A helicopter came close to falling into the North Sea due to a fault with the tail rotor, an investigation has found.
Crew members lost control of the aircraft as it was landing on the West Franklin platform in December 2016, seeing it drag to the right after a heavy descent.
The Sikorsky S92 rolled to the left and continued to rotate 180 degrees before stopping near the helideck’s edge.
A report by the Air Accident Investigations Branch (AAIB) found if the loss of control had happened sooner, the helicopter would probably have ended up in the water.
It said: “If the loss of yaw control had occurred at an earlier stage of the flight, the helicopter would most likely have made an uncontrolled descent into the North Sea.”
The incident happened after a five-minute flight from the Elgin platform.
Problems with the aircraft had appeared at the start of that route, with it yawing 45 degrees to the right, but both the pilot and co-pilot deemed this to have been due to wind.
The report describes the rest of the flight as “uneventful” and the fault only resurfaced as they were trying to land at West Franklin, about 150 miles east of Aberdeen.
Investigators found the problem to have been with the tail rotor bearing, which had not been picked up by engineers, and that no-one on board would have had any indication of the mechanical issue.
There were no injuries - although the helideck surface was damaged - and the AAIB has made safety recommendations.