4 will do you. or 6 youll need if you have duel ailerons

i use JR so mine's like this

1. throttle
2. ailerons (right if duel ailerons)
3. elevator
4. rudder
5. nothing (ratracts are stoopid on a 3Der)
6. left aileron if flaps are mixed

if i go duel elevaotr (like on my new yak) i use ch3 as right elevator, and channel 5 as left

Ian