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KFC 150 Autopilot Trouble


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So recently, on a very long series of flights the following occurred:

From LKU to MMJ, my M20J 201's auto-pilot was tracking on course to a VOR waypoint via the Garmin 530W. All of a sudden, the autopilot banked the aircraft to the right on a standard-rate turn off course nearly 60 degrees before I disengaged the autopilot to correct the course heading. I reset the FD and had the same problem. I had to turn off the autopilot all the way, wait a few minutes while hand flying in IMC, then turn the autopilot on again. It worked for the remainder of the flight.

From MMJ to Lansing, IL, the autopilot worked flawlessly.

From Lansing, IL to MMJ, something weird happened. First, the aircraft started a nose-down attitude and the autopilot disengaged with a beep. I went to turn the autopilot/FD back on and it would not turn on. I looked over to the circuit breaker and it was popped. Cautiously, I pushed the breaker back in and turned the autopilot back on. The autopilot now began to porpoise with the altitude hold on. It was almost like the FD was overcompensating for what it normally makes as slight adjustments in pitch and trim. I didn't seem to have any trouble with the autopilot following the nav course, but once I set the FD to hold an altitude, forget it. Up and down. Each up and down worse than the last. It was a bumpy day and I had to hand fly all the way back to New Jersey and then to Virginia. It was exhausting.

Has anyone else encountered the same problems?

My theory is that the pitch servo clutch finally went. At the same time, it doesn't explain the drastic turn to the right off course. Maybe that was a fluke with the FD? I've had it do that if I am flying a WAAS RNAV approach when I activate the approach data into the GPS too late. I am far more concerned about the pitch.

Ideas?

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Sounds like something is worn causing the slew of other challenges... trim servos get a lot of exercise...

Popping the CB stands out as an obvious hint.

Might want to test as many functions as you can in the control and trim system. See if everything is smooth and goes to the limits...

Auto Pilots Central may be the next stop...?

PP thoughts only, not a mechanic...

Best regards,

-a-

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