F-35A Combat Radius May Not Meet Minimum Requirement

So, the Federation of American Scientists just published the Pentagon’s latest 53-page Selected Acquisition Report for the F-35 Joint Strike Fighter program published in December of 2010. This trove of info is produced annually to give lawmakers the DoD’s latest estimates for the plane’s cost and development performance.

This report shows that Pentagon officials estimate the F-35A Air Force variant of the JSF will to meet its minimum combat radius requirement of 590 nautical miles. Granted, it misses the target by only six miles, but still, it’s missing the minimum performance metric. Program officials had estimated that the plane would have a combat radius of 690 nautical miles. This puts the Air Force version of the jet in between the Marines’ short take-off and vertical landing F-35B and its combat radius of 469 nautical miles and the Navy/Marines’ F-35C carrier variant which has a radius of 615 nautical miles.

This is troubling because some of the combat scenarios Pentagon officials think about the most involve operations in the Pacific theater where the “tyranny of distance” is a major factor.

Apparently, the range shortfall is caused by:

Based on updated estimate of engine bleed, the existing Conventional Takeoff and Landing Variant’s Combat Radius prediction of 584 nautical miles (nm) is below the threshold of 590 nm. The current prediction is based on estimates for bleed usage, aircraft performance, and fuel capacity that are not yet fully known. Current estimates have built-in margin that may not be realized. Non-material (analysis and test) measures continue to reduce key performance parameter (KPP) uncertainty. Realistic aircraft modifications to add fuel capacity exist to recapture the KPP. These design modifications are being matured to sufficient level to allow for a program decision on incorporation if the current estimate remains below threshold as uncertainty is reduced. This estimate is based on preliminary data. The Program is still in the data analysis stage.

What’s all that mean? Basically, the plane’s engine and avionics are running hotter than expected which requires “bleed air” from the F135 engine to be fed into the airframe to cool it down, as Steve Trimble at Flight Global points out. This reduces engine efficiency and therefore combat range. Additionally, the aircraft has less fuel capacity than planned and its stealth targeting pod is causing more drag than expected. All this has reduced the jet’s range.

As the SAR says, the program is looking at “aircraft modifications to add fuel capacity” to get the jet back to at least a 590 nautical mile combat radius.

Trimble’s sources told him:

One simple change under review is a software tweak that would maximise the amount of fuel taken onboard during in-flight refuelling. Another relatively simple fix is to raise shut-off valves higher inside the fuel tank to create slightly more capacity, a source said, adding: “That gets you back a lot of the fuel that you need to recover” to meet the range mandated by the contract.

A more complex solution also being considered is to install new fuel tanks in a small number of hollow spaces within the aircraft’s structure.

But programme officials are also debating whether to change how the range of the F-35A is calculated, the source said. The equation does not include a buffer margin of 5% of fuel capacity, which is intended to be preserved through the end of the flight test period in 2016. Eliminating the buffer margin adds another 72.4km to the aircraft’s combat radius, the source said



  • Franco Gil

    just a pretext to get more tax payers money and develop another engine

  • Prodozul

    So wait is this the new engine? Or the onboard one?

  • STemplar

    I still say dump the A model and just buy the C. The C model exceeded range expectations, which are better than the A. If there is a concern about range coupled with a desire for ‘commonality’ to save on upkeep costs, just buying the C model meet both desires.

  • STemplar

    I think the death spiral is well under way. The costs quoted in the SAR are not encouraging.

  • Mastro

    Apollo had a huge budget- I vaguely remember- but basically they could/and did spend anything.

  • STemplar

    Take a look at http://www.spacex.com , that’s a lot more amazing what a company with innovative leadership and a goal oriented mind set can accomplish on a high tech endeavor. How to make that success happen for the defense department would be a worthy goal.

  • TLAM Strike

    Just stick a extra gas tank behind the pilot like on the P-51…

    or strip the paint off…

    or get smaller pilots…

    Do I have to think of everything?

  • oldsalt

    Missing by 6 nm?
    Grounds to kill the program!

    Whoa wait just a minute….I missed this:
    “The current prediction is based on estimates for bleed usage, aircraft performance, and fuel capacity that are not yet fully known.”

    In other words whoever wrote this has no idea if the plane is long, short or on the money for range. It’s a predication on a estimate for critical unknown factors.

    Nice try at a headline on a slow Friday.

  • DanS

    Just buy the damn C model. God forbid the neckerchief boys from Colorado Springs have to accept the better Naval version. By the time you drop the weight of the tail-hook and beefed up landing gear, the radius should be even better.

  • jamesb101

    This aircraft is turning into a VERY EXPENSIVE joke…..

  • jamesb101

    on us …..The taxpayer

  • A. Nonymous

    Please do be proofreading articles before is posting. Otherwise, is making reporter sound like Boris Badenov trying to find moose and squirrel.

  • USA

    Isn’t the range still pretty good compared to the F-16? (From Wikipedia: 340 mi (295 nm, 550 km) on a hi-lo-hi mission with six 1,000 lb (450 kg) bombs).

  • turtleairships

    “…..One simple change under review is a software tweak that would maximise the amount of fuel taken onboard……”

    huh? ya mean, like….”fill er up!” mabe, instead of “just gimme some”????

    whoa. What a concept!

    listen, wouldn’t it just be easier and cheaper to, say…..move the runway six miles closer to target? huh? or, is that 3 miles? (dang, these are tough calculations)

  • SJE

    Perhaps we need to buy some F15 s or even (gasp) some French fighters

  • STemplar

    This issue with range along with concerns over next generation SAM systems and such makes me wonder how long till we see the RFI from the Pentagon.

    Solicitation will read something like, wanted, proposals for precision stand off strike missile that can be launched from internal F35 weapons bay and deliver 250 lb class weapon a minimum range of 450 nmi, with multiple redundant targeting system both on board and able to receive updates from supporting aircraft, or something like that anyway.

    I know Raytheon is already playing around with the JSOW ER, but curious when the issue will be raised specifically for the F35.

    • Gregory Savage

      It already exists. It’s called the JASSM ER

  • William C.

    As you know I am generally pro F-35. Yet the F-35 should be exceeding the minimum requirements, not just matching them. The costs of correcting this should come out of LM’s pocket.

    • halcyon

      yes, exactly! Great point.

  • Alligam

    From the actual report: “This estimate is based on preliminary data. The Program is still in the data analysis stage.”

    In other words: “We are using a computer to guess at the results based on whatever data we could get our hands on.”

    While this is the best they have right now — there is no way that any procurement decisions (or judgements about the program’s effectiveness) should be made using this.


    This is why development of the F135 or F136 engine didn’t make any sense as the F-35 should have been developed to use the same engine as the F-22 Raptor; the F119 engine used by the F-22 Raptor is capable of supercruise and wouldn’t have any of the combat radius issues that exists with the F-35.

  • Justin H

    Its programs like this that should fundamentally change the way we select/buy weapons from now on. What a massive cluster**** !

  • Tim

    Uh… can we just make it mandatory for all F-35 pilots to carry extra jugs of fuel to get the extra… 6 nm and then call it a day? :)

    Seriously, how can anyone not know this during the design/testing process and had to wait till the darn thing is actually flown?

  • bengals69

    Can’t believe the posting here. Don’t you guys read?

    Here is what it said: “The current prediction is based on estimates for bleed usage, aircraft performance, and fuel capacity that are not yet fully known.”

    In other words the claim of a shortfall is just a guess, based upon more guesses. This is headline hunting. Trolling for eyeballs. This story should never have been published in such a sensational style.

  • Chops

    Question-how far out the window do those ranges go w/ACM?

    • STemplar

      I’m sure those are ideal numbers.

  • Black Owl

    Cancel the JSF and buy more Super Hornets.

    Maybe more F-22s and F-15s too.

    With the amount of money that we will “save” from maintaining a fleet of JSFs (I think the number was around 1 trillion dollars, I’m not sure) we could purchase a much more effective and cheaper fleet of aircraft that are still in production and can be readily used in large numbers against any nations that would cause trouble in the Asian continent.

  • GreyArea

    Longer isn’t always better of course.

  • Bob

    The claim of shortfall is based on computer models used to evaluate the F-35’s performance. These same models currently provide us with the vast bulk of data on the aircraft because the manufacturer cannot seem to build them right, and the ones they do have do not seem to fly right. More importantly, these models are also used to create the design of the fighter. So, either the models are wrong and we should scrap the aircraft because they were designed using faulty methods, or they are right and we should scrap it based on repeated real world failures. Have fun choosing.

  • retired462

    Using the “C” model for BOTH the Navy and Air Force; what a great NEW IDEA (lol)! The F-4’s worked out real well for both, plus the many foreign countries that flew it! I say “go for it”, if it will save money, and bring them into service quicker!

  • Oblat

    Of course the best part of the joke is that trade-offs have already been made to reach even this inadequate range.

    Like removing fire suppression systems and auto-close fuel valves that prevent a fire from spreading. Making the aircraft much more vulnerable to small caliber AAA.

  • arias

    This should all have been known at the design stage, simple questions like how much fuel can it carry or other common sense questions.

  • David Smith

    Apollo got I believe somewhere around 2% of the gross domestic product.

  • Justin H

    The real sad part is that Lockheed Martin is laughing all the way to their offshore bank accounts.

  • Justin H

    Drop stealth parts over enemy territory?

  • Guest

    My information may be old, but isn’t the F-35 equipped with the capability to carry ordinary drop tanks? Sure, the stealth capability is lost, but you could use the extra fuel to get closer to the target, drop the tanks, and use stealth mode when approaching the target area.

    • STemplar

      Yes it is, but drop tanks only add at best 50% to your range, so 25% to your combat radius. So it wold have a combat radius of about 800 nmi. That means it still needs aerial tanker support. It’s also limited by the fact the longest range weapon it has internally at the moment is the JSOW which is about 70 miles. SLAM ERs and JASSMs are too big to fit in the internal bays. You can carry them externally but if you’re going to do that not much use being stealthy.

      A F-16IN has a 890 nmi combat raidius, and well over a 1000 with drop tanks.

  • Nick

    Imagine F-35xl? Delta wing with thrust vectoring. Twice the fuel. Might as well give it two engines too, oops, that sounds alot like a J-20. Hmm, I would buy half the planes and make one that is made for warfare, current and future. I feel we are about 1989 too late to this one. Totally agree with others saying AF needs C model. Didn’t they talk about a laser? Are we banking on that?

  • Alcazar169

    To be honest, we don’t know or believe that the F-35 Lightning will be able to compare to some of our competitors like China. Most of the aircraft’s capabilities can be matched by variations of the F-22. Which was pushed out of production for the “cheaper” F-35. However, even on it’s minimum combat radius it still has an effective range that is wider than most aircraft. This of course includes the F-22. The problem is that this aircraft is really the only key to most of our problems in the WPTO. The F-35 is an overpriced program that can’t be stopped because we need to fight area of denial weapons. As for the Air Force being persistent about the A version. It is probably due to the fact that it has a higher thrust to weight ratio compared to the other versions. I say go for the C version and include more F-22s and other existing airframes.

    • Riceball

      Couldn’t the thrust to weight ratio of the A be incorporated into a C by stripping the extra weight out of it? Remove the wing folding mechanism, tail hook, put in the As landing gear, and don’t reinforce the undercarriage would make the C a lot lighter and therefor (theoretically) increase the thrust to weight ratio.

  • JJMurray

    And just wait…once in production the military will figure out once again that it really DOES need two seats and we’ll see another total rework of the aircraft. It just doesn’t get any better if you’re an aircraft manufacturer.

  • JJMurray

    And how many times have you heard the Pentagon yell “foul” on any multi-billion dollar project that has been in the works for a decade plus? They’re tied to this aircraft now, like it or not. As for meeting specs - of course there are trade offs, but that’s the purpose of establishing specs in the first place. The idea is to build an aircraft that does what the specs laid out, but of course, the Pentagon is always WAY too willing to accept over time, over budget, and not quite up to spec.

    • SMSgt Mac

      How many times? Lots. The DoD officially ‘cries foul’ by issuing a Cure Notice, and they do so whenever it doesn’t look like the contractor can get ‘here to there’ Guess what? If the F-35 6nm ‘estimated’ combat radius shortfall starts looking like it is going to become reality,, a Cure Notice is one of the remedys available, and if the DoD determines a system isn’t worth it (future cost vs. need) or can’t suceed, it cancels..
      RE: The idea is to build an aircraft that does what the specs laid out, but of course, the Pentagon is always WAY too willing to accept over time, over budget, and not quite up to spec.
      Hardly. ..and you sound like you’re under the mistaken impression that the contract objectives are known to be 100% achievable when the contract is awarded in the first place . This happens rarely if at all in the case of combat aircraft - they have to push the edge of ‘possible’ at the start just to be ‘plausible’ 25+ years later at the scheduled end of operational life.

  • USA

    Since the 35 is now no longer cheaper than the 22, we should just keep making the 22. Maybe the only saving grace for the 35 is that the 35 will be cheaper to operate since it’s only a single engine?

  • Jonathan

    Im just confused on why we want so many of these and have such few f22’s. Maybe the air force should cut some of its f35’s for f22’s?
    On a side note these are just calculations the numbers aren’t really known yet. I am sure the f35 in 5 or 6 years will be a solid performer. We had alot of problems with the f16 and f15 when they first came into service, but we eventually overcame them.

  • just4lolz

    Almost as bad as the screen doors for the submarine program that got scrapped ;)

  • Jim

    Its a pity the F-22 went out of production 2 years ago they were at about the same cost per unit 156 mil vs 150 mil from what I have read I can’t see any major advantage of the F-35 over the F-22

  • Tenn Slim

    The whole article is full of caveats.

    Wait til the actual Logistics, Fuel, Flight tests, then comment.
    Semper Fi

  • Tenn Slim

    Compare this F35 program to the F22 EMD phase. The Congress, USAF, etal nearly killed the LM program. Month after month of revisions, indecsions, outright political enmity and the end result, in spite of all this was a D>>>> good Raptor Air Dominant fighter.
    Give LM a chance. They produce the best, whatever the difficulties.
    Semper FI