I recall that, from much earlier in the investigation, data on 777 engine and aircraft handling was checked for many hundreds of thousands of flights (or was that flight hours? Not sure) and the parameters found for BA038 and G-YMMM's last journey were right down at the very tail of the distribution with the lowest rates of climb and hence the lowest incremental thrust/fuel flow, coupled with a very long flight at unusually cold OAT followed by an unusual uninterrupted continuous descent into LHR with only one power application above idle which rapidly resulted in the thrust reduction seen.
I accept that BA038's flight profile might have been unusual, or rather an unusual concatenation of ordinary events, the chance pattern of which placed them at an extreme point on the 'bell curve'. But even the extreme position on the curve does not preclude the possibilty of bilateral 'engine failure' if say, just one extraordinary item was removed and thus something like this ought to have happened before?
I don't know just how sophisticated any tests have been, but it is not beyond the wit of man and an imaginative test rig, to reproduce the accident conditions routinely. Some aircraft components - although not a whole engine I wouldn't have thought - a quantity of appropriate fuel and reliable means of lowering the temperature of tanks, pumps, pipes and control systems. Unless and until someone has done this and reproduced the fault - where
reproduce is the scientific key - it will not be possible to say we have the answer to BA038.
I think Phil Gollin has said as much, but with greater scientific weight than I could possibly aspire to. It seems that the fault condition
could be achieved - intermittently - but only by forcing certain parameters well outside those thought to obtain in G-YMMM. One of which was to artificially increase the proportion of water by direct injection
near to suspected critical components. (Italics my speculation.)
If this localised increase in water density was the only way to trigger the fault condition, then the fact that - according to Phil Gollin's text - ice tends to form on the bottom - coldest - part of the tank (and was extremely difficult to dislodge) suggests that this would keep the bulk of the available water away from anything vital. And even if it did in one tank, enough to choke its engine, why did it happen in the other at the exactly the same time?
All I say is, again in
my opinion, that this accident was extraordinary from the start, but after all this time the answer appears to put it in the category of 'the perfect crime' and only just short of it being caused by an Alien Energy Beam.
Roger.