Gear failure blamed for Norway helicopter crash that killed 13

KJELLER, Norway, June 29 (UPI) -- Investigators confirmed a fatigue crack in a gear is the most likely cause of an April helicopter crash in Norway that killed 13.

They are also looking into the possibility the crack was caused by a 2015 road accident involving a truck that was carrying the gearbox containing the flawed gear.

The helicopter crashed near the small Norwegian island of Turoey as it returned from an offshore oil field.

An interim report Wednesday by the Air Accident Investigation Board Norway said, "The main rotor and mast suddenly detached from an Airbus Helicopters H225 en route from Gullfaks B to Bergen Airport Flesland...the AIBN finds that the accident most likely was a result of a fatigue fracture in one of the eight second-stage planet gears."

While the report stressed the cause of the fracture had not been determined, it added the helicopter's gearbox was aboard a truck involved in an accident, after which the gearbox was "inspected, repaired and released for flight by the manufacturer...whether there is a link between this event, and the initiation and growth of a fatigue fracture, is being investigated."

Airbus Helicopters, manufacturer of the helicopter, said in a statement that no direct link between the road accident and the in-flight crash had been established. The model of the helicopter, the 225 Super Puma, was grounded by the European Aviation Safety Agency after the April 29 crash.