What happened
Shortly after departing the runway, visible sparks were seen near the primary forward door of the aircraft. The flight crew proceeded with the standard climb-out procedure; however, approximately 85 seconds after liftoff, the pilots attempted to reduce engine power to nominal settings. During this maneuver, the number 3 and number 4 engines failed to respond to power reductions, remaining at full thrust.
Due to the resulting imbalance in power, the captain initiated an emergency return to the airfield. During the subsequent approach, the aircraft became unstable. Upon touchdown, the plane experienced a heavy impact and bounced, leading to a loss of directional control. The aircraft veered off the runway surface and suffered a structural failure, breaking into two separate pieces. A fire broke out following the breakup. All six occupants sustained injuries during the accident.
Findings
Investigations concluded that an electrical short-circuit within the engine control system for engines 3 and 4 caused asymmetric thrust. Additional contributing factors included insufficient crew training and high levels of emotional stress experienced by the flight crew during the emergency.