Why or how do flaps increase the curvature of the wing? Do they alter the curvature of the upper surface of the wing?
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1Possible duplicate of Why and when to use flaps? – Simon Aug 08 '16 at 17:50
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Nope it doesnt answer my question there...i want to know how do they increase the camber of a wing? – Karim Elshawarby Aug 08 '16 at 18:00
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is it because they are designed with a camber so that when they are attached to the wing there will be two curvatures or two cambers of the wing which will increase the wing camber? thats why? – Karim Elshawarby Aug 08 '16 at 18:02
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Welcome Karim! Is that what you want to understand? – mins Aug 08 '16 at 18:06
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1@mins link is not working – Karim Elshawarby Aug 08 '16 at 18:14
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@mins Try clearing your cache, still not working for me. – Ron Beyer Aug 08 '16 at 18:16
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There's actually numerous different kinds of flaps. Not all of them increase camber. If you're talking about the ones at the rear of the wing on most airliners then that's a Fowler flap. And they do increase camber because they are angled downward – TomMcW Aug 08 '16 at 18:32
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1@RonBeyer & ymb1 the image works fine here (also before) – Federico Aug 08 '16 at 18:54
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@RonBeyer Link works fine for me, too. – reirab Aug 08 '16 at 20:22
1 Answers
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Flaps change both the camber of a wing as well as its chord line and angle of attack. All the following images were taken from this article.
You can see the camber line here in a retracted scenario:
And here in an extended scenario:
As for the why, flaps are generally used to allow you to slow an aircraft down at a give pitch angle. This allows the pilot to pitch the aircraft down without an increase in speed. Generally a pitch down (given no other things are changed) will result in an increase in speed.
Flaps also change the angle of attack of the wing as well as the chord line:
All of this is a bit of an over generalization as there are many types of flaps and it's worth looking into the different types and how they operate.
Dave
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2Not only to slow the plane down but also to provide greater lift at a slower speed. On short-runway takeoff, for instance. – Raydot Aug 08 '16 at 22:28
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Regarding the change in angle of attack, lift is roughly proportional to the angle between the relative wind and a "zero lift" line which is usually not the geometric chord of the wing. Wouldn't it be more interesting to consider how much the direction of "zero lift" changes, rather than how much the direction of the geometric chord line changes? I think I recall from somewhere that the zero-lift direction changes more than the geometric chord does. – David K Aug 09 '16 at 00:26