What happened
On 22 February 1999, an AS332L2 helicopter, registration G-PUMM, was conducting a routine passenger charter flight. The aircraft was transporting oil company personnel from Aberdeen Airport toward the Glomar field. While cruising at 3,000 feet, the flight transitioned from visual meteorological conditions into a light snow shower as it passed over the Peterhead area.
During this period, the aircraft was struck by lightning. The pilot reported that the strike caused a physical jolt to the helicopter, though the aircraft continued to handle normally. Following the event, the crew requested clearance from Air Traffic Control to descend offshore into clear visibility to facilitate a return to Aberdeen. The aircraft completed the return flight to Aberdeen Airport without further incident, though it was noted that the global positioning system (GPS) had become unserviceable following the strike.
The investigation
Following the landing at Aberdeen, a lightning strike inspection was performed on the aircraft in accordance with the requirements of the Aircraft Maintenance Manual. The inspection revealed significant damage to several critical components. Specifically, all four main rotor blades were found to have sustained damage levels that necessitated their removal from service.
Furthermore, the inspection of the main rotor head led to its rejection based on manufacturer advice. The investigation also identified that the main transmission gearbox exhibited high residual magnetism. The aircraft remained out of service until these specific components were replaced.