What happened
Following takeoff, the pilot engaged the autopilot at 1,000 feet. After engagement, aileron trim was utilized, and the pilot was assigned a heading change to the right. However, the autopilot heading bug was not turned by the crew.
At 2,200 feet, the pilot disconnected the autopilot. Upon disengagement, the aircraft immediately rolled into a left bank of 60 degrees and began a descent. The pilot then applied aileron trim to the right, and working together with the copilot on the controls, the crew successfully recovered the aircraft.
Data from the DFDR and radar indicated that the event occurred at 3,300 feet. Analysis showed that for 45 seconds prior to the event, the ailerons had been deflected to the right by 2 to 5 degrees. During the subsequent descending left turn, the pilots did not reduce power for 60 seconds, causing the aircraft speed to exceed the VNE speed of 250 knots.
The investigation
A post-crash examination of the aircraft structure, flight controls, and autopilot system found no evidence of pre-incident failure or malfunction. Following the incident, the aircraft manufacturer issued a restriction regarding the use of aileron trim while the autopilot is engaged, limiting use to 1 dot rather than the previously permitted 3 dots.