If the seats are fitted with five safety pins and the one in the seat pan was incorrectly fitted, regardless of how, why did the other pins insertion not stop the firing sequence? Is not the removal of the pins the last sequence before engine start as another safety check?
Of the various Pins, in a Mk10 seat only 2 are concerned with preventing the seat firing (IIRC - not flown a Mk10+ since 94, but many recent hours on a Mk4):
- Seat Pan firing
- Main Gun sear
Seat Pan firing is in place "Safe for Parking" which is how aircrew would expect to find and leave the seat.
Main Gun sear is removed "Safe for Parking" but inserted "Safe for Servicing". As posts above state, "Safe for Servicing" may or may not apply to routine night in/out hangar movements depending on policy.
I do not recall exactly from my service days, but on live seats now I am still frequently surprised by arriving at a cockpit, and finding the seat pin not visible, and/or straps over even through the handle. I was taught that you leave the seat as the next person needs to find it - and the 1st thing they will do is check the pin is in, so ensure it is visible without needing to get close to it. And of course, the last thing you do as you leave is check the pin isn't it...
NoD