Fourteen oil workers and two crew died when the Bond-operated Super Puma plunged into the water off the Aberdeenshire coast on 1 April, 2009 while returning from the BP Miller platform.
Verner Hill, an engineer and deputy shift supervisor with Bond at the time, said he was “unhappy” and “uneasy” after a problem was detected in the aircraft days before the tragedy.
Mr Hill, 54, who now works as a fleet support specialist with Bristow Helicopters, was giving evidence at a fatal accident inquiry at Aberdeen’s Town House.
He was on duty on 25 March, 2009 when a colleague flagged up a problem with the helicopter’s health and usage monitoring systems (Hums) during a turnaround inspection after the aircraft’s first flight rotation that day. The helicopter had flown from Aberdeen to the Unity platform in the North Sea, returning at 8:20am.
Mr Hill said data downloaded from the Hums showed a purple flashing warning light on the main gearbox indicator that appeared to indicate its “chip” detector had picked up a particle of metal.
The issue was only discovered after the helicopter had taken off on another flight at 9:25am, the inquiry heard.
Mr Hill said at the time there was no requirement for Hums data to be fully downloaded and examined before a helicopter took off again, but that was now standard procedure.
He said he spoke to his line manager about the problem after further checks were carried out and no more anomalies were found. “I was asking whether we needed to recall the aircraft from flight, if I remember correctly,” he said. “I wasn’t told to recall it.”
He was shown a report prepared after the fatal crash which, he told the inquiry, appeared to indicate that the particle had been detected 94 times.
When the helicopter returned at 11:40am, Mr Hill and another colleague carried out an inspection on the main gearbox and no particles were found, the inquiry heard. But an examination of the Hums after the second flight still showed the warning. Mr Hill said he was “uneasy” with the situation.
“I wasn’t happy with what I was seeing,” he said. “I spoke to the oncoming supervisor about it. I can’t remember who decided but we took it offline.”
It was put it into a hangar for an after-flight inspection to be carried out. The inquiry heard a particle was later found during that inspection.
Asked why it was not found earlier, Mr Hill said: “I’ve thought about this and the only thing I can think of is I missed it because of whatever reason, bright sunlight, I don’t know.”
The particle may also have been caught up in the chip detector when it was taken out of the gearbox, he added.
An investigation into the crash has found that the AS332-L2 model aircraft suffered a “catastrophic failure” of its main rotor gearbox.
The inquiry continues.