Yes you have it correct. The idea is for the upward moving ailerron to travel further than the downward moving aileron. The purpose is to minimise adverse yaw, inwhich the downward moving aileron causes more drag than the upward moving aileron. This in turn causes the airplane to yaw away from the direction of the turn. And it is this which gives the airplane that awkward staggering look during a turn.

What is involved in using that round arm for a single servo aileron setup is causing the differential by deliberately drilling pushrod holes not straight across at ninety degrees as in most cases but drilling holes for the two pushrods (in the case of a high wing airplane) forward of that line straight across so the pushrods are a little longer.

This geometry will induce aileron differential (more up than down) and this in turn will minimise that adverse yaw so your turns will be a lot prettier.

Of course this is also commonly done now with two aileron servo setups in the transmitter electronicaly and folks are forgetting these old mechanical setups which work just as well.

If you want to do this mechanically on a low wing with one aileron servo the opposite is done with pushrods shorter to not quite be lined up ninety degrees to the output bushing.

Sounds complicated but its really pretty simple, just kind of difficult to explain without a diagram. I think I still have an old photo somewhere showing this on a trainer somewhere and will see if I can find it.


John