Offshore helicopter spun out of control after rotor failure
The S92 veered unexpectedly as it was landing on the West Franklin platform off Aberdeen.
An offshore helicopter spun out of control while trying to land on a North Sea platform after a bearing failed in its rotor.
The S92 was touching down on the West Franklin facility on December 28 when it veered unexpectedly and its wheels hit the helideck.
The helicopter spun 187 degrees before the pilot forced it down and its 11 crew and passengers disembarked safely.
An initial inquiry by the Air Accidents Investigation Branch (AAIB) has now concluded a failure in a bearing in the S92's rotor was responsible.
The AAIB said the accident could have happened at any time after the part failed.
S92s were grounded worldwide on Tuesday after manufacturer Sikorsky called for safety checks.
The decision caused widespread disruption to North Sea flights and temporarily grounded the coastguard's Scottish search and rescue fleet.
All coastguard helicopters were cleared to fly by Tuesday evening and the grounding is not believed to have hampered any rescue operations.
Extreme weather is delaying the return of S92s used by the oil and gas industry.