Originally posted by cappio777:
Because engine and prop specs are the only varying factor after the airplane is built according to the plans, the downward forces created by downthrust are also going to vary. Thats why what Rodney and Dalolyn said is very important and necesary specially on a trainer aircraft. Since the airfoil will create different amount of lift at different airspeeds if the downthrust is not compensated properly the trainer will tend to balloon on every change of airspeed. Therefore the beginner will be overcontrolling the airplane at all times.......trying to keep it straight and level. That defies the purpose of having a trainer. A little work doing the downthrust early and the rest of the time is just for enjoyment of your plane not to constantly keep trimming everytime you go flying.
You guys are making this seem way too complicated for a beginner. Most high wing trainers will tend to climb a little when the throttle is opened because of positive wing incidence, their made that way on purpose. I have helped lots of new comers at our field with new trainers and have ALWAYS been able to trim the plane in-flight to where it handles just fine. Most "ballooning" problems on a trainer are caused by too much elevator travel and over controlling.