Fuel System Design Question.
Thanks Sweedish Steve.
So the answer is b). In one sense I hoped as much.
I don't have time to explain my full proposed theory at the moment but I will ask another question if I may.
What prevents the CWT pumps from restarting due to aircraft attitude change once they have initially shut down due to the 9000kg limit being reached. Presumably the answer is nothing.
In which case a "slug" of "bad" fuel could be sent down the lines impacting both engines at a critical time the slight time difference being due to small differences in the LH to RH installation of pickups etc.
The key difference to dxzh post is that the fuel in the CWT is common to both engines. All we need to show is that this fuel was contaminated by high water content. Since the water scavenge pumps presumably shut down with the boost pumps water would have separated out and may well have been liquid due to the heat from the ambient as the aircraft descends, the A/C packs + of course reduced volume left in the tank.
Evidence of such an event may have been removed by a further attitude change causing the CWT pumps to shut down again and purge "good" fuel through the lines from the wing tanks...but too late to save the day. I believe somebody has already posted something similar a long way back in this thread.
Evidence of water in the CWT cannot be validated due to accident damage and contamination.
I'll try to write up the full sequence later today unless somebody shoots me down at this point.
Such a mechanism brings issues like the "spurious" maintenance water warnings, the extra cold temps, low ground temps etc into play and maybe explains why only this aircraft suffered such an event.
I wonder how long an engine takes (at idle) to use the fuel present in the lines from tank to engine? 5 secs, 10 secs, 30 secs, min before starting to spool down?
I'd still love to know if other 777's have shown evidence of cavitation. I suspect they have and that this is a red herring from the point of view of the accident.