DA42 ailerons
 

I have noticed that when flying straight & level in DA42s that the upper surface of both ailerons is not quite parallel with the corresponding upper surface of the wing. It would appear that both the ailerons have been adjusted to a permanent upwards deflection of about 1-2º. The "misalignment" is small, but is just visible in the photo. Since noticing this for the first time about six months ago, I have flown a handful of other DA42s and they have all been the same, so I believe that it is like this by design, rather than just a manufacrturing fault.

Does anybody know why? All I can imagine is that it provides crisper initial roll control because the ailerons get better purchase through the boundary layer at the trailing edge of the wing. Possibly also it is to help reduce adverse yaw in the turn - though the DA42 already has differential ailerons this seems less likely.
http://img822.imageshack.us/img822/1...0207142133.jpg

Check the book for the rigging limits. If both should indeed be rigged a tad up it could be to help reduce any tip stall tendency or to make the winglets more effective or to change the spanwise loading or etc etc

or help the old dogs go a bit faster. :E

It's well known fact, on some aircraft at least, that a small amount of reflex on the aileron rigging gives an extra knot or two.

I have noticed this too on the Airbus A319/320/321, in many hours of staring out of the window. :cool: