I think your theory is quite plausible Mick. Most aviation accidents are a combination of unlikely events and sometimes incredibly unlucky timing.
Thanks. When stepping through what is most assuredly an entirely speculative hypothesis people often throw up Occam's Razor; my usual reply is that Occam was not a air crash investigator. From AF447, with a simple cause but entirely unanticipated crew response, to AF4590, with its utterly improbable and seemingly unrelated chain of events (a month before the accident another airplane has a counterfeit part fitted in an unauthorised manner ...), airplane crashes often have an extraordinarily complicated chain of events leading up to a disaster.
I once spoke to someone involved in the Egypt incident. The notable thing was the intensity of the fire and the very short time for the flight deck to become uninhabitable. The incident report doesn't quite convey the ferocity of it.
I went over every piece of information I could get my hands on regarding MS667. One of the more instructive items was the interior picture of the damaged flight deck; you can see that the inner pane of the FO's windshield has melted away from the frame - that's a quarter inch thick pane of Herculite chemically strengthened glass, you need around 2600°F (1400°C) to achieve that result.
I would love to know if anybody at Boeing ever asked, "Could something like this ever happen in flight?" or "Under what circumstances could something like this happen in flight?" If you had that mindset and looked at the UA027 windshield heater fire (
NTSB Identification: ENG10IA029) where the Captain had his oxygen mask torn off
twice, you may have asked, "What would have happened if instead of the mask coming off, the hose had have disconnected?"
Have you considered the possibility of oxygen bottle explosion? It's location adjacent to the avionics rack could account for selective avionics loss.
Yes, I have; it's an intriguing possibility and it's a one-stop shop, so to speak. When I've looked at what sits on the E1 and E3 racks in the notional "firing line" and back-blast areas respectively, I can't see them losing all of the cockpit display units or all their comms from either of the bottles rupturing in similar fashion to QF30. Accordingly I can't reconcile that cause with a failure to descend at some point and the lack of a distress call but I'm speculating about a hypothesis so who knows.