...standard operating procedures on the 777 (for all operators) is use the centre tank FIRST and then the wing tanks.
Correct. I think one of the reasons is wing bending relief. If you have u/s centre tank fuel pumps and still have fuel in there, on most types it is a) limited to a certain amount and b) has to included as payload, not fuel (and not for the obvious reason!)
Coming at this from an IT perspective, can anyone tell me what the FDR actually records?
Specifically, if it records something that was commanded to happen, would it necessarily know that the 'something' didn't actually happen, if there was no failure signal?
Most of the important valves/actuators, etc. have some sort of feedback as to the actual position or on/off open/shut, so that the operating systems can flag up a problem. Many, many maintenance messages that are generated read "XXX not in commanded position"; they often clear but are a sign of possible future problems. If there are no sensors to show success or failure, then this might be able to be logically inferred from other parameters; don't know how much of this goes on as I didn't design it...
Would it be possible for the FDR to record the open-valve event, but have no knowledge of the valve's failure to do so?
Given the importance of this particular variable, I would wager a serious sum that this information would have been recorded on the FDR, QAR & non-volatile memory in the EECs, to name but a few.
Many thanks to FullWings and Swedish Steve...
Again, this shows us that we are only as good as the (blurry) manuals available to us
Cheers.
NSEU
Glad to be of service
