What happened
While performing an approach, a fire broke out within the wheel well of the aircraft. This fire caused significant damage to the hydraulic lines, resulting in the complete loss of the standby, A, and B hydraulic systems. To manage the emergency, the crew utilized the manual reversion flight control system to complete the landing.
Upon touchdown, the aircraft encountered further complications due to the failure of check valves within the backup hydraulic accumulator pressure systems. These failures specifically affected the inboard pair of wheel brakes as well as the #2 thrust reverser. Consequently, the aircraft was unable to decelerate effectively on the runway. During a two-minute rollout, the plane traveled 14,000 feet, eventually overrunning the end of the runway and striking a concrete structure. The impact caused the nose gear to collapse.
Findings
The investigation revealed that during a recent 'C' check, maintenance personnel failed to identify an electrical wire that was chafing against a hydraulic line. During the flight in question, this energized wire arced, puncturing the line and igniting the escaping hydraulic fluid. Additionally, it was determined that mechanical wear had caused the failure of the hydraulic check valves in the backup systems. The manufacturer's instructions regarding the maintenance of these specific hydraulic components were also noted as an inadequate factor.