Super Puma ditching inquiry finds helicopter fault
Investigators have found a failure in the lubrication system of a helicopter which ditched near Fair Isle on Monday.
A special bulletin issued by the Air Accidents Investigation Branch (AAIB) said the main and standby oil pumps were not working.
All 19 on board the Super Puma EC 225 were rescued safely after it ditched during a flight from Aberdeen to the West Phoenix rig, west of Shetland.
Flights by other aircraft of the same type have been halted.
BBC Scotland has also learned that two North Sea search and rescue Super Pumas operated by BP have been restricted to "life-saving" operations only in the wake of the incident.
The Jigsaw service uses the L2 type of aircraft - similar to the one involved in this week's incident.
BP said it was looking at bringing in Sikorsky aircraft to provide temporary cover while the industry examines the evidence from the CHC-operated Super Puma ditching.
The AAIB report suggests that the helicopter came close to being involved in a much more serious incident on Monday.
The bulletin said a 360 degree crack was found on the bevel gear vertical shaft of the helicopter.
This crack prevented the oil pump gears from being driven.
The AAIB said the European Aviation Safety Agency (EASA) and the manufacturer are urgently reviewing the effectiveness and scope of an airworthiness directive previously issued for this helicopter type.
The crew of another Super Puma helicopter ditched in the North Sea in May after a gearbox failure.
All 14 passengers and crew involved in that incident, about 30 miles east of Aberdeen, were rescued.
Aviation writer Jim Ferguson said: "What is now of some considerable concern is how many other shafts may have the same problem."
He said there could potentially be long-term "serious disruption" for the industry.
Jake Molloy, of the RMT union, expressed serious concern, and added of Monday's ditching: "We were fortunate - good pilots, good weather."
'Safest in world'
Jean-Pierre Dedieu, who is heading the Eurocopter team in Aberdeen to investigate the cause of the latest incident, told BBC Scotland earlier on Wednesday: "We have now to investigate in more detail.
"We do not know yet if it is similar to previous ditching cases."
He added: "This helicopter is one of the safest in the world."
A meeting of the Helicopter Safety Steering Group was held in Aberdeen on Wednesday.
The group is made up of senior figures from the oil and gas industry and union representatives.
The Unite union has questioned whether the make of Super Puma aircraft is "fit for purpose".
CHC, Bristow and Bond have delayed operations of EC 225 and L2 Super Pumas, during the investigation.