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Fuel and Drag Bias for PMDG Aircraft

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I generally like to fly the following PMDG aircraft:


B747-8 Freighter

B737-700 Freighter



I have PFPX profiles for all three A/C, but I would like to obtain fuel bias and drag bias for all three planes.


I have not been successful at calculating accurate fuel loading versus actual flight plan results.


Any ideas on where to get this data?


BTW, is there are bias information available I need to enter into the PFPX aircraft configuration files to improve flight fuel burn results?


Bill Clark

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I was hoping that someone, or others had already analyzed one or more of these three aircraft as to fuel bias and drag bias?





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You can use the Aircraft Performance Monitoring (APM) function in the aircraft database to determine fuel and drag biases for any aircraft using data obtained in flight.


Plan and start a new flight and once you get to cruise altitude, double-click the aircraft you're flying in the aircraft database, click APM, then enter the required fields.  FF/hr can be calculated by using the engine performance, adding together the FF figure for all engines and multiplying by 1000.  All the other fields can be found directly in either the FMC (gross weight) or on the flight displays (altitude/FL, TAS, GS).


You can enter data from multiple flights over time to build up an accurate profile.

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I will have a look tomorrow for the 77F figures I use.


Note that these were before PMDG updated the 777, which now correctly burns differently depending on ISA deviation.


The figures I have for it are for the default 77F profile where I took all ISA deviation burn changes out of the profile.  So in theory, it should be a reasonable number.



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for the PMDG 747-400ER/F i use 'FlyPrecisely' profile with this settings that work very well for me


Takeoff burn: 500kg

Approach burn: 1000kg


Takeoff time: 0

Approach time: 2


Drag bias 0.0% to (minus)-0.1%


LRC:  FF bias 0.0%


Ci 350 to 999 FF  0.0% 


as a rule of thumb i decrease FF by -0.1% per 10 Ci  less than Ci 350 ( e.g.  Ci 340=FF -0.1 %  ;  Ci 330=FF -0.2%  ;   Ci 300=FF -0.5%   ;  Ci 200=FF -1.5%   ;   Ci 100= -2.5% etc )


Ci 0 : FF  (minus)-3.5%  


its quite accurate until PFPX want me to fly 2000ft below the FMC OPT Altitude then everything goes crazy by losing or gaining 200-400kg/h

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All default profiles:


77F: 0.8% fuel bias, drag 0.6%, approach burn 800kg


77W: -0.7% fuel bias, drag 0.5%, approach burn 800kg


738: -2.6% fuel bias, drag 0.3%, approach burn 300kg


744RR: -2.9%, drag 0.3%, approach burn 1000kg


Again, all of these were derived before PMDG fixed (they've now fixed all their aircraft) the fact their aircraft fuel burn didn't change per ISA deviation.  So I edited the PFPX profiles removing any change for ISA deviation.


Further testing on the aicraft have shown that PMDGs do now burn ~ +/- 3% per +/- 10 degrees ISA deviation, as they should.


So in theory, these bias figures should still be sound.



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  • 3 weeks later...

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