Originally Posted by
phil gollin
According to this, the two investigations have been completed (at least they have specific "findings" and are factually known) as opposed to theories or speculation !
I think it is credible that the test rig investigations have moved forward substantially from the last official reports, particularly with another incident providing another dataset. This is supported by the image provided.
Likewise, they have supposedly explained where the additional water came to cause the problem.
Because I don't think this is an issue any more. It looks from the details and the image that we are
not looking at a big slug of ice collecting elsewhere and getting pulled down the pipes by the increased fuel demand, but rather it is small amounts of ice acreting at the entrance to the small diameter FOHE tubes. Increased (cold) fuel flow (as thrust was demanded) would then both cool the area
and probably pull the ice into the tubes, blocking them.
EDIT: The above was based on the NTSB statement and the FOHE image, now looking at the AAIB report it is clear that the ice acretes on the pipework and is swept onto the FOHE inlet.
Leaving aside possibilities of ice in tanks not being detected or removed at sumping, there would still have been 5L or so (according to the AAIB) or water in the fuel. Looking at the FOHE image, I don't think you need anything near 5L of water to create a serious problem. Just the mechanism for small amounts to crystalise in a bad place - which is what appears to have now been established.
Unforunately they haven't bothered to highlight other engine installations in other planes which need similar flight restrictions.
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If you look back on the thread there are plenty of posts identifying the Trent plumbing as different, particularly in the location of the FOHE. The Trent 800 FOHE may well be different again, sufficiently for this not to happen on other Trents.
The publication of the image strongly suggests to me that they have got this ice acretion repeatable on the test rig, in which case testing other FOHEs could have already ruled out this particular problem.