back to article United States Air Force grounds F-35As after cooling kit cracks up

The “ready for combat” F-35 has run into headwinds again, with 15 of the F-35A variant grounded in America because cooling line insulation is cracking up. Various reports state that the problem is non-conforming insulation in lines carrying coolant in the plane's wings. The F-35 passes its poly-alpha-olefin (PAO) coolant …

  1. Jeroen Braamhaar
    Mushroom

    "Not compatible with fuel"

    I'd be more inclined to label the entire F35 project as "not compatible with anything but a paper political specification", since it doesn't seem to be compatible with staying aloft, nor compatible with active service, nor compatible with anything but carefully scripted exercises, after which it must be tenderly coddled by specially-compatible technicians.

    The only compatibility other than the paper spec seems related to large amounts of bacon ... or more precisely pork.

    1. Yet Another Anonymous coward Silver badge

      Re: "Not compatible with fuel"

      You can tell all that from the "F" (Fsck-up) code letter at the beginning of the name.

      Projects beginning with "B" tend to be the same but with $Bn instead of $Mn, I think that's what the "B" stands for

    2. taxythingy

      Re: "Not compatible with fuel"

      I guarantee to you that compatibility is at an all time high:

      Many project-related things are staying aloft;

      Much active servicing is going on; and

      Many completely unscripted exercises are being undertaken.

    3. stu 4

      Re: "Not compatible with fuel"

      It's a replay of this I reckon!

      https://en.wikipedia.org/wiki/The_Pentagon_Wars

  2. Anonymous Coward
    Anonymous Coward

    Hang on a minute...

    So, these lines are used to cool equipment by dumping heat into the fuel. Is that right?

    If so, why do they have insulation round the part of the circuit that's in the fuel tank?

    1. mtp
      Mushroom

      Re: Hang on a minute...

      Probably electrical insulation.

      1. John Brown (no body) Silver badge

        Re: Hang on a minute...

        Electrical? It's cooling fluid passing through pipes which go through another fluid. It's possibly a composite pipe using one material to protect against corrosion from the cooling fluid on the inner layer and a different material on the outside of the pipe which is supposed to be designed to protect against corrosion by the fuel. Whatever it is, I don't think it's insulation of any kind since heat transfer is the primary reason for the pipes existence.

        1. wolfetone Silver badge

          Re: Hang on a minute...

          "If so, why do they have insulation round the part of the circuit that's in the fuel tank?"

          Might be an insulation that allows some heat to be transferred from the coolant to the fuel at a steady rate. So instead of having (however hot) coolant entering in to the fuel from the word go, it instead loses some of its heat gradually as it travels around the circuit in the wing.

          The other reason is that the insulation is there to either stop the fuel from supporting corrosion of the metal pipe work of the circuit, or it's simply preventing the coolant circuit - if it became electrified - from passing through the fuel to cause a spark.

          1. imanidiot Silver badge

            Re: Hang on a minute...

            @Wolfetone, probably that last one. Spark surpression is pretty important in a fuel vapour rich environment.

            1. Anonymous Coward
              Anonymous Coward

              Spark surpression

              If the pipe is made of metal and connected to the fuel tank then there's no chance of a spark.

              Fuel tanks also contain saturated vapor and/or are purged with something like nitrogen to ensure that combustion of vapor cannot take place if a spark occurs.

              1. Mark 85 Silver badge

                Re: Spark surpression

                So there's probably not a bladder inside the tank? I recall as early as the 60's most military aircraft in the US had bladders if for no other reason than to be self-sealing incase of puncture.

            2. Alan Brown Silver badge

              Re: Hang on a minute...

              "Spark surpression is pretty important in a fuel vapour rich environment."

              If you make it rich enough, sparks don't do anything.

        2. Anonymous Coward
          Anonymous Coward

          Re: Hang on a minute...

          Static electricity sparks in partially empty fuel tanks have been known to cause issues.

    2. Thoguht Silver badge

      Re: Hang on a minute...

      Why don't they just use the fuel itself as a coolant like they did on the SR-71 Blackbird?

    3. JaitcH
      WTF?

      Re: Hang on a minute...

      Shhh ... you ask too many intelligent based questions.

      Remember, these are make work programs and this is undoubtedly designed for another expensive upgrade.

  3. Gordon861

    New Carriers

    It is going to be so funny when they have to drop these new planes because they don't work and then we end up with two carriers and nothing capable of flying off them.

    1. Anonymous Coward
      Anonymous Coward

      Re: New Carriers

      "[...] then we end up with two carriers and nothing capable of flying off them."

      Possibly the USA would let us buy back the Harriers and spares we gave them for a goldfish.

      1. Elf

        Re: New Carriers

        We will not sell the Harriers back. -- USA

    2. Anonymous Coward
      Anonymous Coward

      Re: New Carriers

      You can always buy some mig-29k. Will probably save a fair bit of money, too.

    3. Voland's right hand Silver badge

      Re: New Carriers

      Pigs fly, if sufficient amount of thrust can be provided.

      The F-35 can probably work. If sufficient amount of financial thrust has been provided. The issue is that the amount of "financial thrust" provided may exceed the amount of money available in NATO and Japan.

      1. Alan Brown Silver badge

        Re: New Carriers

        "Pigs fly, if sufficient amount of thrust can be provided."

        Manouvering and landing remain unsolved issues though.

        Much like the F35

    4. MrXavia

      Re: New Carriers

      Drones, and helicopters...

      Maybe if they save a bit of cash by NOT buying the F35, they could install a cat n trap system......

  4. GrumpyKiwi Silver badge
    Boffin

    Bring back Lewis

    Bring back Lewis Page.

    Then we might just get some informed comment on defence matters instead of this dribble.

    1. SkippyBing Silver badge

      Re: Bring back Lewis

      Yeah, because Lewis's one sided rants were 'informed comment's.

      1. John Brown (no body) Silver badge

        Re: Bring back Lewis

        "informed" being the operative word.

      2. GrumpyKiwi Silver badge

        Re: Bring back Lewis

        Why don't you tell us all about your time spent in your country's armed forces.

        I'll mention my couple of years at the MoD. You can tell us about your time as a Delta Marines Army SEAL

  5. Magani
    Coat

    Not cool

    "...with 15 of the F-35A variant grounded in America because cooling line insulation is cracking up."

    They've lost their cool? Boy, that just cracks me up.

    Mine's the one with insulation in the pockets...

  6. Michael Hoffmann
    Thumb Down

    Insult!

    "Toothless Tiger Moth"?

    Why is the author dragging the name of this great classic airplane

    https://en.wikipedia.org/wiki/De_Havilland_Tiger_Moth

    into the same realm of this failed boondoggle?

    1. Pascal Monett Silver badge

      Re: Insult!

      Probably because the Tiger Moths were specifically good, and the comparison is in the sense that the F35s are not - they are toothless.

      So it remains an insult, but for the F35s.

      1. PassiveSmoking

        Re: Insult!

        The Spruce Goose (real name Hercules) would be a better comparison. That was ridiculously over budget, so behind schedule that it missed the war it had been designed for, and barely worked with a service ceiling of about 30 feet.

        Then again they did cancel that project and try to hold Howard Hughes to account when it bombed, whereas with this train crash they just keep doubling down and throwing so much money at it that the F22 actually looks like a bargain in comparison now.

  7. tempemeaty

    Is this a war machine or a technology demonstrator?

    I hope a war situation with other countries doesn't disrupt the supply of these kinds of the very specific chemicals for these high tech coatings or any other super high tech parts for the F35.

  8. taxythingy
    Thumb Up

    But sir, it gets 5 star Amazon reviews

    So it has to be good, right?

    Besides, we'll get a genuine certificate of authenticity if we buy now.

    1. Phil O'Sophical Silver badge

      Re: But sir, it gets 5 star Amazon reviews

      So it has to be good, right?

      https://xkcd.com/937/

  9. Bubba Von Braun

    "the US Air Force's first “combat-ready” squadron of the Toothless Tiger Moths."

    Forwarded this to a buddy of mine and ex Viper pilot out of Hill AFB, and he promptly spat coffee all over his screen. Very funny, and it would seem quite accurate. As he points it its a game of numbers and the only group wining that game is Lockheed..

  10. allthecoolshortnamesweretaken Silver badge

    Puzzled

    Is this contraption using the fuel as a heat sink or is it supposed to chill the fuel? (Or was there no room to lay the pipes around the fuel tank?)

    Neither option sounds reassuring. Does anyone know something about the reasoning behind this? Has this something to do with cooling the jet exhaust "because stealth"?

    1. Magani
      Happy

      Re: Puzzled

      "Is this contraption using the fuel as a heat sink ..."

      Yes, I believe so.

      "Neither option sounds reassuring."

      Its use goes back at least as far as Concorde.

      1. Anonymous Coward
        Anonymous Coward

        Re: Puzzled

        What happens to the cooling function when the fuel is getting low? Does such a plane have to carry a level of surplus fuel that it can never burn?

        1. Steve K Silver badge

          Re: Puzzled

          I imagine the lines are towards the bottom of the tanks as that's where the fuel will be coolest - maybe in a channel which is designed not to drain.

          They must also have a good reason for it to go through the tanks rather than attached to the outside (e.g. via a heatsink plate or channels) as otherwise that would seem to be a better way to avoid fuel corrosion effects.

          1. SkippyBing Silver badge

            Re: Puzzled

            'They must also have a good reason for it to go through the tanks rather than attached to the outside'

            Probably because the outside of the tank is also the outside of the aircraft. You can get more fuel in that way.

    2. Eddy Ito Silver badge

      Re: Puzzled

      Does anyone know something about the reasoning behind this? Has this something to do with cooling the jet exhaust "because stealth"?

      No, I doubt it has nothing to do with cooling the exhaust. Typically the coolant, which in this case is essentially a type of synthetic oil, is used to cool high power electronics such as the radar system. Microwave radar is highly efficient at producing heat and also does a reasonable job of providing detection of other objects in the relative vicinity. The use of poly-alpha-olefins, introduced some 20-30 years ago, was because previous coolants were silicate ester based and would absorb water, break down and ultimately create a rather flammable alcohol to which bad things were prone to happen.

      Interestingly this might partially explain a few things such as the need to "reboot" the radar by turning it off and on again. Perhaps it simply overheated because the coolant lines were too heavily insulated, undoubtedly due to non-conforming insulation which is the fault of a subcontractor, and didn't give off enough heat as they passed through the fuel. Shutting it off for a moment or two allowed it to cool enough so that it would restart normally. Of course that's just a bit of speculation on my part.

      To address the comment of why the lines aren't on the outside of the aircraft, it's likely that at higher altitude there isn't sufficient air mass to dissipate the heat in a timely manner without using the entire skin as a heat exchanger. Of course that might raise issues with coolant loss when confronted with things like bullets.

  11. Sirius Lee

    Testing

    Surely this would have been apparent as a result of testing. Would it not be normal to perform extensive tests on items coming from the sub-contractor to make sure they performed to specification?

    Arranging for a pipe to carry one fluid at a given temperature while immersed in a tank of kerosene at the appropriate temperature for an extended duration doesn't seem like a very difficult test to perform yet clearly was not performed.

    Maybe some of the problems of this aircraft are the result of the failure of the various parties to demand (on the part of the US Air Force) and perform (on the part of the supplier) adequate tests. In this regard to me the story is reminiscent of the problem uncovered by Richard Feynman with 'O' ring seal on the Space Shuttle. In that case it turned out those involved knew about the risk but failed to disclose the issue for political reasons.

    1. AndyS

      Re: Testing

      > Surely this would have been apparent as a result of testing. Would it not be normal to perform extensive tests on items coming from the sub-contractor to make sure they performed to specification?

      Yes, that's what a Conformity issue means. The design is good, the product did not conform to the engineering. Most Aerospace parts are delivered with a Certificate of Conformity, in which the supplier states that the part has been manufactured and tested according to specification. Something in that process has gone wrong here, and you can be sure the supplier will receive a very good kicking because of it.

      1. Captain Badmouth
        Devil

        Re: Testing

        "Most Aerospace parts are delivered with a Certificate of Conformity, in which the supplier states that the part has been manufactured and tested according to a decent profit."

        Fixed.

  12. Anonymous Coward
    Anonymous Coward

    Hello as the manufacture of the F35 can we please talk about the failures of the Euro fighter . Thx please. I need to keep the congress critters confused.

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