Why and how do flaps increase the curvature of the wing?

Why or how do flaps increase the curvature of the wing? Do they alter the curvature of the upper surface of the wing?

• Possible duplicate of Why and when to use flaps? Aug 8, 2016 at 17:50
• Nope it doesnt answer my question there...i want to know how do they increase the camber of a wing? Aug 8, 2016 at 18:00
• 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? Aug 8, 2016 at 18:02
• @mins link is not working Aug 8, 2016 at 18:14
• @RonBeyer & ymb1 the image works fine here (also before)
– Federico
Aug 8, 2016 at 18:54

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.

• Not only to slow the plane down but also to provide greater lift at a slower speed. On short-runway takeoff, for instance. Aug 8, 2016 at 22:28
• 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. Aug 9, 2016 at 0:26