<Phil Gollin>
Feathers ;
I have to say that I can't see that there is much difference in reality, six or seven seconds can be accounted for by a slightly different amount of ice (in some form) being present and the 'detaching' behaviour of that accumulated ice by the slightly different fuel flows noted in each engine. .........
......... Let's face it, it has been shown that ice is the only remaining possibility, and how else can such a restriction occur other than that some form of solidified ice arrives at a constricted area in high concentration, overwhelming the ability of the fluid part of the flow to pass at sufficient rate.
But this is like having your cake and eating it.
The engines had their commands at the same time, but the roll-backs occured at slightly different times, HOWEVER the effect on final thrust was almost exactly the same.
</Phil Gollin>
I like cake!
On the assumption that a similar ice/fuel mixture was present, then the fuel flow that could pass the obstruction would be limited by the consistency of the ice and the throat area it is trying to pass. This will be the same in both engines (although perhaps there is a 'handedness' to the fuel piping, I do not know).
<Phil Gollin>
You say "ice is the only remaining possibility" - but this is what annoys me. They can only reproduce one aspect (the cavitation damage) but without any real expalantion (the two icing scenarios are not really supported by the report) so grasp that one straw. If they could reproduce the icing that leads to the cavitation damage AND show that that icing condition can be variable in time but not effect - THEN they would have something that would convince me.
Don't get me too wrong, as a cautious warning (as opposed to a "finding") I would be happy, but fail to see why this mysterious icing wouldn't affect 777s powered by other types of engines.
</Phil Gollin>
Well, the latter statement is quite correct, and you will see that AAIB are saying that an urgent investigation into precisely that condition is needed, it clearly isn't just a Trent issue it's just that the one instance so far happened to be on a Trent-powered airframe.
As for the reproducibility, yes, so far they have shown that a problem is seen in circumstances not that alike to the real fuel system. More work is to be carried out to improve the test to mimic reality better. They may not succeed, but they have to try.
The ultimate mimic though would be a 12 hour flight from China in similar TAT conditions and flight profile with the same approach clearances, descent rates, power profiles. If they are lucky they get to see it happen again, but maybe this time with a 777 embedded in Hatton Cross tube station.
The other thing to note, they state quite clearly that very little is known about the precise effects of ice in fuel under varying circumstances. So a major research task would be called for to understand it better, that will take time.
Do you feel that it wasn't ice? Because there surely are precious few other culprits lurking.