Let me start off by saying hi !
Okay. I'm not quite sure how to explain this, so bear with me. On rare occasions, such as today, I will takeoff from any planned airport, and while ascending or at cruising altitude on a valid flightplan (as far as I know), the plane (ranges from different types, this time a 737-700) will trim full left, then full right. It will then try to correct itself by trimming full left again, then full right to fix that mistake. It almost seems as if two lines of code are contradicting with each other. When says go left... the other says to go right, ultimately flying me in a straight zig-zag... wasting a ton of fuel. Now I don't mean the aircraft will bank 30 degrees, but more like 10 degrees or less each time. Yet it keeps happening. When left trimmed, it will be maybe 6-7 seconds when it is full right trim, then back to left all over again.
I tried fixing this by switching off Nav Hold, then using heading. Then I went back to nav hold. All the while, the plane is set to follow GPS not NAV. Then I disengaged both Nav Hold and Heading, and corrected it manually until I was steady and on course. I re-engaged Nav Hold, then the plane continued to trim right/left!!! Of course, frustrated, I disengaged master-autopilot, corrected everything, re-engaged master-autopilot and everything else... same thing. Any ideas on the situation? If so, how can I fix it?
Thanks in advance.
Joe.