PA-28 Flight Instructor and student reported the ailerons became stuck during departure climb. During return to departure airport; flight instructor turned off Autopilot master restoring aileron control and flight landed safely.
Synopsis
PA-28 Flight Instructor and student reported the ailerons became stuck during departure climb. During return to departure airport; flight instructor turned off Autopilot master restoring aileron control and flight landed safely.
Narrative
A student and I planned to practice pre-solo maneuvers today. The METAR reported an 1;800 ft broken ceiling but the ZZZ1 airport TAF and flight visibility outside looked much better; so we planned for a southbound departure.The aircraft being flown has an STEC-55X Autopilot installed. The Autopilot trim has been inoperative and placarded. The Autopilot master was turned on after engine start and the Autopilot self test did not display any issues.My student conducted a runup using the aircraft's checklist; which included checking the flight control freedom of movement and correct movement. I visually observed this.No abnormalities were noted by my student during the takeoff. He made a right turn to the south and didn't notice any issues until around 1700 feet. He said that the ailerons were stuck. I took control and observed the same. I checked to ensure nothing was obstructing the yoke; there was not. I checked for visible damage outside; there was not. I checked if the rudder trim made any uncommanded movements; it did not. At the time; I did not observe myself or my student engaging the Autopilot. There is no flight director on this install either. The only indication of an engaged Autopilot would be on the STEC unit itself; which I did not think to check in the moment.At this point; I thought I was dealing with a serious flight control issue. I requested priority handling and stated my intention to land immediately. Tower cleared me to land any runway; and I told him that I'd plan to land Runway XX; as I was already in a high left downwind for it.I tried making left and right turns using rudder which seemed to be adequate for controlling the airplane. I configured full flaps as I wanted to make sure there were no adverse handling characteristics at a higher altitude; and avoid changing configuration close to the ground.Eventually as I was attempting to turn back and descend towards the airport; I thought about the possibility of an Autopilot engagement; despite my student and I not thinking that we've engaged it. In the moment; I never checked the STEC unit for flight director modes; but what I did do was turn off the autopilot master to remove all power from the unit. The servos freed up and the issue was resolved. I stated this to the Tower but still continued to land. I steepened my rate of turn and landed uneventfully back onto Runway XX. The Tower requested that I hold on the runway for about a minute; then instructed me off.I for one; should've slowed down my handling of the issue. I felt as if I was in a rush to get back towards the ground; but the aircraft was flying straight and I should've given myself more room; especially if this was a real flight control issue. If I had taken more time to troubleshoot; it's also possible I would've noticed a mode displayed on the Autopilot; and I could've had my student disconnect that mode with the disconnect button instead of powering down the unit.Moving forward; I'd like to conduct more training on the Autopilot with students. It's possible that if the student was aware of the possibility that the Autopilot servos were the reason behind the resistance on the ailerons; that he would've troubleshooted on his own and resolved the issue. I also discussed with the owner of the flight school to revise our POH based checklist to add on a pre-flight check to ensure that the autopilot is off before takeoff; which although may have not helped us on this flight as the servos were disengaged prior to takeoff; may help a future pilot flying that airplane from departing with the Autopilot engaged.
Second reporter narrative
Student pilot operating the plane. Had taken off and was in initial climb on right downwind for Runway XX of ZZZ. Plane behaving normally on base turn and climb out. I (student pilot) noticed a sudden stiffening of the yoke and inability to move the ailerons. I applied a significant amount of pressure with very little feedback from ailerons. Immediately gave controls to instructor who verified same inability. Due to proximity of airport; instructor (pilot in command (PIC)) requested priority handling to ZZZ Tower and requested an immediate return. On the descent; instructor cut power to Autopilot system; which deactivated servo motors and allowed yoke to move freely again. Normal landing occurred; no further assistance needed.The Autopilot (S-Tec Fifty Five X) seemingly engaged on its own; stiffening the yoke. The servo motors were unable to be overcome with pressure. The Autopilot was never used by student prior to this event and was not planned to be used. At the time; there was no button press to activate the system nor was there any activity near the Autopilot panel. The plane was taken out of service by flight school for evaluation.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.