If the media were to examine what actually happened in the four recent Super Puma accidents since 2009 in the North Sea, it would understand a lot better than it does what kind of situation Eurocopter – and the oil support helicopter operators – are facing following the 23 September accident at Sumburgh.
At present the press is just lumping all the quoted events together as “crashes” with no attempt to understand the very different levels of risk they presented to those on board in each case, and what continuing risk is indicated by these occurrences for the Super Puma fleet as a whole.
Puma helicopters have been in service since the early 1970s, and their safety record with military and civil operators all over the world since then has borne comparison with any other type doing the same work.
The first “recent” North Sea Super Puma event was in February 2009. It was non-fatal, and was the result of a crew mis-perception of how close they were to the sea at night while they were approaching an oil rig. The cause was an optical illusion presented by the reflection of the rig’s lights on the sea surface. The aircraft hit the sea at low speed and floated. Everyone got out safely.
But the accident in April the same year, was horrific. The main gearbox failed catastrophically in the cruise at 2,000ft, the rotor ripped off and the fuselage fell like a stone into the sea off Peterhead. All 16 on board died of impact injuries.
A severe compounding shock to the industry from that accident was the fact that the helicopter’s health and usage monitoring systems (HUMS) had given no warning to the crew or the operator that such a serious event was imminent. This shook faith in HUMS’ effectiveness to the core.
With such a painful event still in people’s memory, when an accident like the 23 August CHC Super Puma crash in the sea near Sumburgh occurs, it’s natural to look for precursors or indicators.
Superficially, the 2009 disaster could be a relevant precursor, especially because it is the same marque of Super Puma - an AS332L2 – as at Peterhead, but on closer inspection it’s not at all likely to be. If the main rotor had detached at Sumburgh, everyone on board would also have died of impact injuries. In fact there were 14 survivors, and it seems unlikely that the four that died will have received their fatal injuries through impact alone.
Now let’s look at the two other recent Super Puma North Sea events. They were both non-fatal precautionary ditchings. The main gearbox oil pressure dropped, the crews turned on the emergency gearbox lubrication system but received no indication it was working, and made the decision to ditch.
The Air Accident Investigation Branch discovered that, in both cases, the emergency lubrication system was working, which would have given the crews 30min flying time to get them back to base – if they had known it was working. So the standby safety system worked, but the indicator didn’t. The crews made the right decision according to what they knew, and no-one was hurt.
Following those two ditchings the Super Puma model affected – the EC225LP – was grounded until the fault that caused the main gearbox oil pressure failure was understood and an inspection regime approved while Eurocopter redesigns the errant component and tests it. Just over a month ago in July the model was cleared back into service. Now it has been grounded again because of a loss of confidence in the Super Puma range as a whole, although the Sumburgh machine was a different marque.
When you work out what is happening here, the grounding decision has been influenced primarily by a fear of the unknown: what caused Sumburgh? As soon as the AAIB is sure of the answer, the Super Puma fleet or part of it, will be cleared to fly again after the completion of checks relating to what was discovered.
Behind the fear is the knowledge that helicopters – all types – are more vulnerable to critical single-point failures than fixed wing aviation is. That may be a rational concern, but no-one is suggesting helicopter flying as a whole should be stopped.
Meanwhile the decisions regarding the Super Puma fleet should be influenced by rational deduction based on technical knowledge and operational risk assessment, not a primitive desire for a scapegoat.