About ten pages back, there seemed to be an emerging consensus that the reason the RR engine was being singled out for changes in operating procedures was the presence/position/design of the FOHE. If blocking of the heat exchanger was the immediate cause of the loss of power, then the time between the demand for increased thrust and the start of uncommanded power reduction could give an indication of where in the system the ice came from. I could dig out the time from the AAIB report, but I have no information on the speed of fuel flows or the geometry of the pipework. Does anyone in possession of the relevant information care to do the sums?