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mikesflight

Advanced FDE Question Regarding Fuel Flow

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Guest jase439

Right now, I have a 757 performing almost exactly as I want. The N1/N2 ranges are right; temps are reasonable...everything scales correctly with the gauges, and my cruise performance is good...with 1 exception: fuel flow. I'm burning about 14.2Klbs/hr at M0.80 at FL310 under ISA conditions. I need to bring this back to about 9K. But this seems to be a damned-if-you-do-damned-if-you-don't scenario. I've tried mucking with thrust, performance tables, and inlet area...but the upshot is that if I get the fuel flow right, I have to reduce my net calculated cruise thrust (reducing inlet area, changing the thrust tables 1502-1506, etc...) and I lose my ability to climb and hold altitude, or else I'm back to cruising at 99% N1 :). Conversely, if I get the flight dynamics and climb/cruise performance to "feel" right, then my fuel output is much too high, and I end up having to bring the throttles back to 65-70% N1 to get realistic fuel flow (but this usually results in a loss of airspeed and down we go). Round and round. About the only thing I can think of at this point is to start mucking with parasitic drag. I'm not too concerned if this aircraft suffers from excessive fuel burn at lower altitude - it's cruise performance that matters. Right now, the aircraft range is about 3000nm and it needs to be upwards of 3900nm. Any suggestions here??JPS. This is an FS2000/2K2 airfile; no magic fuel consumption scalars :(

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Hi JaseI thought I must be the only person who was concerned about fuel flow as I have not seen previous posts about fuel flow. I am a keen Airbus flier and am building up a full range of these aircraft and the one I am concentrating on at present is an A300.I was astonished to find halfway through a 4000nm trip (supposed to have this range) it ran out of fuel over China. What I have done is to play with the aircraft.cfg file (make a backup before you make adjustments) and adjust the fuel_flow_scalar variable. This was originally set as 1.00000[GeneralEngineData]engine_type=1Engine.0=8.583333,-11.500000,-3.166667Engine.1=8.583333,11.500000,-3.166667fuel_flow_scalar=0.520000It does take longer to take off , but I am now looking at the engine thrust_scalar settings and starting to increase them to compensate the lower fuel flow.[jet_engine]thrust_scalar=1.133I know nothing at all about this other than to experiment and tweak and hope that the aircraft performs in a manner that the manufacturer specifies.CheersMike

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Just to make sure you understand, some areas of the *.air file are copied to the aircraft.cfg file. If you make a change in the *.air file but the aircraft.cfg file already has a value, it will use the value in the aircraft.cfg file and not the updated value of the *.air file.You will notice the default FS2002 aircraft *.air files missing the lines that are covered in the aircraft.cfg file. One must be very careful not to invoke either the MS Flight Sim Aircraft Editor or FS2002 internal editor when making changes to either the *.air or aircraft.cfg files.

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Thanks for the information. I was not aware of how the relationship between the *.air file and aircraft.cfg file worked, so appreciate your guidance.CheersMike

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