What happened
During a functional evaluation flight (FEF) intended to test the aircraft following recent modifications, a DC-8 struck mountainous terrain. The flight was being conducted by two crew members: the pilot flying (PF) and the pilot in command (PNF), who was acting as an instructor for the evaluation procedures. During a clean stall maneuver, the pilot flying applied incorrect back pressure on the control column while attempting to recover from a stall. This recovery attempt did not adhere to the established procedures outlined in the Airborne Express operations manual.
As the aircraft entered a full stall, the pilot in command failed to identify or rectify the improper control inputs being made by the pilot flying. The crew was also unable to rely on a stall warning system, which was inoperative at the time of the accident. The impact resulted in fatalities for those on board.
Findings
Several contributing factors led to the accident. The pilot flying maintained aft control column inputs that induced the stall, a behavior influenced by previous training in a low-fidelity flight simulator that did not accurately replicate the actual stall characteristics of the DC-8.
Additionally, the investigation noted that the crew lacked recent experience handling actual stalls in this aircraft type. The lack of formal structure in the evaluation training program allowed for the pairing of two pilots who had not previously managed a real-world stall. The accident might have been avoided if the airline had implemented and utilized the updated stall recovery procedures that had been agreed upon in 1991.