CL600 flight crew reported the aural trim warning sounded as the aircraft was capturing the selected altitude. After following QRH procedures; it was discovered the autopilot had not been disconnected. Autopilot was disconnected; ATC was informed; and the flight continued to the original destination.
Synopsis
CL600 flight crew reported the aural trim warning sounded as the aircraft was capturing the selected altitude. After following QRH procedures; it was discovered the autopilot had not been disconnected. Autopilot was disconnected; ATC was informed; and the flight continued to the original destination.
Narrative
We were operating from ZZZ - ZZZ1. Our initial altitude was 3;000 on the ZZZ departure; XXL. Due to wind shear advisories; we selected full takeoff thrust. I called for NAV mode at 400 ft. and autopilot on at 600 ft. We got an altitude cap at 3;000 and as the airplane leveled off; the stab trim aural warning went off; which happens occasionally. This time it went much longer than normal and I pressed the stab trim disconnect just as a precaution. I assumed manual control and found the controls to be very heavy and unusually difficult to move. We [requested priority handling] with Departure and began the process of returning to ZZZ; including preparing the cabin for a [priority handling] landing. As we maneuvered the aircraft and further investigated our problem; we determined that the autopilot was still engaged and I had been overpowering it. Once the autopilot was disconnected and the airplane was re-trimmed; everything worked normally. We cancelled the [priority handling] and continued to ZZZ1 without further incident.
Second reporter narrative
Takeoff was a non-flex takeoff from Runway XXL on the ZZZ Departure and was conducted per SOP guidance from busy airports - autopilot at 600 ft. Our initial altitude was 3000 ft. As the aircraft began to level off the trim clacker began to sound. At this time the CA (Captain) did the memory items for stab trim runaway and called for the abnormal checklist. We proceeded to conduct QRH checklist and communicated as required with ATC; the FA (Flight Attendant); and company via 'free text' on ACARS as time permitted. [Priority handling was requested] initially. However; after completion of QRH and further troubleshooting; we discovered the autopilot had not been disengaged. Once the CA disengaged the autopilot; the aircraft was re-trimmed and returned to its normal state per phase of flight. The CA and I noted to assess the fuel state and agreed we should continue on to ZZZ1. The [priority handling] status was rescinded and ATC proceeded with us as per normal operations.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.