Archives For Aerospace Safety

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 the term means whatever you make of it. What it usually results in is the standard invoked between a supplier and customer, with the customer 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.

Interesting documentary on SBS about the Germanwings tragedy, if you want a deeper insight see my post on the dirty little secret of civilian aviation. By the way, the two person rule only works if both those people are alive.

What burns in Vegas…

Ladies and gentlemen you need to leave, like leave your luggage!

This has been another moment of aircraft evacuation Zen.

Piece of wing found on La Réunion Island, is that could be flap of #MH370 ? Credit: reunion 1ere

Piece of wing found on La Réunion Island (Image source: reunion 1ere)


Why this bit of wreckage is unlikely to affect the outcome of the MH370 search

If this really is a flaperon from MH370 then it’s good news in a way because we could use wind and current data for the Indian ocean to determine where it might have gone into the water. That in turn could be used to update a probability map of where we think that MH370 went down, by adjusting our priors in the Bayesian search strategy. Thereby ensuring that all the information we have is fruitfully integrated into our search strategy.

Well… perhaps it could, if the ATSB were actually applying a Bayesian search strategy, but apparently they’re not. So the ATSB is unlikely to get the most out of this piece of evidence and the only real upside that I see to this is that it should shutdown most of the conspiracy nut jobs who reckoned MH370 had been spirited away to North Korea or some such. 🙂

In celebration of upgrading the site to WP Premium here’s some gratuitous eye candy 🙂

A little more seriously, PIO is one of those problems that, contrary to what the name might imply, requires one to treat the aircraft and pilot as a single control system.

The enigmatic face of HAL

The problem of people

The Hal effect, named after the eponymous anti-hero of Stanley Kubrick and Arthur C. Clarke’s film 2001, is the tendency for designers to implicitly embed their cultural biases into automation. While such biases are undoubtedly a very uncertain guide it might also be worthwhile to look at the 2001 Odyssey mission from Hal’s perspective for a moment. Continue Reading…

Comet (Image source: Public domain)

Amidst all the online soul searching, and pontificating about how to deal with the problem of suicide by airliner, which is let’s face it still a very, very small risk, what you are unlikely to find is any real consideration of how we have arrived at this pass. There is as it turns out a simple one word answer, and that word is efficiency, the dirty little secret of the aviation industry. Continue Reading…