To have an explosion in the CFT you need several individually very unlikely events to coincide:
- an empty CFT (not likely in this case, as a SSH-LED flight is fairly long, not sure if wing tanks alone sufficient)
- extended exposure to high temperatures (unlikely, as departure was at 6am, just after sunrise, turnaround was in the cool of the night)
- an ignition source to explode the vapors
Also a CFT explosion would cause a very different disintegration pattern than what we see on the wreckage. The wing box with both wings attached reached the ground in one piece, with forward fuselage also attached. Whatever happened here happened in the back, close to the tail section.
what, if anything, could cause the tail cone to be detached from the rest of the tail in midair?
Good question, probably the key question. From some photos of the tail section it is clear that the entire rear tail section comprising the HS structure and the APU/tail cone broke away cleanly just aft of the pressure bulkhead, leaving just some of the top fuselage skin held by the rudder structure that remained attached to the tail section before the pressure bulkhead. I see three possible explanations:
A) Aerodynamic forces tore the HS from the remaining tail section with a downward force as it tumbled following initial disintegration, leaving the surviving tail section and the tail cone with APU initially attached. With the weight of the APU the weak remaining link eventually broke, and the two pieces landed separately (but only 350 metres apart, suggesting this scenario). This scenario assumes that the failure occurred somewhere in the rear fuselage (bomb ?). Any rear fuselage pieces further back along the flight path from the tail would confirm this scenario.
B) A catastrophic failure of the entre HS structure (fatigue or bomb carefully placed in the bay to achieve this). As the role of the HS is to
pull the tail down (and the nose up), a failure would result in the HS parting with the rest of the structure downwards. The subsequent sequence is similar to A. If this is the case, the HS should be the first piece of wreckage to be found along the flight path (where is it ?)
C) Rupture of RPB creating a pressure wave strong enough to rip off the HS together with the tail cone and APU. This could only happen in the pressure relief doors do not function properly. If this were the case, examining the fairly intact tail section would confirm it instantly.