A report urges European aviation safety officials to take immediate action to ensure Super Puma H225 helicopters are safe.
The Norwegian Air Accident Board warned that current fault detection measures may be inadequate.
Iain Stuart from Aberdeenshire was among those killed in the crash.
Mr Stuart, 41, from Laurencekirk, worked for the oil field services company Halliburton.
The Airbus Super Puma was travelling from the Gullfaks field to Bergen when it crashed near the small island of Turoey on 29 April.
A preliminary report issued by the  Accident Investigation Board Norway (AIBN) said it had found "features strongly consistent with fatigue" in parts of the main gearbox (MGB).
It added: "It cannot be ruled out that this signifies a possible safety issue that can affect other MGBs of the same type.
"The nature of the catastrophic failure of the LN-OJF main rotor system indicates that the current means to detect a failure in advance are not effective."
The Super Puma H225 helicopter is currently grounded in the UK and Norway but the manufacturer Airbus has lifted a recommendation that flights be suspended worldwide.
Airbus said at the time there was no evidence to link the crash with two previous incidents in Scotland involving the same model of helicopter.
An online petition calling for all Super Puma 225s to be "permanently removed from service" has attracted nearly 30,000 signatures.

The 60-year-old Frenchman has been suspended along with Fifa president Sepp Blatter and secretary general Jerome Valcke. They deny wrongdoing.
Platini, a Fifa vice-president, is the Football Association's preference to succeed Blatter at Fifa.
The French FA wants the Court of Arbitration for Sport to intervene to ensure Platini can stand for election.
Fifa's ethics committee began its investigation after the Swiss attorney general opened criminal proceedings against Blatter in September.
He is accused of signing a contract "unfavourable" to Fifa and making a "disloyal payment" to Platini.
The ethics committee also opened an inquiry into Platini over the 2m euros (£1.35m) payment, which was made nine years after the former France footballer carried out consultation work for Blatter.
Fifa will hold an emergency meeting on 20 October in Zurich to discuss February's presidential election, at which a successor to Blatter will be chosen.
Platini, Uefa's president since 2007, has been backed by South America's football confederation following his suspension.
Conmebol said he should be regarded as innocent until proven guilty.
The French Football Federation is expecting a decision from Fifa's appeal committee within eight days.
"The FFF has adopted the principle of an appeal if the decision of the Fifa appeal committee does not go Michel Platini's way," said a FFF spokesman.
Blatter, 79, won a fifth consecutive presidential election in May but announced he would be stepping down just days later following the launch of two investigations into Fifa by United States and Swiss authorities.
Platini is one of the favourites to replace him and still plans to stand. He has the full backing of Uefa, which is holding an emergency meeting next week.
Air Accident investigators have found signs of metal fatigue in the gearbox of a helicopter that crashed off Norway, killing 13 people in April.
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Uefa chief Michel Platini is appealing after Fifa banned him for 90 days while corruption claims are investigated.