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Consider the effect that the choice of a single word can have upon the success or failure of a standard.The standard is DO-278A, and the word is, ‘approve’. DO-278 is the ground worlds version of the aviation communities DO-178 software assurance standard, intended to bring the same level of rigour to the software used for navigation and air traffic management. There’s just one tiny difference, while DO-178 use the word ‘certify’, DO-278 uses the word ‘approve’, and in that one word lies a vast difference in the effectiveness of these two standards.

DO-178C has traditionally been applied in the context of an independent certifier (such as the FAA or JAA) who does just that, certifies that the standard has been applied appropriately and that the design produced meets the standard. Certification is independent of the supplier/customer relationship, which has a number of clear advantages. First the certifying body is indifferent as to whether the applicant meets or does not meet the requirements of DO-178C so has greater credibility when certifying as they are clearly much less likely to suffer from any conflict of interest. Second, because there is one certifying agency there is consistent interpretation of the standard and the fostering and dissemination of corporate knowledge across the industry through advice from the regulator.

Turning to DO-278A we find that the term ‘approver’ has mysteriously (1) replaced the term ‘certify’. So who, you may ask, can approve? In fact what does approve mean? Well the long answer short is anyone can approve and it means whatever you make of it. What usually results in is the standard being invoked as part of a contract between supplier and customer, with the customer then acting as the ‘approver’ of the standards application. This has obvious and significant implications for the degree of trust that we can place in the approval given by the customer organisation. Unlike an independent certifying agency the customer clearly has a corporate interest in acquiring the system which may well conflict with the object of fully complying with the requirements of the standard. Give that ‘approval’ is given on a contract basis between two organisations and often cloaked in non-disclosure agreements there is also little to no opportunity for the dissemination of useful learnings as to how to meet the standard. Finally when dealing with previously developed software the question becomes not just ‘did you apply the standard?’, but also ‘who was it that actually approved your application?’ and ‘How did they actually interpret the standard?’.

So what to do about it? To my mind the unstated success factor for the original DO-178 standard was in fact the regulatory environment in which it was used. If you want DO-278A to be more than just a paper tiger then you should also put in place mechanism for independent certification. In these days of smaller government this is unlikely to involve a government regulator, but there’s no reason why (for example) the independent safety assessor concept embodied in IEC 61508 could not be applied with appropriate checks and balances (1). Until that happens though, don’t set too much store by pronouncements of compliance to DO-278.

Final thought, I’m currently renovating our house and have had to employ an independent certifier to sign off on critical parts of the works. Now if I have to do that for a home renovation, I don’t see why some national ANSP shouldn’t have to do it for their bright and shiny toys.

Notes

1. Perhaps Screwtape consultants were advising the committee. 🙂

2. One of the problems of how 61508 implement the ISA is that they’re still paid by the customer, which leads in turn to the agency problem. A better scheme would be an industry fund into which all players contribute and from which the ISA agent is paid.

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The GAO has released its latest audit report on the FAA’s NextGen Air Traffic Management system. The reports updates the original GAO’s report and when read in conjunction with the original gives an excellent insight into how difficult cybersecurity can be across a national infrastructure program, like really, really difficult. At least they’re not trying to integrate military and civilian airspaces at the same time 🙂

My analogy is that on the cyber security front we’re effectively asking the FAA to hold a boulder over its head for the next five years or so without dropping it. And if security isn’t built into the DNA of NextGen?  Well I leave it you dear reader to ponder the implications  of that, in this ever more connected world of ours.

787 Battery after fire (Image source: NTSB)

The NTSB have released their final report on the Boeing 787 Dreamliner Li-Ion battery fires. The report makes interesting reading, but for me the most telling point is summarised in conclusion seven, which I quote below.

Conclusion 7. Boeing’s electrical power system safety assessment did not consider the most severe effects of a cell internal short circuit and include requirements to mitigate related risks, and the review of the assessment by Boeing authorized representatives and Federal Aviation Administration certification engineers did not reveal this deficiency.

NTSB/AIR-14/01  (p78 )

In other words Boeing got themselves into a position with their safety assessment where their ‘assumed worst case’ was much less worse case than the reality. This failure to imagine the worst ensured that when they aggressively weight optimised the battery design instead of thermally optimising it, the risks they were actually running were unwittingly so much higher.

The first principal is that you must not fool yourself, and that you are the easiest person to fool

Richard P. Feynman

I’m also thinking that the behaviour of Boeing is consistent with what McDermid et al, calls probative blindness. That is, the safety activities that were conducted were intended to comply with regulatory requirements rather than actually determine what hazards existed and their risk.

… there is a high level of corporate confidence in the safety of the [Nimrod aircraft]. However, the lack of structured evidence to support this confidence clearly requires rectifying, in order to meet forthcoming legislation and to achieve compliance.

Nimrod Safety Management Plan 2002 (1)

As the quote from the Nimrod program deftly illustrates, often (2) safety analyses are conducted simply to confirm what we already ‘know’ that the system is safe, non-probative if you will. In these circumstances the objective is compliance with the regulations rather than to generate evidence that our system is unsafe. In such circumstances doing more or better safety analysis is unlikely to prevent an accident because the evidence will not cause beliefs to change, belief it seems is a powerful thing.

The Boeing battery saga also illustrates how much regulators like the FAA actually rely on the technical competence of those being regulated, and how fragile that regulatory relationship is when it comes to dealing with the safety of emerging technologies.

Notes

1. As quoted in Probative Blindness: How Safety Activity can fail to Update Beliefs about Safety, A J Rae*, J A McDermid, R D Alexander, M Nicholson (IET SSCS Conference 2014).

2. Actually in aerospace I’d assert that it’s normal practice to carry out hazard analyses simply to comply with a regulatory requirement. As far as the organisation commissioning them is concerned the results are going to tell them what they know already, that the system is safe.

…and the value of virtuous witnesses

I have to say that I’ve never been terribly impressed with ISO 61508, given it purports to be so arcane that it require a priesthood of independent safety assessors to reliably interpret and sanction its implementation. My view is if your standard is that difficult then you need to rewrite the standard.

Which is where I would have parked my unhappiness with the general 61508 concept of an ISA, until I remembered a paper written by John Downer on how the FAA regulates the aerospace sector. Within the FAA’s regulatory framework there exists an analog to the ISA role, in the form of what are called Designated Engineering Representatives or DERs. In a similar independent sign-off role to the ISAs, DERs are paid by the company they work for to carry out a certifying function on behalf of the FAA.

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New Battery boxes (Image source: Boeing)

The end of the matter…well almost

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X-Ray of JAL Battery (Image Source: NTSB)

A bit more on Boeing’s battery woes…

The NTSB has released more pictures of the JAL battery, and there are some interesting conclusions that can be drawn from the evidence to date.

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JAL JA829J Fire (Image Source: Stephan Savoia AP Photo)

Boeing’s Dreamliner program runs into trouble with lithium ion batteries

Lithium batteries performance in providing lightweight, low volume power storage has made them a ubiquitous part of modern consumer life. And high power density also makes them attractive in applications, such as aerospace, where weight and space are at a premium. Unfortunately lithium batteries are also very unforgiving if operated outside their safe operating envelope and can fail in a spectacularly energetic fashion called a thermal runaway (1), as occurred in the recent JAL and ANA 787 incidents.

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