Firing details unimportant, Deliverance, Mrmungus?
There's an uninterrupted chain of events from the last time the seat was secure and inert to it being accidentally fired and then failing to operate as expected.
I'd say that all the steps are relevant, especially if 19 other instances were recorded. The procedures are presumably designed to prevent any cases of accidental firing, and so any errors are notable.
I agree with Deliverance that the parachute failure was particularly serious, since it was unexpected. If that element of the seat had worked properly, then there probably would have been an injury not a death. While it might not have been a problem at speed, the seat is billed to protect at zero speed, and so its failure to do so is notable. In an uncontained engine failure and fire at the beginning of take off would it have required that performance?
The opportunity to mistighten the bolt does seem to be flaw in the design; however, if there was a shoulder to the bolt to ensure its position, it seems possible that it could contact the frame without the correct tension being set, and what would be the consequences of that? If a bolt needs to have play, then it seems particularly dangerous to lose sight of that over the years, as the natural tendency would be to tighten loose bolts. Fancy German bicycle components usually have a torque setting (with units) anodized next to the bolt hole (granted because it's easy to chew up the alloy); maybe a similar practice could have helped here
"Don't assume check?". The biggest problem seems to be a lack of appreciation somewhere in the chain from manufacture 30 years ago to accident in 2011 that the tension on the bolt is a crucial think to check. Are there other aspects of the design that could be sensitive to mis-setting and drifting to being less safe with time?
Last edited by awblain; 2nd Feb 2014 at 19:48.
Reason: typo