An offshore helicopter span out of control during an emergency landing, prompting an inquiry.
The CHC S92 was attempting to touch down on the West Franklin oil platform on December 28 when it began to respond unexpectedly to commands.
The helicopter span and as it landed its wheels gouged the helipad, reportedly damaging the helicopter's undercarriage and the deck.
None of its 11 passengers and crew were injured and the S92 was taken back to Aberdeen by boat two days later.
The Air Accident Investigation Branch (AAIB) announced it had launched an inquiry into the incident on Thursday, focusing on potential problems with the helicopter's tail rotor.
Parts of the rotor will be flown to America to be analysed by S92 manufacturer Sirkorsky. CHC is also undertaking its own inquiry.
A CHC spokesman said: "Our notification to the Civil Aviation Authority, which was done immediately, follows a standard process which can trigger the involvement of the AAIB.
"We welcome the involvement of the AAIB. Their expertise and input will support our own ongoing investigation, which was launched on the day of the event, together with technical experts from Sikorsky to understand the failure on the aircraft."