Forum: F-35 Lightning II

outlaw162 wrote:

>1200 NM covers a lot of territory.

At a high estimate average 3000 pph for an F-35 at 0.8 Mach, burn 17,000 LBS, land with 1000 LBS, you'll cover over 2500 NM with a specific range around .16 to .17 NM/LB. That's similar to the specific range for a Viper, but more fuel on board.

1,200 nm is too short, but 2,500 is too long.

LM had said that F-35A's A-A radius is about 750 nm, so its ferry range is more than 1,500 nm.
I think it's about 1,800 nm.

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At a high estimate average 3000 pph for an F-35 at 0.8 Mach, burn 17,000 LBS, land with 1000 LBS, you'll cover over 2500 NM with a specific range around .16 to .17 NM/LB.
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0.16 to 0.17 nm/LB is too high.

e.g.
a clean F/A-18E/F , weigh 42,000 pounds and at 35,000 feet, is only 0.11 nm/LB.

cola wrote:

@bumtish,
you can't seem to understand that range is range, no matter how called.
If you stick 4 missiles on the plane, the range is still close to ferry, but you got combat capability and all of a sudden, it's not a ferry anymore.
IIRC, that's how's F35's range given.

Ferry range and combat radius/range are 2 separate things. Combat radius doesn't merely mean flying ~600nm and then immediately turning around, and flying home, and landing on fumes. Combat radius also factors station time, several minutes of afterburner usage, and a certain amount of reserve fuel left on the return leg, if one has to divert.

So if you hypothetically accept that the F-35 (MRC) specific range is at least the equal of the 2 engine F-18 specific range figure of .11 NM/LB and apply it to the F-35, now we're up to 1980 NM 'FERRY' range, clean.

If you accept the published 'FERRY' range figure of 2280 NM for a 3 bag F-16 (13,760 LBS fuel) you will get .165 NM/LB.

Why is it so difficult to accept that a newer turbofan and an aircraft with no external tanks could possibly achieve an MRC specific range of .16 NM/LB?

I certainly don't know what the actual figures are, but I think it is short-sighted to think the F-35 has a MRC specific range of only .07 NM/LB resulting in that 1200 NM range figure.

Last edited by bumtish on Oct 03, 2011 - 05:03 PM; edited 2 times in total

cola wrote:

@bumtish,
you can't seem to understand that range is range, no matter how called.
If you stick 4 missiles on the plane, the range is still close to ferry, but you got combat capability and all of a sudden, it's not a ferry anymore.
IIRC, that's how's F35's range given.

@outlaw,
ASRAAM is a nice weapon too, a bit short, though. Very Happy

Combat radius' are always a moot point, but there you go...http://www.fas.org/programs/ssp/man/uswpns/air/fighter/f16.html

F16 "740 nm (1,370 km) w/2 2,000-lb bombs + 2 AIM-9 + 1,040 US gal external tanks"
F35, same load with external tanks 728 nm (Norway JSF bid, LM) and that was when everyone thought the F35 has 673nm combat radius on internal fuel (today revised to 586nm).
The point: F35 can't match F16's combat range.
The conclusion: By Spudman's logic, F35 can't match F16's acceleration at 740nm.
Or even, if these data aren't true, the F35 can't match B1's range.
Does it mean the B1 has better acceleration?
I'm pretty sure, one need to observe performance within design limits,
If not, what would you call a HiMAT then?

What's funny though is that, if the F16 didn't have the ability to carry external tanks, the F35 wouldn't be able to out accelerate it at all and we wouldn't be having this conversation. Very Happy

(and since when external tanks config. qualifies as a "clean" jet?)

Hey, I missed that reply from cola.

But to summarize: The F-16 needs ~5k lb of external fuel to meet the F-35 range. The F-35 weighs 50% more empty, but also carries 50% more fuel!

So what's the TWR during the flight then?

@ takeoff fully fueled,
F-16 dry 0.52 wet 0.81
F-35 dry 0.58 wet 0.90

@ 50% of total fuel consumed (that means the F-16 still has barely just emptied and punched the externals)
F-16 dry 0.63 wet 1.00
F-35 dry 0.72 wet 1.10

@ 25% of total fuel consumed.
F-16 dry 0.69 wet 1.10
F-35 dry 0.81 wet 1.25

Get it now?

Btw, that 728 nm with externals is a Norwegian MARPAT (surveillance) mission profile done at 5-25k feet. Are you kidding me!!! You would use that as a direct substitute for the ferry range a 35 k feet optimum cruise altitude?!!!

Seriously?!

Why you (with Bill Sweetman) insist on jumping off a steep cliff from pure joy over this is beyond me!

Compare mission profiles. Wink

outlaw162 wrote:

So if you hypothetically accept that the F-35 (MRC) specific range is at least the equal of the 2 engine F-18 specific range figure of .11 NM/LB and apply it to the F-35, now we're up to 1980 NM 'FERRY' range, clean.

If you accept the published 'FERRY' range figure of 2280 NM for a 3 bag F-16 (13,760 LBS fuel) you will get .165 NM/LB.

an F-35 or F/A-18E/F's empty weight is about 30,000 pounds, is much more heavy than an F-16.
so 0.165 nm/LB may be impossible to an F-35 or F/A-18E/F.

an F-35A has about 18,000 pounds fuel internal, but every jet need a lot fuel to take-off, climb up, land, reserve furl for safe....it cannot use all fuel to do cruise.

bumtish, I get it.
What you don't get is the irrelevance of that argument (lame propaganda).

Outlaw,
F18E has been given a ferry range of 1800nm, with ~30klb (assuming 5 tanks) of fuel and with total 22klb PPH on the bench.
This is quite similar to F35's internals and 4x426 gal. externals for a total of ~30klb and with F135's SFC being anywhere from 0.7 to 0.886 (Wikipedia??), bench flow goes to 20-25klb PPH, meaning SH-like.
How do you figure the F35 does 2k+nm with 18klb of fuel, then?

F18E has been given a ferry range of 1800nm, with ~30klb (assuming 5 tanks) of fuel
--------------------------------------------------------
ferry range 1,800 nm, should with 3*480 gallon drop tanks, not 5.

cola wrote:

bumtish, I get it.
What you don't get is the irrelevance of that argument (lame propaganda).

So you'd rather stick to a purely theoretical argument with no connection to reality as opposed to how aircraft are actually employed?

But why?

qwe2008 wrote:

ferry range 1,800 nm, should with 3*480 gallon drop tanks, not 5.

Possibly (didn't find that explicitly stated), but then again F18 still sucks ~13lb per nm.
That would make 18.5klb last for about 1400nm, still a (too) long way to go to 2k+nm.

bumtish,
there's an explanation on the previous page.

Possibly (didn't find that explicitly stated), but then again F18 still sucks ~13lb per nm.
That would make 18.5klb last for about 1400nm, still a (too) long way to go to 2k+nm.

--------------------------------------------
but F/A-18E/F is not clean, is more heavy than F-35A......

QWE2008: I understand that you cannot use all the fuel for cruise. In 47+ years of flying I have never landed anywhere without fuel.

The original comment that I’m responding to from Cola concerns whether an F-35 with 18,000 LBS of internal fuel can go as far as an F-16 with 3 bags (13,760 LBS fuel, purportedly 2100 NM+) at whatever its MRC (max range cruise) thrust setting is. You can put whatever same fuel reserve requirements on them but academically it is just simpler to have them both takeoff from the same place, fly MRC until they run out of gas and see who is farther down the road when he gathers up his chute..

If the clean F-35 indeed has an average specific range equal to an F-16 with 3 bags then this is a no brainer. It may not, but neither you nor Cola know this to be the case either.

COLA: I have never flown a bench. Very Happy

And MRC is certainly not done at Mach 1.0 or military thrust. If you accept that the F-35 can achieve a ‘Specific Range’ (SFC is only a part of the equation) of .16 NM/LB it will easily exceed 2000 NM. Cruise power settings at optimum altitudes are obviously well below the dry maximum test numbers on the ‘bench’. And the 0.8ish Mach MRC fuel flows are obviously not linearly decreased from those at Mach 1 (i.e. 80% of Mach 1 pph) or even 80% of the mil power fuel flows. The F-4 J-79 indeed ran around 6-8000 pph in mil at altitude, but cruise setting was all the way back to 3000 pph at 0.8 Mach (That’s 50% or less of the mil power value)

To fly 2000 miles and land with 1000 LBS of fuel, the F-35 would need only an AVERAGE specific range of .117 NM/LB (i.e. 2000/17000).

Admittedly, I don’t know that the F-35 has this capability, but I don’t think you can be sure it doesn’t from bench test numbers and SFC. What do you postulate for a specific range (not SFC) value?

Maybe I’ve just been dealing with these super efficient airliner engines too long and am out in left field on this. I’m old (and she did say short also). Very Happy

OL

cola wrote:

bumtish,
there's an explanation on the previous page.

If you're referring to your post on engine fuel consumption I know too little on this specific topic to really contribute. Will keep back and follow your discussion with curiosity.

Can we at least agree that the F-35 should make a 2,100 ferry range with 2 x 426G tanks as a conservative minimum estimate?

According to the af.mil website, the F-15E has a ferry range of 3,000nmi with 36,200lb of gas, or ~0.83nmi/lb . I would expect the F-35 to beat this, but still be closer to the mudhen than the viper.

^^Bumtish: I can't agree that a conservative estimate for the F-35 is 2100+. I'd say 2,000 is pushing it. Again, that is if they are able to bring the range back up to original specifications.

qwe2008 wrote:

F18E has been given a ferry range of 1800nm, with ~30klb (assuming 5 tanks) of fuel
--------------------------------------------------------
ferry range 1,800 nm, should with 3*480 gallon drop tanks, not 5.

Exactly. The drag with five bags is so high that the added fuel has a negligible effect on range.

Forum: F-35 Lightning II

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