Originally Posted by Green-dot
If the temporary reverse logic is corrected in less than 15 seconds, the spar valve moves [open->close->open] and will be in transit for almost but less than 30 seconds without ever reaching the closed position. Result, obvious limitations to the fuel flow. No alerts are presented and no visual indications if fuel synoptic and/or fuel management maintenance page are not displayed at moment of occurrance
In normal circumstances, MMM should have been around one minute from touchdown, so I figure out it was only 30 to 40 seconds from impact on this day when right engine reduced to 1.03 EPR
According to AAIB, both EPRs reduced and
maintained steady values, 1.03 and 1.02, therefore I don't see as plausible scenario that spar valves were constantly in transit, which would have produced, I think, anything but
steady values.
I'd rather go for your previous hypothesis:
Focussing on the T7 dual engine roll back again, just suppose both spar valves had temporarily closed for, say, 80 percent (only 20 percent capacity remaining) with boost pumps on. Could that have resulted in engine roll backs to a stabilized thrust level above flight idle and cause cavitation at the engine pumps as the engines initially responded and then rolled back because reduced fuel flow did not meet engine demand?
And I totally support the following:
I assume similar simulations such as mentioned above would have to be performed to find answers or are there other means (computer simulations?) to observe engine behaviour under such conditions?
I would easily conceive a fuel flow restriction by mechanical means, like a partial spar valve closure, but I don't see how the fuel itself would produce its own restriction in a way that such a restriction stabilizes for the remaining of the flight and don't deteriorate any further ?