A 2009 North Sea helicopter crash that left 16 people dead might have been avoided if agreed maintenance procedures had been carried out, according to a judge.
Sheriff Principal Derek Pyle, who headed a six-week fatal accident inquiry into the crash, said it would be an “extraordinary coincidence” if admitted inspection and maintenance failings, which meant faults were overlooked, were not the cause of the catastrophic failure of the Super Puma’s main gearbox a matter of days later.
However, he outlined how, given the evidence he had heard, such a coincidence remained a possibility because a vital piece of the helicopter had not been recovered from the seabed.
Following the inquiry the families of the deceased called for authorities to initiate criminal proceedings. However, the Crown Office said reasonable doubt remained over the cause of the crash and their initial decision taken in March 2013 not to instruct criminal proceedings was the correct one.
On Wednesday 1 April 2009, the AS332 L2 Super Puma, owned by Bond Offshore Helicopters, was flying over the North Sea, en route from the Miller oil platform to Aberdeen, when it plunged into the sea, killing all 14 passengers and two crew.
At 1.54 pm, a warning appeared on the helicopter's flight deck indicating low oil pressure in the main gearbox, immediately followed by a grinding noise that lasted for four seconds. It was accompanied by a sudden increase in airspeed. The helicopter was just 20 minutes from Aberdeen airport.
Six seconds later the pilot Paul Burnham issued a mayday call, which was followed by a further one five seconds later by co-pilot Richard Menzies.
The grinding noise was the beginning of the break-up of the main gearbox, which was attached to the main rotor. Twenty seconds after the appearance of the warning light the main rotor broke away before severing the tail boom in a series of strikes.
After hearing evidence from witnesses that included Dr Emmanuel Mermoz, a gearbox expert from Eurocopter, the helicopter’s manufacturer, and Mark Jarvis, a senior engineering inspector with the Air Accident Investigation Branch (AAIB), Sheriff Pyle concluded that “spalling” in the gearbox – fatigue cracks in the metal, known also as “rolling contact fatigue” – was the likely cause of the main gearbox’s failure.
However, the possibility of a material defect in a gear or damage due to the presence of foreign object debris could not be discounted.
Prior to the inquiry, after 30 months of investigation, AAIB released a report outlining how a metallic particle had been discovered on the gear’s chip detector during maintenance on 25 March 2009, some 36 flying hours prior to the accident.
Examination of the helicopter after the crash revealed that the failure of the main gearbox initiated in one of the eight second stage planet gears in the epicyclic gear module, which is part of the main gearbox.
In the wake of the incident, Bond Offshore admitted a series of maintenance and inspection failings, including a failure to follow correct maintenance procedures on the discovery of the metal particle; failing to ensure subsequent communication with the Eurocopter was carried out in line with recognised procedures, which led to misunderstandings between the two parties; and a failure to identify the nature of the substance of the metal particle.
In the FAI determination, Pyle noted: “The essential fact is that everyone in the company well knew that maintenance must be done by the book. On one occasion, that fundamental rule was broken. It resulted in the failure to detect a significant fault in the helicopter's gearbox, which possibly – but only possibly – resulted in the crash.”
Following the release of the inquiry determination, Audrey Wood, whose son was on the flight, said: “On hearing the evidence of the Fatal Accident Inquiry we were surprised and disappointed with the decision by the Crown Office not to proceed with prosecution. However, how they arrived at that decision will haunt us, as not only did we hear about multiple breaches of health and safety but the decision was also made without all the evidence being present as vital witness statements had not been taken.
“Safety is absolutely paramount and everything must be done by the book. There can be no excuse for not doing this. The length of wait of nearly five years has been intolerable for all the families, and we the families feel let down by the system.”
Explaining its reason for not bringing criminal proceedings, the Crown Office released a statement saying: “For a criminal prosecution to have taken place, the Crown would have to prove its case beyond reasonable doubt. The Sheriff Principal makes clear that a reasonable doubt remained over the technical cause of the crash.
“This would have to be established before the Crown could begin to consider any systemic failures. The evidence presented during the FAI has not altered the insufficiency of evidence therefore the decision not to hold criminal proceedings remains the correct one.”
The FAI set out recommendations for helicopter safety authorities, including incorporating improvements in the ability to avoid catastrophic failures of primary structures, including rotor transmission components, into European certification standards.
Pyle also suggested that helicopter manufacturers should carry out research to establish whether alternative materials could be used in gearbox manufacturer to eliminate or reduce the risk of spalling and therefore decrease dependence on maintenance procedures as the primary method of ensuring safety.
A statement released by Bond Offshore said the firm hoped the determination would bring “a degree of closure to the families, friends and dependents of those who died in the tragedy of 2009”.
The statement continued: “We are pleased the Sheriff Principal recognised that Bond engineers understood the vital importance of their role in ensuring the safety of their pilots and passengers. But we have always accepted that we made mistakes through honest confusion over telephone calls and emails. Lessons needed to be learned, lessons have been learned and lessons continue to be learned. We are absolutely committed to continuing to drive safety improvements across the business, and will study the Sheriff Principal’s recommendations carefully, along with our industry colleagues.
“We would like to express again our deep sorrow at the sixteen lives lost in 2009. We owe it to their memories, and to the 160,000 men and women we carry every year, to continue to deliver the highest standards of safety in everything we do.”
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