Help with determining flying behavior
Hi, everyone. I had been away from the hobby for 25 years and decided to get back into flying with a new GP PT-40. For the first flight I had an old KB .45 on the plane and had a good flight. The plane behaved well from flying characteristics perspective except for the fact that I had to use full down elevator trim to get the plane from continuously climbing at full throttle.
I had some issues with the motor so decide to upgrade to a new OS .46 AX II. Obviously a big difference in power output. The weight of the two motors was close but not exactly the same so I checked the CG. Originally with the KB the plane was very nose heavy, had to put the battery towards the very back of the electronics compartment and with an empty fule tank the plane was still nose heavy. The OS seems to be a bit lighter so the balance came out better, not quite as nose heavy. I flew the plane today and again had to supply full down trim to keep the thing from trying to continuously climb.
About 1 minute into the flight, doing the second circular track over the flying field I allowed the plane to go into a moderate dive still under power. I started to apply a modest amount of up elevator to pull the plane out of the dive and the nose snapped up so fast I can't believe the wing did not fold up! From there anytime I allowed to the plane to dive, when I applied even a small amount of up elevator the nose to pitched up so fast and ended up be pointing between 60-80 deg vertical. I decided there was something not right and brought it in for a landing. As the plane slowed down it's flying characteristics calmed down and I landed.
I checked the CG on the bench based on the markings I have on the wing (4 1/8" from LE) and the plane still showed nose heavy.
At this point I'm trying to figure out if the plane was behaving like this due to a CG issue, or if I simply was flying the plane faster than it should be going with this powerful motor on it. To a degree I would expect the plane to behave the way it did if it is tail heavy, which I don't believe it is, or if I was using a lot of control surface throw, which I'm not, I'm using the recommended beginning throw from the manual.
Would like to know what other people may think the issue is...hopefully I've overlooked something.
Thanks,
Matt