Specific fuel consumption

[Hummingbird]

So was wondering, running the F-16 vs F/A-18 ingame and with both in full AB the F-16 tends to run out of internal fuel way quicker in DCS.

 

Looking at the RL max AB SFC figures I could find I don't understand how that can be the case:

 

 

SL

 

F110 GE-129 tsfc = 52.59 mg/Ns (1.90 lbf/h)

F404-GE-402 tsfc = 49 mg/Ns (1.74 lbf/h)

 

F110 GE 129 = 130 kN

F404 GE 402 = 78.2 kN x 2

 

F-16C internal fuel capacity = 7,200 lbs

F/A-18C internal fuel capacity = 10,860 lbs

 

 

Fuel consumption difference = 18.5%

Internal fuel difference = 32.8%

 

In other words shouldn't they be rather close in time on AB? Currently the difference appears as massive.

 

Is this a known bug or am I missing something?

Edited October 2, 2020 by Hummingbird
clarrified question and figures

[pchRage]

Doubt it, but maybe that 49 number is for both engines (total)?

 

I also thought the old joke was after the cat launch, first voice comms was to query the tanker :-)

[Zergburger]

since the update if you watch the fuel flow meter its pulling A LOT more fuel in AB, you can watch it peg the fuel flow meter at 80000 lbs/hr now where before even on the deck the most you'd ever see was about 60000.

[Hummingbird]

What I find odd is how two F404's aren't using up more fuel pr. time than one GE-129 at the same speeds, that strikes me as odd.

 

Does anybody have fuel flow charts for the F/A-18C engines?

[SirJ]

If you have two engines, the sfc does not change.

You have twice the consumption, but also twice as much thrust, so looking at the sfc it crosses out:

 

sfc = FUEL_FLOW / THRUST = 2x FUEL_FLOW / 2x THRUST.

 

 

You have to multiply the sfc with the thrust to get the fuel consumption, since you want compare the consumption to the fuel available:

 

FUEL_CONSUMPTION / FUEL_AVAIL = TIME

 

I never tried to fly the viper without any bags, but with bags it has longer flying time compared to the hornet.

Viper has less fuel bus also is way lighter, has less drag and one engines consumes less fuel than two...

[Hummingbird]

You're right sir J, what Im interested in is the combined fuel flow, which I'd expect to be higher for two F404's vs one GE-129.

[Hazardpro]

You're right sir J, what Im interested in is the combined fuel flow, which I'd expect to be higher for two F404's vs one GE-129.

 

If you calculate the fuel flow ratio correctly using the SFC ratio and the max thrust ratio you get that the single GE-129 does indeed consume about 11% less fuel than the 2 F404's at max thrust. Of course, since the F16 has 34% less internal fuel available that still means it will exhaust its internal fuel first.

 

Works out to about 25% less endurance for the F16.

Edited October 1, 2020 by Hazardpro

[Hummingbird]

If you calculate the fuel flow ratio correctly using the SFC ratio and the max thrust ratio you get that the single GE-129 does indeed consume about 11% less fuel than the 2 F404's at max thrust. Of course, since the F16 has 34% less internal fuel available that still means it will exhaust its internal fuel first.

 

Works out to about 25% less endurance for the F16.

 

Problem is I don't know what altitude/speed the SFC numbers I listed are for, hence I would need a fuel flow chart for the F/A-18C to do an exact comparison.

[Bouli306]

So you are trying to prove something is a bug but am unable to back this up.

[Spurts]

Problem is I don't know what altitude/speed the SFC numbers I listed are for, hence I would need a fuel flow chart for the F/A-18C to do an exact comparison.

TSFC numbers, like thrust numbers, are always SLSU (Sea Level, Static, Uninstalled). And like Thrust itself, TSFC changes with speed, altitude, and throttle setting. With the only F100-PW-200 the F-16 had 7minutes of fuel at Sea Level, with the F110-GE-129 that would be much lower.

[Hummingbird]

So you are trying to prove something is a bug but am unable to back this up.

 

No, I'm not trying to prove it's a bug, I'm asking a question.

[Hummingbird]

TSFC numbers, like thrust numbers, are always SLSU (Sea Level, Static, Uninstalled). And like Thrust itself, TSFC changes with speed, altitude, and throttle setting. With the only F100-PW-200 the F-16 had 7minutes of fuel at Sea Level, with the F110-GE-129 that would be much lower.

 

Well I have the fuel flow vs mach charts for both engines, and they're actually quite similar.

 

What I would like is a similar chart for the F404.

[Spurts]

Well I have the fuel flow vs mach charts for both engines, and they're actually quite similar.

I imagine you have the fuel flow chart for the F100-PW-229, not the -200, if you are saying it is very similar to the F110-GE-129.

[Hummingbird]

I imagine you have the fuel flow chart for the F100-PW-229, not the -200, if you are saying it is very similar to the F110-GE-129.

 

Correct, missed you wrote 220 ;)

 

For the GE-129 it goes from ~60,000 lbs/hr @ 0.4 mach, to ~98, 000 lbs/hr @ 1.3 mach.

For the PW-229 it goes from ~59,000 lbs/hr @ 0.4 mach, to ~96, 000 lbs/hr @ 1.2 mach

Edited October 3, 2020 by Hummingbird
98,000 & 96,000,not 98 & 96 lbs/h :'D

[Spurts]

Well, I can see that sea level at M1 full AB is 1,320ppm or 79,000pph, slightly less than that at 0.95M, but that is for the F404-GE-400 motors, not the -402s. Even the 402s are only making 19,062lb thrust each at M1. You can probably cut that by 10% to reach 34,200lb total. Meaning at this altitude and speed the -400 motor has a TSCF of 2.3, not the 1.7 of the sea level - static.

Edited October 3, 2020 by Spurts

[gavagai]

What is early access?

 

What is DCS World Early Access?

Early Access is an option for you to play this module in an early state, but it will be incomplete with bugs. The time a product remains in Early Access can vary widely based on the scope of the project, technical hurdles, and how complete the module is when it enters Early Access. Eagle Dynamics and all of our third parties strive to make this period as short as possible. An Early Access module can be played on both the Open Beta and Release versions of DCS World. Once the module exits Early Access, you will automatically have the Release version.

 

Many things will change during the development process. Have no doubt that some stuff is incorrect right now. Don't know about the AB fuel consumption specifically, but there is a lot of room for improvement for the Viper (wheel brakes and NWS are in a much worse state). The Hornet has the benefit of data from Boeing, while the Viper lacks the same level of support.

[r4y30n]

What is early access?

 

 

 

Many things will change during the development process. Have no doubt that some stuff is incorrect right now. Don't know about the AB fuel consumption specifically, but there is a lot of room for improvement for the Viper (wheel brakes and NWS are in a much worse state). The Hornet has the benefit of data from Boeing, while the Viper lacks the same level of support.

 

I'm not sure how this is relevant to the discussion.

[BuzzU]

Who cares how it compares to the Hornet? Just tell me the Viper is accurate to the real plane.