For those interested, here’s a draft of the ‘Fundamentals of system safety‘ module from a course that I teach on system safety. Of course if you want the full effect, you’ll just have to come along. :)
Archives For Safety
The practice of safety engineering in various high consequence industries.
MH370 and the problem of privileging hypotheses
The further away we’ve moved from whatever event that initiated the disappearance of MH370, the less entanglement there is between circumstances and the event, and thus the more difficult it is to make legitimate inferences about what happened. In essence the signal-to-noise ratio decreases exponentially as the causal distance from the event increases, thus the best evidence is that which is intimately entwined with what was going on onboard MH370, of less importance is evidence obtained at a distance in time or space.
“Data! Data! Data!” he cried impatiently. “I can’t make bricks without clay.”
If anything teaches us that the modern media is for the most part bat-shit crazy the continuing whirlwind of speculation does so. Even the usually staid Wall Street Journal has got into the act with speculative reports that MH370 may have flown on for hours under the control of persons or persons unknown… sigh.
After the disappearance of MH370 without trace, I’d point out, again, that just as in the case of the AF447, disaster had either floating black boxes or even just a cheap and cheerful locator buoy been fitted we would at least have something to work with (1). But apparently this is simply not a priority with the FAA or JAA. I’d note that ships have been traditionally fitted with barometrically released beacon transmitters, thereby ensuring that their release from a sinking ship.
Undoubtedly we’ll go through the same regulatory minuet of looking at design concepts provided by one or more of the major equipment suppliers whose designs will, no surprise, also be complex, expensive and painful to retrofit thereby giving the regulator the perfect out to shelve the issue. At least until the next aircraft disappears. Let’s chalk it up as another great example of regulatory blindness, which I’m afraid is cold comfort to the relatives of those onboard MH370.
1. Depending on the jurisdiction, modern airliners do carry different types and numbers of Emergency Locator Transmitter (ELT) beacons.These are either fixed to the airframe or need to be deployed by the crew, meaning that in anything other than a perfect crash landing at sea they end up on the bottom with the aircraft. Sonar pingers attached to the ‘black box’ flight data and cockpit voice recorders can provide an underwater signal, but their distance is limited, about a thousand metres slant range or so.
There’s been a lot of ink expended on examinations of the causes of the Challenger disaster, whose anniversary passed quietly by yesterday, but are we really the wiser for it?
Gregory (Scotland Yard detective): “Is there any other point to which you would wish to draw my attention?”
Holmes: “To the curious incident of the dog in the night-time.”
Gregory: “The dog did nothing in the night-time.”
Holmes: “That was the curious incident.”
What you pay attention to dictates what you’ll miss
The point that the great detective was making was that the absence of something was the evidence which the Scotland Yard detective had overlooked. Holmes of course using imagination and intuition did identify that this was in fact the vital clue. Such a plot device works marvelously well because almost all of us, like detective Gregory, fail to recognise that such an absence is actually ‘there’ in a sense, let alone that it’s important.