BACKGROUND
Moreover, SR depends on aerodynamic characteristics (Mach number and lift-to-drag ratio), engine performance (Specific Fuel Consumption)1, aircraft weight (mg) and sound velocity at sea level (a0).
Aerodynamics
Where SR is the Specific Range in NM/kg a0 is the celerity of sound at sea level in m/s M is the Mach Number L/D is the lift-to-drag ratio SFC is the Specific Fuel Consumption M is the aircraft mass in kg T is the static air temperature in degrees Kelvin T0 is the static air temperature in degrees Kelvin at sea level
M . L/D ê. SR . m ê. SR . SFC ê. SR .
3.3.3. Principle of the method
The following parameters is determined based on data recorded during stable
cruise flight legs:
-the actual specific range,
-the delta (difference in) specific range in percentage relative to the book level
(predicted specific range), -the delta EPR/N1 required to maintain flight conditions, -the delta fuel flow resulting from this delta EPR/N1, -the delta fuel flow required to maintain this delta EPR/N1.
1 Specific Fuel Consumption (SFC) is equal to the fuel flow (FF) divided by the available thrust. It is expressed in kg/h.N (kilogram per hour per Newton) and represents the fuel consumption per thrust unit.
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
BACKGROUND
The predicted specific range can be obtained thanks to Airbus featured software: -The In-Flight Performance calculation program (IFP) or -The Aircraft Performance Monitoring program. This program effectively
compares recorded data with the performance book level.
This predicted specific range corresponds to the book level. It is consistent with the FCOM performance charts.
The specific range method is the only technique, which enables to assess the respective contribution of the airframe and the engines in the observed delta specific range, even though utmost precautions must be taken when doing so.
3.3.4. How to obtain Specific Range
In the FCOM, cruise tables are established for several Mach numbers in different ISA conditions with normal air conditioning and anti-icing off. Basic aircraft performance levels are presented in Figure B1 on next page.
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
BACKGROUND
IN FLIGHT PERFORMANCE CRUISE 3.05.15 P 9
SEQ 110 REV 31
R
CRUISE -M.78
MAX. CRUISE THRUST LIMITS NORMAL AIR CONDITIONING ANTI-ICING OFF ISA CG=33.0% N1 (%) MACH KG/H/ENG IAS (KT) NM/1000KG TAS (KT)
WEIGHT (1000KG) FL290 FL310 FL330 FL350 FL370 FL390
50 84.0 .780 1276 302 180.9 462 84.0 .780 1189 289 192.5 458 84.0 .780 1112 277 204.0 454 84.1 .780 1044 264 215.4 450 84.7 .780 992 252 225.6 447 85.9 .780 955 241 234.1 447
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