Gentlemen,

My Great Planes, PT40 flies with a tail down attitude. The balance has been checked and if anything, the model is slightly nose heavy. The experienced flyers in the club have advised me not to fly this model as it wallows and is hard to control. The engine is an OS 46 LA that can be leaned out to about 11,000 RPM. In a nutshell the model appears tail heavy and equipped with an engine with NO power; the prop is 10X6. It appears like the after part of the airplane doesn't want to fly. Any suggestions?

Check your wing incidence against that of the stab.

Well, I fly a PT-40. Goes beautifully, with an OS46LA as well. For what it's worth, I have an APC11x5 up front. Inverted, loops, stall turns, hammer-heads, everything you would expect from a trainer, and a lot more. The only time the plane feels "tail heavy" and "wallowy" is when inverted... which is no surprise for a flat-bottomed wing.

So, I can happily say that your plane is not behaving as it is supposed to, which means that it can be fixed... only I wish I knew how to do that.

gus

Did you set up aileron differential when you built it. Mine drug its tail through the turns until I added differential to the ailerons. If it is flying tail low in straight flight minn is right check your incidence.

If it is perfectly ballanced at the CG (about 4 1/8 from the LE of the wing), and all other things seems to be in order I can think only about 2 things:

1. (easy) try to trim elevator a little bit - just to see if it hels in any way.
2. (hard) is it possible that the firewall is NOT PERFECTLY perpendicular to the "ground" or may be engine is mounted slightly tilted upwards? If tis is the case I guess I would advise the same thing the guy from the club told you - do not fly this model until you can somehow fix this problem.

Good luck!

You can try a 10x5 or 11x4 prop, it might help.

But I agree with Minn, check your wing and stab incidence. Also check the thrustline of the engine compared to the wing and stab as ekrcflyer suggested. I don't know for sure in your case, but most trainers should have tad of down thrust.

Double check your CG on the wing. If your wing is somehow too far forward, and the CG mark is on the fuse, you can wind up tail heavy.

Check your ailerons for too much reflex or droop. This could easily cause the problem.