Forum: F-35 Lightning II

Do have any idea the fuel burn rate for either of the JSF Engines? Are they more efficient than the F-110 or F-110 series for example?

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According to the following website, the specific fuel consumption for the F135 is 0.7 lb/lbt/hr when dry and 2.0 lb/lbt/hour in afterburner. I don't know where they got the information from.

http://www.turbokart.com/about_f135.htm

Kryptid wrote:

According to the following website, the specific fuel consumption for the F135 is 0.7 lb/lbt/hr when dry and 2.0 lb/lbt/hour in afterburner. I don't know where they got the information from.

http://www.turbokart.com/about_f135.htm

How would that compare to other modern turbo fans???

Kryptid wrote:

According to the following website, the specific fuel consumption for the F135 is 0.7 lb/lbt/hr when dry and 2.0 lb/lbt/hour in afterburner. I don't know where they got the information from.

http://www.turbokart.com/about_f135.htm

I just got done working a night shift so I may be reading this wrong...but something reads fishy here in the fuel consumption of those two engines. But let me get this straight, the f135 burns ONLY .7 lbs of fuel in MIL power an hour? If that were true then it could fly for a really long time. Doesn't make sense if you ask me.

I think they are saying .7 pounds per fuel, PER POUND OF THRUST, per hour.

TimmayMan wrote:

I think they are saying .7 pounds per fuel, PER POUND OF THRUST, per hour.

Hmmm, that would make alittle more sense. But at that rate I dont think the f-35 would have a very long endurance with internal fuel, and that would be on MIL power. But again, I have been up for quite a while and am very tired, so I may just be not getting it right now.

singularity wrote:

TimmayMan wrote:

I think they are saying .7 pounds per fuel, PER POUND OF THRUST, per hour.

Hmmm, that would make alittle more sense. But at that rate I dont think the f-35 would have a very long endurance with internal fuel, and that would be on MIL power. But again, I have been up for quite a while and am very tired, so I may just be not getting it right now.

I agree. .7lb/lb of thrust/hour, is a pretty high rate. The throttle settings would have to be very conservative, to have any kind of endurance.

Forum Veteran Joined: Jul 01, 2007 - 07:22 PM Posts: 579

.7 works out to about 30k pounds per hour at mil. The Viper burns about 36k in max AB. So it seems logical.

Let's suppose that the F119 has a SFC of .8 lb/lbt/hr. After all, the F135 is quite similar to the F119 except perhaps a bit more efficient at mil power thanks to its larger fan. At mil power the F119 puts out roughly 23000lbt so consumes (0.8 * 23000) = 18400lb per hour. So at mil power, the twin F119's of the F-22 consume about 36800lb of fuel. This gives the F-22 a supersonic endurance of about 20 mins, permitting a 10-minute 150-nm dash each way. Note that I have allowed about 5000lb fuel for subsonic loiter. This is reasonably consistent with the publicly disclosed figures for the F-22's combat radius (see for example http://www.f22-raptor.com/technology/data.html). So the .7lb/lbt/hr figure for the F135 is probably not far off the mark.

Snake,

About what kind of altitude is that fuel burn number for? I know at sea level the -229 is in the upper 50's, -220 is more like mid 50's.

Thanks

Forum Veteran Joined: Jul 01, 2007 - 07:22 PM Posts: 579

Yeah, but the key is that we'll have to use much less power to maintain loiter in the Lightning than in the Viper. I'd be surprised if we have to use more than 3-5k pounds per hour most of the time, much like the Viper.

Forum Veteran Joined: Jul 01, 2007 - 07:22 PM Posts: 579

Jet,

I'm just going off of what I see in the mid altitude regime that we fly in most of the time. When we get up into the high 30s and even 40s we can use min AB and burn less than 9k (which is mil at lower altitudes, say below 25000).

Quote:

Specific fuel consumption (SFC) is the conventional fuel efficiency metric for jet engines. This metric assumes different forms.

For turbojets and turbofans, SFC is often referred to as the thrust specific fuel consumption (TSFC) and is the ratio of the fuel flow rate to the thrust. Clearly, low values of TSFC are good. Measured in pounds of fuel per hour/pounds of thrust, which is usually shortened to 1/hour. In Systeme Internationale (SI) units, SFC is measured in units of kilograms of fuel per second/kiloNewtons of thrust). When only one value of TSFC is reported for an engine, it is often the TSFC corresponding to the military thrust level, rather than the maximum (augmented) thrust level.

F100-PW-229
(MIL) 17,800lbs @ 0.726 lb/Hr/lb st
(MAX) 29,100lbs @ 2.060 lb/Hr/lb st

F110-GE-129
(MIL) 17,000lbs @ 0.745 lb/Hr/lb st
(MAX) 29,000lbs @ 1.900 lb/Hr/lb st

F414-GE-400
(MIL) 14,700lbs @ 0.840 lb/HR/lb st
(MAX) 22,000lbs @ 1.850 lb/HR/lb st

F119-PW-100
(MIL) 25,000lbs @ (~0.800?) lb/HR/lb st (Speculation varies between 0.600 - 0.860...)
(MAX) 37,000lbs @ (~1.950?) lb/HR/lb st

F135-PW-100
(MIL) 28,000lbs @ 0.886 lb/HR/lb st
(According to J@ne'$, but seems too high? 0.700 is more likely)
(MAX) 43,000lbs @ (~1.950?) lb/HR/lb st

F136-GE-100 (According to J@ne'$)
(MIL) 26,000lbs @ ?
(MAX) 40,500lbs @ ?

(~x.xxx?) figures based on "guesstimates" from differing public sources, figures are still guarded for this type of performance data

SFC does change with speed and altitude; comparative figures are typically given for static-sea level data.

SnakeHandler wrote:

Yeah, but the key is that we'll have to use much less power to maintain loiter in the Lightning than in the Viper. I'd be surprised if we have to use more than 3-5k pounds per hour most of the time, much like the Viper.

I agree with SnakeHandler; with ALL that power, you won't need much to just fly around in a loiter or cruise. The full MIL thrust will be used for penetration and egress. MAX will be used for escape or engagements. It is the same benefits gained by the newer engines in the Viper, you use less throttle overall and save fuel over the mission compared to the original PW-200s.

Keep 'em flyin' Thumb

TEG

Salute

I go with Snake-breath and TEG-breath.

With the original equipment I flew a Red Flag NOE profile one time with two external tanks and 6 x MK-5OO eggs on ters.

We cruised in at five forty knots and were burning about ten thousand pounds per hour. Nice, as we had more gas than that and only needed to go about two hundred miles to the tgt. Then we could come out FAST.

Fuel management is just like the dweebs you see in ground traffic. If you don't need the max power, why use it? Save your gas for when it really counts, then light the burner and worry about running outta gas later. Every time I see some dweeb come around me from a turning intersection and they move outside and are pushing the pedal to the medal, I crack up. Hell, I get there about seconds later and I save thirty % on my mpg.

Later,

Gums sends ....

Makes more sense now. I assumed max thrust in my statements----> which was my mistake. interesting though, I did'nt know they burned that much fuel in so little time. really shows how inefficient these things are in the long run.

Forum: F-35 Lightning II

F-135 or F-136 fuel burn rate