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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Can flaps on Airbus/Boeing airliners be deployed at high speeds during cruise, still?

Brief Background of the Incident Mayday Season 22 Features an Episode "Terror over Michigan" (Episode 6) based on the events of TWA Flight 841. The Episode revolves around a Boeing 727 ...
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1 vote
1 answer
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How do GA aircraft flaps stay in place?

On most small GA aircraft such as the well-known Cessna 172P "Skyhawk", the flaps are electrically actuated. Now - how do they stay at the setting selected by the pilot after extension ? Is ...
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1 vote
2 answers
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Is it possible to reduce the angle of fully extended flaps of an aircraft without affecting lift generated?

I think flaps are inspired from eagle feathers which increase the overall wing surface area and help provide the necessary lift at lower speeds. However, fully extended flaps hang lower and cause more ...
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2 answers
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Reasoning for an inboard flap- take off [duplicate]

so Ive been looking into airplane flaps, like the longer one for take off- Is it correct to say that the only reason to have one is for take off, to make it take off easier? And so when they take off, ...
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1 answer
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Elevator or Aileron?

I was just looking at an airplane take off, and when it was taking off, some flaps were facing down at the back of the main wings- Are these Ailerons or elevators please? I did some research but the ...
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2 votes
1 answer
132 views

How can I calculate 'Max aircraft Load Factor' and 'Max aircraft Speed' when flaps are fully extended on a civil aircraft? [closed]

I am trying to calculate the critical loading conditions for Flaps (in order use them inside my Finite Element Analysis to, determine if the Flaps will be able to bear these critical loads) during the ...
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3 votes
1 answer
107 views

Does use of flaps or ailerons affect the aerodynamic forces distribution on the wing area before them?

Assume I want to use the flaps or ailerons at a specific altitude for some maneuevers on an aircraft. We know that the overall aerodynamic forces like lift and drag on an aircraft wing will change ...
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15 votes
6 answers
6k views

Why aren't takeoff flaps used all the way up to cruise altitude?

In general aviation aircraft such as Diamond star DA-40, flaps to take-off are used until 500ft AGL and speed before retracting flaps is Vy (best ROC speed)-67kts and after retracting flaps is 80kts. ...
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Typical flaps/slats extension chord ratios?

Fowler flaps for example extend the chord of the airfoil by about 25%. So their chord ratio is C'/C = 1.25. Does anyone know similar values for other types of flaps, like double/triple slotted Fowler ...
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4 votes
1 answer
455 views

Is all the extra lift from flaps added upstream where the spars sit?

Flaps can significantly increase the lift for a wing, is all that extra lift added upstream where the spars sit? I ask this question because the flaps in airliners seem to be only connected by a few ...
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Does the A220-300 have krueger flaps or are all of its leading-edge highlift devices slats?

They look like slats to me, but I could be wrong. I'm asking because I know the 737, a very similar airplane, has inboard krueger flaps. Also, what number of slats/krueger flaps does it have?
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2 votes
1 answer
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What trailing edge flap design does the A350 use? Is it similar to the A380?

Both Airbuses have similar flap deployment based on some YouTube videos I have watched, just wondering if they both have the same flap design being "Single-Slotted Fowler Flaps".
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3 votes
1 answer
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How many Krueger flaps does the 737-700 have?

How many Krueger flaps does the 737-700 have? It has inboard krueger flaps, but I'm trying to make out if it has one or two.
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7 votes
2 answers
2k views

What flap design does the A380 use? Is it Fowler flaps, slotted flaps or a combination?

I have looked at maintenance manuals, the Airbus website, and Wikipedia but still could not find a definite answer as to what trailing edge flaps the Airbus A380 uses.
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2 answers
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What are the approach speeds for each flap setting in a Cessna 152?

I am still trying to understand how the approach speeds for different flap speeds work. I cant find it in the handbook but I want to know the different approach speeds for the following flap settings: ...
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2 votes
0 answers
116 views

How can I design a slotted flap?

I have not been able to find satisfactory methods on design of slotted flaps, or flaps in general. Most of the answers are about eyeballing or experience. Can you guide me on what could be good ...
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Comparison between Split and Slotted Flaps

Question 4: As we know, the more complicated design of high lift systems, gives us more maximum lift @ takeoff, such as slotted (single - double) or fowler flaps type. Beside the point of view of ...
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2 votes
1 answer
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Why does the Information Manual say "C172S - Flaps 10 (Preferred) for Normal Takeoff", when the models before S-model do not have this note?

Do Flaps 10 really do anything performance-wise other than reducing ground roll and distance over a 50-foot obstacle? If not worried about clearing an obstacle, does a Flaps UP-normal takeoff make ...
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2 votes
1 answer
133 views

Who manufactured the 737 MAX flap track fairings?

I can't seem to find the information online, would anyone of you know where / by who the flap track fairing for the B737 MAX is produced?
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Is pitch-flap coupling an aerodynamic effect or an intrinsic property of a delta 3 offset?

I am modelling a propeller, in particularly the equations of motion of the various pitch/lag/flap angles as the propeller is turning around. The blade includes a $\delta_3$ angle, which provides pitch-...
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9 votes
6 answers
2k views

Can flaps be used to perform rotation and flare?

TL; DR using flaps to directly control sink/climb rate near ground = simpler and faster response = easy to fly airplane? Rotating is the pitch up during takeoff that causes the aircraft to leave the ...
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2 votes
2 answers
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Is there a cockpit indication if the B737 flap load relief is not working properly?

On a 737, does the pilot get any cockpit indication that his Flap Load Relief is not working properly? Say for instance due to a Flap Lever Position Switch failure?
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Why does it feel like a plane stops in mid-air during approach?

At some stage while on approach to an airport in a commercial jet, it feels like the plane is almost coming to a complete stop in mid-air. Is this maybe as a result of the flaps engaging or the ...
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7 votes
1 answer
484 views

Is it safe to fly if the flaps won't retract on ground?

The Piper Archer (PA-28) i had this morning had issues returning flaps to normal after being fully extended ON THE GROUND. It required a non trivial amount of push on the air-frame itself to restore ...
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Is flap-asymmetry protection on airliners still active even on the ground?

On aircraft with flaps, a general certification requirement is that it must not be possible for the aircraft to suffer a loss of lateral control secondary to an asymmetric-flap condition. This ...
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3 votes
1 answer
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Are overwing exits still useable if the flaps can’t be lowered?

Essentially all narrowbody airliners (except for the very smallest propliners), and many widebodies as well,1 are equipped with one or more overwing exits for use in an emergency evacuation; these ...
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18 votes
1 answer
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Why is the DC-9-80 ("MD-80") prohibited from taking off with a flap setting between 13 and 15 degrees?

A bit of digging into the 7Z9363 accident investigation has brought up some interesting information regarding the DC-9-80 ("MD-80")'s flap system: Flaps may be positioned in any of the six ...
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5 votes
1 answer
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Why is there an altitude limitation on operating the slats/flaps on the A320?

As per the FCOM limitations chapter there is an altitude limitation of 20000 feet for operating the flaps/slats on the A320? Why this specific altitude?
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What is the temperature of flap linkages during takeoff and landing in passenger and fighter aircraft? [closed]

During takeoff and landing, what is the temperature of flap linkages in passenger or fighter jet aircraft?
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0 answers
51 views

How can the flap deflect to higher angles (than the wing) without experiencing loss of lift? [duplicate]

For a simple aircraft wing, assume the stall angle of attack of this wing is 16 degrees. Now, if I use the same airfoil as used in the wing for the flaps, I am able to deflect the flap at quite ...
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2 answers
355 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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0 votes
2 answers
311 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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14 votes
4 answers
7k 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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0 votes
0 answers
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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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1 vote
1 answer
184 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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1 vote
5 answers
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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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2 votes
1 answer
688 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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2 votes
4 answers
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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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25 votes
4 answers
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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3 votes
4 answers
575 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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2 votes
1 answer
199 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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18 votes
7 answers
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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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0 votes
2 answers
2k 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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1 vote
2 answers
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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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3 votes
5 answers
708 views

Can thrust vectoring be used to enable the use of flaps on 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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4 votes
1 answer
799 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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0 votes
1 answer
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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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4 votes
1 answer
7k 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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5 votes
1 answer
709 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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7 votes
2 answers
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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