Mistakes Led to Helicopter Deaths

A problem was highlighted with a North Sea helicopter a week before it crashed killing 16 people, according to an accident report published this week.

Operators had planned to replace the main rotor gearbox of the Eurocopter Super Puma a week before the unit suffered a "catastrophic failure" and caused the crash.

The Air Accidents Investigation Branch (AAIB) reported that a magnetic particle had been discovered on the chip detector within the gearbox.

As a result, there were plans to remove the gearbox and replace it with a spare, but this was subsequently changed when it was not recognised as an indication of the second stage planet gear's degradation.

The report said: "The gearbox was declared serviceable by the operator and its planned replacement cancelled."

But it was the failure of the second stage planet gear, due to a fatigue crack, that contributed to the main rotor gearbox's problems and caused the death of all 14 offshore workers and two crewmen.

The helicopter was flying from the Miller Platform in the North Sea on April 1, 2009, when the main rotor separated from the fuselage, sending the aircraft into the sea.