A North Sea helicopter had to return to base in Aberdeen after parts fell off during a flight, an investigation has found.
A report from the Air Accident Investigation Branch (AAIB) said the AW139 helicopter took off on May 6 last year from Aberdeen.
Crew members felt an “unusual vibration” at around 2,500 feet which was later found to be caused by a lightning protection bonding strip and cable fairing becoming detached from one of the rotor blades.
The AAIB report said the European Union Aviation Safety Agency classified the event as “not unsafe”.
Four crew members were on board the helicopter, which returned to base after reaching 3,000 feet.
An inspection found the issue was fault was due to “fatigue” in the bonding strips.
The report said requirement for detailed visual inspections of the bonding strip will be added to maintenance tasks for the model.
Manufacturing processes are also being reviewed.
Leonardo, the parent company of manufacturer Augusta Westland, has been contacted for comment.
The missing parts were not recovered.
The report stated: “Investigation by the helicopter manufacturer established that the bonding strip had failed due to fatigue and loss of the fairing was a secondary effect.
“The manufacturer concluded that the occurrence was not safety related and EASA
classified the event as ‘Not-Unsafe’.
“The requirement for a Detailed Visual Inspection of the bonding strip will be added to extant maintenance tasks and the manufacturer is reviewing the manufacturing process.”