Questions tagged [flaps]

Surfaces that extend from the wings to increase lift, allowing flight at slower speeds (such as for takeoff and landing).

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2answers
131 views

On large aircraft, why do flaperons not run the full length?

This is a 777 flaperon. It looks rather tiny, compared to the flap. There have been air disasters where the airplane rolled uncontrollably for one reason or the other. It seems to me that a larger ...
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2answers
63 views

How do airplane designers determine flap deflection angles for flaps of various % wing chords?

How do airplane designers determine flap deflection angles for flap chords of various % wing chords? E.g. flap chord of 30%, 40% or 50% of wing chord. I understand most flaps' chords are about 25% of ...
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1answer
3k views

Why not always take off with 10 degree flaps in a Cessna 172?

10 degree flaps increase our lift, reduce stall speed, reduce ground roll. Seems like all advantages with no disadvantages. So why does the Cessna 172 POH say normal take off is 0-10 degree flaps? Why ...
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0answers
114 views

How can a designer deal with a strict requirement when designing an aircraft?

I'm working on designing an aircraft with some specific requirements (Vstall, Vmax, Ceiling, Payload, Range, RoC, Slanding/takeoff etc). I'm following Anderson's and Raymer's ways (trying to find the ...
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1answer
155 views

At which point in scale reduction do slats and flaps become unnecessary?

Imagine some Fi-156 Storch, and reduce its scale down gradually to 10cm span. Let's assume full scale Fiesler Storch is 100% efficient at, for example, minimizing stall speed. During this reduction ...
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5answers
433 views

How does retracting flaps help extend the glide of an aircraft?

As per the video from Smithsonian channel BA flight 38's captain retracted the flaps of the Boeing 777 by 5 degrees to extend glide, to travel further. Why?
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2answers
129 views

Does the flap settings for the best lift/drag ratio change with speed on the Diamond DA20-A?

As I've recently started time building in DA20, I've noticed the AFM suggests flaps at T/O for a glide. Being very intrigued by this I run across this post. Although I appreciate Peter's reply that ...
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4answers
471 views

How do slats actually work?

I want to know what is the difference between slats and flaps and the mechanism of the slats This what I know and researched about flaps: Flaps are a kind of high-lift device used to reduce the ...
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4answers
5k views

Why are heavy flaps better than just a bigger wing?

Flaps increase lift during landing and T/O. But when retracted, they do nothing. The space needed to stow the common fowler flaps can't be used for anything else - fuel or structure. Extended flaps ...
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4answers
250 views

Why do flaps retract?

Why do flaps retract? I know, it might seem obvious at first, because of drag, but instead of retracting the flaps, can't they just make the flaps flexible enough to get into a reduced drag position, ...
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1answer
152 views

Does leading-edge droop increase or decrease lift, other things being equal?

Consider a conventional subsonic airfoil in level flight. Typically it is cambered and with a small positive incidence, both of which features contribute to lift. Now droop the leading edge, as with ...
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7answers
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Is lowering V1/VR (and runway length required) the only reason for flaps at take off?

I've read that some aircraft (examples include the Saab 340 and the Fokker 100) can perform flapless take offs, provided there is enough runway available. It's also my understanding that, in terms of ...
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2answers
476 views

A320 flap settings

Can anyone please explain about the 5 types of A320 flap settings - Up, Flap 1, Flap 2 and FULL. What do these mean? I've read that the A320 gives 2 outputs for the corresponding flap settings. What ...
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2answers
420 views

Do MD-11 pilots ever use flaps 50?

I'm curious if there is ever a purpose to use full flaps like that? Was it a bit of an overkill?
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5answers
516 views

Can thrust vectoring be used to enable the use of flaps on canardless tailless delta-winged aircraft?

I'm considering flying wings as well as airplanes with only vertical stabilizer for their compact size, efficiency and high speed. As I can't find a working example of such scheme, theoretical ...
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1answer
258 views

Why does lift curve slope increase when Fowler Flaps are deployed?

Below is an image for a Fowler Flap: Notice that as the flap is deployed, both the camber and the area increase. This change in wing shape modifies the lift curve as follows: (source: Development of ...
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1answer
54 views

What does the lift coefficient take into consideration for flaps?

Angle of attack increases lift for two reasons, Camber and increased flow deflection, What reason does the lift coefficient use? Both?
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1answer
2k views

What is the difference between an aileron and a flap?

I have already been searching Google for the difference between an aileron and a flap, but I am not much satisfied, so now I am asking here on SE. What is the difference between an aileron and flap? ...
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1answer
383 views

Why do Boeing planes have more flap settings than Airbus planes? [duplicate]

The Boeing 737 and Airbus A320 are similar in size and performance. They are direct competitors. Boeing seems to have eight flap settings (1, 2, 5, 10, 15, 25, 30, 40) whereas Airbus seems to have ...
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2answers
3k views

What does “speed checked” mean?

Here is a Scenario: PF: Flaps one. PM: Speed Checked, Flaps one. What does that mean and why do they have to say "speed checked" every time?
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1answer
134 views

Does deploying flap change the aspect ratio of the wing?

Specifically when a Plain flap is defleted the geometry of the wing will be altered (Camber is increased). Does this have any effect on aspect ratio? What's the connection between Camber and aspect ...
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2answers
3k views

Why are Krueger flaps called flaps and not slats?

I always thought that flaps are trailing edge high lift devices and slats are leading edge high lift devices. This is also confirmed by the accepted answer for What is the difference between flaps and ...
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2answers
2k views

Is it right to extend flaps only in the white arc?

If the cruise speed is >80kts on the downwind leg but I can only extend flaps in the white arc, am I right in saying I need to get to the white arc, even if I'm on - for example - 100kts? For ...
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8answers
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Could flaps be raised upward to serve as spoilers / lift dumpers?

I should preface that I'm by no means an aviation person. I'm just in a aircraft knowledge obsession phase and daydreaming about designing my own ultralight (will never happen). The idea would be to ...
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1answer
296 views

How beneficial are flaps when landing with a tailwind?

I understand that flaps are devices used to increase the amount of lift and drag. When landing with a tailwind your groundspeed will be higher. Therefore, flaps would help reduce this groundspeed, ...
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3answers
1k views

How does the A350 variable camber system decrease drag?

Just curious how the A350 reduces drag/fuel burn by extending the flaps ever so slightly during cruise. Everything I've read about extending flaps says that extending them pushes the centre of ...
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1answer
318 views

What is this loose object above the flap fairing? [duplicate]

During my flight, I noticed a loose object above one of the flap fairings. You can see it in this video: https://imgur.com/wCPSEem. Is it normal or should I notify the airline? People pointed out to ...
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1answer
276 views

Would adding a slat and a slotted flap increase the max CL of a multi element airfoil to 6.5?

Would adding a slat and a slotted flap increase the of a multi element foil to 6.5? I understand, as a general rule, the max $C_L$ for a classic NACA airfoil is as follows: Base: 1.5 Slat: + 0.7 ...
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1answer
3k views

What happens to Cessna electric flaps that are moving when power is lost?

On final in a C182T you move the flap control arm from 20 to FULL, and when halfway there, the breaker pops (or BUS1 fails, a wire falls off, etc.) Does the flap stay where it is, slide back to 20°, ...
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2answers
4k views

What is the reason for setting flaps 1 on the ground at high temperatures?

Yesterday I've seen an A320 standing at the gate with flaps 1. While this question answers, why the flaps should be up, is there any reason to retract the flaps to 1 instead of up? In addition it ...
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2answers
1k views

Why doesn't extending the flaps on a B-2 send it into an uncontrollable dive?

The Northrop-Grumman B-2, a tailless-flying-delta-wing aircraft, has a set of flaps along its trailing edge, as seen (for instance) in this cutaway diagram: (Image from Funker530.) But tailless ...
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2answers
129 views

Are flaps a good idea for airfoils with a lot of camber?

I have a wing with an airfoil s1223 which is an airfoil with a lot of camber. the take off distance is limited so I want to implement flaps for this issue but I have the doubt if this is a good idea.
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1answer
465 views

Why does the DHC-6 pitch down when the flaps are retracted, rather than up?

Air Moorea Flight 1121 crashed because one of its elevator cables broke immediately after the pilot retracted the flaps, but before he could trim out the resulting pitch-down moment - to quote the ...
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1answer
279 views

What is the name for a flap that increases the wing's area but not its camber?

Flaps are high-lift devices mounted to the rear portion of an aircraft's wing. Some types of flaps increase lift by increasing the wing's camber, or, at least, that of its lower surface (plain flaps, ...
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4answers
319 views

Could flaps replace spoilers by deflecting more than 90°?

Could flaps replace spoilers by deflecting more than 90° after touchdown?
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1answer
754 views

Why does the A320’s maximum allowable aileron deflection decrease, rather than increase, when the flaps are extended?

According to this answer to why the A320 uses mainly spoilerons for roll control during landing, rather than conventional ailerons, the ailerons can’t extend as far when the flaps are extended, for ...
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1answer
605 views

Is it normal procedure to lower flaps at high altitudes?

I was flying on a Boeing 747-800 today and the pilot opened up flaps at high altitude. This caused sharp descend for about 5 seconds ( Causing slight panic onboard ) , the pilot leveled the flaps ...
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1answer
750 views

What are possible causes for the flaps not deploying on a Cessna 172?

I would like to seek some expert opinion on why my flaps failed to deploy when I took it to Flaps 20. I was turning from Downwind to Base when I took flaps 20 and noticed that my speed was creeping ...
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2answers
1k views

What is this unusual leading edge flap on a B737-200?

On this video of Air North's gravel runway-equipped B737-200, there's what appears to be a small leading-edge flap (Krueger flap?) inboard of the engine. Refer to the screen shot below. What is this?...
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2answers
461 views

What flaps and throttle settings are used on takeoff, climb, cruise, descent, and landing? [closed]

What degree of flaps and throttle setting are used on takeoff, climb, cruise, descent, and landing? This question is for private and general aviation aircraft. I have looked everywhere for FAA manuals ...
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2answers
183 views

What backup systems are in place for flaps actuated by sliding block guides?

Looking at this video of a 737's flap extension, it looks like there is just one screw per side driving all of the flaps. Are there any systems in place that will allow the flaps to extend in the ...
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3answers
4k views

To flap or not to flap?

I am learning to fly an Ikarus-C42. The instructor I have recommends to all students that they land without flaps, because it is less to think about and because it gives you more airspeed, thus less ...
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1answer
583 views

Which photo more accurately represents Flaps 1 in a 737-800?

or A recent update in a sim craft changed the visuals from what I'm used to, but from my research it looks to be more realistic. This post clearly reflects the more extended option being more ...
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4answers
1k views

How does setting takeoff flaps improve aircraft performance?

A study guide I recently found indicates that Vmc and aircraft performance improve with takeoff flaps set. The Vmc improvement makes sense but the performance improvement does not. At a basic level, ...
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3answers
2k views

What does the extending the flaps do (or any high lift device) to the Rate-Of-Descent of an airplane?

I know that deploying flaps will increase both drag and lift, thus increasing L/D ratio. But how exactly does that correlate with the increase/decrease of the rate-of-descent?
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1answer
209 views

Is using flaps the same as increasing the AOA? [duplicate]

The purpose of trailing edge flaps is to give the aircraft more lift at lower speeds. But do simple flaps beneficent more than increasing the angle of attack? The image looks like part of the wing ...
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2answers
174 views

Why flaps can deflect up to 25°+ without stalling the wings? [duplicate]

According to this graph,plain flaps have their highest Cl at about 2 and stalls at about 15°,my question is how then do airplane flaps reach 25°+ of delflection when this gragh clearly states that ...
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2answers
120 views

Is the lift produced by a wing with a 10° flap equal to the lift created by a wing with 10° AOA but with no flap?

After reading this article I would like to know if the lift produced by a wing with a 10° flap is equal to the lift created by a wing with 10° AOA but with no flap?
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1answer
1k views

Where is the F-4 Phantom II's flap lever?

I'm trying to fly this fighter for the first time in X-Plane 11 but I can't seem to find the flap lever in the cockpit. Where is it on the real plane?
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2answers
706 views

Why is the critical AoA of most flaps 40° when most airfoils stall at 15°?

A plain flap deflected 40 degrees is largely stalled (...) Flaps stall at 40° according to an answer on Quora, why is this so when typical airfoils stall at 15°?