Search: Helicopter crash investigation
An initial report into the North Sea helicopter crash in which 16 people died found that the aircraft suffered a "catastrophic failure" in part of its main gearbox, it has been revealed.
An initial report by the Air Accidents Investigation Branch (AAIB) found the failure caused the helicopter's main rotor to break away from the aircraft, and its tail boom to become severed from the fuselage.
There was also a rupture in the helicopter's right-hand engine casing, accident investigators said.
The 14 passengers and two crew were returning from BP's Miller platform when the helicopter crashed in the sea, 11 miles north-east of Peterhead on April 1.
The bodies of the victims have all been recovered and identified. Half of the victims came from the north east of Scotland, seven from the rest of the UK, and one from Latvia.
In the report, the AAIB says: "Examination of the wreckage indicates that the accident occurred following a catastrophic failure of the main rotor gearbox.
"This resulted in the detachment of the main rotor head from the helicopter and was rapidly followed by main rotor blade strikes on the pylon and tail boom, which became severed from the fuselage. It is apparent that there was also a rupture in the right-hand engine casing."
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It adds that the investigation revealed that the gearbox had suffered a "major failure", which was not yet fully understood.
The AAIB report recommends the helicopter's manufacturer, Eurocopter, to carry out "additional inspections and enhanced monitoring" on its AS332L2 models of Super Puma helicopters, to ensure the airworthiness of the gearboxes.
It also recommends that the European Aviation Safety Agency evaluates these checks and, when satisfied, makes them compulsory. In addition, investigators advise that Eurocopter improves its gearbox monitoring and warning systems on its AS332L2 helicopters.
