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| Afterburner Fuel Consumption https://jkpeterson.net/forum/viewtopic.php?f=6&t=1792 |
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| Author: | eburger68 [ Thu Nov 08, 2007 21:37 pm ] |
| Post subject: | Afterburner Fuel Consumption |
Hi All: I'm wondering about fuel consumption rates at military thrust vs. afterburner ("wet") thrust. The default FA values and many of the "importable" LIBs that I've looked at generally set afterburner fuel consumption somewhere between 8-12 times that of military fuel consumption For example, a typical fighter might have military fuel consumption set at 3 and afterburner fuel consumption set at 26 or even higher. In doing a bit of searching online, however, I'm beginning to wonder whether afterburner fuel consumption (even for older jets) is really that high. Start, for example, with this page at the definitive online Tomcat site: http://www.anft.net/f-14/f14-detail-engine.htm Afterburner fuel consumption for both the P&W TF30 and the GE F-110 is around 3 times that of military thrust. Another example: http://www.dassault-aviation.com/filead ... age_02.pdf Page 7 of that commercial PDF doc specifies afterburner fuel consumption for the Mirage 2000 is a little over 2 times that of military fuel consumption. Obviously older aircraft will have less fuel efficient engines. This book: http://www.amazon.com/Wings-That-Stay-E ... 1563115689 ...states that, generally speaking, afterburner fuel consumption ranges from 2 to 4 times that of military fuel consumption, with older fighters/engines (e.g., a 'Nam era F-100D) coming in at around 4 times military and newer 5th generation aircraft coming in at around 2 times military. Am I missing something here? Why do FA and so many LIB authors set afterburner fuel consumption at 8-12 times that of military thrust fuel consumption? Thanks, Eric L. Howes |
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| Author: | CAG Hotshot [ Fri Nov 09, 2007 02:00 am ] |
| Post subject: | |
What libs are you exactly speaking about? Also you have to remember that FA does not model drag correctly. Modeling higher rates can compensate for this by producing higher fuel burn. And, as usual, your data is interesting and your use of multiple referrences is helpful in reinforcing your points. Keep up the good work! 
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| Author: | eburger68 [ Fri Nov 09, 2007 03:51 am ] |
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CAG Hotshot: You wrote: CAG Hotshot wrote: What libs are you exactly speaking about? OK, I hadn't named any specifically lest I appear to be pointing fingers. Since you ask: my own (for starters), Global Tribunal, Zephyr's JKPFA, Hawk's AngelLIB, FlopDog McSporran Airlines, VarkLIB, FA_Planes. The KAPSET LIBs also use afterburner fuel consumption settings above the figures I've found, but not as high as the other LIBs (more like 4-6x as opposed to 6-8x military). CAG Hotshot wrote: Also you have to remember that FA does not model drag correctly. Modeling higher rates can compensate for this by producing higher fuel burn. Ahhh, that's interesting. Could you elaborate on this a bit? Wouldn't that failure also affect military thrust fuel consumption rates as well? I should mention that while I've been suspecting that afterburner rates in many LIBs (my own included) might be on the high side, military thrust rates were LOW. The other consideration on my mind is the absolutely profligate use of AB by AI pilots/wingmen, even when you try to keep them on a tight leash. CAG Hotshot wrote: And, as usual, your data is interesting and your use of multiple referrences is helpful in reinforcing your points.
Thanks! Here's another interesting page on the GE J79 engine (used in the F-104 and F-4): http://en.wikipedia.org/wiki/General_Electric_J79 AB fuel consumption is listed as 2.3 times that of military thrust. In any case, I've been working up a rough formula to use when revising fuel consumption rates in my own LIB project. The formula is designed to impose some consistency and get figures roughly "in the ballpark," after which they can be further tweaked as warranted for individual aircraft: Code: ----------------
Fuel Consumption ---------------- military = thrust / 5000 (older aircraft) = thrust / 7500 (newer aircraft) afterburner = military x 2-5 (older the plane higher the AB multiplier) Basic Afterburner Multipliers: Era/Gen Multiplier Examples ------- ---------- -------- 1950s (3rd) 5 F-86, MiG-15, MiG-17 1960s/Nam (3rd) 4 F-100, F-8, F-105, F-4, MiG-21, MiG-23 1970s/80s (4th) 3 F-14, F-15, F-16, F/A-18, MiG-29, Su-27 1990s/2K (5th) 2 F-22, F-32, F-35, Su-54, MiG 1.44 Of course, fractions always result. For older aircraft I tend to round up; newer aircraft I round down. Using the above produces numbers like the following (MT/AB): F-105: 3/14 F-4: 4/15 F-14: 4/13 F-15: 4/13 F-16: 2/6 F/A-18: 3/8 MiG-17: 1/5 MiG-21: 2/8 MiG-29: 3/9 Su-30: 4/13 Thoughts? Thanks, Eric L. Howes |
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| Author: | KAPTOR [ Fri Nov 09, 2007 05:36 am ] |
| Post subject: | |
One of the nice things about the FA engine settings is that you can compose the engine to do about anything, for instance a 5,000lb thrust motor with a SFC of 127 lol. If an aircraft is known to fly at XXX speed at mil power then you dont need to worry about FAs drag problems ( there is no AoA drag setting and no modeling of the Mach-1 drag bump which is a HUGE problem when trying to adhere to doghouse charts). I dont remember what the numbers for my kapsets were, everything I have done for CAGs FAF is leap years ahead of what I did in the kapsets. SFC for FAF are spot-on for every jet I could find ( and that is by far the vast majority ) remember too that when you set the fuel burn in FA you have to do your own math for multi-engine aircraft. |
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