Fuel Flow In Burner

So yesterday my ANG wing had a Tactical Resiliency Pause, and part of the pause was several hours of gaming. Seeing that up until 2010 we were a Block 30 F-16 unit and are now are repair and overhaul center for the F110-110C, F110-129, QF110-100B, TF34 and F118, and there are several ex-viper pilots, crewchiefs and maintainers, I of course brought my gaming laptop with the F-16 for people to fly and enjoy. My Wing Commander, who has oodles of hours from the F4 thru F16A, and F16C Block 30 was impressed with the flight model. However he noted that when in burner the fuel flow rates would drop as he was going uphill and increase as he was going downhill, his comment was burner is burner there shouldn't be such a dramatic difference in fuel flow rates. Also he was getting the "Altitude" warning with gear down and he commented that that shouldn't be happening.

I think since he is retiring next month DCS World will be seeing a new member, along with some of the other Viper Drivers and a couple of Hog Drivers that tried out the sim yesterday.

Scott, NDI Technician, F15, F-111, F4, T-33, A-10, E-3,C-141, C-130, etc, if the AF flew it, I worked it!!

Yea I think it's still WIP. It does drop pretty dramatically while going to altitude. Engine fuel flow at altitude will decrease, but burner is just dumping raw fuel, it should still be a firehose.

Great to hear some experience drivers had some time with the Viper. Even better when they can point out the issues the viper currently has. Hope to see more new faces on the boards and in the skies. Thanks for sharing the experience with others.

FF should drop off quite a bit with altitude, even in burner.

Max AB, 0.9 Mach, Standard day.

5000ft = 72k PPH

20000ft = 45k PPH

40000ft = 16k PPH

Notice these are figures pulled from the good book, may or may not be accurate to the sim.

Burner fuelflow will drop dramaticaly going up in altitude. If it was not, the engine would just spit out unburned fuel. It is all about the mixture of around 1:14,7 of fuel/air ratio.

True, as altitude increases fuel flow decreases and vice versa. However he didn't go much over 18K and the numbers were spinning, I think he was noting that they were changing way to fast. Looks like for the Wing Thanksgiving party I'm bringing my laptop back and there are a few more that want to try it out. Plus a couple of engine shop Hush House want to try it out, and since they run motors almost daily I'm interested as to what they think about the fuel flows.

This will for sure be accurate eventually as ED have the fuel flow pr. altitude & throttle setting figures for the jet available.

Burner fuelflow will drop dramaticaly going up in altitude. If it was not, the engine would just spit out unburned fuel. It is all about the mixture of around 1:14,7 of fuel/air ratio.

I don't think that the burner runs up to the stoichiometric ratio @ sealevel.

Hi!

... burner is burner there shouldn't be such a dramatic difference in fuel flow rates!

For For GE129, Afterburner Fuel Control is a fuel-operated electrohydromechanical control which regulates fuel flow to the AB in conjunction with the DEC.

Regards.

This makes for interesting reading if you are so inclined to learn more about AB thrust augmentation, using F-111 TF-30 & F-16 F-100 engine as examples.

https://authors.library.caltech.edu/21303/1/251_Zukoski_EE_1978.pdf

Of specific interest as while Afterburner operation in the various 'zones' (or number of spray rings in use) is controlled a metered quantity of fuel, the AB operation is also dependant on local pressure, which is controlled by the diameter of the exhaust.

So while the core engine Specific Fuel Consumption (SFC) is directly relative to the external conditions such as pressure/density/temperature, and subsequently the fuel flow is directly proportional to these inputs (so FF reduces with altitude - as with less oxygen you need less fuel, which would actually result in less performance, but this is offset by the benefits gained by the standard 'temperature lapse rate' of 1.98°C /1000' to 36,000' increasing density) - the AB is not so much entirely constrained by these as augmentation occurs in an entirely isolated environment which has been controlled already to provide for engine combustion, hence you see the exhaust nozzle movement with altitude changes which subsequently controls the local pressure in the exhaust - and therefore not such a large change in AB fuel flow is required as seen with the core engine.

Also take note of the Air-Fuel ratio used in the augmentation system varies from the standard stoichiometric ratio, being considerably lower thanks to the inherent design of the flame holder system.

Hope I explained that clearly lol. Obviously the entire process is a little more complicated, - feel free to read the document at the above link.