North Sea smash that killed Brit oil worker was caused when rotor head suddenly flew off
Thirteen people were killed when 'a sudden catastrophic failure developed in 1-2 seconds' as they flew off Norway coast
A HORROR helicopter crash in Norway that killed 13, including one Brit, happened in "seconds" after the rotor head suddenly flew off.
An initial report into the crash, which killed oil worker Iain Stuart, from Laurencekirk in Aberdeenshire, found the flight appeared normal until a "sudden catastrophic failure developed in 1-2 seconds".
Eleven workers and two crew members died after the Super Puma aircraft came down near the city of Bergen on April 29.
A report by the Accident Investigation Board Norway released today found the black box recorder recovered from the wreckage revealed the tragedy unfolded in seconds.
It said: "The recordings on the CVFDR (combined cockpit voice and flight data recorder) showed everything appeared to be normal until a sudden catastrophic failure developed in 1-2 seconds.
"The CVFDR recordings ended abruptly at the same time. There are no indications that flight crew actions were a factor in the accident.
"The helicopter was cruising at 2,000ft when the main rotor head (MRH) and mast suddenly detached. The helicopter impacted on a small island and caught fire.
"The main wreckage thereafter ended in the sea where it came to rest at a depth of 1-9 metres. The accident was not survivable."
The preliminary report is intended to give an update on the investigation and includes no conclusions or safety recommendations.
Investigators said examination of the wreckage is ongoing and a land and sea search is hunting "several key components", which were scattered across a wide area after impact.
The probe currently centres on the main rotor head, its suspension bar assembly and the main gearbox.
Accident Investigation Board Norway's report added: "At this preliminary stage of the investigation, detailed metallurgical examinations have not been performed. The examinations so far have not shown any sign of fatigue failure."
The board previously said the crash indicated sudden mechanical failure.
The Super Puma was travelling from the North Sea Gullfaks B oil field, about 74 miles (120 kilometres) off the Norwegian coast, when it crashed en route to Flesland Airport.
The aircraft shattered into pieces when it smashed into the rocky shoreline of Turoey, a tiny island outside Bergen, western Norway.
Iain's family have said they are "heartbroken" by the death of the 41-year-old dad-of-two.
The 10 other passengers who died were Norwegian while helicopter operator CHC lost two pilots, a Norwegian and an Italian.