20241207021079I

Upon departure from ksav, the instrument rated private pilot programed the autopilot for the desired heading and engaged it. The aircraft began to bank off course and the student pilot gave the controls to the CFI who disconnected the autopilot and re-entered the desired heading, altitude and vertical speed. The autopilot was reengaged; however, the aircraft did not respond to the new programming and the CFI again disengaged the autopilot. The aircraft began a descent and both pilots pulled back on the yokes but were unable to arrest the descent. The instructor elected to return to ksav; however, his altitude and descent rate precluded that option and an off-airport landing was made. The pilots were able to flare the aircraft and bleed airspeed for landing. The aircraft sustained minor damage to the left-wing tip during the landing.

Following recovery of the aircraft, the autopilot pitch servo, and pitch trim servo were inspected visually with no discrepant issues noted, the drum pulleys moved smoothly as the controls were operated stop to stop. The yoke was pulled to a full aft position, the controls moved smoothly and the stabilator “up” mechanical stop was contacted. The yoke was pushed full forward, the controls moved smoothly and the stabilator “down” mechanical stop was contacted. A visual inspection of the stabilator control system behind the instrument panel, under the rear seat and in the tail of the aircraft was performed; no issues were noted. The stabilator trim system was operated manually, the trim wheel, cables and tab moved smoothly with no binding. The trim wheel was operated to a full “up” indication and the trim tab moved to a trailing edge down position. The trim wheel was operated to a full “down” indication and the trim tab moved to a trailing edge up position. Battery power was applied and an attempt to engage the autopilot was made; however, an afcs red message indicating a system failure was present which prevented engagement. System failure information was downloaded in accordance with the garmin G1000 nxi afcs fault log retrieval procedure and was forwarded to the NTSB for analysis. The NTSB did not note any anomalies during their evaluation of the fault logs. During interviews with the CFI, he stated he the pressed and released the a/p disc / trim inter switch on the yoke to disengage the autopilot and then re-trimmed the aircraft with the electric trim switch on the yoke. He stated he did not visually note the position of the trim indicator however he did reach down and verify by feel that the trim wheel was at the stop. This is contrary to the autopilot malfunction procedure in the PA-28-181 archer iii POH which requires the a/p disc / trim inter switch to be depressed and held while the aircraft is manually trimmed and the autopilot circuit breaker is pulled prior to releasing the a/p disc / trim inter switch. (Note: depressing the a/p disc / trim inter switch disconnects the autopilot; however, it only momentarily interrupts the electric trim while the switch is depressed.)

During an interview with the instrument rated private pilot, he stated that he had experienced the autopilot not maintaining the desired attitude in the past and that firm pressure opposite to the autopilot input (overpowering autopilot servos) would result in an autopilot disconnect; however, this did not occur during the incident flight. This is contrary to the POH autopilot emergency procedures and demonstrates a lack of understanding of procedures which contributed to the incident. Garmin states “in an emergency the pilot can forcibly overpower the servos and move the controls throughout their full range of motion without disengaging the autopilot, however even a small amount of pressure or force applied by the pilot in the pitch axis may cause the automatic trim to run. If the action is prolonged this will result in an out-of-trim condition and significant control forces upon autopilot disengagement".