Lancair Evolution
Flight Crew Instrument; Flight Crew Private
Flight Crew Last 90 Days 30; Flight Crew Total 2900; Flight Crew Type 500
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Inflight Event / Encounter Weather / Turbulence
General Maintenance Action
Aircraft
I was entering route points into the G-900 database as I had received a re-routing. I was flying in and out of IMC weather. My autopilot was not working correctly as it would not hold a vertical or a horizontal path. I was repeatedly manually correcting the deviations with difficulty; having to reset the autopilot in flight. This required aggressively holding the single-arm yoke stick as it tended to deviate left; while putting in the re-routing; with my other hand. Essentially the yoke was frozen at cruise speed; I had little or no ability to do any trimming. Once I landed I called ATC as instructed. I also had mechanics go over the plane and diagnose the problem; which was major; as 3 separate avionics/A&P personnel said I was lucky to be alive. The roll servo's frame or bracket vibrated loose from the frame of the plane thus making the autopilot inoperative as well as any steering extremely hard.The roll servo is attached to the frame of the plane by four screws. One screw was the wrong size. The other three screws vibrated loose and the servo/bracket was resting on the aileron push rods; making contact with the rods. I do not have pictures documenting this mechanical issue. I feel strongly that those planes with the same A/P and roll servo should be alerted to this potential problem. The fix is simple: lift off the back bulkhead and inspect the bracket. Make sure each screw has either lock-tight or a locking nut and the brace/frame is not cracked from the servo's stress.
The reporter stated that the bracket for the autopilot servo came loose from its mount. The reporter stated that all the early Lancair Evolution with the 'TruTrak' autopilots may have this issue. He would like all owners of this type of aircraft be aware of this problem concerning the installation of the 'TruTrak' autopilots. The reporter claimed that later Lancair Evolution aircraft have Garmin autopilots and do not have the problem with the bracket installation.
A Lancair Evolution pilot reported the autopilot would not hold a vertical or horizontal path. The roll servo's bracket had vibrated loose making steering extremely hard.