F-35 Range

Discuss the F-35 Lightning II
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idesof

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Unread post25 Jul 2006, 17:31

I am confused. The F-16 Block 40, at least according to Janes, goes 500 NM with two bags of gas, two Mk-84 type stores, two AAMs. Meanwhile, advertised range for the F-35A with a similar internal load and a completely clean exterior is only about 600 NM. This despite the fact that in this configuration it should have something like half the drag of the F-16, and its internal fuel load is a whopping 18,000+ pounds, two-and-a-half times that of the F-16. What gives? Either they are drastically understating the range so they can claim vast advances during testing, actual range is classified, or the F-35 engine is the most inefficient piece of egineering on the planet. And yet, from everything I know, it should be more efficient than the F-100 and F-110 given that its dry thrust is a much higher percentage of its afterburner output. With 18,000+ pounds internal fuel, an external clean configuration and a more efficient engine, there is no reason whey the F-35A's range should not easily exceed 1,000 NM. We're talking about an aircraft whose internal fuel load is something like 70% of its empty weight (compare that with the F-16 Block 40, whose internal fuel load is only about 37% of its empty weight). Anyone care to weigh in?

By the way, the Viper's range in that mission was for a hi-lo-hi profile, if I remember correctly. The F-35A's mission profile should be hi-hi-hi, zipping around at 50,000 ft. (same engine, only more powerful, as F-22, which cruises around at 60,000 ft.). No way in hell the F-35A's range is only 600 NM.
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DeepSpace

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Unread post25 Jul 2006, 18:01

According to Global Security the range is around 1,200 NM.
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idesof

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Unread post25 Jul 2006, 18:05

DeepSpace wrote:According to Global Security the range is around 1,200 NM.


Right, but look at its combat radius. Only 590 NM. Viper's radius 500 NM with above mentioned load...
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Unread post25 Jul 2006, 19:00

No... >590nm, not ONLY.
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toan

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Unread post25 Jul 2006, 19:25

http://www.globalsecurity.org/military/ ... -specs.htm

F-16C:
1. Empty weight: 8,372~8,710 kg
2. Internal fuel: 3,160 kg
3. Thrust of engine: 23,770 Ib~29,000Ib class
4. Combat radius: 740 nm (with 2,000 Ib bomb*2 + AIM-9L*2 + 1,040 Gal external fuel) --> The total fuel of F-16C in this condition is 3,160 + 1,040*3.785*0.8 = 6,309 kg.

======================================================
F-35A:
1. Empty weight: 12,000~12,500 kg
2. Internal fuel: 8,390 kg
3. Thrust of engine: 40,000~43,000 Ib class
4. Combat radius: 600~700 nm (with 2,000 Ib bomb*2 + AIM-120*2l)
--> The total fuel of F-35A in this condition is 8,390 kg.
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toan

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Unread post25 Jul 2006, 19:41

Comparing with F-16C, F-35A is a much bigger and heavier fighter that is almost as heavy as F-15C (12,973 kg). Therefore, it should be reasonable that it needs to exhaust more thrust and fuel than F-16C to achieve the same combat range. However, the internal fuel capacity of F-35A is big enough to achieve the combat radius that F-16C needs another 2 to 3 auxillary tanks to do the same performance.
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Guysmiley

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Unread post25 Jul 2006, 19:43

Exactly, thrust ain't free. A big motor burns more gas than a little one.
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toan

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Unread post25 Jul 2006, 19:59

PS: The performance of strike radius of JSF family today should be just the "minimal requirement" from USAF (600 NM+ for F-35A), USN (700 NM+ for F-35C), and Marine (450 NM, for F-35B) not the actual one ~ Don't forget, the maiden voyage of F-35 hasn't begun, so it should be impossible to know the "real" performance of combat radius of F-35A/B/C right now.
Last edited by toan on 25 Jul 2006, 20:03, edited 2 times in total.
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locum

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Unread post25 Jul 2006, 20:00

The USAF has officially said that the (clean configuration) ferry range of the F-22 raptor is 1,499 nm/ 2.776 km, a Specific Range of 0.082 nm/lb at Mach 0.8 with 2,500 lbs recovery fuel would give this ability. With drop tanks at Mach 0.9 the range would be 2,700nm+ / 5.000 km+.

The F-35 Lightning has a longer range than the F-22!
F-35A, ~ 1,200nm/ 2.222 km with 18,498 lbs gas
F-35B, ~ 900nm/ 1.667 km with 13,326 lbs gas
F-35C, ~ 1,400nm/ 2.593 km with 19,624 lbs gas

I think the above mentioned Triple Ugly ranges are clean configurations but with gun ammo, 2 JDAMs and 2 AIM-120s.
Just for comparison: The FB-111A has a range of 1,300nm/ 2.408 km with 4 internal JDAMs.

More comparison: F-22 with 20,649 lbs gas.
Range without reserves, clean and at Mach 0.9: 1,569nm / 2.906 km
Range with 5,000lbs / 2.270 kg gas at M 0.9 : 1,189nm / 2.202 km

Range no reserves, clean Mach 0.8 : 1,692nm / 3.134 km
Range with 5,000 lbs gas Mach 0.8 : 1,283nm / 2.376 km

Remember that the F-119 + the F-22 wing is optimised for supersonic flight and the F-35 + F-135/F-136 combination is optimised for subsonic flight.
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Unread post25 Jul 2006, 21:40

Umm... I don't know about this whole optimization for supersonic vs. subsonic flight. While there may have been some design point, off design performance was by no means neglected. And the F-135 engine is a derivative of the F-119, correct? It's not optimized for subsonic flight as far as I know.
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idesof

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Unread post26 Jul 2006, 03:39

toan wrote:Comparing with F-16C, F-35A is a much bigger and heavier fighter that is almost as heavy as F-15C (12,973 kg). Therefore, it should be reasonable that it needs to exhaust more thrust and fuel than F-16C to achieve the same combat range. However, the internal fuel capacity of F-35A is big enough to achieve the combat radius that F-16C needs another 2 to 3 auxillary tanks to do the same performance.


You are forgetting that stores and fuel in the configuration you cited for the F-35 are all internal, whereas the F-16 must haul bombs, fuel, not to mention jamming and targetting pods, externally. This should more than offset the F-35's heavier weight, given that with the same attack configuration (2 X 2,000 bombs, 2 AAMs), the F-35 is a hell of a lot less draggy and the Viper. Also, I would not say that the F-35's empty weight is anywhere near that of the F-15C, certainly not anymore. They have shaved something like 3,000 lbs. off its empty weight in its redesign prior to FSD. The empty weight of the F-35A is now about 26,000 lbs. vs. more than 30,000 for the F-15C. The F-16 Block 40 is no lightweight fighter anymore, either (19,000 lbs. empty). My very educated guess is that when all is said and done, the F-35's combat radius on a hi-hi-hi mission is AT LEAST 1,000 NM. Add a couple of 600 gal. drop tanks you can get rid of before penetrating enemy airspace, you're talking 1,250 NM easy.

Picture this: F-35, two 600 gal. drop tanks, two JASSMs, eight SDBs, two Amraams, stealthy from the minute it penetrates enemy airspace (having fired the JASSMs and dropped the tanks). Or four JASSMs without the drop tanks, plus the internal load. The F-35 is going to be a beast of a striker! :D

I used to have my reservations about it, but the more I look at it, the more I like it. And I still can't get over that internal fuel load: 18,500 lbs! To put it into perspective, the F-15 carries only about 13,000 lbs, and in a substantially bigger and heavier airframe. And the -35C carries even more fuel. AND, a large internal armament load. A miracle of engineering in my book.

The only one I'm still skeptical about is the -35B. In my mind, the other two models have had to trade off too much in terms of absolute performance for the sake of commonality with the STOVL, and I'm still not certain it will work on the long term. Just look at the V-22. Totally different program, yes, but this vertical flight stuff is not easy for airplanes to perform naturally...
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idesof

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Unread post26 Jul 2006, 03:43

Guysmiley wrote:Exactly, thrust ain't free. A big motor burns more gas than a little one.


It is my understanding that the F-135 is a more efficient motor than the F-100, with a substantially higher percentage of dry vs. afterburner thrust. Moreover, you are talking about an aircrat that is far less draggy in combat configuration. Also, the Viper's range hasn't decreased appreciably with the advent of higher thrust engines. Higher thrust also means the same relative thrust at lower power settings.
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idesof

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Unread post26 Jul 2006, 03:47

Raptor_One wrote:Umm... I don't know about this whole optimization for supersonic vs. subsonic flight. While there may have been some design point, off design performance was by no means neglected. And the F-135 engine is a derivative of the F-119, correct? It's not optimized for subsonic flight as far as I know.


If memory serves, the F-119 and F-135 are both leaky turbojets, basically, with bypass ratios far lower than those of the F-100 or F-110. This may, in fact, contribute to a less fuel-efficient design optimized for supersonic vs. subsonic flight. Although, I haven't read it, but the F-135 may have a higher bypass ration than the F-119, given that it is designed for an airframe that will not supercruise (although I have my doubts about that, since I suspect the F-35 will easily supercruist but the USAF is not shouting that fact from the rooftops as it may provide amo to those who would have the F-22 cut).
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Unread post26 Jul 2006, 04:09

I'm not really sure about how everything work with this, but it may also not always be in full Mil. thrust all the time. The thing is good at full Mil. thrust, but if you're trying to putter along and extend range, this may not be best. I couldn't say exactly, need more schooling. The more advanced the engine, the lower the SFC almost always. This may have a higher bypass ratio than the F100/110 which would make it much more efficient. It will cause longer spool up (more spinning mass), but hopefully not that much as this thing is going off a carrier.

As for the 35B, I'd be worried mostly about maintenance on the lift fan. I know that maintenance is good, but if the thing breaks and throws a blade... the pilot is dead. I belive the tech to make it safe is there, but it may take out a little while to work the bugs out unfortunately.
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