An inquiry into a 2009 Super Puma helicopter accident that killed 16 men is underway in Aberdeen with the aircraft’s main rotor gearbox in the centre of the investigation.
Speaking in front of a sheriff in Aberdeen, two pilots who used to fly the tragic helicopter before its fatal accident on 1 April 2009 that killed 14 passengers and two crew-members, explained the technical workings of the helicopter and spoke about issues the aircraft had encountered prior to the North Sea crash.
47-year-old Andrew Miller piloted the aircraft on its last completed journey before the crash. He said he had experienced some ‘minor’ problems but nothing to explain the disastrous crash.
He explained several features of the oil system in a helicopter gearbox, believed to be responsible for the disaster, and said he would be seriously concerned if pressure in the system dropped below 3.7, on a scale from zero to seven.
Previously, the Air Accidents Investigation Branch (AAIB) concluded the failure in the gearbox caused the helicopter's main rotor to break away from the aircraft and its tail boom to become severed from the fuselage.
The second witness, 50-year-old John Constable worked as a trainer of helicopter pilots for helicopter operator Bond at the time of the crash.
He told the inquiry it was an eight-week process to give a pilot who already has a commercial licence the additional knowledge to enable them to fly Super Pumas.
Helicopters also have various colour-coded warning lights, the witness told the hearing, with red being reserved for the most serious events which require immediate action.
He added that he had never had such a thing as a "gearbox chip warning light" in a Super Puma helicopter in his experience.
At the time of the accident, the helicopter was travelling from a BP’s Miller platform in the North Sea, with all the passengers being oil-industry workers.
Two senior executives of Bond Offshore Helicopters, the company running the tragic helicopter, have also already spoken during the inquiry.
Former managing director of Bond William Munro, responsible for the day-to-day operations at the time of the incident, said gearboxes were covered by a special insurance policy, meaning the company wouldn’t have incurred any extra cost changing a faulty system prior to scheduled maintanance.
Engineering director James Gilmour said the helicopters would be given turnaround inspections if they had been fully shut down between flights.
"Each time it was shut down and the rotors were stopped, there would be an inspection," he said.
He agreed that Bond had a programme in place for routine maintenance of helicopters.
"You can never go over the (time) limit. It's actually cast in stone when you can do these maintenance inspections," he said.
"You have to do them when they're actually due. You cannot extend beyond that."
The inquiry is expected to continue for the next six weeks.
The 2009 accident was the first in a string of fatal crashed involving the Super Pumas in the past five years in the UK.