Woolly thinking about Sumburgh helicopter accident

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.




6 Responses to Woolly thinking about Sumburgh helicopter accident

  1. Jim 17 September, 2013 at 5:51 am #

    Hi David,
    You say:- “was grounded until a fix for the fault that caused the main gearbox oil pressure failure was found, approved and fitted”.
    You are wrong. No parts have been retrofitted to the EC225 since the 2 ditchings. In fact the only thing Eurocopter has done is find out why the shafts keep snapping.
    The replacement part will be another 10 months in design and testing BEFORE the EC225 is upgraded.
    You complain about the press jumping to conclusions but you are inept at getting your facts right. Sounds pretty hypocritical if you ask me.

    • David Learmount 17 September, 2013 at 8:51 am #

      You’re right, Jim, and the correction has been posted elsewhere, including in the magazine this week where the full feature on the state of North Sea ops has been posted. Meanwhile, can’t you just post a correction without the insults? I make mistakes from time to time, and am glad to be corrected. We try to run a civilised ship here.

  2. TC 27 September, 2013 at 6:12 pm #

    Your article has served bring a sense of reason and logic to the subject of helicopter accidents which seems to have escaped most others.
    I have similarly attempted to suggest that events must be examined individually before there are any conclusions drawn or actions taken on the basis of relationship.
    The real problem remains with the Bond fatal accident which you rightly describe as ‘horrific’.
    It alone served to undermine the basis of certification – yet there is a simplicity to this event which is to some extent lost within the complexity of the AAIB report.
    The question which must be answered is – ‘ have actions now been taken which restore the helicopter systems to the original certification standard ?’.
    So far as the two ditchings associated with oil pump drive shaft are concerned – these events do call into account the basis of testing and certification – for the first event to have occurred is very surprising – as for the second – that was really unforgivable and begs questions of Eurocopter which they may find difficult to answer.
    The last event at Sumburgh was clearly a candidate for an operational category event from the beginning – but there was no attempt to allow the authorities to reach even the earliest observations before the ‘kneejerk’ grounding mandate. Now we know that decision to have been in error – but look at the damage that has been done to offshore passenger confidence.
    Your call for reason is applauded – let us hope that your article is widely read.

  3. Lou de Marco 30 September, 2013 at 8:01 pm #

    The latest oil support accident has spooked me as much as its recent predecessors. My suspicion is, and no doubt I’ll be corrected if I’m wrong, that the UK sector accident rate is now worse than it was at the height of the exploration/production rush of the 1975-1990 period. If so, how can this be? Then, the workhorse of the N. Sea was the S61, a comparatively unsophisticated helicopter operated 24/7 in a looser regulatory environment. Now the state of the art helicopters, at least two generations down the design line, are fitted with HUMS and the like to forewarn of potentially catastrophic mechanical failure and have avionics far removed from the Decca and wing levelling/heading hold AFCS of S61 days.. Crews are trained with more advanced synthetic devices and the regulatory environment (EASA) is common to all European operators. So what has gone wrong? I am not going to speculate on any aspect of the present circumstances but for sure, both industry and regulators need to get a grip of this sorry situation. I write as a former (S61) N. Sea Training Captain and subsequently Head of Flight Operations (Helicopters) at the CAA)

    • TC 1 October, 2013 at 12:54 pm #

      The Oil and Gas UK statistical analysis of North Sea helicopter operations confirms your suspicions that current helicopter safety does not compare well with earlier day operations.
      Perhaps the differences between past and present have some relevence.
      Is the regulatory framework as robust as it used to be?
      Are Accident Investigations compromised by seemingly having to avoid making comments which would suggest responsibility for system or human failings?
      Has the culture within the Operators relationships with both the manufacturer and other operators changed?
      The current calls for various forms of enquiry will do little to enhance helicopter safety in the short term – but it is short term answers that are needed.
      Industry should look at the individual events and be open and robust in their declarations of cause and responsibitity.

      • Lou de Marco 7 October, 2013 at 7:40 pm #

        Operators are responsible for the safety of their operations and regulators are responsible for the legal framework within which they take place. They must also audit the operator Safety Management Systems that form part of this framework to ensure they are effective. Regulators must also set the Airworthiness Requirements for Certification and continued airworthiness.

        Clearly the Airworthiness Certification or Continued Airworthiness Requirements are lacking and the latest accident suggests that human factors risks of whatever kind have not been adequately managed. So the enquiries need to make a top to bottom examination of the ‘offshore helicopter’ part of the aviation industry and its management.

        It also seems to me that there may be too many ‘fingers in the pie’, with industry, operator and regulator enquiries taking place, in addition to the statutory Fatal Accident Enquiry and AAIB Investigation. In the first named three there is a danger of replication of effort and dilution of conclusion unless they are well coordinated.

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