Barit1 - I am really surprised that Boeing let the R-R Triple7 out of the barn without very aggressive fuel heating capability. Boeing's experience with fuel icing goes back six decades - and they have a library full of lessons learned from B-47, B-52, 707 etc.
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Any chance Boeing and R-R had a difference of opinion, and R-R stated "our engineering says it's good enough, and you're just operating on opinion" ?