Riddle of identical false alarms before Super Puma helicopters ditched
LAST month’s Super Puma ditching off Shetland was a carbon copy of the forced landing of another helicopter in May, a new safety bulletin issued by French aviation company Eurocopter has revealed.
A previous bulletin, issued by the Air Accident Investigation Branch (AAIB), reported that a crack in the main gear shaft was discovered after the chopper carried out a controlled ditching following indications of a failure of the main gearbox lubrication system and emergency lubrication system.
But Eurocopter, the company which manufactures the aircraft, has now revealed that the warning of a lubrication system failure on the CHC-operated Super Puma was a false alarm – identical to the scenario in the ditching in May involving a Bond-operated Super Puma.
In both ditchings, the pilots made controlled landings because of false lubrication warnings. And in both cases, the ditchings led to the discovery of “potentially catastrophic” mechanical failures in the gearbox – identical cracks near a weld in the main vertical gear shaft.
The Eurocopter report on the 22 October ditching by the CHC-operated Super Puma EC225 states: “An emergency lubrication warning light came on and resulted in the crew making the decision to perform a controlled ditching, as required by the flight manual.
“The objective of the emergency lubrication system (EMLUB) is to provide MGB lubrication – with glycol fluid – in the event of a total loss of oil lubrication and in order to provide the crew with additional flight time to perform a safe landing or ditching.”
The report adds: “The initial examinations performed in Eurocopter under the supervision of the AAIB have shown that glycol was found throughout the gearbox casing and on all the gears and bearings of the aircraft that performed the controlled ditching on 22 October.
“There appears to be no visual evidence of heat distress or damage to any of the other components in the MGB, which seems to indicate that the EMLUB system had operated but that a false alarm indicating malfunction had illuminated.
“The root cause of the false failure warning has not yet been identified. ”
Jake Molloy, the offshore organiser of the RMT union, said he found the discovery of the matching faults in both helicopters “astounding”.
He said: “This is beyond belief. Both these false warnings have led to the discovery of major faults in the main gearbox. It appears to be a carbon copy of the May ditching, which only goes to strengthen the concerns that the entire fleet is suspect.
“Until they can not only ensure the reliability of the shafts, but also the emergency back-up systems, then these aircraft should not be allowed back in the air.”
He claimed: “Clearly the system is not fit for purpose and needs to be redesigned by the manufacturer.”
Meanwhile, Bond Helicopters has announced plans for six of its nine-strong fleet of Super Pumas to resume flights by tomorrow after the earlier L2 models of the aircraft were fitted with new vertical shafts.
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