The (Trainer) plane like the popular Nexstar Trainer is disigned for the new pilot who has never flown an RC plane before.It has a flat bottom wing with alot of wing area. The trainer is disigned to teach the new pilot how to make left & right turns or roll, less sensitive pitch up and down on elevator movement, and Yaw or up and down with the elevator. When combining all three movements along with the forward thrust (engine) makes the trainer less sensitive and the pilots sucsess in comleteing his first solo flight (without an instructor) much more suscessfull and less stressfull.
Well I tried to best explain a trainer planes function, and Im sure you get more opinions to follow.
NEDYOB