Fatal Accident Inquiry - Super Puma Helicopter Crash
Summary of FAI Determination into the deaths of 16 people following the helicopter crash on 1 April 2009.
On Wednesday 1 April 2009, a Super Puma helicopter, owned by Bond Offshore Helicopters Limited, was flying over the North Sea, en route from the Miller Oil Platform to Aberdeen, when it plunged into the sea killing all 16 people on board.
A Fatal Accident Inquiry took place in Aberdeen over a period of six weeks and was presided over by Sheriff Principal Derek Pyle. In October 2011, following some 30 months of investigation, the Air Accident Investigation Branch of the Department of Transport published an extensive report into the accident. That report describes most of the relevant facts which might otherwise be set out by a FAI as Findings in Fact.
Noting that no party to the FAI questioned the technical data in that report, Sheriff Principal Pyle limited the Inquiry to addressing two key questions: first, why did the accident happen; and, secondly, what has been done and, if appropriate, what more can be done to avoid such an accident happening again?
The conclusions reached by the AAIB inspectors in their report were as follows:
1. There was a catastrophic failure of the helicopter’s main gearbox (“MGB”);
2. The failure of the MGB initiated in one of the eight second stage planet gears in the epicyclic module which itself is part of the MGB;
3. The planet gear had fractured as a result of a fatigue crack;
4. The precise origin of that crack could not be determined, although it is likely to have occurred in the loaded area of the planet gear bearing outer race;
5. A metallic particle had been discovered on the epicyclic chip detector during maintenance on 25 March 2009, some 36 flying hours prior to the accident;
6. This was the only indication of the impending failure of the second stage planet gear;
7. The lack of damage on the recovered areas of the bearing outer race indicated that the initiation was not entirely consistent with the understood characteristics of spalling;
8. The possibility of a material defect in the planet gear or damage due to the presence of foreign object debris could not be discounted.
After considering all of the evidence, but particularly that of Mr Jarvis, one of the AAIB inspectors, and Dr Mermoz, the gearbox expert from Eurocopter, the manufacturer, the Sheriff Principal concluded that on the balance of probabilities the spalling in the gearbox was the probable cause of the accident. That conclusion meant that it was relevant to consider whether the admitted maintenance and inspection failures by Bond engineer failed to identify the spalling and therefore perhaps failed to prevent the accident happening.
Bond’s maintenance and inspection failures, which it readily admitted, were
• A failure to follow the correct task in the aircraft maintenance manual on the discovery of a metal particle, or “chip”, on G-REDL’s epicyclic chip detector on 25 March 2009, which would have resulted in the removal of the epicyclic module and an examination of the magnets on the separator plates;
• A failure to ensure that communications with the manufacturer of the helicopter on 25 March 2009 were done in accordance with the recognised procedures, with the result that misunderstandings arose between the parties, which contributed to the failure by Bond to perform the correct task;
• A failure to identify the nature of the substance of the metal particle when on 25 March 2009 performing a specified task in the aircraft maintenance manual and in doing so might have lost the opportunity to avoid the consequences of its failure to perform the correct task.
The Sheriff Principal found that on the evidence it was not proved that if any or all of these failures had not occurred the accident would not have happened, but that it still remained a possibility.
The following facts were found to be relevant to the circumstances of the deaths:
• The joint working group of the European Aviation Safety Agency (“EASA”), the Federal Aviation Administration, the rotocraft industry and the Technical Oversight Group for Ageing Aircraft has considered a proposal by EASA to introduce improvements in the ability to avoid catastrophic failures of primary structures, including rotor transmission components, of helicopters. EASA intends to incorporate this amendment into its certification standard 29.517. It should do so as soon as possible.
• Eurocopter, as the manufacturer of Super Puma helicopters, the Civil Aviation Authority and the EASA have not together considered methods of oil analysis of Super Puma helicopters, other than by means of a spectrographic oil analysis programme. They should do so.
• The traditional means by which helicopter safety is ensured is by way of rigorous maintenance procedures. Helicopter manufacturers should consider whether future research and development should focus upon whether alternative metals or other materials can be developed to reduce, or eliminate, the risk of spalling in helicopter gearboxes and thereby lessen the dependence upon maintenance procedures as the primary method of ensuring safety.