Sequence of Events
Shortly after takeoff, the Copilot pulled back the thrust levers of both engines to the desired positions, but the left engine thrust lever could not move and the engine remained at full power. The Pilot in Command (PIC) informed Air Traffic Control (ATC) of a technical problem and requested a return to the airport.
The crew managed to land safely. During the approach and landing, the Copilot and an accompanying company maintenance engineer struggled to control the left engine, which remained at a high power setting, while the PIC controlled the aircraft using only the right-hand engine.
After landing, the aircraft taxied to parking bay number 4 with the left engine still at full power. The captain applied the parking brake, and the aircraft stopped for a while. Before chocks were placed, the aircraft started moving forward at high speed, passed through a jet blast fence, and crashed into the Control Tower building.
Injuries and Damage
A passenger was killed, six people were injured, three of them seriously. The aircraft and control tower sustained damage.
Probable Cause
The flight crew’s failure to identify corrective action and their lack of knowledge of applicable airplane and engine systems in response to a jammed thrust lever, which resulted in the number 1 engine operating at high power and the airplane configured in an unsafe condition that led to the need to apply heavy braking during landing. Also causal was the flightcrew failure to recognize the safety hazard that existed from overheated brakes and the potential consequence on the braking action needed to park the airplane. Contributing factors included the possible failure by maintenance crew to correctly stow the upper core cowl support strut after maintenance, Flight crew’s failure to follow standard operating procedures, the company’s failure to be availed to manufacturer safety literature on the subject, and the susceptibility of the cowl core support shaft to interfere with the throttle control mechanism when the core strut is not in its stowed position.