Oil & Gas UK says that it welcomes the Air Accidents Investigation Branch (AAIB) report published on 24 November on the tragic crash of helicopter Flight 85N which took place off the Aberdeenshire coast on 1 April 2009.
The accident occurred whilst the helicopter was operating a scheduled passenger flight from the Miller Platform in the North Sea, to Aberdeen. Whilst cruising at 2,000 ft amsl, and some 50 minutes into the flight, there was a catastrophic failure of the helicopter’s Main Rotor Gearbox (MGB). The helicopter departed from cruise flight and shortly after this the main rotor and part of the epicyclic module separated from the fuselage. The helicopter then struck the surface of the sea with a high vertical speed.
Debris from a helicopter, two life rafts and eight people wearing survival equipment were observed within the area. A fast rescue boat crew, however, found no signs of life.
An extensive and complex investigation revealed that the failure of the MGB initiated in one of the eight second stage planet gears in the epicyclic module. The planet gear had fractured as a result of a fatigue crack, the precise origin of which could not be determined. However, analysis indicated that this is likely to have occurred in the loaded area of the planet gear bearing outer race.