Visible damage to the lugs indicates plug separated by moving up then out.
The lug cap-screws appear to have sheared.
The aircraft was reported to have suffered pressurization issues on previous flights.
At a guess, I would suggest that the two upper roller track blocking bolts (center) were missing, or the two lower spring restraining bolts (not shown) were missing.
In either case, cyclic pressurization loads flight by flight would only be restrained by the lug cap-screws (top left hand corner of plug - labeled 1 and 2).
Since the door is curved (the fuselage is circular), and extends down to the floor (which is below the cross-sectional 'waist') the resultant net load on the door would be slightly upwards - not horizontal.
This would put cyclic shear loads on the lug cap-screws with every pressurization cycle (flight) which they are clearly not designed to carry.
I suggest that one or more progressively failed, (flight by flight), until eventually, the remaining cap-screws were unable to resist the load, and simultaneously failed catastrophically.
![[Image: attachment.php?aid=437]](https://auntypru.com/forum/attachment.php?aid=437)
The lug cap-screws appear to have sheared.
The aircraft was reported to have suffered pressurization issues on previous flights.
At a guess, I would suggest that the two upper roller track blocking bolts (center) were missing, or the two lower spring restraining bolts (not shown) were missing.
In either case, cyclic pressurization loads flight by flight would only be restrained by the lug cap-screws (top left hand corner of plug - labeled 1 and 2).
Since the door is curved (the fuselage is circular), and extends down to the floor (which is below the cross-sectional 'waist') the resultant net load on the door would be slightly upwards - not horizontal.
This would put cyclic shear loads on the lug cap-screws with every pressurization cycle (flight) which they are clearly not designed to carry.
I suggest that one or more progressively failed, (flight by flight), until eventually, the remaining cap-screws were unable to resist the load, and simultaneously failed catastrophically.
