Thread: Question Understanding flaps
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Old Nov 10, 2012, 06:41 PM
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Originally Posted by ciurpita View Post
why does a flap, or any trailing edge device creating a concave airfoil shape, cause an increase in the max CL?
In the table I posted yesterday the one labeled "plain flap" is also called a "camber flap". It's just modifying the airfoil camber. As with an airfoil with too much aft camber dropping the flap very far causes separation and high drag. Generally you get lift and drag increasing linearly up to some angle, about 30 degrees IIRC, and larger angles of flap deflection cause the drag to increase much faster than the lift because of separation.

A droop nose is also a camber changing device.

Properly shaped slots anywhere on the wing are stall delaying devices. That's why the various slotted flaps can be deflected to larger angles and produce larger lift increments.

Sorry I don't have time to explain all the columns in that table. However you know most of the notation so can figure a lot of it out on your own. Just remember that delta is the algebraic symbol for rate of change

when near stall, would moving a aileron down induce a stall, or like a flap, increase lift as well as increase the max lift coefficient, avoiding a stall?
Yep, that's why full size pilots are trained to turn with the rudder when close to the ground and slow

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