Is it sensible to have the same single fuel temperature sensing system for both fuel/engine systems on an ETOPS aircraft?
In hindsight, you would have to say no. By the way, British Airways 747-400's have 2 probes (in the
same tank), with a switch in the cockpit to select either A or B probe (for MEL relief), but as far as I know, there is no automatic monitoring to compare the two probe temperatures. You would only know if one had failed if the reading was blank or showing unreasonable values. Our airline and many others don't have dual probes on our 747-400's. I'll have to check, but I'm not sure if BA has a dual system on their 777's. I'd be surprised if they didn't (it would seem to be a backward step).
Anyway, I'll try to confirm this later today.