Fuel Consumption Adjustment

[OBIO]

I am working on the Alphasim Cessna T-50 Bobcat. I have the speed pretty much dialed in (160ish MPH cruise, 190ish MPH max...these change as fuel is used up). I am now trying to get range dialed in. The real Bobcat has a range of 750 miles. The AS Bobcat currently has a range over 1000 miles....have not flown it to the empty point...but a 400 mile flight used up less than half of the 80 gallon fuel load.

I have found some specs for this plane....real USAAF spec sheets (cessnat50.org has lots and lots of manuals for the Bobcat) and according to the charts, at 19 inch Hg manifold pressure, fuel burn should be 30 gallons per hour. Currently, at 19 inch Hg manifold pressure, fuel burn in the Alpha Bobcat is 11.2 to 11.4 gallons per hour per engine...or 22.4 to 22.8 gallons per hour....at 5000 feet.

How can I get the plane to burn more fuel? I know there are lines in the air file and config file for fuel consumption, but I have never messed with them.

OBIO

[Paul Anderson]

I believe what you are looking for is fuel_flow_scalar in the section:

[GeneralEngineData]
engine_type = 0 //0=Piston, 1=Jet, 2=None, 3=Helo-Turbine, 4=Rocket, 5=Turboprop
Engine.0 = 0, -7.73, 0.0
Engine.1 = 0, 7.73, 0.0
fuel_flow_scalar= 1.10
min_throttle_limit = 0.0

Higher number burns more fuel, lower is less.
You might start with 1.50000 and tweak from there.

[WarpD]

I just did a real quick "check" and I think the value you want 0.20. That's based on:

FF = fuel flow
HP = horsepower
SFC = specific fuel consumption

HP = 245 (read off one of the pages you provided from cessnat50.org)
FF = 24.9 (read from the same page)
SFC = 0.10

Where FF = SFC x HP, translates to SFC = FF/HP

24.9/245 = 0.10

0.10 / 0.5 = fuel_flow_scalar

[sparks]

fuel_flow_scalar does not affect horsepower at all. It simply scales the amount of fuel used. If you want to double the fuel used per hour, then set fuel_flow_scalar to 2.0 The power output will remain unchanged.

[fliger747]

A good tool to use for a check on specific fuel consumption is Herve Sors's AFSD (Google or Bing it). A small popup utility that has instant access in real time to the goings on with your plane. For dedicated flight test Jerry (Sparks) has a 2 D instrument panel showing most parameters of interest.

Range figures in the book are hard to figure sometimes as they sometimes incluse a reserve, a particulat power and altitude, and sometimes not. For Piston engines a lean of peak operation might be used.

Efficencies can vary a lot. in general for WWII type aircraft a specific fuel consumption of 0.5 lbs/hp/hour delivered was a reasonable ball park figure.

Good luck! T

[Ivan]

Pardon me for reviving an old thread, but how is this done in earlier simulators without the CFG file entries? Just for fun, I changed the value that is labeled fuel flow scalar and it did absolutely nothing that I could see. Perhaps I have an old AirEd.ini?

- Ivan.

[sparks]

If remember the testing I did on the older versions of FS (and CFS) correctly, the fuel flow is directly related to power produced and nothing changes the power to fuel consumption ratio.

[fliger747]

I did get a PPH variation from the fuel flow scalar.... and.....

I also got a fuel flow adjustment by adjusting the following parameter in the engine section in the .cfg file:

idle_rpm_mechanical_efficiency_scalar=1.00000
max_rpm_friction_scalar=1.00000
idle_rpm_friction_scalar=1.00000
emergency_boost_type=1
power_scalar=1.00000
BestPowerSpecificFuelConsumption=0.65000 (original was 0.45)
detonation_onset=63.80000

Two ways?

Cheers: T