A further thought on the supply tank capacities. We know that the right tank holds 4kg less than the left tank, the idea apparently being to prevent both engines flaming out at the same time due to fuel starvation.
Given that the aircraft would have been flown exclusively from the right hand seat, would there not be a natural tendency for orbits to be flown to the right, as was the case here? In such circumstances, unless the turns are perfectly balanced, there would be a tendency for fuel to cross the tank divide from the tank which was supposed to hold more, to the tank which was supposed to hold less?
For as long as there is sufficient fuel in the main tank to keep the supply tanks topped off, this situation would correct itself, but once you have insufficient fuel to top them off, and/ or the transfer pumps are switched off, there is no way to correct this situation, so all bets should be off as to which engine would flame out first, and how long a gap there would be between flameouts.
Would the situation not be better if the supply tanks were in fact completely separate from each other, giving greater predictability over what their relative contents would be?
The manual said he had 4 minutes from first flame out to get the aircraft on the ground, and it is very hard to imagine the shock when the second engine flamed out so quickly thereafter. The odds against a successful autorotation from that height in those circumstances were always significant; that degree of shock made them overwhelming.
Which does nothing to address the elephant in the room: why does there seem to be no sign of fuel anxiety in any of the pilots actions? Everything in hindsight screams "land" and yet he was taking on additional apparently routine tasking beyond what would seem any point of reason. I must confess to being a little underwhelmed by the report in its lack of exploration of this aspect. We learn that the initial tasking was to do with an incident on a railway, but what were these routine tasks at the key stage of the sortie which seem to have cropped up at such short notice? Could they have affected the pilots judgement, for example relating to a threat to life, sufficient to persuade him to stretch the elastic a bit further?
I appreciate it is not the AAIBs remit or style to speculate, but the report just seems to fall short.