Plumbing query
Where does the fuel for the APU come from? Is the supply from a specific tank; is it from any and all, with its own complex of valves and pumps; or is it take off the fed to one or both main engines? Does the pipework between the supply point and the APU pumps remain full at all times, or do the pipes drain during normal flight?
Hypothesis: if there are empty pipes leading to the APU, and the APU supply is taken from some point in the system downstream of the first pumps in the path to a main engine, then starting up the APU will cause a low-pressure transient in the supply system. The short term effect, possibly for a few seconds, would be for almost all fuel to take the path of least resistance and so starve the main engines.
I understand from some posts too far back to find easily that the APU start sequence was initiated before impact. Was it before of after the start of the final "glider" phase.
On a different sub-thread, would flying through and knocking down the boundary fence, rather than hopping over it, have had any significant effect on the outcome?