Hello all,

I tried to understand the calculation of the fuel consumption
of the A320. In the engine configuration file I found the

   TSFC          thrust-specific fuel consumption (lbm/hr/lbf)

parameter set to 0.657 . Then I compared the fuel consumption with thrust (/engines/engine/fuel_flow_pph with /engines/engine/thrust_lb)
and when I set N1=100 %


   TSFC = fuel_flow_pph/thrust_lb


But this formula is only valid, when N1 is 100 % For values lesser then 100 % the formular is not valid. The fuel consumption is much greater then it should be.

I compared this result with the ICAO ENGINE EXHAUST EMISSONS DATA BANK
where I found some performance values for different power settings (100 %, 85 %, 30 % 7%) of the A320 engine CFM56. There the formula is always valid.


Is this behaviour a bug or a feature ?

Where is the fuel consumption calculated ?

In the jsbsim-code FGSimTurbine.cpp I only found  this peace of code:

    if (!Augmentation) {
     FuelFlow_pph = Seek(&FuelFlow_pph, thrust * TSFC, 1000.0, 100000);
     if (FuelFlow_pph < IdleFF) FuelFlow_pph = IdleFF;

But there the fuel flow is calculated in the way I understand


Thank you for any help

Kind regards

Hans-Georg





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