What happened
On 26 June 2003, a Boeing 777-236B, registration G-VIIA, departed London Gatwick bound for Antigua with 272 passengers and 14 crew. During the initial climb, as the aircraft accelerated, the flight crew and cabin attendants experienced a loud bang and a physical tremor through the airframe.
An Air Driven Unit (ADU) bay access door, weighing approximately 70 lb, had detached from the fuselage. The door'ob movement caused it to strike the aircraft skin, damaging two cabin windows and the vertical fin. Fragments of the door even entered the passenger cabin, causing minor damage to the interior trim and window seals. The aircraft was forced to terminate its fuel dumping procedure and return to Gatwick for an overweight landing.
The investigation
The AAIB investigation focused on why the large composite door became unsecured during flight. Examination of the aircraft revealed that the hinges had fractured due to overload. Investigators found that while some catches were distorted, at least 11 of the 13 available catches were found in an open state.
Investigators also scrutinized the maintenance history, noting that the aircraft had recently undergone a heavy maintenance check. The investigation looked into the procedures used by the operator, specifically how the door could have remained unfastened despite multiple walk-round inspections by various personnel in clear daylight conditions.
Findings
- The primary cause of the incident was that the ADU bay door had been left inadequately secured following a maintenance check.
- It is believed the door was temporarily closed with only one catch fastened to allow for flap operations, and the remaining catches were never engaged.
- The maintenance system contributed to the error; the use of duplicated or unnecessary work cards and the separation of panel closure tasks from the primary maintenance tasks made strict adherence to procedures difficult.
- Subsequent walk-round inspections failed to detect the open catches, likely due to the routine nature of the checks and the fact that the protruding latches were not highly conspicuous.
Safety action
Following the investigation, a safety recommendation was issued to the operator to review maintenance management systems. This included suggestions to simplify work packs, combine opening and closing tasks on single cards, and provide better illustrations of panel locations to prevent similar maintenance omissions.