Eurocopter, the EC225 Super Puma, and its operators and passengers have a problem in the North Sea.
Though the Super Puma has served as a safe and reliable aircraft for decades, a change in manufacturing processes of the bevel gear vertical shaft in the main transmission has caused two notable failures this year alone, resulting in two controlled ditchings with no injuries, but two aircraft in the water nonetheless.
The bevel gear vertical shaft is manufactured in two pieces which are welded together. It is at this point that the gear fails, which causes both transmission oil pumps to go offline. To further complicate the already critical situation of no oil pressure while inflight AND overwater, the emergency backup lubrication system displays false indications that the BACKUP system has failed. The crews therefore have no prudent options other than landing on the water and letting the accident investigators sort out the details. Happily in both instances the sea states and weather conditions were such that everyone was able to be recovered safely, which is the best case scenario in the often harsh conditions of the North Sea.
After the first accident in May of 2012, Eurocopter initiated an investigation and believed that they had isolated and dealt with the failing component, and assured customers that the aircraft was safe to fly. Then in October of 2012, only five months later, a nearly identical ditching occured. Operators and regulators elected to ground all EC225s until more definite action can be taken to fix the gearbox issue, and Eurocopter had a credibility crisis on their hands.
As of the time of this writing, several EC225s with older model vertical shafts have resumed operations in the North Sea, while all others remain grounded. The best guess for when these aircraft will return to service is February 2013. In the meantime, operators are doubling up on the flight time on their remaining aircraft, to include Sikorsky S92s (which carry a similar passenger load) and Agusta AW139s.
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