The flaps of the MD80s seem to have two sections as these pictures show:
Photo © Niksa Radicevic - CroSpotterTeam
Photo © Dion Fuchs
Photo © ChW - Aviapix Worldwide
They look to me as if each section were on a different sweep angle of the wing, the inboard section being at a lower wing sweep angle, and the outboard at a higher one. If this is true, I don't see how the flap sections will go to the up position without interfering with each other. The flap hinges appear to be not colineal, and if so I don't see how the flap sections can be joined by that riveted patch and still go up and down together. Does anyone know what I'm missing here?
If it is not clear, please let me know and I'll try to do a drawing. Thanks in advance!