What happened
On 8 November 2006, a Boeing 767-2Q8, registration N330LF, was conducting a non-revenue ferry flight from Nimes to Bristol (Filton) Aerodrome for repainting. During the flight, the crew selected the landing gear to the down position at approximately 8,000 ft. While the deployment was within allowable speed limits, the aircraft subsequently experienced the loss of a left main landing gear door.
Upon landing and during taxi at Filton, the crew observed a loss of pressure and fluid quantity in the right hydraulic system. This was followed by a reduction in the centre hydraulic system as well. When the aircraft reached its parking stand, ground personnel discovered that the left landing gear door was missing and that hydraulic fluid was leaking from the rear of the landing gear leg. The missing door was later recovered from a residential garden in Chippenham.
The investigation
Technical examination of the aircraft revealed that the separation of the door had caused significant damage to the landing gear leg. Specifically, six hydraulic pipes were bent or crushed, and two hydraulic fuses for the rear brake units had operated.
Investigators analyzed the door attachment hardware and found that the upper rod mounting bracket had failed due to an overload condition in bending. This failure occurred because the loss of the mid-mount bolt meant the remaining forward mounts had to carry much higher tensile and compressive loads. The investigation also reviewed maintenance records, noting that the landing gear had been recently overhauled and reinstalled in Nimes, a process that involved multiple retraction and extension cycles to achieve correct rigging.
Findings
- The loss of the landing gear door was initiated by the failure of a castellated nut on the door mid-mount fitting.
- The failure of this nut prevented the mid-mount from supporting the door, leading to an overload on the remaining attachment brackets.
- The investigation could not rule out the possibility that the nut failed due to stresses encountered during the repeated landing gear cycling required for the door rigging procedure prior to the flight.
- The damage to the hydraulic lines was caused by the door attachment hardware making contact with the pipes after the door began to separate.