More than half the fleet of Eurocopter AS332L2s serving the offshore oil and gas industry in the North Sea will be airborne again today after undergoing checks to their main gearboxes, says the aircraft manufacturer.

The remainder will be flying again as soon as the checks, proposed in a second UK Air Accidents Investigation Branch report and quickly mandated by the European Aviation Safety Agency, have been completed across the fleet.

The decision to ground all Super Pumas operating on the North Sea was voluntarily taken by the operators following the AAIB's initial statement that the 1 April fatal crash was caused by catastrophic failure in the epicyclic reduction gear module of the main gearbox. Although the reason for the failure has not yet been identified, the AAIB notes that it occurred with little or no warning and ruptured the load-bearing gearbox casing and allowing the main rotor to separate.

It was the lack of warning of the failure that led the AAIB to recommend that Super Puma fleet gearbox inspections should go beyond frequent checks on the metallic chip detectors and magnetic plugs designed to warn of possible impending failure.

Super Puma
 © Eurocopter

The EASA emergency airworthiness directive, which mandated checks before the next flight, says: "In the light of this information, enhancement of the means for detection of main gear box contamination was deemed of the utmost importance."

It ordered operators to follow the procedure set out in Eurocopter's alert service bulletin issued on 9 April after the AAIB's initial statement. The manufacturer says that, provided the outlined procedure is followed precisely, it will provide sufficient assurance of gearbox airworthiness.

Meanwhile the British Airline Pilots Association has called for "a North Sea safety summit", saying there are indications that "commercial pressures could be undermining safety in the North Sea oil and gas industry". BALPA general secretary Keith Bill says: "What we need to do is to throw a spotlight on the oil and gas industry who, with one hand, are squeezing suppliers to make huge cost reductions while, in the aftermath of the recent tragedy and the AAIB report, are urging more investment in safety."

Bill used the opportunity to criticise an industry proposal that a new sea survivor recovery technique should allow helicopters to operate over the North Sea when waves are higher than 5m (16.4ft), the present limit for overwater operations. Bill says the industry wants helicopters to be allowed to operate with waves up to 7.5m high, on the grounds that survivors of a ditching could be recovered by fast rescue launches trailing a "Dacon scoop" - a net which, it is claimed, can gather up survivors despite the sea state.

Source: Flight International