And 9° is way too steep for any aircraft. <S> There are similar maxima for the localizer, called side-lobes, but they are a bit easier to avoid by comparing your heading with the runway number. <A> To try to make things totally clear: Suppose that the aircraft is making an approach in knife-edge flight, banked 90 degrees to the right. <S> Suppose that the runway heading is north (it's runway 36). <S> If the aircraft is too low, the glideslope needle in the course deviation indicator will deflect "up" (towards the ceiling), indicating that the aircraft is too low. <S> The pilot will correct for this by adding more left rudder input (which is to say, pressing harder on the left rudder pedal). <S> If the aircraft is too far to the east (right), the localizer needle in the CDI will deflect "left" (towards the left wing), indicating that the aircraft is too far to the right. <S> The pilot will correct for this by giving down elevator input (which is to say, pushing forward on the stick). <S> The readings on the CDI will be correct in that they will correctly describe the location of the aircraft relative to the glidepath. <S> However, they will not directly indicate what the pilot has to do; the pilot will have to recognize that, since they are flying in an unusual attitude, they will have to react to the CDI indications in an unusual way.
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As long as the aircraft accurately flies down the ILS, it doesn’t matter if it is knife edge, inverted, etc.
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Why is "runway behind you" useless? I was recently answering this question and for some reason it made me think of this fairly famous aviation saying The three most useless things to a pilot are the altitude above you, runway behind you and fuel on the ground Now, I get altitude above you - you may as well use some of it lest you meet a mountain. I also get fuel on the ground - if in any doubt fuel up before you go. But I'm not sure I understand why "runway behind you" is useless in this context Could someone explain? <Q> If you enter (or touch down) <S> the runway in the middle, you will not be able to benefit from the part of the runway behind your entering point. <S> It is the same as if that part would not exist. <S> Therefore it is useless. <A> It refers to takeoff from an intersection rather than using the full runway length. <S> The part of the runway behind you is now useless. <S> It is part of the saying because the TODA (takeoff distance available) is now reduced and this needs to be taken into account when doing performance calculations. <S> It is e.g. discussed in this thread on pprune.org . <S> One could also interpret it to refer to landing: When touching down half way down the runway, the part behind you is useless for stopping. <A> In case of engine failure during the takeoff run, it might be possible to land immediately and stop if there's enough runway. <S> But if the run was started partway down the runway, there will be less room to do that, possibly resulting in a more severe result. <S> The point of all three "useless" items is that, by using them before a problem arises, the results of the problem may be greatly mitigated. <S> It's an indirect way of recommending making use of the resources available to be prepared. <A> I've always known the saying as "The three most useless things to a pilot are the altitude above you, runway behind you, and the fuel you had" What the saying is really talking about, is give up your margin grudgingly, especially when you don't need to. <S> This works for all aspects of life. <A> All three of the useless data are contrasts with useful information: the altitude above you <S> What matters is how much air is below us. <S> runway behind you <S> We're only interested in how much runway is available in front of us. <S> fuel on the ground <S> We care about how much fuel is in our tanks .
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The runway ahead of you is useful to accelerate and - if needed - to decelerate.
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Is there a age limit to become a CFI? I’m a new PPL and I would love to become a CFI in the next 2 years (or so). My objective would be to transfer what I know (and will have learned) to aspiring pilots. I’m older, though (just about to turn 60). Put it bluntly: am I too old? I know that we can’t talk about people being too old for almost anything these days, but I really would like to know if anyone (e.g. a flight school) would hire an instructor who not only brings rather thin experience (300-400 hrs by then) but combines it with rather ‘advanced age’. The benefit for a school would be that this would be my ‘forever-job’ (first, part-time and then full-time after I retire from my ‘day-job’ in a few years), not a stepping stone to an airline career. Please, feel free to tell me what you really think… <Q> A flight school won't care too much about your age if you have the required medical. <S> And mentally, your age is an overall plus since <S> a flight school would generally prefer a mature individual in it because they want to teach to a 25 year old who's just building time. <S> The turnover with flight schools is quite high so the prospect of getting say at least 5 years out of you is another plus because they may be only getting 2-3 years out of younger instructors in the current environment (often they are basically only hanging on to get to 1500 hours under the "Colgan Rule" craziness). <S> I would say that that if your health is fine and shows no signs of problems over the next 5 years at least, you should definitely go for it. <S> You might even get a school to commit to hiring you, or at least giving you a shot (it's going to come down to how good a teacher you are), if you train with them. <S> With the general shortage of bodies all through the system, I don't see any downside if you really keen on doing it. <S> If you gain a reputation as a good teacher students will gravitate to you over the youngsters. <A> Age is no barrier to becoming a CFI. <S> You bring a lifetime of experiences that you can use to teach and mentor new pilots. <S> Some of my best instructors that I have ever had were in retirement age. <S> They generally took more time to correct deficiencies and were more patient. <S> They weren't concerned with external pressures at home or looking to sit right seat in the multi engine King Air across the ramp. <S> If you ever lost your medical you can still teach ground school classes, sim sessions and still flight instruct in aircraft provided you are flying with a client who can be the legal pilot in command (i.e. no private or instrument students or expired flight reviews). <S> There is no requirement in the FAR <S> §61.23 for instructors to hold a medical certificate with the exception of also acting as a required crew member or legal pilot in command. <A> Absolutely not. <S> If you love flying airplanes and love to teach others how to fly, we need more CFIs like you. <S> These days you can practically pull out a sectional chart and toss a pub dart at it, and whatever airport <S> the dart lands next to <S> , you can probably get a flight instructor job out there. <S> Keep in mind <S> the pay is not very glamorous until you get a couple thousand hours of instruction time under your belt. <S> Some schools may want you to hold an instrument rating on your flight instructor certificate so you can do instrument training. <A> A medical is necessary for primary instruction where the student is not rated. <S> A medical is necessary for instrument instruction, as the instructor must act as PIC for the safety of the flight. <S> A medical is necessary to perform flight reviews and IPCs as each requires flight solely by reference to instruments, by the applicant. <S> One can obtain a CFI with a third class medical, and the local FSDO has provided CFI initial rides to applicants with only a third class medical. <S> 14 CFR 61.39 (a) (4) <S> (4) Hold at least a third-class medical certificate, if a medical certificate is required; <S> The above requirement may be defacto amended by the Basic Medical rules, where the aircraft to be flown is compliant with Basic Med requirements. <S> While I have heard stories of ATP rides in Level D simulators, without medicals, I do not have first hand knowledge of any cases. <S> IMO likely possible, because a medical is not required. <S> Other ratings may be accomplished if the DPE is willing to act as PIC for the flight, and I know of one example of that. <S> A third class medical will be sufficient for instruction. <S> A Basic Medical may also be used with many common general aviation training aircraft. <S> But as for the age limit on CFI, there is only a lower limit, which you have long since blown through. <S> I would suggest that you consider a AGI and IGI ground instructor certificate, which you can work on immediately. <S> Good luck and have fun!
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There is no upper limit on age for a CFI. The only real obstacle would be maintaining a medical certificate if you intend to do primary and instrument flight instruction. Aside from that, no there aren’t any age restrictions and it can be a very rewarding side job if you’re so inclined.
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Does a CFI need an Instrument Rating https://www.ecfr.gov/cgi-bin/retrieveECFR?gp&n=14y2.0.1.1.2&r=PART#se14.2.61_1183 The or below is very confusing. Doesn't it mean I need an Instrument rating or one of the things that follows it in the list? Or means one or the other, not both.Furthermore, when would one of the things that follows in the list NOT apply? (2) An instrument rating, or privileges on that person's pilot certificate that are appropriate to the flight instructor rating sought, if applying for— (i) A flight instructor certificate with an airplane category and single-engine class rating; (ii) A flight instructor certificate with an airplane category and multiengine class rating; (iii) A flight instructor certificate with a powered-lift rating; or (iv) A flight instructor certificate with an instrument rating. <Q> For most people, the answer is yes <S> It is possible to become an ATP by using military experience. <S> In that specific case a person has instrument privileges but may not have an instrument rating. <A> A CFI is required to have an instrument rating on their pilot certificate. <S> On the bottom of each FAR is citations pointing to the background and revisions of that regulation. <S> Here is the quote from 62 FR 16298 <S> In proposed paragraph (c), the FAA added requirements for an applicant for a flight instructor certificate with a helicopter, airship, or powered-lift rating to hold an instrument rating. <S> This was in addition to the existing requirement, which only specified that an applicant for a flight instructor certificate with an airplane or instrument rating hold an instrument rating on his or her pilot certificate. <S> The website ecfr.gov shows the reference as 62 FR 16220 but Cornell Law Website shows it as 62 FR 16298. <S> I don't know why the ECFR website is incorrect. <S> From 62 FR 40907 <S> The FAA has clarified the eligibility requirement contained in paragraph (c)(2) for persons seeking a flight instructor certificate. <S> Under new paragraph (c)(2), an applicant is required to hold either a commercial pilot certificate with an instrument rating or an ATP certificate with instrument privileges on that applicant’s pilot certificate that is appropriate to the flight instructor rating sought. <S> The word ‘‘privileges’’ refers to the instrument privileges held by airline transport pilots. <A> What they mean by that is <S> if you hold an ATP - AIRPLANE SINGLE ENGINE, OR AIRPLANE MULTI-ENGINE, these certificates do not have instrument ratings associated with them, though you may serve as PIC on an IFR flight with an ATP ASE/AME. <S> (you must hold an CPL ASEL/AMEL with an IA rating to apply for an ATP ASE/AME Certificate). <S> So you may apply for a flight instructor certificate if you have an ATPL only.
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—you need an instrument rating to be a CFI or CFII for the categories that are listed.
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How do planes maintain constant speeds at cruise altitudes? I'm a noob so pardon my ignorance. So my understanding is that as the plane gets lighter during the flight, its mass reduces therefore reducing the lift needed to maintain the altitude. At those altitudes and speeds, my understanding is that we can't engage slats or flaps. As a result, we would have to reduce thrust to reduce the lift to account for the loss in fuel and maintain the same flight level So what can one use to continually reduce lift coefficient at those altitudes to maintain constant airspeed and flight levels? I understand that ATC also clear aircraft to higher FL thereby reducing the air density and therefor reducing lift and enabling higher airspeed but that still leaves us with the problem of flying at constant airspeed at cruise altitudes. <Q> The autopilot pitches to hold the flight level when it captures the level at the top of the climb, so later on as the aircraft gets lighter and wants to climb further, the A/P will lower the nose as required to hold the flight level (the A/P is able to move the elevator through its servo's link to the elevator controls; it can also work the trim if the servo has to hold too much out-of-trim force for too long, to avoid wearing out the servo - in effect <S> it does what the human pilot does, more or less). <S> It happens very slowly and significant amount of pitch over is not apparent until some time has passed. <S> Effectively, AOA is being reduced by the A/P to compensate for the reduction in wing loading. <S> Because induced drag is being reduced, if thrust is not reduced to compensate for the drag reduction, the A/C will accelerate. <S> If your clearance requires you to maintain a certain Mach #, this is a problem. <S> If the jet has an autothrottle system that can be configured to hold a Mach # while the A/P holds the altitude, the thrust is adjusted automatically. <S> If not, the pilot monitoring at some point will notice the Mach # creeping up, and will reduce thrust in very small increments compensate and maintain the flight planned/cleared Mach #. <A> There are a lot of things that affect lift beyond just the speed and air density. <S> For instance, the angle of attack. <A> As pointed out by HiddenWindshield, the pilot will pitch the nose down slightly as the fuel load is burned off. <S> The pilot does this using the elevator trim control and will from time to time in a long flight add nose-down trim to maintain zero vertical speed. <S> With less load, less lift is required, and trimming away the unnecessary lift will cause the plane's speed to rise slightly unless the pilot reduces power. <A> That's easy. <S> Just push the nose down a teensy bit. <S> (or rather, pull the nose up less .) <S> That will reduce AoA, reduce lift slightly, prevent you from climbing and will hold altitude. <S> " <S> But then, we'll speed up!" <S> Correct. <S> So, reduce thrust as needed. <S> Another option is to intentionally climb. <S> Then, you enjoy the fuel economy benefit of higher altitude. <S> A large plane heavy with fuel is unable to reach its max design altitude. <S> So, as the aircraft sheds fuel, it can seek higher and higher altitudes, to gain the fuel efficiency of pushing through thinner air. <S> It's common for a long-haul flight to start at 31,000 feet, then climb to 33, 35, 37, 39,000 as fuel is burned off. <A> As pointed out in other responses, there are many factors that influence how and why an aircraft will need constant adjustments made to maintain speed and altitude while cruising. <S> You are correct in assuming that as the mass decreases as you burn off fuel, there will be less lift required to counteract gravity. <S> It will also take less thrust to counteract the drag of the air, so either the pilot or the autopilot will need to make continuous adjustments inflight, small though they may be. <S> One thing that has not yet been mentioned is Air Traffic Control. <S> Each aircraft at "cruise altitude" (which is usually above 18,000 feet, or Flight Level 180, and most often above 29,000 feet, FL290) is in controlled airspace, and has an altitude assigned to them by Air Traffic Control (ATC). <S> You must maintain this altitude to maintain proper separation from other aircraft. <S> Of lesser importance, but still something to keep in mind, is that ATC expects you to maintain your airspeed while cruising, and not to significantly increase or decrease your speed unless you notify them. <S> Again, this is to allow them to maintain separation between you and other aircraft. <S> With that in mind, I hope you can better understand why the constant pitch and throttle adjustments mentioned above, even if small, are essential.
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As the weight of the aircraft decreases, the pilot (or autopilot) will pitch the nose down slightly to reduce the AoA, and therefore lift.
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When do commercial aircraft tail numbers change? Each (large, commercial and most other) aircraft has a registration number, painted or stickered on its hull: the tail number . I was under the false impression that tail numbers don't change, and that a number identifies an aircraft until it's decommissioned. That's not true, apparently! This article , for example, explains how new owners may want to change numbers when they buy aircraft. My question: Under what other circumstances do tail numbers of commercial aircraft typically change? Other than changes-of-ownership? Notes: I'm not asking about considerations for changing tail numbers during ownership changes. That's covered. Of course, someone can arbitrarily change a tail number on a whim, but that's probably very rare; I'm asking about somewhat-common situations in which tail numbers are changed. Motivation: Want to be able to use tail numbers to distinguish different aircraft, but need more information to qualify that assumption. So, I realize different owners may invalidate the assumption; looking to qualify it further. <Q> I was under the false impression that tail numbers don't change Tail numbers (AKA registrations) <S> are changeable by definition since each country is allocated codes with different prefixes and formats . <S> If an operator from country X buys an aircraft from an operator in country Y, <S> then the tail number <S> must will most of the time be changed to a valid tail number of country X. Depending on local laws, in some rare cases a tail number of another country will be used, for tax purposes (much more common with sea vessels). <S> This is why some Aeroflot aircraft have VP-B* registrations that belong to Bermuda. <S> What does not change is the manufacturer serial number (which may be analogues to a road vehicle VIN). <S> I think the source of the confusion is that the Wikipedia article that you linked to uses "tail number" of civil and military aircraft interchangeably, and that is wrong. <S> Military aircraft's tail numbers do not conform to their countries' ICAO-issued civil registration format, and they may or may not be changed whenever said air force want. <S> Already know that different carrier + same tail number may mean different aircraft <S> This assumption is wrong. <S> Tail numbers are unique. <S> However, they can be re-used over time. <S> Under what circumstances do tail numbers of commercial aircraft typically change? <S> That is, other than arbitrary whims (which I assume are rare), when do airlines/aircraft owners go through the number changing procedure? <S> As mentioned above, the most likely case is when an aircraft is being bought from an operator from another country than the previous operator. <S> Sometimes the new operator will change the tail number even if the aircraft was bought from an operator in the same country in order to fit the registration scheme that said operator may use (for example, N737* for 737 aircraft, N747* for 747, etc). <S> Other than the mentioned cases above, it's impossible to answer this question in general terms. <S> Every operator may or may not change tail numbers of aircraft it buys. <A> Aside from ownership changes, tail number change is very rare : The cost to change the tail number with the same national registry, on the aircraft itself and in the maintenance logs plus the cost of the aircraft being out of service for some time will far outweigh any minor cosmetic benefits. <S> The only reason I can think of is changing the registration to a different country for tax or regulatory cost savings. <S> Since the first 1-3 characters of the tail number are a national prefix, it must changed in that case. <S> This also often coincides with a change in ownership, though possibly just to a shell corporation to make the registration in the new country allowable, which then leases it back to the original owner. <A> The most common time for a tail number to change would be when an aircraft changes ownership. <S> However, if the airplane is staying in the same country, it may not be worth the paperwork to change. <S> Some examples include US Airways aircraft like N167US <S> retaining their registration with American, and AirTran aircraft like N937AT retaining their registration with Delta. <S> Although it's possible for an airline to operate foreign-registered aircraft, a foreign sale is the point where it may make more sense to get a new registration. <S> The livery is the most important part for brand image of the airline. <S> Few people pay attention to what the tail number is, and it's more of a regulatory/paperwork detail. <S> Records such as for maintenance may refer to the tail number and it makes more sense to leave that consistent even if the ownership changes. <S> Unlike private operations, commercial flights will typically be identified to ATC under a callsign rather than their tail number, so that is not as much of a factor. <S> A smaller operation that may want to keep some sort of registrations scheme might find it worth changing the registration on aircraft when they change hands. <A> The rules are different in different countries. <S> In some countries the aircraft gets its registration, and keeps it forever <S> (the registration may be suspended if the aircraft transfers to a different country, but will regain its original registration on return). <S> In some countries you cannot choose the registration, the authorities do that. <S> In some countries, the owner can choose a registration, and change it as often as they want. <S> In some countries you have to re-register the aircraft every few years (3 for FAA-land??), in others the registration is for life. <S> So, it varies.
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An operator may even decide to change tail numbers of aircraft it already owns just because.
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Could the Aurora D8 have Ramjets instead of traditional jet engines? By the design of the Aurora D8 , the engines would receive the boundary layer of air atop the fuselage, however, because jets have what I am calling "moving parts", and the pressure differences would cause problems for the turbines. Could we eliminate this factor with ramjet engines? <Q> The Aurora D8 doesn't have traditional jet engines at all. <S> The design incorporates a very large bypass fan which due to its size is not mechanically linked to the engine core. <S> It's more like a turbo-prop engine, but driving a ducted fan instead of a propeller. <S> The fan is specifically designed to cope with the flow disturbance in the boundary layer. <S> Indeed, according to the Wikipedia article Clustering the engines together atop the wide tail of a flattened fuselage enables them to reenergize the slow-moving boundary layer over the fuselage <S> Take a look at that article. <S> It might answer a few more of your questions. <A> Hi Rauligio and welcome to ASE. <S> As an answer to your question: no. <A> Replacing the turbines with ramjets won't work. <S> If the airplane had ramjet(s), it would still need enough thrust from non-ramjet engines to reach about Mach 0.5, because ramjets can't accelerate from a standstill, and they make hardly any thrust below that speed. <S> See the Nord Griffon , for example.
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As the Aurora D8 is designed to fly at subsonic speeds, and ramjets work most efficiently at supersonic speeds around mach 3 , they simply would not be feasible on Aurora D8.
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If the pilots used the brakes upon landing, would the force essentially slam the front wheel down? So if the pilots braked immediately, with only the back wheels down, and nose wheel still up, would the force from braking cause the front wheel to come slamming down? <Q> If you get on the brakes hard after main touchdown, once the anti-skid is active following wheel spin-up (you can't land with brakes applied on any airliner with anti-skid - brakes are depressurized until after the main wheels start to spin <S> and/or you are weight-on-wheels for a minimum time) and don't apply any additional compensating elevator, the nose will come down faster than if just hold the existing elevator input, and will contact a bit harder, but "slamming down" would be a bit extreme unless you also relieved some of the control back pressure as you did so. <S> Then it would be a bit firm and if you were reckless enough you might blow the nose tires, and somebody would have a chat with you. <S> In practice though, on most jets you land the mains, then the nose in two separate actions and during that "second phase" you are applying elevator to modulate the sink rate of the nose to make it touch down reasonably gently for that "2nd landing". <S> If you were on the brakes hard at that point you would normally just compensate instinctively with extra elevator input to get a gentle landing of the nose. <S> You would certainly have enough tail power available to counteract the nose down torque of the braking at high speed. <S> But you would probably get scolded for getting on the brakes before nose wheel contact anyway, and a lot of pilots will keep their feet low on the pedals to avoid applying brake, then move them up once the nose wheel is down. <A> Yes. <S> Hammering on the brakes right at touchdown will apply a torque to the airplane which will tend to rotate the fuselage "nose down". <A> Yes, it would. <S> In the case of the A320, you would actually put the nose down smoothly (fly it down).
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If you hold the nose up and apply harsh brakes (or have Med autobrake set), then the nose wheel will slam down eventually.
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Does the sterile cockpit rule mean flight attendants could not inform the pilots if a passenger is in the lavatory while on final? Context: I've seen this interesting question just the other day, asking what would pilots do after receiving this information while on final: either go around or continue with the landing. However many others mentioned the Sterile cockpit rule under 10,000ft. Meaning that they could not discuss this issue. So what would this mean exactly? The flight attendants could inform the pilots but they can’t respond?? Or the FA’s just can’t/won’t inform the pilots about the situation at all? <Q> "Sterile Cockpit" refers to the concept that pilots should not discuss anything not related to the flight during certain phases of flight (often defined as below FL100). <S> A passenger occupying the lavatory while the flight is on approach and passengers are supposed to be in their seats definitely does have an impact on the flight, so it does not fall under the "sterile cockpit"rule. <A> "Sterile cockpit" doesn't mean abject silence; it means no idle chitchat. <S> An issue relating to the safety of passengers is not idle chitchat, so it can be discussed at any time during the flight. <A> Any paperwork, work on the pedestal (the table on AIRBUS) and non-essential conversations between the cockpit members and crew should be avoided. <S> But:- <S> During take-off : from the time the wheels are rolling until landing gear is up and the chime sounds, the cabin crew shall not contact the cockpit crew. <S> During landing : The cabin crew can contact the cockpit crew at any time during the approach, but when the landing gear is extended until aircraft lands and reaches the taxi speed, the cabin crew shall not contact the cockpit crew. <S> It will all depend on when that passenger decides to hide in the lavatory, but I doubt he can. <S> Cabin crew will not allow him to. <A> You have got the answer before <S> but I would like to add that some airlines have more restrictions on talks between cabin and flightdeck. <S> For example, in my airline after the call from flight deck to the cabin for cabin crew to be seated for landing, there should be no call from the cabin until landing, even if they spot a fire or something else.
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" Sterile cockpit " means also that the cockpit crew shall only perform the duties that are required for the safe operation of the aircraft.
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What does a reduction gearbox do in a turbofan engine? I've read that the P&W PW1000G engine has a reduction gearbox. What is it and does it have any relation to the fan or compressor speed? Does it improve fuel efficiency? <Q> The problem is that in bypass engines, the fan blades are much longer than the turbine blades that drive them. <S> Both compressors and turbines should rotate as fast as possible, without shock waves occurring at the tip - so linear tip speed has an upper limit, meaning the compressor with longer blades must turn much slower than the turbine driving it. <S> This is what the geared turbofan does, reduces the rotational velocity relative to that of the turbine so that both can rotate at their optimum angular velocity. <S> The forces involved and the required reliability make it not an easy design task, as noted in this answer , Does it improve fuel efficiency? <S> It does, when both the fan and the compressor can rotate at their optimum speed, and when the gearbox does not add much friction. <A> The gearbox is located between the front fan and the rest of the engine. <S> It lets the front fan spin at a lower rate than the main shaft. <S> Image source: aerospaceamerica.aiaa.org <S> Image source: <S> www.aviationpros.com <A> The purpose of the reduction gearbox is to improve engine efficiency. <S> Normally in a turbofan engine the low speed turbine and fan are connected by a direct drive turbine shaft that requires the low turbine and fan to run at the same speed. <S> In a geared engine, the gearbox allows both the fan and turbine to run at their optimum speeds. <S> In this case, the turbine can run faster with fewer stages and airfoils, which increases efficiency. <S> The fan can run at a slower speed but at a larger diameter to push larger amounts of air at a slower velocity. <S> A simple formula for propulsive efficiency is: $$ N = \frac{2}{1 <S> + V_e / V_o} <S> $$ <S> Where <S> $V_e$ is the exhaust velocity of the engine and $V_o$ is the velocity of the aircraft or inlet of the engine. <S> As $V_e$ lowers to the point where it equals the speed of the aircraft, efficiency <S> N approaches 100%. <S> The larger slow moving fan in a geared engine allows large mass flow with low velocity which improves efficiency. <S> The low velocity also makes the fan quieter. <A> To increase the propulsive efficiency (total efficiency is the product of gas turbine thermodynamic and propulsive efficiency) we need to accelerate more mass flow less fast: this requires larger fan diameters. <S> See e.g. this answer which describes how the bypass air provides thrust. <S> The formula: $$ F = \frac{\text{d}}{\text{d}t} p = m \frac{\text{d}}{\text{d}t} v = m \cdot a $$ shows that increasing the mass flow <S> $m$ for the same amount of thrust requires less acceleration <S> $a$ . <S> This can potentially improve the fuel economy, but there is a limit, increasing frontal area will also cause the drag to increase. <S> As said in this answer , tip speed is a limiting factor, so we need to reduce the spool speed. <S> The problem with decreasing the spool speed is that the work generated in the low pressure turbine (which is coupled by a shaft to the fan) needs a large diameter and more stages to get enough power from the gas to power the fan <S> (let's not get too technical in discussing blade loading). <S> A large low turbine diameter is not very effective for the bypass flow of the engine (how do you get the bypass air around it), therefore the spool speed of the low pressure turbine is increased to be able to use a smaller diameter. <S> This mismatch in spool speed requires a gearing solution. <S> Note that very large amounts of power are being transmitted through the gear box, even with very high efficiencies <S> this requires a lot of heat to be dissipated. <S> Getting rid of the waste heat and the large loading has proven to be a very difficult design task. <A> The preceding explanations are good. <S> But - interesting add-on is the notion that the gearing of a turbine is hardly a new concept - it's been around for decades in the form of turboprop engines. <S> The Allison T56 is an example of a geared Turboprop engine. <S> Simplistically, the difference between earlier turboprop designs and the more recent GTF design(s) - are the difference between a ducted fan and unducted propeller.
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The advantage of this setup is that the front fan can have longer blades to cover a larger cross-section area, while the low-pressure compressor and turbine blades in the core can spin faster to improve fuel efficiency.
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How does the bypass air provide thrust? To my knowledge, bypass air produces 80% of total thrust. But I don't understand to how it does that. By accelerating the air, by increasing the speed or increasing the pressure of the air? Is it doing this by Bernoulli's principle or something like that? <Q> The bypass air is accelerated by the fan at the front of the turbofan engine. <S> This changes its velocity and therefore its momentum, which is the definition of a force (in this case: thrust): <S> $$ F = \frac{\text{d}}{\text{d}t} p = m \frac{\text{d}}{\text{d}t} v = m \cdot a $$ <S> This thrust contributes to the total thrust of the engine. <S> How much will depend on the bypass ratio of the engine and other parameters, but 80% is plausible for a high bypass turbofan. <S> Bernoulli's principle has nothing to do with this. <S> You can see the accelerated airflow in the following animation: <S> (source: Wikimedia ) <S> The air coming from the engine core will move even faster, but there is less of it in a high bypass turbofan resulting in less total thrust coming from the core: <S> The fan airflow, referred to as the cold air stream, is accelerated by the fan and passes through the engine remaining outside of the engine core. <S> The cold air stream moves much slower than the hot stream gas flow passing through the engine core. <S> ( skybrary.aero ) <A> The added energy is most effectively converted into thrust by allowing it to expand until internal pressure is equal to ambient pressure, so all added energy is converted into kinetic energy. <S> This expansion takes place in the cowling behind the fan. <S> But the initial energy addition is a mixture of both increased pressure and increased velocity: the gas will require time to accelerate to the outlet velocity. <A> It doesn't bypass everything , just the combustion chamber. <S> Notably, the air still goes through a fan . <S> High-bypass turbofan engines make most of their thrust from the ducted fan. <S> Very much like a turboprop except the blades <S> are smaller and enclosed by the cowling. <S> @Harper's answer on <S> What is the difference between turbojet and turbofan engines? <S> explains that nicely: a high-bypass turbofan extracts most of the exhaust energy from the jet part and uses it to spin the fan, instead of exhausting really high speed air from the jet part directly. <S> Low-bypass turbofans have a mix of thrust from fan + jet, while a pure turbojet has zero bypass, just compressor blades and no fan.
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A bypass fan provides thrust in the same way a propeller provides thrust: by increasing the energy content of the gas mass passing through the disk.
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What was this vehicle doing? On a trip a few weeks ago traveling out of Charlotte (CLT), I took this picture of a vehicle at the airport. Our plane was fueled as we were about to board but due to various factors, boarding didn’t occur until almost five hours later. As we were finally about to board, this vehicle arrived and connected a tube to a port in the vicinity of the fuel input port. My question is this: what was the vehicle doing and what circumstances necessitate the usage of it? Edit: Although not immediately obvious without zooming in, the yellow pieces visible are the ends of a spool around which the hose is wound. It is not one single large tank as it appears from a distance. <Q> This looks like an Aircraft Fuel Servicing Cart , which transfers fuel from an underground network to the aircraft. <S> There are two types of vehicles that transfer fuel at larger airports with these fuel networks: Hydrant trucks: (image source: Wikimedia ) <S> Aircraft fuel servicing hydrant vehicles do not have tanks. <S> ( ICAO - International and FAA Fuel Fire Safety ) <S> Towed Carts: (image source: aeroexpo.online ) <S> Aircraft fuel servicing carts are equipped with facilities to transfer fuel between a Airport Fueling System hydrant and an aircraft and are normally parked at a fixed location near a gate. <S> ( ICAO - International and FAA Fuel Fire Safety ) <S> The cart in your picture seems to be the latter of the two (a different model though). <S> You can see the hose that will be connected to the aircraft on the metal staircase. <S> The other hose on the ground connects to the hydrant (hidden behind the aircraft in your image). <S> Your picture shows an Airbus A321, which has the fuel coupling typically located under the right wing (number 11 in the following image): (image source: Airbus A321 Aircraft Characteristics and Airport and Maintenance Planning Document ) 11 <S> − <S> REFUEL/DEFUEL COUPLINGS (OPTIONAL−LH WING) <S> Your picture was taken at Charlotte (CLT), which according to this page is equipped with a Jet A Fuel Hydrant Facility . <S> Airports without an underground fuel system will use tank trucks (self-contained fuel trucks) instead: (image source: shell.com ) <A> My guess would be that this is a bowser used for aircraft de-fueling. <S> Sometimes, very seldom though, aircraft need to be de-fueled to lower the weight for take-off. <S> For example: if the aircraft is refueled for a flight to a destination and back (which is common for various reasons), but for some reason the payload for the first leg increases, the aircraft could be loaded over maximum take-off weight. <S> In that case, a certain amount of fuel could be defueled to lower the weight. <S> The de-fueling would be done via the same fueling port as refueling, but a normal fuel truck wouldn't necessarily be used. <S> You can see the fuel hose from the cart connected to the scaffold. <S> The fixed part of the hose in the scaffold is there to facilitate climbing up and attaching the hose to the fuel port under the wing. <S> Also, there are no other inlets or outlets in the wing near the fueling port. <A> That looks like the ground heating/cooling rig. <S> It is a long flexible hose that connects to the plane (snf the other end connects to a heater or cooler. <S> This way the plane does not have to run the engine or the APU at the gate. <S> -Skip
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These vehicles connect to a pressurized Airport Fueling System hydrant and transfer the fuel to the aircraft through a filter.
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How close is a pilot allowed to get to a runway without landing clearance? I heard it was 100 feet above minimums, I'd just like verification. <Q> From the Pilot/Controller Glossary: CLEARED TO LAND −ATC authorization for an aircraft to land. <S> It is predicated on known traffic and known physical airport conditions <S> A clearance to land is exactly that: a clearance to land. <S> A pilot without landing clearance hasn't violated ATC instructions until their aircraft has, in fact, landed. <A> Imagine going for the <S> "I'll come within 1 foot then go-around" <S> option at night when due to a comms failure a plane was lined-up (also, ATC is allowed to withhold the landing clearance in this scenario), or there is a departing plane that has just rejected its takeoff and the comms were blocked due to a simultaneous transmission. <S> While nothing seems to prohibit that option, it isn't the best of advice. <S> While not regulation, AC 91-73B is aimed at flight schools, and advises to go-around if landing clearance is not received and could not be confirmed when on final approach (no height is specified). <S> Instruct students that on final approach, if they have not received landing clearance, to ask the tower, "Flight School call sign, am I cleared to land?" <S> and, if there is no response, to execute a go-around. <S> A pilot that is trained with that mindset, should keep it after finishing the flight school – always ask, or as the AIM puts it: <S> NOTE- <S> ATC will normally withhold landing clearance to arrival aircraft when another aircraft is in position and holding on the runway. <S> i. Never land on a runway that is occupied by another aircraft, even if a landing clearance was issued. <S> Do not hesitate to ask <S> [emphasis added] the controller about the traffic on the runway and be prepared to execute a go-around. <S> In short, there is no minimum, but best practices and good judgement (not hesitating to ask) should apply. <S> On a related note: <S> Did You Know? <S> There have occurred collisions and incursions involving aircraft holding in position awaiting a takeoff clearance. <S> The FAA's analyses indicate that two minutes or more elapsed between the time a line up and wait instruction was issued and the resulting incident. <S> CURRENT GUIDANCE IS TO CONTACT <S> ATC AFTER HOLDING IN POSITION FOR 90 SECONDS. <S> ( Runway Safety , FAA) <A> Disregarding all other factors (like weather etc) an approach can be made as low as you can without touching the pavement. <S> It is not uncommon in major airports with a lot of traffic to get landing clearance very low, well below approach MDA or DA. <A> TL;DR there is no minimum distance <S> An aircraft landing on a runway of a controlled aerodrome may do so for a variety of reasons. <S> For example they might be on final approach and due to communication loss <S> they don't get a final clearance and land anyway. <S> In a controlled aerodrome you are usually given a clearance to enter the TMA (terminal movement area) as well as a STAR (standard arrival route). <S> Entering a TMA without clearance will surely cause more trouble, especially at busy and / or sensitive aerodromes. <S> There are even incidents, where pilots landed on the wrong runway or even the taxiway. <S> Also landing at the wrong airport in the same TMA has happened. <S> Landing on uncontrolled aerodromes is also regulated. <S> There is usually a frequency to listen to and a pattern to fly, to make sure you are the only one landing.
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So the answer to how close you can get is: anything that isn't touching the surface.
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Technical factors to consider for retrofitting aerial refueling for commericial aircraft What are the factor that need to be taken into account to retrofit and an airliner like an a330 or 777 or maybe even a business jet like a global 5000 to an aerial refuelable (receiving) aircraft. Is it even possible? <Q> Yes, of course this is possible. <S> The main factor taken into account is pilot training. <S> Mid-air refuelling puts the receiving aircraft into an unstable position which needs to be held manually for the duration of the operation. <S> Without proper training, the refuelling operation will carry a high risk of being unsuccessful. <S> The best example is a Boeing 747-200 B which has been converted as the US presidential transport . <S> The fuel receptacle sits ahead of the cockpit on the upper side of the aircraft's forebody. <S> From the linked site: Capable of refueling midair, Air Force One has unlimited range and can carry the President wherever he needs to travel. <S> modified Boeing 747-200 being refuelled by <S> a KC-135 (picture source ) <S> However, this capability has never been used with any US president on board and is likely to be deleted from the next version of the plane. <S> From Popular Mechanics : <S> As part of the effort to cut costs by $1 billion, aerial refueling was cut from the program as well, as reported by Defense One earlier this month. <S> Proponents of the cut argue that aerial refueling is not necessary considering no president has ever used the capability, not even George W. Bush who loitered over the Gulf of Mexico in Air Force One for eight hours after the 9/11 attacks. <S> Opponents of removing mid-air refueling say that the ability to take on fuel and fly for long periods of time, even days, is vital to ensure the government can continue operating in a crisis, including nuclear war. <A> Several aerial tankers currently in service are based on airliners, for example the Airbus A330 MRTT : <S> As Wikipedia states: <S> In November 2015, it was announced that an RAF A330 MRTT would be refitted to carry government ministers and members of the Royal Family on official visits. <S> The refit would cost £10m but would save around £775,000 annually compared to the current practice of chartering flights. <S> The aircraft, nicknamed "Cam Force One" by some in the media, will be fitted with 158 seats.[38] <S> The aircraft entered service on 6 May 2016, with the then Prime Minister David Cameron making his first flight on it to visit the 2016 Warsaw summit. <S> So we know the airframe has enough commonality with the original airliner design to convert from one role to another. <S> After all, Airbus produces the A330 MRTTs as standard A330s, which are then delivered to the Airbus Defense and Space plant in Getafe (near Madrid, Spain) where the refuelling systems are fitted. <S> As for what it involves, the redesign itself is the most complex part, since it involves aerodynamic changes due to, in this case, the boom. <S> In fact Airbus suffered a mishap during testing where the boom broke off due to aerodynamic forces (I have heard the root cause was in the software laws of the boom control system, but don't quote me on that). <S> Other than that, adding a boom operator crew station and housing more fuel tanks inside the fuselage is fairly straightforward. <A> I don't think that the physical / mechanical modifications to the aircraft would be that big. <S> You essentially just need a receptacle at the front and a fuel line from the receptacle to the tank(s). <S> Obviously, on transport category aircraft, everything has to be super-safe, so everything would have to be multiply redundant. <S> E.g. two receptacles, each with two fuel lines running along both sides of the fuselage into at least two different tanks. <S> The problem lies elsewhere: aerial refueling is an extremely dangerous and complicated maneuver with very small safety margins. <S> It requires an amount of constant, regular practice that is just not financially viable for an airline operator. <S> Also, there is no way that such a dangerous procedure would ever be certified by any agency. <S> There are a couple of prototypes of military UCAVs that are capable of autonomous aerial refueling. <S> Maybe , when the military has demonstrated a couple of thousand autonomous aerial refuelings without any incident, regulators might think about certifying such a software. <S> But that is way into the future.
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Mechanically the modification is simple: Add some fuel lines, valves and the standard receptacle for the Air Force boom system of refuelling (at the fuel mass needed only the boom system would make sense). It is possible, although expensive.
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Why are propellers de-iced before the engines are started, and does ice on the fuselage affect the flight characteristics of the plane? I recently flew on a flight out of Montreal on a DHC8 turboprop. The plane had been parked at the airport overnight during a winter storm, and as I walked out to the plane, there were visible icicles accumulated on the wings. There was also a layer of ice completely covering the windows on one side of the plane, presumably because of the direction of the prevailing wind during the storm. The plane was successfully de-iced and took off without a problem. However, I had some questions about the de-icing process as I observed it from inside the plane. The ground crew had to de-ice the propellers manually before the engines could be started. Is this mainly because of the risk of ice ingestion in the engines, or is there a problem with the propeller being imbalanced because of uneven weight? Or both? Or neither? The de-icing by the trucks seemed to focus on the wings, and it looked like there was still some ice left on the exterior windows when we left the de-icing pad. My understanding of icing is that ice on the wings is extra-bad (I remember a fatal crash happened near me due to wing ice when I was growing up), but does ice on the fuselage affect the flight characteristics of the plane? Or is it not really a concern? <Q> The props are done before starting because you need to make sure the blades and spinners are fully cleaned off while they are stationary. <S> Otherwise, they'd vibrate like hell when starting and shed bits of ice all over. <S> Also, if you just sprayed the props while running the engines would ingest a lot of glycol, which, if it doesn't make the engine flame out, can gum things up and cause cabin smells as cooked fluid makes its way into the air conditioning system through the compressor bleed system (a lot of turn-backs from "cabin smoke" reports on departure are from the stink from cooked glycol getting into the cabin via the bleeds). <S> Even done stationary, some fluid will make its way into the engine and it's typical to run the engines at a moderate power setting after the treatment for a couple minutes to try to purge whatever glycol residue is in the compressor before opening the bleeds. <S> Fuselages are deiced depending on the airplane and the conditions. <S> On some jets, especially those with tail mounted engines, the upper fuselage is treated as if it was a flying surface and must be clear of ice and frost, even small amounts (it varies with the regulatory jurisdiction). <S> Otherwise it will depend on whether there is any significant accumulation, mostly for weight considerations. <S> If there is an obvious layer of snow/ice on the fuselage, it will be removed... <S> mostly; don't expect a perfect job and they won't normally shoot down as far as the windows. <S> If it's just morning frost, the fuselage may be left alone although the wings and tail must still be done (ANY frost on leading edges can be fatal). <S> The Capt is in communication with the deicing personnel working the boom and will give instructions on what is to be covered, and what to avoid (like APU air inlet in the tail, or heat exchanger inlets, etc.), whether to use Type I only or Type I and II/III/IV <S> (Type one is for melting/removal and II/ <S> III/IV is for follow-on residual protection for a limited time). <S> A deice with follow on residual anti-ice protection costs the airline a couple thousand bucks per flight <S> so avoiding unnecessary fluid application is important in the long run. <A> Ice flying off the propellers can damage something, or someone. <S> Also unbalances the propeller assembly overall, leading to vibrations. <S> Little bit of ice left on the fuselage is not bad, only causes some extra drag until it sublimates off, and of course a little extra weight. <A> Ice on airplanes causes two main problems. <S> It adds weight and drag. <S> It changes the shape of the aerodynamic surfaces. <S> Problem 1 is fairly obvious. <S> How serious a problem it is depends on the airplane and how fully loaded it is. <S> If it is a problem, then ice needs to be removed from any or all surfaces to reduce the problem to an acceptable level. <S> If the plane is sufficiently over-powered or under its maximum gross weight, then this may be ignored. <S> Problem 2 is the main reason for deicing. <S> The shape of the wings, propellers, and tail are carefully designed to achieve the desired airplane performance. <S> (It may not be obvious, but propellers have an airfoil shape just as wings do.) <S> Any change in shape is inevitably detrimental. <S> If the shape of the propellers is affected by ice, then engine performance will suffer. <S> If the shape of the wings is affected by ice, then lift will suffer. <S> If the shape of the tail is affected by ice, stability and maneuverability will suffer.
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Ice Will impact the lift created by the wings, that is very bad, unless the ice is along the wing/fuselage joint, where it disrupt smooth airflow, altho probably just creating some more drag until it sublimates off.
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Why were the windows on the Concorde about the size of a hand? I just saw a comparison between the 787 and Concorde windows. I could be wrong but it almost seems like a hand could cover the majority of the window. <Q> The Concorde flew above 15,000m. <S> At this altitude a sudden reduction in cabin pressure would prove hazardous to crew and passengers with most falling unconscious within a few seconds. <S> The low air-pressure would also render the oxygen supply system inefficient and most passengers would suffer from hypoxia. <S> Thus we have the reason for the smaller windows <S> , should a breach occur then the size of the hole being small would reduce the rate if loss of air-pressure inside the cabin. <S> This, combined with a reserve air-supply to augment the cabin-pressure as well as a rapid rate of descent manoeuvre to bring the aircraft to a safe altitude would reduce the the risk of hypoxia. <S> So basically the small windows were designed to reduce the rate of air escape from the cabin should a hull breach occur. <A> The fuselage is a pressure tank, the window is a hole in the construction of the pressure tank. <S> Adding windows also adds weight: the pressure vessel construction must be reinforced around the hole. <S> The window glass is obviously airtight, but does not contribute in absorbing any of the stresses of the pressure differential. <S> The window size is a function of: <S> The pressure differential. <S> The higher the aeroplane flies, the larger the pressure differential between internal and external pressure. <S> The relative size of the hole, relative to the fuselage diameter, fuselage length, and aerodynamic bending forces. <S> For construction engineers, the best size of a window is zero. <A> Airflow Rate through an Orifice will help give some idea of the time it takes for the cabin of the Concorde to evacuate after one window blows at 60,000 feet as follows: Volume of the cabin: $50m × pi × 2m^2 = <S> 620 m^3$ , Diameter of orifice: <S> $0.15 m$ Rate of outflow from calculator software, averaged for pressure difference from T0 to T fully evacuated: around $150 m^3/min$ yielding roughly 180 to 240 seconds to full evacuation, without pressure equalization (reserve air-supply), with debilitating unmasked hypoxia sooner. <S> The location of the orifice (open window), on the side of the fuselage, could possibly cause even lower evacuation time values due to the Bernoulli effect of the passing airstream. <S> This underscores the point of view that strengthening the windows was indeed of critical importance. <S> Further examination of air replenishment capacity and emergency descent capability are in order, as newer versions of these supersonic transports may yet return to commercial use.
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The windows in Concorde must be smaller because the fuselage diameter is much less than that of a B787 while it must handle a higher pressure differential.
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Will the 737 Max 10 have MCAS? With the fuselage plugs forward of the wing, would this mean the engines are closer to CG, therefore no need for MCAS? <Q> The fuselage length is immaterial. <S> The problem of the Max series relates to the positions of the engines versus the wing , and their aerodynamic interference near the at high alpha. <S> The amount of fuselage ahead of the wing or behind the wing is not a major factor here. <A> The MAX 10 fuselage is also lengthened behind the wing: <S> In October 2016, Boeing's board of directors granted authority to offer the stretched variant with two extra fuselage sections forward and aft with a 3,100 nautical miles (3,600 mi; 5,700 km) range reduced from 3,300 nautical miles (3,800 mi; 6,100 km) of the -9. <S> Wikipedia: <S> Boeing 737 MAX 10 Basically the center of gravity of MAX 7,8,9 <S> and 10 is in the same location (range) in respect to the wing, or <S> mean aerodynamic chord (MAC) of the wing to be more precise. <S> As the engines are essentially the same in all MAX variants, and so is the location of them, the engine location from CoG is pretty much precisely the same. <S> The need for MCAS cannot be solely determined by CoG of MAX 10, as the longer fuselage may have some other effect on stability, but my personal guess is, some kind of maneuvering augmentation is necessary. <A> It looks like the 737 MAX 10 will also have MCAS: <S> The Boeing MAX 10 will contain an upgraded version of a flight handling system that has been seen as a key factor in both crashes involving casualties of 346 people. <S> The mechanism - the Maneuvering Characteristics Augmentation System (MCAS) - has been tweaked to give the pilot more control. <S> But regulators, including the Federal Aviation Administration (FAA), have yet to sign off on the changes. <S> "I'm honoured to take this aeroplane on its first flight and show the world what you've put your heart and soul into," 737 chief pilot Jennifer Henderson told the employees gathered for the debut of the first 737 MAX 10 at the company's Renton, Washington factory. <S> ( aviationpros.com , emphasis mine) <S> They only say MCAS, or Maneuvering Characteristics Augmentation System, is a flight control law implemented on the <S> 737 <S> MAX to provide consistent aircraft handling characteristics at elevated angles of attack in certain unusual flight conditions only. <S> ( boeing.com ) <S> without distinguishing between the different variants. <S> Their 737 MAX 10 page does not include any details on MCAS.
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As far as I could find, there is no official statement from Boeing on this.
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Has the "Foote takeoff" technique really existed, and how did it work? Reading The Crash Detectives: Investigating the World's Most Mysterious Air Disasters by Christine Negron, I came across the following description, in relation to some early de Havilland Comet accidents, notably G-ALYZ at Rome (Oct 26, 1952): Pilots were instructed to nurse the plane off the ground by raising, lowering, and then slightly raising the nose again at takeoff speed, a technique called the "Foote takeoff" I was quite puzzled by this. Has such a technique really existed? "Foote takeoff" returnedliterally two search results, one pointing to the book mentionedabove, the other to another book on the Comets. What exactly is the point/purpose of "raising, lowering, and then slightly raising" the nose? Why not simply rotating at VR? <Q> The 1952 takeoff accident <S> you read about <S> was piloted by Captain Harry Foote. <S> The technique got its name after the accident, which Captain Foote was blamed for ( Comet! <S> The World's First Jet Airliner , page 125). <S> Pushing the nose down is not standard though, rather a corrective measure to over-rotation past 6°. <S> The article quoted below covers the proper technique and the 1952 accident: <S> The B.O.A.C. Training Manual recommends the following take-off technique: <S> At 80 kts. <S> the nose should be lifted until the rumble of the nose wheel ceases. <S> Care should be taken not to overdo this and adopt an exaggerated tail-down attitude with a consequent poor acceleration. <S> (...) <S> Take-off tests by the manufacturers have shown that a constant 6° incidence of fuselage during the ground run gives good results for distance run and for climb-away behaviour. <S> They have also shown that an increase of incidence to 9° results in a partially stalled wing inducing high drag which appreciably affects the aircraft’s acceleration, and that the symptoms are noticeable to the pilot as a low frequency buffet. <S> The aircraft recovers from its semistalled position if the nose is pushed well down. <S> [emphasis added] (...) <S> It was the opinion of the investigators that the accident was due to an error of judgment by the captain in not appreciating the excessive nose-up attitude of the aircraft during the take-off. <S> ( flightsafetyaustralia.com ) <S> As @RAC said, V R didn't exist. <S> Judging by the historic FAA regulations , <S> V R and the takeoff speeds in general for Part 25 came about in the mid-60s. <A> At the time of the Comet disasters, Vr did not exist. <S> The problem was that the low thrust of the early jet engines was easily beaten by the drag of a wing over-rotated early in the takeoff run, and the airplane would run off the far end of the runway in a non-accelerating nose-high attitude. <S> So the Foote technique was a way of taking the weight off the nose wheel in a consistent and calibrated way, and to not over-rotate. <A> "Naked Pilot" by David Beaty suggests that this technique was introduced by engineers following Foote's accident. <S> Behind the scenes, BOAC and de Havilland were worried too. <S> The manufacturers had been doing further tests and a new take-off technique was introduced. <S> The nose-wheel had to be lifted off the ground at 80 knots, but afterwards it had to be placed on the ground again - a most extraordinary manoeuvre. <S> Beaty's piece suggests the technique was an incomplete attempt to salvage the Comet without really understanding the issues involved in the crash.
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The standard takeoff technique was what was used on all previous airplanes - line up, release the brakes, apply full power (derated thrust did not yet exist), accelerate, apply some back pressure to take the weight off the nose wheel, start feeling the airplane off the ground.
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Is the F-16 cockpit pressurized? Is the F-16's cockpit pressurized? If so, why does the pilot receive oxygen from the mask (please state the correct terminology for this)? Is it due to redundancy in case cabin pressurization fails? <Q> Yes, the cockpit of the F-16 is pressurized. <S> However, there are two types of cabin pressurization: Isobaric Pressurisation: <S> The system maintains a constant cabin pressure (usually between 2000 and 8000 ft) as the atmospheric pressure decreases. <S> This is used in commercial aircraft. <S> Hypobaric Pressurisation: <S> In such a system the pressurisation commences at a given altitude and cabin altitude is maintained at this value until a preset pressure differential is reached. <S> With continued ascent the pressuredifferential is maintained. <S> This is used in military aircraft including the F-16, as the weight penalty of the Isobaric system would seriously affect the range. <S> Provision of supplemental oxygen in the aircraft ensures that the occupant receives increasing quantity of oxygen in the inspired air. <S> The aircraft oxygen system (regulator assembly) ensures that the correct percentage of oxygen is added from the on-board Oxygen reserve to the inspired air in order to maintain lung pO₂ at 103 mm Hg. <A> Source: F-16 Flight Manual (T.O. GR1F-16CJ-1) <S> It is pressurized <S> yes. <S> Above you can see the schedule. <S> Note that at high altitudes the cockpit altitude would be considered high (low pressure) and insufficient to avoid hypoxia. <S> If the oxygen system (OBOGS) fails, the procedure is to "Descend to cockpit altitude below 10,000 feet", which is about 24,000–26,000 feet based on the pressurization schedule. <A> Yes. <S> Like most fighters the cockpit of an F-16 is pressurized, primarily for pilot comfort. <S> Use of an oxygen mask is required equipment for high altitude operations and for emergency situations.
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The pilot has a pressure breathing on demand oxygen mask, which is required equipment for high-altitude operations.
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