What happened
On 21 January 2005, an Aerospatiale AS3/32L Super Puma, registration G-TIGF, was conducting a passenger service from Den Helder, Holland, to an offshore platform located approximately 150 km from the Dutch coast. While cruising at 2,000 feet and maneuvering to avoid a cumulonimbus cloud, the crew observed a flash of lightning in the clear air to the left of the aircraft.
At the time of the flash, the crew noted no accompanying bang, electrical failures, changes in vibration, or variations in compass indications. Based on the absence of immediate physical symptoms, the crew determined the lightning was clear of the aircraft and proceeded to the offshore platform according to standard operating procedures. The remainder of the flight and the return journey were completed without further incident. However, upon returning to base, the crew briefed engineering staff on the event, which led to a physical inspection of the aircraft.
The investigation
The AAIB investigation focused on the extent of the damage and the meteorological conditions. An examination of the aircraft revealed damage to the main and tail rotor blades. The investigation reviewed photographs of the main-rotor blades and verbal descriptions of the tail rotor condition. While initial assessments suggested the tail rotor blades might have been affected, subsequent inspections by company personnel cast doubt on that conclusion.
Investigators compared the damage to previous incidents involving the same aircraft type. It was noted that the damage to the main blades in this instance was significantly less severe than in previous recorded strikes. The investigation also reviewed meteorological data, including a sferics plot, which showed low-intensity lightning activity in the Dutch sector during the period, despite more extensive activity over northern Germany. The crew had not received a forecast including lightning for their route.
Findings
- The aircraft sustained damage to both the main and tail rotor blades.
- The crew observed a lightning flash but did not perceive any immediate impact on the aircraft's systems or flight stability.
- The lightning strike caused damage to the rotor blade skins, though the severity was lower than in previous AS332 incidents.
- Meteorological reports indicated that while lightning activity was present in the wider region, the specific area of the flight had low-intensity activity and no lightning was forecast for the route.
- The investigation noted that the presence of an aircraft can sometimes trigger a discharge in conditions where lightning is otherwise dormant.