And of course there is the assumption....
....that the fuel recovered was entirely representative of the bulk fuel loaded. If fuel stratification occurred, it is possible that the fuel that was being consumed in the hours before TOD was much higher in water content than the average water content in the fuel as a whole when loaded.
The theory has already been advanced in PPrune that in a steady-state (cruise) condition the ice accreting on the face of the FOHE was removed at a rate equal to its deposition and that it was only when the flow dropped during descent that the equilibrium changed (despite higher OAT) and ice buildup began. When the aircraft piled in, the remaining fuel that didnt leak de-stratified and the ice remixed as dissolved water, and the ice that built up in transit from wing to engine dropped out mainly as free water (because the concentration of water to fuel was higher in the lines) ("ingress of fire fighting foam" doesnt do it for me). Because the proportion of water consumed during the flight was higher than that in the bulk of the fuel loaded, it follows that the concentration of water in the remaining bulk fuel at the end of the flight - into which the ice redissolved - would be less.
IF, repeat IF you accept that buildup model, then you also have to accept that it is possible that the water content of the fuel sampled at end of journey may not have been the same as that loaded prior to departure and that the water content in the fuel delivered to the FOHE was not homogenous during the flight.
Anyone who has experience of returning to a frozen Margarita on a hot day after an extended potty break knows what I am suggesting.
Pinkman
Last edited by Pinkman; 5th February 2009 at 22:33.