411A, it's difficult to argue with that brief yet highly perceptive analysis!
Bearing in mind that the A310 has ample Fuel Quantity Indicators, Fuel Flow Indicators, an ECAM fuel page and low fuel state warning lights and does not just rely on FMS fuel-at-waypoint predictions, there seems little mitigation. In fact none whatever.
Perhaps the FMS should be required to be capable of displaying fuel at waypoint values for any conceivable a/c configuration to make it more idiot-proof?
Would it not be better to delete fuel-at-waypoint information completely - or display "NOT AVAIL" if the performance degradation is outside the range which the FMS can display?
This case holds a professional interest for me as I have concerns about the FMS fuel remaining information in modified versions of the a/c which can carry more fuel than the max value assumed by the current FMS - and which also have greater drag than the baseline A310. My view is that the FMS must be modified to accept the actual fuel value from the volume in tanks corrected by the Cadensicon (Fuel SG sensor) for all fuel loads - and that the assumed burn rate must represent the modified a/c's actual burn rate. If that can't be done, then N/A or NOT AVAIL should be displayed on the FMS fuel prediction column - rather than optimistic lies! Currently the FMS only displays fuel predictions based upon the PERF FACTOR used during preparation. Interestingly, the FCOM advises
" PERF FACTOR: It reflects the A/C performance status. The FMC makes all the calculations and predictions upon the value of the PERF FACTOR. It is defaulting to zero but may be changed by WRITING/INSERTING the new value in line 6L. This value should not be changed by the crew."
So it is pretty clear to me that if the ac is in a condition which does not reflect the pre-loaded PERF FACTOR, and the crew is recommended not to change that value, then the fuel on board predictions will be incorrect.
Last edited by BEagle; 5th May 2004 at 08:02.