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30

Stays where it is. The mechanism is a leadscrew and like most leadscrews it's "self-locking", which means that it's held in position by frictional forces whenever the motor isn't turning and it can't be back-driven even by substantial loads. The 20 degree (etc) "stops" are just reference positions for which aircraft performance and load limit data have been ...


29

From the A320 Flight Crew Operating Manual (FCOM): And the image to text: On ground, hot weather conditions may cause overheating to be detected around the bleed ducts in the wings, resulting in “AIR L (R) WING LEAK” warnings. Such warnings may be avoided during transit by keeping the slats in Configuration 1 when the OAT is above 30 °C. (Emphasis mine) ...


22

Yes you must slow down to the white arc, or whatever your flap extension speed is for a given condition, regardless. If you are 10kts above the white arc and drop flaps anyway, it's not going to make the airplane come apart, and if you did it once, slap yourself on the wrist and don't do it again. It's putting stress on the flap attachments beyond what ...


18

Because there is a maximum deployment speed for things like flaps, gear extension (and sometimes retraction). Exceeding these speeds and using those devices can cause damage to control surfaces or other equipment. The speed check is there so that when the PF calls for flaps, the PM remembers to check the speed before performing the action.


11

A flap increases airfoil camber, and can be on the leading edge or trailing edge. The Krueger Flap is a Leading Edge Flap, the actual generic term. The Krueger dude developed the LE flap used on some airliners so his name is attached. A slot increases stalling AOA, without necessarily increasing camber, as in the fixed slots used on a lot of light ...


10

It depends upon what the manufacturer recommends on the form of the AFM in cockpit placards. Certain aircraft do allow extension of the flaps outside the white arc for certain flap settings. For example the Cessna 182T is placarded for 10° flaps at or below 140 KIAS, 20° flaps at or below 120 KIAS and 30° flaps at or below Vfe of 100 KIAS, despite the fact ...


9

An Aileron is used to control the roll of an aircraft. Ailerons are found on the trailing edge of the wing, typically closer to the wing tip. Ailerons will move in opposite directions to each other, as one goes up, the other goes down. Flaps are used to increase the amount of lift that a wing produces by increasing the camber and surface area of the wing. ...


9

One function of common inner span flaps that's not often discussed is stall management. Not only does some flap lower the stall speed, but it ensures the wing root stalls while the tips are still flying; this prevents an incipient stall from turning into a low altitude stall-spin if a wind gust or unplanned maneuver pushes the aircraft from "controlled ...


9

For an aircraft designed for cruising efficiency it is important to have as little trim drag as possible. See ATR 72 link: The wing may appear unusually small, but it is made to produce the needed lift at cruising speed at its most efficient Angle of Attack, where lift to drag ratio is highest. If the wing produced too much lift for level flight at its ...


7

You assume that the lower attack angle of the unflapped, aileron-containing portion of the wing should allow the ailerons to deflect further without stalling. but that only looks at the geometric angle of attack. What counts, however, is the induced angle of attack. Since the flaps on the inner wing create much more lift, the induced angle of attack is ...


7

Aside from the decreased takeoff speeds, there are a couple reasons why typical Part 25 aircraft do not allow flapless takeoff: There is usually a sweet spot at lower flap settings that generate the best climb gradient at V2, and it's usually not with flap retracted. It is typical to see several takeoff flap settings that cater to best climb and best field. ...


6

The BAe Jetstream 31 is one of a few aircraft that had a "lift dump" flap position after touchdown. It is not "more than 90°", but it is quite effective. (Jetstream 31 Lift Dump in action; YouTube)


6

One reason is that any device you want to use as a lift dumper needs to be able to be instantly retracted and this is really difficult to do with a flap. On an airliner when the lift dumpers come up, if you slam the thrust back up to TO, they immediately come back down. A flap system with its slow moving drive line can't do this, and it's enough that it ...


5

For a leading edge high-lift device to be called a slat, it has to have a slot behind it. Otherwise, it is a leading edge flap (or, if it's of a specific design, a Krueger flap). Because: By definition, the word slat means a thin, narrow strip. Its etymological roots lay in Middle English word slate, first recorded use in the aforementioned meaning dates ...


5

I don't think the flaps are used as high lift devices. Watch this video of a B-2 landing. Perfect view:


5

The Twin Otter isn't unique. Flaps have varying effects on different airplanes. Some pitch up with flaps extended, some pitch down. The pitching moment from flaps isn't just from the nose down moment from the increase in airfoil camber; it includes effects of increased downwash on the tail, which creates a pitch up moment, and to some degree, changes in ...


5

In addition to the previous answers, you could argue that yes: provided you had a long enough runway you could theoretically perform a takeoff run that accelerates you to a speed which is sufficient for taking off and remain airborne with no flaps (and for this exercise let's assume an A320 has a flaps-up speed of 210 knots, give or take), but you'd be ...


4

In principle yes. However, there are practical reasons which stand against this: The flap mechanism is already very complex with only 40° of deflection. Going further would make it even more complex and heavier. Spoilers, on the other hand, have a very simple mechanism: A simple hinge and hydraulic actuators are all that is needed. By sitting closer to the ...


4

I’ve been flying several types of Airbuses for the past decade and have never seen this kind of procedure before. There certainly is no such limitation in the manuals. In general, it sometimes happen that there has been such a practice in a previous aircraft type the company has operated and these kind of procedures carry on as best practices or company ...


4

Forget about tailwind/headwind for flap use. Flaps allow landing with a lower airspeed. And you always want a lower airspeed. The wind itself is irrelevant except that your groundspeed will be higher or lower depending on where the wind is, and which you always want to be slow as possible. On light aircraft you want to avoid tailwind components over 5kt. ...


4

Henning Strüber, one of the Airbus engineers behind this system, has written a paper on it. In cruise: This can be applied in early cruise phases to shift the center of lift more inboard and by that reducing the wing root bending moment, which can be transferred into a structural weight saving. A plane that can be built lighter will have lower drag [for ...


4

And some older Mooneys have infinite flap settings depending on how much you pump them up... The reality is that there are no regulations on how many flap settings an airplane must have and on an airliner that may also have things like speed breaks or slats as well, flap settings may vary by design or simply by engineering choice. Flaps are used for ...


4

Note that your plots show lift coefficient over angle of attack. This lift coefficient is referenced to a reference area which must be defined somehow. It is customary to use the projection of the clean wing area in the x-y plane for all flap settings in order to keep coefficients comparable. The lift curve slope increases because the real wing area ...


3

The aspect ratio of a wing is defined as: $$ \text{AR} \equiv \frac{s^2}{A} , $$ where $s$ is the wingspan and $A$ is the total wing area. Some types of flaps are not only increasing wing camber, but also the wing area: The Fowler, Fairey-Youngman and Gouge types of flap increase the wing area in addition to changing the camber. (Wikipedia) Since the ...


3

It’s a neoprene seal which may be a little loose there at the end like that and made to flutter by the flow of the boundary layer air around it. That’s a common part used sometimes around the edges of enclosures eg flaps, landing gear fairing doors, etc. 1) to prevent scuffing or abrading parts during operation and 2) to seal out boundary layer flow, ...


3

The theoretical maximum lift of a cylinder is 4π. At that point the forward and rear stagnation points coalesce on the bottom of the cylinder. Practical solutions use rotating cylinders (Flettner rotor) but will not reach this theoretical limit. This should illustrate that 6.5 is not outright impossible but the distance between a cylinder and an airfoil is ...


3

I assume the question means optimum climb speed. From the Boeing 737 NG FCTM (3.30 Takeoff and Initial Climb): V2 + 20 is the optimum climb speed with takeoff flaps. It results in the maximum altitude gain in the shortest distance from takeoff. Acceleration to higher speeds reduces the altitude gain. If airspeed exceeds V2 + 20 during the initial ...


3

Gliders have been doing it for decades. The Schreder HP-14 , has flaps that go all the way to 90 degrees (going more than 90 doesn't make much difference), producing nothing but drag at that setting, in place of traditional spoilers/dive brakes. Normal aircraft don't do it because the drag is so high it precludes going around and if you couldn't retract ...


3

No, for several reasons What you want is to compensate for the additional lift from downward deflected flaps at the back of a flying wing with vectored thrust. As @Sean points out this will not bring a noticeable net benefit if the lengthwise location of both forces is similar. But that is not all. Besides the force equilibrium around the flying wing you ...


3

The MD-11 has one of the highest approach speeds, which is comparable to the 747-400 (Boeing), while having higher wing loading: 806 vs. 756 kg/m$^2$. In other words, the MD-11's wing is small, so flaps 50 is not an overkill. The standard MD-11 landing flaps are either 35 or 50 depending on the weight, altitude, available stopping distance, etc. Aircraft ...


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