F-35 internal fuel, range

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Gums

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Unread post15 Oct 2017, 21:05

Salute!

@010 Need a better callsign, man.

With ppm versus pph, are we talking about the Stubby or the Bug?

Either one it's depressing. My trusty J-57 back in the 60's burned about 3,000 pph, or 50 ppm, I guess. That was a basic cruise or loiter, although I managed to get that down to 2,200 pph or so if I was smooth at best AoA.

In the Deuce, the fuel flow was for one motor, but in the VooDoo you could almost double it but normally about 5,000 pph. Later in life I wondered about shutting down a motor in the VooDoo, as we could maintain 1.15M at 49,000 ft with one in mil and the other at min burner. But A-37 was so overpowered it was an easy decision to shut one down.

Then I flew the Sluf and Viper. We cruised at 2,000 pph ( 33 ppm ? ) , 35K and 0.8M in the Sluf or 0.9M in the Viper or so when RTB with only pylons and missiles on 1 and 9. Maybe a centerline tank.
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Unread post15 Oct 2017, 21:48

Gums wrote:Salute!

@010 Need a better callsign, man.

With ppm versus pph, are we talking about the Stubby or the Bug?

Either one it's depressing. My trusty J-57 back in the 60's burned about 3,000 pph, or 50 ppm, I guess. That was a basic cruise or loiter, although I managed to get that down to 2,200 pph or so if I was smooth at best AoA.

In the Deuce, the fuel flow was for one motor, but in the VooDoo you could almost double it but normally about 5,000 pph. Later in life I wondered about shutting down a motor in the VooDoo, as we could maintain 1.15M at 49,000 ft with one in mil and the other at min burner. But A-37 was so overpowered it was an easy decision to shut one down.

Then I flew the Sluf and Viper. We cruised at 2,000 pph ( 33 ppm ? ) , 35K and 0.8M in the Sluf or 0.9M in the Viper or so when RTB with only pylons and missiles on 1 and 9. Maybe a centerline tank.


Ppm is for the f-35. Pph displayed for the hornet. You would be amazed at the ppm burned in blower... 90ppm at .85m (or 10.5 lbs/nm) is pretty awesome for a motor that produces 40k thrust, especially with how much internal gas we have.
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Unread post16 Oct 2017, 07:12

010137 wrote:
Ppm is for the f-35. Pph displayed for the hornet. You would be amazed at the ppm burned in blower... 90ppm at .85m (or 10.5 lbs/nm) is pretty awesome for a motor that produces 40k thrust, especially with how much internal gas we have.


Is that with internal GBU's? what F-35 variant?
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Unread post16 Oct 2017, 15:23

geforcerfx wrote:
010137 wrote:
Ppm is for the f-35. Pph displayed for the hornet. You would be amazed at the ppm burned in blower... 90ppm at .85m (or 10.5 lbs/nm) is pretty awesome for a motor that produces 40k thrust, especially with how much internal gas we have.


Is that with internal GBU's? what F-35 variant?


Yes, w ord. B model, but they’re all about the same.
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Unread post16 Oct 2017, 19:06

010137 wrote:
Yes, w ord. B model, but they’re all about the same.


Thanks for answering. The Air Force had a stat posted saying at 30k and .7 (or .75) they burn around 4000 PPH. Your burning around 5400pph going .85, would that small reduction in speed really reduce consumption that much?
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Unread post16 Oct 2017, 22:28

No surprise. The drag at 0.85 is about 50% greater than at 0.70.
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Unread post16 Oct 2017, 23:21

johnwill wrote:No surprise. The drag at 0.85 is about 50% greater than at 0.70.


transonic is that bad? I had read like 30%
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Unread post16 Oct 2017, 23:36

I think johnwill simply meant that drag is roughly proportional to the square of speed in this region, since (0.85/0.7)^2 = 1.47.
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Unread post17 Oct 2017, 02:00

geforcerfx wrote: The Air Force had a stat posted saying at 30k and .7 (or .75) they burn around 4000 PPH.


Specifically it was .75M, 32,000ft, 4,600pph (76.7ppm), with 2500lb tactical loadout internal.
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Unread post17 Oct 2017, 02:24

I think he's talking about this one:

Image

Mach 0.75, 40kft, no payload specified, 593 gal/hr (= 4032.4pph = 67.21ppm)
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Unread post17 Oct 2017, 03:22

5 gal/hr for the Predator ! :shock:

Even with the relatively small Cessna 172P, our instructors told us to use the conservative 10 gal/hr fuel consumption, and we didn't fly above 100 kt IAS !
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Unread post17 Oct 2017, 04:44

Dragon029 wrote:I think he's talking about this one:

Image

Mach 0.75, 40kft, no payload specified, 593 gal/hr (= 4032.4pph = 67.21ppm)

Ooh, more data, excellent.
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Unread post17 Oct 2017, 04:51

Have therr been any credible reports discussing the F-35 range where it's explicitly stated it's got empty bays? I 've always assumed a full internal ordnance load.
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Unread post17 Oct 2017, 05:16

Not that I'm aware of; even on a slide describing a surveillance mission they have a payload of 2x AIM-120s and 2x GBU-12s:

Image

(Just note that this was from something like 2012, so I'm not sure how accurate those performance figures are - if they're based off the SAR performance estimates though then they'll be even higher).
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Unread post17 Oct 2017, 05:36

also the altitude is varying between 5-25k. We don't know time at any altitude or the speed, to give a the breakdown of the mission requirements that give the range.
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