it has not been possible, due to limitations in the available recorded data, to totally eliminate the possibility that a fuel restriction, from ice, formed elsewhere in the fuel system which, in addition to an FOHE restriction, contributed to the engine roll backs on G‐YMMM. It should be noted that extensive testing and data analysis has not identified any features elsewhere in the aircraft fuel system which would have caused a large enough concentration of ice to accumulate and cause a restriction.
The report refers earlier (p7) to the possibility of water accumulating during the flight rather than being ingested with the fuel burned
some of the water settled and froze on the bottom of the fuel tank
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and on page 8 to the effect of water injected into the fuel flow.
It seems to me that there is a serious possibility that at warmer levels, ice which has accumulated in the centre tank will melt, allowing the fuel scavenge pumps to feed it into the (still cold) main tanks, where on its way down to the boost pump inlets it will freeze. If the centre tank melt water is suddenly presented to the scavenge inlets, by a decelleration or a change of attitude, it will result in a significant temporary production of ice in the main tanks.