What happened
During the initial flight of the day, an aircraft carrying eight passengers intended for skydiving departed with approximately 70 US gallons of fuel. While cruising at an altitude of roughly 11,000 feet, the crew determined that heavy cloud cover prevented a safe approach to the designated drop zone, leading to the cancellation of the jump.
As the aircraft descended and was exiting a left turn at approximately 4,500 feet, an audible bang occurred, followed by the partial detachment of the left aileron. This was immediately followed by intense lateral oscillations of the control column and the subsequent partial detachment of the right aileron. Following the pilot's instructions, all eight parachutists successfully exited the aircraft.
Despite the application of full left rudder, the aircraft maintained a right bank of about 45 degrees. As the descent continued toward the village of Yarwell, the pilot increased engine power in an attempt to clear nearby buildings. However, the bank angle steepened to 60 degrees, and the aircraft struck the ground with the right wing low. The wreckage remained upright after the impact, and no fire was reported. The pilot survived the accident with minor injuries.
Findings
Post-accident investigations determined that the structural integrity of both ailerons was compromised when one of the three attachment points on each surface failed. Specifically, fatigue in the rear angle brackets located inside the wing caused the failure. Evidence suggests the primary failure originated at the left aileron's rear angle bracket, with the subsequent failure of the remaining brackets being a result of the resulting structural overload.