[Pat Schmitz]

Looking to see if any of you have ever experienced this problem?

Today, while finishing up the last hours (!) of my required 25 hours dual for insurance coverage in my 73' T337G, I experienced a problem w/ my trim.. upon reflection of other events earlier in the day, I realized that this had been 'building' for several hours unnoticed.

On my last takeoff - as usual, I set the trim to the takeoff position, and flaps to 1/3 as recommended by my 337 instructor.. When I reached 85 for rotation, I immediately realized that the plane had a tremendous amount of Nose Down trim...things did not feel right at all, and I had to apply a lot of back pressure to keep the nose pointed in a climb attitude.. In spite of the takeoff trim position indicated on the indicator, I immediately applied nose up trim to attempt to correct the problem. It helped. I carefully made my way around the pattern and landed without further incident. On the ground, we tested the trim, to find that it would go into full nose down trim when the indicator shows 'takeoff'. Eventually, we concluded that the trim would travel to full nose down, and back to Neutral - but had no ability to travel to the nose up position. The trim tab just stops at the neutral position (Even though the indicator on the panel moves the full range.)

We removed the access panels on the right tail boom to inspect the trim motor and cables - all looked fine, tension, etc...

Then, I realized that on two occasions while flying earlier in the day - I had set my autopilot for a 500ft/min climb (which the autopilot normally maintains w/ no effort) only to see it goto a 1000+ ft/min climb attitude.. Since this did not 'feel' right to me, and I wanted to avoid getting too slow, I disconnected the autopilot - reestablished a manual 500ft/min climb attitude and just assumed that the autopilot did not 'catch' the climb rate I had set it at.. I now realize that this was related to the same trim problem, as the AP uses the trim to maintain pitch.

My plane is grounded (by me) at a distant airport, and I want to get a grip on what is 'likely' to be the cause before I let a different mechanic who has no 337 experience touch my plane. I could probably fly it back without using the trim to my home airport, but I don't want to take ANY chances. Who knows what is wrong, and how that might affect elevator and rudder control???... I don't want to take any unneccesary chances..

Is there another bell-crank, or push/pull location up in the Wing, or forward boom?? It seems like it 'pulls' the trim from one direction, and probably 'pulls' it back from the other (rather than push..) Given that, I am assuming that the other end is where the problem is located..

Let me know if any of you have ever experienced this problem, and how you came out..

Thanks!!