What happened
During the approach phase of flight, a fire erupted within the wheel well of the 22-year-old airplane. The fire burned through the aircraft's hydraulic lines, resulting in the loss of the A, B, and standby hydraulic systems. To manage the descent, the crew utilized the emergency manual reversion flight control system to land the aircraft.
Despite the successful landing, the aircraft could not stop within the confines of the runway. Due to prior failures of the check valves in the backup hydraulic accumulator pressure systems, the #2 thrust reverser and the inboard pair of wheel brakes were non-functional. During a two-minute rollout, the aircraft traveled 14,000 feet, overran the end of the runway, and collided with a concrete structure. The impact caused the collapse of the nose gear. There were no injuries reported.
The investigation
The investigation revealed that the aircraft had recently undergone a 'C' check. During this maintenance period, mechanics failed to identify and repair an electric wire that was chafing against a hydraulic line. On the flight in question, the energized wire arced, puncturing the hydraulic line and igniting the escaping fluid.
Findings
Investigators determined that the failure of the hydraulic check valves, which prevented effective braking and thrust reverser use, was caused by mechanical wear.