Seems quite clear...
29 April 2016 the Main Rotor Head (MRH) and mast suddenly detached from an Airbus Helicopters H225 enroute from Gullfaks B to Bergen Airport Flesland. The helicopter impacted on a small island east of Turøy. All 13 people on board perished.
On 28 June 2016 a preliminary report is published to disseminate findings from the ongoing investigation.
At this stage of the investigation, the AIBN finds that the accident most likely was a result of a fatigue fracture in one of the eight second stage planet gears. It appears that the fracture has propagated in a manner which is unlikely to become detected by existing mandatory or supplementary systems for warning of an imminent failure.
Scenarios under consideration as part of this investigation have included failure of a suspension bar
attachment or failure of the MGB conical housing as the initiating event. The investigation activities
since the previous report do not suggest that either of these scenarios were the initiating event.
What initiated the fracture has not yet been determined.
Over to you Airbus.... seems those 225 ashtrays are going to be sat on the ground for some considerable time..