Figure F1 - Effect of the FLHV on the monitored fuel factor for the FMS predictions
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
101
USING THE MONITORED FUEL FACTOR
The arrows “1” represent the monitored fuel factor, based on a 18590 BTU/LB. If this monitored fuel factor is entered in the MCDU, the fuel predictions will be consistent with LEVEL 2 (see figure F1). FMS predictions will be hence somewhat penalized. Correcting the monitored fuel factor (arrow “2”) ensures the FMS predictions are consistent with LEVEL 1 (see figure F1).
For example, if:
1.
the cruise performance analysis is performed with a FLHV equal to 18590 BTU/LB, and
2.
the monitored fuel factor is equal to 2%
Keeping in mind the FMS predictions are based on a 18400-FLHV, the corrected monitored fuel factor is equal to the monitored fuel factor corrected for the FLHV effect, that is to say:
18400 .
2.0% . ..1. .×100 ≈ 0.98% ≈ 1.0%
. 18590 .
2.4.4. FMS PERF FACTOR
The FMS PERF FACTOR must be entered in the aircraft MCDU on the A/C STATUS page. The PERF FACTOR for the FMS predictions is the sum of the basic PERF FACTOR (in percent) and the monitored fuel burn deviation (in percent).
2.5. Basic FMS PERF FACTOR
On A300-600/A310 aircraft and fly-by-wire aircraft fitted with FMS1, the default PERF FACTOR is defined in the hardware and is equal to 0.0.
On aircraft fitted with FMS2, the default PERF FACTOR is either 0.0 (hardware) or is defined in the FMS Airline Modifiable Information (AMI) file, also called FM airline configuration file. The basic value defined in the AMI file corresponds to 1.0. For more information on that subject, read Flight Crew Operating Manual (FCOM), section 1.22.10 P2.
Of course, the PERF FACTOR that is entered in the MCDU overrides the default value.
This paragraph details the basic FMS PERF FACTOR to be considered when updating the FMS PERF FACTOR. The following figures are given in percentage.
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
USING THE MONITORED FUEL FACTOR
2.5.1. General assumptions
All these factors were determined with the following hypotheses:
.
Anti-Ice OFF
.
FLHV: 18400 BTU/LB
.
Air conditioning: -NORM for A319, A320 (except A320 CFM fitted with FMS2), A321, A340
with FMS1
-LO/ECON for A320 CFM fitted with FMS2, A330, A340 with FMS2
Note: The FMS performance databases are based on a default Fuel Lower Heating Value (FLHV, see also paragraph "B-3.4.3.1.Fuel Lower Heating Value (Fuel LHV)") set to 18400 BTU/LB. So, when FLHV goes up from 18400 BTU/LB to 18590 BTU/LB, it is necessary to reset the performance factor values to –1.0%. 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：getting to grips with aircraft performance monitoring(58)
