What happened
During a recent departure, a Boeing 787 experienced a mechanical failure that prevented the retraction of the main landing gear. The issue originated during the ground handling and maintenance phase, where the aircraft departed the gate in a configuration that physically blocked the gear from retracting. The presence of the pins was not detected by the engineering, flight, or dispatch crews during their respective pre-departure inspections.
The investigation
An investigation into the incident revealed a breakdown in the verification process regarding the removal of landing gear pins. While the aircraft requires five pins to be removed, the tow crew only identified and removed three pins, believing these were the only ones installed based on the visible streamers. The investigation found that the maintenance engineer (LAME) did not verify that all five pins had been removed and stored before signing the technical log. Instead, the aircraft maintenance engineer (AME) performed a physical check for pins without a clear understanding of the total number required for removal.
Several environmental and procedural factors hindered the detection of the remaining pins. The ladder used to access the pin stowage area was too short to allow for a clear visual inspection of the receptacles. Furthermore, the streamers attached to the pins were difficult to see because they were degraded and likely stuck to the landing gear due to grime and recent wet, windy weather.
Findings
- The tow crew relied on the presence of streamers to identify pins and mistakenly believed the three they found represented the total count.
- The flight and dispatch crews did not expect to find any gear pin streamers during their external inspections, as they believed the pins had already been removed by engineering.
- Two landing gear pins remained installed, preventing the main gear from retracting.
- Human factors, specifically expectancy bias, played a role; the tow crew expected to see pins based on their recent movement of the aircraft, while the flight crew expected none.