Water quantities.
The AAIB Interim report no. 2 (my bold) states (page 7) that the
"... accident flight might have contained up to 70 ppm of dissolved and entrained (suspended) water ...."
whilst their post accident samples showed
".... Fuel samples taken from G-YMMM after the accident indicated that the water concentration in the fuel taken from the left main tank sump, APU line and Variable Stator Vane actuator was approximately 40 ppm ......".
However, the tests took place using 90 ppm something like 28 to 125% more than was in the crashed aircraft - as
".......the industry standard for continuous system operation tests, aiming to condition the fuel with 90 ppm of water. ......"
So, not only is the incident report rather cagey about what actually happened, but the tests do not seem (unless I missed something) truely representative of what happened. The report still doesn't explain where the additional water might have come from.
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However, it does look like there is a whole new bunch of research on fuel/ice mixtures to come about.
.