Originally Posted by
Ivor_Bigunn
In the absence of any visible frame distortion or tearing, I would deduce that all 4 securing bolts must have been U/S or missing, so the door could slide upwards 4" under the fitted bottom springs pressure, become completely clear of the retaining devices, and be fired out into space by cabin pressure. But how that could come about I do not have a theory.
What function do those springs have when a plug door is fitted?
It's clear what role they perform when a live door is being opened, but do we know they are even present when the aircraft has the plug door (which is only ever going to be opened on a check)?