The families of 16 men killed in a helicopter crash wept yesterday as they heard that a gearbox failure caused the aircraft to plunge into the North Sea.
It took three minutes and 23 seconds for the Super Puma AS332 L2 to hit the water after the gearbox failed, leaving pilots Paul Burnham and Richard Menzies powerless to avert the disaster on April 1, 2009.
The failure – which investigators believe was caused by a crack in the epicyclic gearbox’s casing – caused the aircraft’s rotor to break off and slice through the tail boom.
Yesterday Mark Jarvis, a senior engineering inspector for the Air Accidents Investigation Branch (AAIB), told the fatal accident inquiry into the deaths of those killed in the crash that his team had pieced together the terrifying final moments of those on board the helicopter.
Investigators listened to the flight data recorder, which was recovered from the sea bed.
Mr Jarvis – who led the salvage operation and analysed operator Bond’s maintenance records – said that there had been a “step-change” in the frequencies heard on the recordings.
“Analysis indicated that a defect was apparent on the ring gear on the second stage of the gearbox,” he said. “It indicated that it had failed or the crack had progressed to the stage that it had completely cracked through the casing and material from that gear was being liberated and lodged on the ring gear.”
He said the noise of the metal being gone over by the gear could be picked up on the recordings.
“The gear continued to operate for three minutes and 24 seconds from the step change,” he added. It then began to fail, causing the rotor head to twist – which, Mr Jarvis had earlier explained, could cause the blades to detach from the aircraft.
“The helicopter failed to respond to the pilots’ commands and they lost the gearbox oil pressure and the warning light in the cockpit came on,” the 50-year-old added.
“The helicopter started to descend and we believe the rotor remained intact for about 20 seconds after the failure of the gearbox before it released and struck the tail of the helicopter. The fuselage fell into the sea without the rotor or the tail.”
Mr Burnham, 31, of Methlick, and Mr Menzies, 24, of Broitwich Spa, died instantly along with their 14 passengers.
The other victims were Brian Barkley, 30; James Costello, 24; Alex Dallas, 62; and Vernon Elrick, 41, all of Aberdeen; Stuart Wood, 27, of Newmachar; Warren Mitchell, 38, of Oldmeldrum; Leslie Taylor, 41, of Kintore; Raymond Doyle, 57, of Cumbernauld; James Edwards, 33, of Liverpool; Nairn Ferrier, 40, of Dundee; Nolan Goble, 34, of Norwich; Gareth Hughes, 53, of Angus; David Rae, 63, of Dumfries; and Mihails Zuravskis, 39, of Latvia.
The inquiry at the Town House in Aberdeen, continues.