Hi, there is some 9 pin connector on the inside of the wing of a Sukhoi model I saw; it is on the fuselage side of the detachable wing. Is that for the wing servo connections? is it a common thing to do?

thanks.

Sounds like a jr matchbox to me. It's pretty common on wings with multiple servos for each side. You use it to match the end points and travel for each servo etc.

very commonly used on large thermal gliders. very simple and neat. plug the wing on and the servos are connected.