The RMT transport union is calling for Super Puma helicopters to be suspended from use following an initial report into the crash that killed 16 people off the coast of northeast Scotland this month.
The report by the Air Accidents Investigation Branch said the gearbox failure caused the helicopter’s main rotor to break away.
The report recommended that the helicopter’s manufacturer carry out “additional inspections and enhanced monitoring”.
Jake Molloy from the RMT said he was “unconvinced” that inspections of the helicopters would restore confidence among offshore workers.
“Close maintenance was carried out on the helicopter for a week before the crash, but it did not prevent the aircraft going down,” he said.
“There are still so many unknowns that we think it is best for the aircraft to be grounded.”
Since the accident two Super Puma helicopters, though a different model, have been involved in safety incidents.
Pieces of metal were seen coming from the exhaust of a helicopter on Friday last week after it landed on Total’s North Alwyn platform.
The previous Monday, another helicopter was forced to land on a rig after reporting a fuel problem on its way to Aberdeen.