Norway's Accident Investigation Board says "the connection between the engine and the main gearbox has led" Airbus Helicopters to issue an alert as "a precautionary measure to ensure the continued airworthiness of the helicopter type."
The affected models are recently delivered Airbus AS350, AS550 and EC130 helicopters. The Airbus AS350 helicopter, which was transporting five Norwegian youth and a Swedish pilot to and from a nearby music festival, crashed southwest of Alta on Aug. 31.
The agency said that the helicopter that crashed in Norway had "less than 73 flight hours," adding that it "has, at this stage, not concluded whether, or not, failure of the connection between the engine and the main gearbox is a causal factor."
It added that its probe was still ongoing. After the crash, the Norwegian company Helitrans AS immediately grounded its 25-strong fleet out of respect for the relatives of the victims and its staff. The company said at the time that there was no technical reason for grounding the aircraft.