10-Aug-2018 Source: Allan Blake
It seems a long time ago. On 29th April 2016, the Main Rotor Head and mast suddenly detached from an Airbus Helicopters H225 flying from Gullfaks B to Bergen Airport Flesland. The helicopter impacted on a small island east of Turøy. As the final accident report is published our thoughts have to be with the relatives, friends and work colleagues of the 13 passengers and crew who perished on that day. In April 2017 the Accident Investigation Board Norway (‘AIBN’) issued a Preliminary Report concluding that
“…the accident was a result of failure of the main rotor gearbox (MGB) due to a fatigue fracture in one of the eight second stage planet gears in the epicyclic module.” (para 2.1.1)
The crew, engineers and operator couldn’t have done anything to avoid this accident. There were no indications that the Main Gear Box (‘MGB’) was moving towards a catastrophic event. The main question that remained unanswered until this Final Report was issued on 5th July 2018 was why, in such a heavily regulated aviation industry, two similar catastrophic accidents could happen to helicopters with near identical MGBs only seven years apart? There were clear similarities to an AS 332L2 accident off the coast of Scotland in 2009 (G-REDL). The AIBN’s Preliminary Report was also critical of the European Aviation Safety Agency (‘EASA’) regulatory oversight that enabled a return to service of the H225 without clear assurances that the root causes of the accident had been identified and remedied (see HUMS: Safety Alert, February 3rd 2017 Helihub.com, and LN-OJF Preliminary Report: H225 Concerns Remain Open, May 3rd 2017 Helihub.com).
The AIBN’s Final Report (reference 2018-04) can be found on the AIBN reports page. It is comprehensive at 171 pages with more detailed investigations confirming the findings in the Interim Report and making 12 safety recommendations.
The Final Report is also worrying. The following are the key features that cause most concern:
Airbus do state that they have reduced these risks by replacing planet gears equipped with the type present on LN-OJF to the alternative manufacturer, while at the same time reducing the life limit.
In response to the Final Report, Gilles Bruniaux, Head of Aviation Safety issued a statement on the Airbus website which includes the following quote:
“the available degree of scientific and technical knowledge meant it was neither foreseeable nor foreseen that a crack in a plant gear could propagate in a sub-layer, and as a result generate very low levels of detectable particles…With knowledge gained from this investigation, Airbus Helicopters has introduced a series of safety measures on the H225. Some of the technology that has been developed is ground-breaking for the helicopter industry. Airbus Helicopters will continue to pursue innovations and improve safety standards through a proactive approach that sees us challenge internally everything we do. Work on a number of potential improvements to the H225 are in progress, and I remain optimistic that this concerted and complex work will yield new advances.”
HeliHub.com has estimated that 126 H225s and AS332L2s are currently in storage around the world. Until the issues raised in this accident report are fully resolved, Accountable Managers will no doubt be thinking that that is where they should stay.
*Copyright and full responsibility for the content of this article remains with Allan Blake, an independent Aviation Consultant & Journalist. He is the author of “Dynamic Directors: Aligning Board Structure for Business Success” (Macmillan).