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By Pierre Chopard
#344 April 28, 2017

Dear HPilot Club members,

As you’ll no doubt know by now, the Norwegian Accident Investigation Board has today released its interim report on the tragic H225 accident a year ago off the coast of Norway. Airbus Helicopters has been working closely with the Norwegian authorities, as well as other industry bodies, to get to the root cause. Today’s report is still an interim report.

The report stresses that the it is an interim report and that the AIBN will continue its investigations into the cause of the accident. Airbus Helicopters has a lot of confidence in this aircraft – the Super Puma dominates the oil and gas industry, as well as the global search and rescue fleet. So it’s been important for the company to work as hard and as closely as possible with the investigators every step of the way.

You will recall that he 2009 accident in Scotland involved an AS332 L2. Not all the relevant parts were recovered then, and so it wasn’t possible to build a clear and true picture of what happened. Today’s report from Norway acknowledges this, crucially saying that actions taken by Airbus after the 2009 accident “were based on the available knowledge and circumstances at the time.” It adds: “This knowledge was naturally limited for several reasons; most importantly, key elements of information were missing due to the fact that not all gear parts were recovered.”

The investigative work that Airbus and the AIBN have done on last year’s accident has moved a long way toward understanding the earlier crash. And this can only help improve safety and maintenance of the aircraft.

Like earlier reports issued by AIBN, today’s report reiterates that the investigations so far have shown the accident was a result of a fatigue fracture in one of the eight second stage planet gears in the Main Rotor Gearbox (MGB). The part that failed and how it failed have been identified, but the exact initiating cause of the fatigue fracture is still to be reproduced. It appears that the fracture propagated in a manner which was unlikely to be detected by the maintenance procedures and the monitoring systems fitted to LN-OJF at the time of the accident.

Since, as you all know, numerous Service Bulletins have been issued by Airbus and EASA. One of the central measures that Airbus Helicopters has taken is to change the roller parts within the gear box. Previously, Airbus used two suppliers for the roller bearings within the gearbox, which is a perfectly normal industry practice. Both 2009 and 2016 accidents involved helicopters equipped with the (#07) model.

It is now clear that the design of one of these roller bearings (#07) was causing more degradation on the gearbox than the other design (#06), and so all #07 roller bearings were replaced with #06.

The release of the latest interim report today is another step on the way to a final analysis by AIBN. Of course, as things become clearer over the course of the next week or so, we will be in a position to let you know more.



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