FSX Nav Log and Fuel Burn Qs

[Sir Puma]

Hello everyone. Been a LONG time since I've been here posting stuff (not that I did a bunch of that to begin with.) I've had about a year hiatus from flight sim and was just getting back to it. It took me a couple days to get my Saitek gear working right and I was working on reinstalling my downloaded aircraft and ran across a perplexing problem. This may be long so forgive me as you will. This will mostly be for the "experts" in FSX.

So to get to the crux of my point and ask the ultimate question (no, the answer isn't 42.) When you set up a flight plan and look at the navigation log, you get a distance measurement, an estimated fuel burn and an estimated time for the flight. What files/data does FSX use to actually calculate that data?

Here's the long version and the specifics of my conundrum. One of the aircraft I'm currently playing with is the most kick ass (can I say that here?) Howard Aero 500. Now per the game files its fuel capacity is barely over 9000 lbs when in actuality it's just over 9300 lbs. In reality its range is 2600 miles. I went through the .cfg file and corrected a few things like compression ration, empty weight (the game file was 1000 lbs more than a real one is) and a few other things. The Fuel_Flow_Scaler was at .935. When I create a flight from Arcata, CA (KACV) to Hilo, HI (PHTO), a flight of some 2300 miles I should be able to expect to see the flight planner spit out a estimated fuel burn of approximately 9000 lbs. With the default file it spits out an estimated fuel burn of just over 16000 lbs. After doing a few tweaks I get a result of just under 13000 lbs. But no matter where I set the Scaler it doesn't change the estimated fuel burn. So, the point of my question, what data does FSX actually use to compute estimated fuel burn?

I know all the standard responses about fuel consumption (FSX doesn't know what it's doing, set your game to unlimited fuel, fuel scaler will make your engines use less fuel) but that's not the Q.

Anyway, can anyone actually tell me what the game uses to calculate burn?

Thanks,
Puma

[Sir Puma]

Ok, going through the two copies of the cfg file I found that "Reference Speeds"-"Cruise_Speed" directly effected the output. Not sure how this setting will actually effect the flight characteristics though.

[Sir Puma]

Just wanted to edit the previous reply, but I can't. I just wanted to say I also noted the power_scalar under "piston engine" also changed the fuel burn rate.

[XNAVFLYR]

Sir Puma:

I have found in my military aircraft, that the FF #, the Engine and prop Power % and the shown Cruise Speed, when set to the specs closest to the Real A/C that the burn comes closest to scale numbers. I have had to adjust the wing incidence on some A/C (Military C-118, P-3 and P-2) to get the desired prototype flight attitude and then a more correct power setting. I know especially with the C-118's I needed to drop the nose to achieve the correct cruise profile. Even when heavy a real life Liftmaster noses over "On the Step.

XNAVFLYR

[Andiroto]

Good question!
I must admit, i have never much think about it because i always started with a new plane with full tanks and then see how much fuel is left after a certain time . . .
But i have figured out (if you havent already found out) that changes in the "inlet_area" and "static_thrust" entries have also influence of the fuel consumption in the Nav log!
So it looks like its a calculation of distance, cruise speed and height, some engine params and maybe some weight params (but not tested)!