Or, I should say flaperons. Question is, at what point-degrees-do they become ineffective as ailerons. This is perhaps, an "it depends" question. Building a Fiesler Storch where the 1:1 has flaps and flaperons. I figure to start with 40 degrees max for the flaps, wondering where to max out the flaperons. Frankly, I have flaperons on a Pilatus Porter and don't see much use for the 'flaps', that is, no noticeable effect. Any ideas? Bill S.

The two models that I've used them on produced adverse yaw effects with as little as 10 to 15 degrees of deflection.

However if you use drooping ailerons in conjunction with flaps and keep the aileron droop to about 1/2 the flap action then the wing will have serious washout angles with full deployment and you may not see the adverse yaw effects.

And for pure landing drag I'd consider upping the flap portion to a full 80 to 90 degrees and use about 20 degrees flap droop in conjunction. Any more aileron droop than that and the adverse yaw will be back. Even then you'll likely need rudder used in conjunction with aileron to avoid adverse yawing.

If you have flaps, I suggest that you use them as intended & leave the ailerons to do their thing.

While flapperons can have impressive lift boosting properties, they often aren't great at slowing you down, and if deployed too far, they can be lethal devices. In addition to powerfull pitch changes, extreme adverse yaw and aileron reversal are some of the surprises waiting for you.


As to how much is too much -- you just have to suck it & see.