What happened
On 9 March 1998, an AS332L Super Puma, registration G-PUMK, was performing a scheduled public transport flight to offshore platforms from Aberdeen Airport. Shortly after departing from Runway 34, while the aircraft was climbing through 1500 feet, Air Traffic Control notified the pilot that a large object had been observed falling from the helicopter. The object, identified as a cowling, appeared to have landed on the threshold of Runway 16. The pilot immediately initiated a return to the airfield, and the aircraft landed safely. A subsequent inspection revealed that the external cover for the right-hand heli-raft container pod had become detached during flight. There were no fatalities and no injuries among the 15 passengers or the 2 crew members on board.
The investigation
The investigation focused on the maintenance history of the heli-raft pods, which had been returned to the aircraft on 7 March 1998 following recent servicing. Due to staffing shortages over the weekend, the shift supervisor had personally begun installing the rafts. To verify alignment, the supervisor had only used three of the eight required screws to secure the right-hand pod cover before being interrupted by supervisory duties. He then delegated the remaining work to another engineer.
This engineer mistakenly believed that only the rear cover needed fitting to the right pod. During the process, the engineer was also interrupted by a radio call, preventing a clear exchange of information with the supervisor. The engineer subsequently completed the installation of the rear cover and signed for the work, unaware that the primary large cover was not properly secured. The night shift engineer, performing a pre-flight inspection, failed to identify the missing fasteners while checking fluid levels and cowlings. The commander's final pre-flight inspection, conducted in low-temperature, early morning light, also did not detect the deficiency.
Findings
- The primary cause of the incident was the incomplete installation of the right-hand pod cover, which was held in place by only three of the eight necessary screws.
- Maintenance errors were driven by significant human factors, including staff shortages and the decision by the supervisor to perform multiple roles simultaneously.
- A lack of clear, explicit handover instructions between the supervisor and the engineer led to a misunderstanding of the task status.
- Distractions, such as radio calls and urgent organizational tasks, interrupted the maintenance workflow and prevented the identification of the error.