FOHE, I find it suprising that the fuel is directed to flow through the narrow bore pipes & oil throught the larger bore outer casing. Why not have it the other way round? the heat exchange would surely be the same?
There still seems to be some confusion over how the correct oil temperatue is maintained. Does the oil flow switch on & off to give the desired result? if so, this could effect ice melting, which has been said to take only a few seconds when engine power is demanded? (That was said on one report, but clearly did not happen when engine power was demanded on the incident in question)