Leicester Helicopter Crash

[Sooty655]

This makes chilling reading. Appears that the failure of a "sealed for life" bearing caused the yaw control system to physically disconnect itself from the pilot's pedals, despite the specified locking arrangement being correctly fitted.

AAIB Interim Report

[Spitfire]

This is similar to the Red Arrow incident where the chute failed to activate on premature ejection ...

It seems one shackle bolt was done up 1 or 2 mm too tight - jamming the shackle so it could not release and deploy ...
Martin Baker were aware of the issue but had not informed the RAF...

The premature ejection itself due to the problem with the firing handle safety pin should not have been fatal ...

Its the swiss cheese issue where all the holes line up to create the seemingly impossible scenario which sadly then becomes possible

Such inconsequential minor maintenance issues with such catestrophic consequences

I have discussed this here before - having done a brief law study course at college many moons ago during which we were told there are usually two causes of any accident ...and it has stuck with me ever since ...
1) Causa Causans - the causing cause or causation - that car hit the other car
2) Causa Sine Qua Non - the 'without which not' - all the things that happened in sequence that day to put those two drivers at that precise spot at the same time ... so - 'an intervening cause of loss which, though not direct, may nonetheless contribute to the loss' - had one driver had a second bowl of cereal - or broken a shoe lace - or had to stop for petrol the cars wouldnt have collided because they wouldnt have been in the same place ...

Sadly aircraft accidents are usually riddled with such sequences, that seem unconnected, but then line up to create the problem. The AAIB are to be congratulated every time for finding these issues.

[Sooty655]

I'm not sure there is much similarity between the incidents. I don't think the AAIB are suggesting the nut which was found over-tight had actually been over-tightened. Seems more likely it was tightened by the same bearing failure which caused the nut on the other end to unscrew. Opposite effects at opposite ends when the supposedly stationary shaft started to be turned by the bearing.

[Spitfire]

Well alright - not exactly 'similar'

But the 'swiss cheese' principle and 'Causa Sine Qua Non' still applies and I am also gobsmacked how good the AAIB were at pinpointing the errors/faults in both cases... ...