FS2004 How to modify the fuel flow on idle ?

Hi Friends
i'm looking for a help about the follow problem. I own some aircrafts (for example the Feelthere Wilco A320) where the fuel flow at idle is extremely high compared to the official fuel burn data. The strange thing is that on all other flight phases (takeoff, climb, cruise, descent) the flow is near to the reality but, as saied, at idle (after the engine start and untill taxi) the fuel burn is too high.

Maybe some of you can tell me wich parameter in the aircraft.cfg (or somewhere else) control the fuel flow at idle ? Or how can i apply a work-around to resolve this problem ? Thank you in advance for your gentle coperation.

Haven't used fs9 in years but at least in FSX/P3D increasing idle thrust is a method to overcome the friction problem. Higher thrust means higher fuel flow and since you can't control thrust and fuel flow independently, I don't think that there's a solution.


Roy Holmes

Resource contributor
As Bernt said, fuel flow is tied to thrust in the definition of Thrust Specific Fuel Consumption TSFC which is pounds fuel burnt per pound of thrust. Typical values for a modern turbofan are in the 0.5 region. You can reduce idle thrust and that would reduce idle fuel consumption, but you would have to know whether the real aircraft taxies at idle throttle or requires some throttle to move on the ground. If it requires throttle to move, then you can set the idle RPM in air file record 1502. to give you reduced N1 RPM which is what governs thrust. However real engines have TSFC that varies with RPM but in the sim TSFC is a constant once set.
Hi Roy and Bernt,
thank you for your answers. I'm not very familiar with this type of editing, but i can try to modify the air file as Roy told me. Which editor must be use to modfiy the air file ? Maybe you know where i can find some utilities to do this operation ? Thank you again for your help.

Roy Holmes

Resource contributor
I use Aircraft Airfile Manager V2.2 which is a free download and probably the best air file editor. There are umpteen different ways to go wrong and only one to go right when you start editing airfiles. Just be sure you have backups for anything you edit.
In addition to Roy answer, know there is a minimum fuel consumption and very often you will get it at idle power.
Normally sim calculates fuel consumption (PPH) as TSFC*engine net thrust
However if PPH calculated this way is below a minimum value, this minimum value is always observed whatever the engine thrust is
This minimum value is
MinPPH=0.065*StaticThrust*TSFC (StaticThrust=static_thrust*thrust_scalar)
I'm afraid there nothing you can do to lower this value, except hacking the Sim1.dll or rewriting Sim memory with some available tools

Thank you both for you help but i don't get any good result.
I have downloaded and installed the Aircraft Airfile Manager V2.2 as Roy told me but it crash every few clics and it's impossibile to editing something without chrashes or application errors. Thank you anyway for your help, i'll continue to load some more fuel for the idle times in my fuel calculations ;-)

That's very strange. I never had the AAM crash in all the years I'm using it. Isn't there any error message when it crashes?
as stated- You will never be able to set the correct FF for idle thrust and get accurate N1 breakaway settings because of the ridiculous legacy values for rolling friction coefficients in sim1.dll. You have to set a high FN value at mach 0 for the low idle to overcome the friction, this results in a high FB. If you then try and scale this using TSFC, it will screw up your cruise burn.

I make my own sim1.dll and AI player.DLL for personal use to get around these legacy problems, this with a custom airfile for my 777 sim, sadly nobody has listened to this issue until now with FS2020. So roll on FS2020 and the SDK!

but it crash every few clics and it's impossibile to editing something without chrashes or application errors
I've had this too, got the error as in the thread below. Even though AAMv2 claims to work with FS2004, it seems it doesn't...
So I use AAMv1 or AirEd.

Thak you Dirk for your good tip !
I've downloaded AirEd and it open the air file without crashes. When i have some free time in the next days i try to play with the record 1502 as Roy told me, but is just to try something because i'm a little scared to edit such a complicated and important file. Anyway many thanks to all for your cooperation.