Wednesday, March 23, 2016


The Navy is developing an Infrared Search And Track (IRST) sensor as a means of producing passive, infrared target location and tracking with accuracy sufficient for weapon guidance.  This would be useful for combat while remaining “stealthy” and not broadcasting with one’s own radar and for operating in an electromagnetically challenged environment where normal radar operation is degraded.  The system is initially intended for the F-18 Hornet.

DOT&E has reported its assessment of the IRST in the 2015 Annual Report.

“The system tested in OA 1 [ed., Operational Assessment 1, conducted in 2014] could not detect and track targets well enough to support weapons employment in an environment that reflects realistic fighter employment and tactics.”

Disturbingly, the unit’s basic design criteria is questionable, according to DOT&E.

“The Key Performance Parameter (KPP) and the derived contract specification for detection and tracking describe only a narrow subset of the operational environments where the Navy will employ IRST. Meeting the KPP (with a narrow reading of the KPP requirement) does not ensure a useful combat capability.”

Who came up with the initial spec????

IRST Mounted in Nose of Fuel Tank

Despite this, the Navy granted approval to enter into Low Rate Initial Production (LRIP).  This is a growing trend in the Navy, to accept products that fail to meet specs or fail to demonstrate useful combat capabilities.  Why are we building and buying a product that is not yet useful?

IRST Fuel Tank Mount

All of that aside, an IRST ought to offer a much needed capability for very little impact on aircraft performance (the IRST is mounted in the nose of the centerline fuel tank so fuel/range will be slightly reduced).  This is just one more incremental improvement that will help keep the Hornet viable.  I just wish the Navy would complete development before entering into production.  This is concurrency, again, which will require the initial IRST’s to be remanufactured, eventually.

Update:  This is why the DOT&E is so important and why there is tension between the Navy and DOT&E.  The Navy is entering into LRIP even though DOT&E testing shows the IRST to be of very questionable combat value.  If DOT&E didn't exist, we'd never know about the problems until combat revealed them and the Navy would have already committed to full scale production of a marginally useful system.  Why the Navy insists on putting badly flawed and substandard systems into full production is beyond me.


  1. For something like this (a relatively small-scale weapon system), a simple fix would be to allow an easier rephrasing of procurement funds so that a delay would not be "punished". With budgets locked two or three years in advance, it puts pressure on the program to start expending the first year procurement dollars, even if the system is not truly ready for production. In addition, long-lead of production hardware and a need for LRIP hardware to support OT requirements puts another incentive on the program to start production, with the belief that any "minor" performance deficiencies can be addressed in parallel with the long-lead production in order to maintain schedule.

    Not excusing it...merely explaining some of it.


  2. This is too bad.

    Like it or not, the Hornet is the craft that we will have to rely on for numbers in the near to mid term; regardless what happens with the F-35.

    The recent deployments have really put the hours on them, and our choices are get the SuperHornets refurbished, buy new, or both.

    To that end, I think that with things like EPE (unlikely) CFT's (more likely) and avionics upgrades and sensor pods it could, for not a ton of money, be a good 'filler' for the air wings. If those avionics and pods have real capability, and we maybe borrow something like a meteor with a high Pk, the Hornet is something people have to worry about.

    (Oh, Add in a real tanker too so we can mitigate the air wing degradation in numbers and hours in the future).

    But if we just put crap on it, its not worth the money. And, if we just put junk airwings on the CVN's... why bother the billions for the CVN's. Its like deploying the Iowa's with all their complexity and cost and having them carry 11 inch guns.

    I hate to say it, but part of me thinks that only committed congresscritters (hard to get) going after admirals and industry (harder to get) have a shot at shaking things up.

  3. CNO;

    we've had the one commenter earlier provide his experience with government contracts.

    Do you have any references that might show how the Navy did things when they had BuShips and their own yards? It would be interesting to compare and contrast.

    1. I have no idea and no documentation. That was before the days of Internet access to everything.

      BuShips never had their own yards. BuShips generated the designs/contracts and then monitored the construction. The key was that they had in-house engineers who thoroughly understood naval ship design and actually designed the ships. They knew everything there was to know about ships. We've lost that in-house knowledge. Now, industry designs the ship and we don't have people who can spot problems in the design. That's how we get an LCS without bridge wings. That's how we get ships built without galvanic corrosion protection. And so on.

    2. Ah. I misunderstood. I thought Mare Island and places like that were linked to BuShips.

    3. Mare Island was a naval base and conducted all kinds of support work for naval construction. They did build some ships (notably some subs) but it's unclear to me that it was a Navy construction yard versus a private yard located on a Navy base. Evidence supporting that tentative conclusion is that Mare Island had to bid on contracts like any other shipyard. You would think that wouldn't be the case if the Navy directly controlled it. In any event, the ships they built were subs and smaller or support vessels as opposed to front line warships.

      To the best of my knowledge, BuShips did not control any construction.

    4. My understanding is that Mare Island was owned by the Navy. It and several other naval shipyards used to build as well as repair ships. The naval shipyards had to bid against other shipyards to get the contract, just like a privately owned shipyard.

      Quite a few ships, including all four Iowas, ten of the 24 Essex class carriers and two of the four Forrestals, were built in navy yards.

    5. Interesting. I'll have to look deeper into it. As far as I know, Mare Island never built major warships other than some subs.

    6. "I thought Mare Island and places like that were linked to BuShips."

      Jim, I stand partially corrected. The Navy had more shipyards than I realized and they were more active. What I still don't know is what relationship they had with BuShips, if any. It seems the Navy shipyards had to bid on contracts like any other shipyard which suggests that BuShips had no more contact or control over them than any other shipyard. I'll continue to look at this. Let me know if you find out anything else.

    7. Actually, Mare Island constructed the only dreadnought battleship ever built on the West Coast, namely the USS California. It built a great many destroyers as well. It specialized in submarine construction from 1936 onwards and some of the navy's most famous boats were built there. The last submarine to be built at Mare Island, the USS Drum, was completed in 1970.

      The ships referenced in my previous comment were all built in East Coast navy yards.

    8. Thanks CNO. I will look into it and let you know.

      I suppose my biggest interest is that people complain about the lack of competition now (myself included). I wonder if a Naval Shipyard or two could help on that front.

      So far I haven't found much on the relationship between BuShips and the Navy yards, but it does appear the Navy Yards, however they got the contracts, did some big work. Brooklyn Navy Yard built Arizona and North Carolina, in addition ot the ships Blueback mentioned.

      I thought I remembered a section on Mare Island on my favorite website from my 20's,

      but sadly that stopped getting updated in '03 and I can't find the article I was looking for.

      I'll let you know anything I find!

  4. Hi. Am new here so apologies if I seem a little green in these matters. My understanding is that the Air Force either already has or is developing an IRST for its fighters (F15, F22). What I don't understand is why can't the navy just use the air force's version. It's not like its a whole new plane which needs to be navalised (F35), it's just a piece of kit that is attached to the plane

    1. Welcome!

      I'm not aware that the AF has a fielded IRST although they are looking at acquiring one. If you know of a fielded system, let me know. Many foreign AF's have IRST systems of varying types. I think the AF may have some pod'ed IRST systems although I'm not sure about that.

      Why the AF and Navy wouldn't develop/acquire a common system is a good question. It may be a physical mounting issue more than anything. Beyond that, the AF and Navy simply don't like using equipment that the other service has - childish, I know.

  5. Actually its well know the US is somewhat behind other countries in IRST.

    Without getting into the really complex bits of the technology. The general idea is as CNO says that this is a passive alternative to using your radar. In F35 it’s very much about stealth, and F35 promises to be the ultimate IRST system (if it ever works, although I understand it’s pretty much there)

    In other aircraft it about low observability ( as Radar can be ”heard” from twice the distance the pinging aircraft can use its radar from). And it’s about detecting stealthy and concealed targets. (As nobody has invented an IR stealth plane )

    In simple terms the way it does this is by having a very sensitive IR detector that scans the environment, and lays down what it sees as tracks for the pilot to peruse much like a radar contact. Then as CNO says launch weapons on this track.

    IT IS NOT IR night vision, although on Typhoon it can be used for this as an interesting by-product.

    [Eventually getting to my point]

    IRST generally need to be somewhere it can see lots, and is generally on a ‘turret’ to scan as wide an arc(s) as it possibly can. F35 has 360 by 360 IRST. I’m afraid just mechanically I’m not overly impressed by the F18 solution.

    You probably could have bought the Typhoon version, the leader in its class, or even taken the F35 kit, but that would be silly. Right?


    1. Good point about location of the sensor, I may be wrong, but with the sensor on a center line fuel tank, isn't it's field of vision masked by the aircraft's fuselage? It would appear that the sensor could detect targets in an arc (depending on range) forward and below the aircraft but not above. The pilot would have to tip the nose up to bring the sensor to bear on higher altitude contacts. Is that correct?

    2. I guess I'm wondering why we have issues with this. We came up with IRST for the F-14 (AN/AAS-42 IRST). I'm sure it wasn't great compared to what's on the market today, but you'd think we would have updated it, or gained some decent experience.

    3. Lawrence, correct. No one, including the Navy is claiming that this is an optimum solution or placement for the IRST. It's just a "quick" and cheap solution that offers a fair amount of capability.

    4. "... you'd think we would have updated it ..."

      You'd think we would have maintained our MCM capability. You'd think we would have maintained our amphibious assault capability. You'd think we would have maintained our naval gun support capability. You'd think the Navy would have maintained a naval design capability. You'd think ...

    5. IRST was in use well before the F-14.

      "The first use of an IRST system appears to be the F-101 Voodoo, F-102 Delta Dagger and F-106 Delta Dart interceptors. The F-106 had an early IRST mounting replaced in 1963 with a production retractable mount. The IRST was also incorporated into the Vought F-8 Crusader (F-8E variant) which allowed passive tracking of heat emissions and was similar to the later Texas Instruments AAA-4 installed on early F-4 Phantoms.Wiki

      As CNO says, it was something they used to be quite good at.

    6. *grin*. Touche, CNO.

      Looking at the Navy nowadays is like listening to my Uncle vent about his job at Ford back in the late '70s.

  6. Contrarily, perhaps this is the place for concurrency?
    If the Navy isnt sure what it can get from a fuel pod mounted IRST system, isnt sure what it wants, and whatever else, perhaps buying a dozen test sets is a viable way forward?

    Doing it with several hundred fighters or a couple of patrol ships or a carrier is the height of idiocy, but these are pretty much throw away

    Dependant on cost and such.

    1. There is never justification (short of war) for concurrency. Immature systems should stay in R&D until ready. A dozen sets, as you suggest, will just have to be thrown away or remanufactured as the problems and solutions occur. Note that it's also in doubt that the IRST will ever function as intended. Also, we've grown so used to wasting billions of dollars on flawed programs that we've come to think that throwing away hundreds of thousands of dollars is perfectly acceptable. It's NOT!!! That's my taxpayer dollars being cavalierly and irresponsibly thrown away.

      By all means, build a test unit (or several, if that makes sense) but don't put units out into the fleet.

      Further, units put into the fleet are represented by the Navy as being combat effective when they aren't. That's going to get some poor trusting pilot killed when he finds out the hard way that the unit didn't perform as claimed.

  7. Actually to be fair. Ive just been checking out the internals of an F18.

    Its hell.

    IRST is not a small system. The ball turret is small. But usually the processor and cooling is quite large.

    Hornet simply doesnt have the space anywhere in the nose where you might get good arcs. Not even anywhere close to the space.

    And due to its shape no other position or even multiple places. ( Like in the conformals. ) covers any decent angles.

    Where they have chosen is definatly the best place. Though not that great. Its just a directly forward upper slight missing.

    Its proberbly better than some for maritime attack missions.

    The truth is sometimes there are limits to an airframes ability to cope with future changes in technology.

    Stealth and particually anti-stealth is what F35 is all about. Certainly in this one respect. You will have to wait for that.

    Perhaps when the distributed apature system is working. That type of system can be retrofitted ?

    1. Put it on top, lose the gun. Buys you a bunch of internal space. I know, the horror. Load an extra 9X.

  8. You will notice that the rest of the Western aircraft have IRST apertures under their cockpits.

    The Eurofighter has PIRATE, a QWIP IRST system that is beyond what the US has. Rafale also has a QWIP system and I think that the Gripen NG will as well. The Russians are developing their own QWIP system, the OLS-50, which will appear on the PAK FA.

    These are better for air to air than the DAS system on the JSF and the F-22 does not have an IRST at all. This is a major design failure. Actually there was originally an IRST that got axed for cost reasons.

    I think that the most prudent option for the US is to license build a European system.

  9. So what happens when the plane carrying the drop tank mounted IRST finds itself engaged in air to air combat? Keep the tank and suffer a considerable loss of maneuverability, possibly enough to give the enemy pilot the advantage? Or drop the tank and lose the IRST?

    I'm really surprised no one thought that one through. To me, that just shows how complacent we've become when it comes to air combat. With the new Russian and Chinese fighters, not to mention advanced air defense systems like the S-400, entering service, that attitude of complacency is going to become a huge liability.

    1. Now that's a great question and I'm embarrassed not to have thought of it.

    2. Let's just say that there is a reason why most fighters have their IRST systems in front below the cockpit.

    3. "So what happens when the plane carrying the drop tank mounted IRST finds itself engaged in air to air combat? Keep the tank and suffer a considerable loss of maneuverability, possibly enough to give the enemy pilot the advantage? Or drop the tank and lose the IRST? "

      I always thought the goal of IRST was to get a BVR shot 'silently', so if you do get mixed up WVR you'd drop it?

      I don't know. Just trying to think it out.

      Alt; I think you have a point about us buying a European system.

      As you may have noticed before I'm also fond of the meteor and its fully powered flight profile. There's a few things I wish we'd be willing to license build.

      I get confused as to how that works. I'm told we'd never license build a frigate, say a type 26. Yet, the LCS is an Austal design built here by a foreign yard, and the L7 and later Rhienmetal (sp?) cannons graced many armored vehicles we've had over the years.

      Heck, dare I say it, if we could make the logistics work out a wing or two of Rafales on our CVN's would look good to me.

    4. IRST can be used for that.

      Remember that radar is an active system and that like sonar, the distance at which you can be detected with active radar exceeds the distance at which you can detect.

      IRST combined with a long-range IR guided missile could allow for fully passive IR.

  10. Whats wrong with just mounting a LITENING pod ?

    1. Nothing I can think of. The mount would likely be the centerline fuselage or side fuselage stations, none of which would offer a good A2A view. It would also result in one less weapon station being available. That may be the advantage of mounting the IRST in the fuel tank - it saves a weapon station. Don't know.

    2. A litening pod is a FLIR and targeting pod. This is not the same thing.

      IRST is ( lets call it an ) infra-red passive radar. It automatically scans the sky and the ground, all around searching and finding targets, identifying and then tracking them, just like a modern radar. It does this automatically and constantly. With a wide field of view. Shorter range than a radar but often with wider angles of regard.

      Strictly speaking its not like litening, a targeting device for Semi Active Laser weapons. Concentration on one spot intensely.

      IRST is about constant wide area search. And continuously tracking multiple targets. Enough to derive A2A firing solutions.

      Here is one of those 'CNO hated' ;) promotional videos for Typhoons IRST;

      Try to ignore the bits where typhoon can use it for night vision and looking at targets. Those bits are extra to the pure definition of IRST and really just a very nice by-product.

  11. The new Navy LM IRST21 pod for the F-18 is driven by the new third generation silicon allowing short wave band, 1.5 microns, infra red which can track targets at a range of 60km.

    Quote taken from Bill Sweetman's article in Aviation Week July 2015 - Advanced Electro-Optical System A Priority For F-35 Block 4
    "The main innovations in Thales Talios and Raefael Litening 5 are the introduction of a third operating band—the short wave IR (SWIR) band, around 1.5 microns—and a switch from monochrome to color HDTV. SWIR operates well in night time conditions, but its most important attribute is that it is absorbed less by atmospheric moisture than visible light (0.5-0.7 microns) and provides longer oblique range than either MWIR or HDTV. According to Rafael, Litening 5 will be able to detect and track vehicle targets at ranges up to 60 km, using an ultra-telephoto SWIR sensor with a 0.3-deg. field of view."

    As the current technology used in the F-35 is obsolescent due to the long years in R&D Lockheed and likely Rafael will compete compete to replace it with the new silicon.

    1. So... why the issue that DOT&E reported then?

  12. A couple of links to the Selex PIRATE and LM IRST-21, specs and such like

    Interestingly, Northrop Grumman signed a deal with Selex last year to market PIRATE in the US


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