Well here’s the question, supposing it was an electrical fault that was the root cause of the accident for a moment and the engines not performing as they spills was a side effect for just a moment, what sort of performance could we expect here? You mention the engines could be gravity fed fuel but performance would likely be less than TOGA power.
Probably a lot less. Call it 50-60% of TOGA (this is really based on aircraft like the 767, with dumb fuel systems, that didn’t need electricity for everything). That would be enough to keep flying, but less than you’d need for a normal approach. Nowhere near enough to fly away.
Well we know the aircraft crashed at take off, so then the question is when departing an airport like AMD with the aircraft loaded as it was, what was the minimum amount of engine power required to maintain a safe take off?
Presumably 50%, given that it has to be able to fly away on one engine, although that does assume gear up. It can still be done gear down, but would require the weight to be below the nominal max. I’d guess about 40 tonnes less than max.
It seems unlikely that the full TOGA power would be required since there is always a safety margin built into these calculations since the cost of getting it wrong can be huge.
TOGA is used a lot, especially when it’s hot. Don’t assume that there’s lots of margin. Having said that, the twins have more margins than the quads, for obvious reasons.
Another point, in Boeings design of the jet did they account for a failure mode where the entire electrical bus was non operative to the point where a RAT is less useful than an indoor fan?
There comes a point at which they’d just decide it’s a bad day. Loss of all busses (and not just the generators and batteries) is unlikely to end well.
My theory is based on the idea that the jet was so poorly maintained that electrical power distribution degraded to the point where you couldn’t count on power being delivered anywhere.
Possibly, but it’s the sort of aircraft that becomes very unhappy if it can’t get past all of its internal checks. I can easily accept that the cabin and fittings were in poor shape, and comments about the lack of a/c make me wonder if the APU was serviceable.
Again that’s an insane failure mode and one I suspect not even Boeing would design for in their wildest dreams.
But we don’t really know what the failure was. We know the outcome, and some of the symptoms, but have no idea what started the ball rolling. Is it something specific to that aircraft, or is it in every 787. That’s what everyone is waiting to hear. The support pilot making a mistake with the flaps was what Boeing wanted to hear, as it would let them off the hook. Now everybody is looking at them again. Deserved or not.
