Originally Posted by ciurpita
not sure this question was ever really addressed.
in all other cases, the flaps or slats(?) change the airfoil shape into one that is concave while maintaining a unique trailing edge. But the split flap creates an airfoil with two trailing edges.
are split-flaps more like a spoiler, which decrease lift and increase drag, than flaps which increase the lift curve and max CL?
I would tend to think that they are Like a Drag Break while not Decreasing lift.