An investigation into a fatal helicopter crash off the Norwegian coast which killed 13 men, including an Aberdeenshire oil worker, warned there are “significant lessons” to be learned for gearbox safety and monitoring.
The Super Puma 225 came down near Bergen in April, 2016, while returning from an oilfield.
Iain Stuart, 41, from Laurencekirk, was one of 11 passengers and two crew who died.
An Accident Investigation Board Norway (AIBN) probe into the crash found a critical structural component in the helicopter “could fail totally without any pre-detection by the existing monitoring means”.
The investigation found the main rotor suddenly detached with no warning as a result of a gear fracturing due to “fatigue”.
It established the failure “developed in a manner that was unlikely to be detected”.
The report found “clear similarities” between a Super Puma crash off Peterhead in 2009 in which 16 people were killed.
A UK probe following the incident “clearly established” that it was caused by a fatigue failure in the main gearbox.
The Norwegian report makes recommendations to the European Aviation Safety Agency to commission research into the development of cracks in such components.
Manufacturer Airbus said it had made significant changes to the design of the gearbox and monitoring, and was working on a new vibration detection system.