INVESTIGATORS may finally be closing in on the cause of a “potentially catastrophic” mechanical failure in the gearbox of a Super Puma helicopter which was forced to ditch in the North Sea six months ago.
Eurocopter, the French manufacturer of the Super Puma EC225, which was involved in two separate ditchings last year, has been carrying out tests on the faulty gearbox since the helicopter, operated by CHC Helicopters, ditched into the North Sea off Shetland on 22 October.
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.
Eurocopter revealed in November 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 a new statement, issued today, a spokesman for the helicopter manufacturer announced: “The third round of tests at Eurocopter – which focused on the bevel gear shaft – is complete. The investigation timetable is proceeding according to plan, with each step bringing us closer to the probable causes and solutions.”
He continued: “The investigation results are currently being analyzed and will be reported by Eurocopter in accordance with the confidentiality rules of the official investigation which is led by the UK Air Accident Investigation Branch. Additionally, independent experts from Georgia Technology Research Institute will validate the methodology and conclusions of key elements of the investigation. The institute has great depth of experience in crack propagation and metallurgical investigations.”
The spokesman continued: “The test campaign performed on the EC225 main gearbox emergency lubrication system (EMLUB) confirmed that the system was operating correctly throughout both the 2012 events. The tests have identified the root cause of the in-flight false alarms. The false alarms were a result of wrong electrical signalling and the different tests have also shown that the pressure sensor settings of the air and glycol system must be modified.
“Corrective solutions for the EMLUB system have been developed and the final fix will be implemented with the support of Eurocopter by the end of March 2013.”
He added: “Eurocopter will continue to regularly communicate with customers and operators and industry representatives concerning the EC225 main gearbox shaft failures, whilst respecting the confidentiality of the official accident investigation”
All 16 EC225s operating in the North Sea - one-fifth of the entire fleet - have been grounded since last October when the CHC-operated Super Puma EC225 was forced to ditch off Shetland. Another Super Puma ditched 30 miles off the coast of Aberdeen in May last year.