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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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    $\begingroup$ Possible duplicate of Why and when to use flaps? $\endgroup$ – Simon Aug 8 '16 at 17:50
  • $\begingroup$ Nope it doesnt answer my question there...i want to know how do they increase the camber of a wing? $\endgroup$ – Karim Elshawarby Aug 8 '16 at 18:00
  • $\begingroup$ 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? $\endgroup$ – Karim Elshawarby Aug 8 '16 at 18:02
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    $\begingroup$ @mins link is not working $\endgroup$ – Karim Elshawarby Aug 8 '16 at 18:14
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    $\begingroup$ @RonBeyer & ymb1 the image works fine here (also before) $\endgroup$ – Federico Aug 8 '16 at 18:54
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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:

enter image description here

And here in an extended scenario:

enter image description here

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:

enter image description here

enter image description here

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.

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    $\begingroup$ Not only to slow the plane down but also to provide greater lift at a slower speed. On short-runway takeoff, for instance. $\endgroup$ – Dave Kanter Aug 8 '16 at 22:28
  • $\begingroup$ 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. $\endgroup$ – David K Aug 9 '16 at 0:26

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