Tomcat Eyes

Observers are looking with excitement and anticipation at the development and eventual inclusion of an Infrared Search and Track (IRST) sensor into the F/A-18E/F Super Hornet.  This will be a significant advance for the Hornet and broaden the aircraft’s capabilities.

The Boeing/Lockheed Block II IRST, under development in an $89M contract, will be housed in the nose section of an external centerline fuel tank.  Development is scheduled to be completed in 2020. (1)

"IRST is yet another addition to the Super Hornet Block II arsenal, and it will truly change the nature of the air-to-air fight," said Capt. Donald "BD" Gaddis, U.S. Navy F/A-18E/F and EA-18G program manager, PMA-265.” (2)

This revolutionary, first of a kind capability will …huh? … what?  …  Hold on a minute.  Someone is interrupting me.  What?  It what?  Back then? 

Uh, I’ve just been informed that this state of the art IR sensor may not be quite as revolutionary as I thought, having been lead to believe, by the Navy, that nothing like this has been achieved before.  Apparently, I’m told, the F-14 Tomcat had this sensor capability, and more, decades ago.  Okay, let’s take a look back and see what the ancient, outdated, hopelessly outclassed Tomcat had in the way of sensors.

The Tomcat’s non-radar sensors were mounted in distinctive chinpods under the nose. 

ALQ-100 E/F/G/H-Band Track-Breaker – The early F-14A had the ALQ-100 mounted under the nose.  While not a sensor, the electronic countermeasure device was a prominent chin-mount and I mention it for clarity.

ALR-23 IR Seeker - The early F-14A had an IR seeker in a chinpod mount.  The seeker could be slaved to the radar or used independently and was gimbal mounted and could be steered.  I’ve been unable to find much additional information about the sensor’s capabilities or how it was used tactically.

AXX-1 Television Camera System (TCS) – The Northrop TCS was an optical sensor consisting of a telescopic television imager and cockpit display and provided telescopic images of targets far beyond unaided visual range.  Identification ranges are stated to be 10 miles for small fighters and out to 85 miles for large bombers and cargo planes. (4)   The TCS had a 30 degree conical field of view and could be slewed at a rate of 30 degrees/second and was gyroscopically stabilized in pitch/yaw at up to 150 degrees/second.  Thus, the TCS was unaffected by the aircraft’s maneuvering within the field of view.  The TCS also had a tracking-lock capability to enable the target to be continuously followed.  Automatic scan-lock was another built in feature which allowed automatic target detection during continuous scanning.  The Tomcat’s AWG-9/71 radar could be slaved to the TCS or vice versa.  The TCS was first fitted to the late model F-14A.  Additional information is available in a summary report (5).

TCS System

AAS-42 IRST – A more advanced IR sensor, the AAS-42 appeared on the F-14D in 1990.  The sensor provided search and track capability as well as IR imagery.  From Deagel website,

“Operating in six discrete modes, the AN/AAS-42 provides the aircraft mission computer track file data on all targets while simultaneously providing infrared imagery to the cockpit display.” (3)

F-14D’s often utilized a potent side by side, dual combination of IRST and TCS which may have had detection ranges as much as 110+ miles, thereby greatly enhancing air-to-air targeting and useful missile launch ranges. (6)

 

AAS-42 IRST and TCS

While the Navy is loudly and proudly proclaiming the coming use of IRST on the F-18 Hornet, we see that the reality is that effective IR and optical sensors existed on the F-14 Tomcat long ago.  Why the Navy abandoned these sensors when the Hornet was developed is baffling.  Today, as we look at the F-35 and all its problems and costs, we view the Hornet fondly and think of it as a good, if not great, aircraft.  The reality is that the Hornet was a very compromised and, as regards combat effectiveness and range, a very ineffective aircraft.  The addition of IRST is a welcome development but, good grief, we had that and better in the F-14 many decades ago.  Even with the IRST, the Hornet will still lack the F-14’s highly effective TCS.

The eyes of the Tomcat were highly effective combat enhancers that the Navy is only now, and only partially, matching with the Hornet’s cobbled together IRST/fuel tank conglomeration. 

As the Soviet pilots of the era knew well, the eyes of the Tomcat were always on them.  We need to remember the capabilities we had decades ago and begin designing actual combat aircraft again that can at least match what we once had.  What passes for a combat aircraft today is a sad reflection of what once was.

Note:  I’m well aware that other aircraft in the ‘60’s and ‘70’s also had similar sensors – no need to list them in a comment.  Again, it just shows how far we’ve drifted away from actual combat aircraft design.

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(1)Defense Systems website, “Navy integrates new F-18 infrared sensor”, Katherine Owens, 20-Jun-2017,

https://defensesystems.com/articles/2017/06/20/navy-irst.aspx

(2)Boeing website,

http://boeing.mediaroom.com/2007-07-02-Boeing-Selects-Supplier-for-Super-Hornet-Block-II-Infrared-Search-and-Track-Capability

(3)http://www.deagel.com/Sensor-Systems/F-14D-IRST_a002575001.aspx

(4)Air Power Australia website, “Electro Optical Systems”, Carlo Kopp, Mar 1984,

http://www.ausairpower.net/TE-EO-Systems.html

(5)Forecast International,

https://www.forecastinternational.com/archive/disp_old_pdf.cfm?ARC_ID=462

(6)http://theboresight.blogspot.com/2009/07/airborne-infrared-and-supersonic.html

F-18 IRST Status

Infrared Search and Track (IRST) is one of the hot topics in aviation.  Supporters claim it greatly enhances the stealth of a fighter since it allows search and tracking via passive modes as opposed to active radar use.  It also allows detection of enemy aircraft that are radar stealth’ed and, thus, negates an enemy’s stealth advantage. 

The Navy has an IRST development program underway to equip the F-18E/F Hornet fleet with IRST as an effort to keep the non-stealthy F-18s relevant and combat effective in an age of stealth.

Following is a discussion of the F-18 IRST program as reported in the DOT&E 2016 Annual Report.

The F-18 IRST sensor will be mounted on the nose of a centerline fuel tank under the fuselage of the Hornet.  The current IRST21 unit is being developed by Boeing and Lockheed Martin and is descended from the F-14 IRST.  The Navy plans to procure 170 IRST units.  The current Block I will be fielded as test units and eventually upgraded to the future production Block II. 

Block I was originally scheduled to enter full rate production but the Navy decided to forego production in favor of the Block II version after a program review of the Block I test results.  This suggests that the Block I was deemed insufficiently successful to warrant production and, in typical Navy thinking, the unsuccessful Block I is bypassed in the hope that the non-existent Block II will somehow attain the success that the Block I did not.  There is nothing inherent wrong with this approach as long as we don’t commit to the Block II production before its capabilities are proven.  Too often, the Navy, faced with a failure, opts to incorporate undemonstrated “improvements” that exist only on paper and then immediately commit to production without waiting for demonstrated success.

The key development in the program thus far, Operational Assessment 2 (OA 2), took place in November 2015 when the IRST was tested under realistic combat conditions.  Unfortunately, the results were less than successful.

“The system … could not reliably detect and track targets well enough to support weapons employment in an environment that reflects realistic fighter employment and tactics.”

Immediately subsequent to this assessment, a program review was held.

“Assistant Secretary of the Navy (ASN) for Research, Development, and Acquisition (RDA) held an IRST program review on January 27, 2016, and in a September 8, 2016, Acquisition Decision Memorandum (ADM), ASN (RDA) approved a restructured program that foregoes full-rate production of Block I sensors and proceeds directly to development of the Block II system. The Block I system will not be fielded and IOT&E did not begin in 2016 as planned.

The Navy plans to hold the Block II Preliminary Design Review in May 2017 and begin IOT&E in 2020.”

As discussed, it is clear that the results of the assessment test and subsequent review indicated that the Block I IRST was not successful.  Unfortunately, instead of pausing until development could overcome whatever problems were seen, the Navy has opted to leap into Block II and has already scheduled production.

It is noteworthy that the Hornet-IRST-fuel tank combination has been approved for the full flight envelope as long as the fuel tank is empty.  Some restrictions have been placed on both launch and flight conditions with varying loads of fuel in the tank.

With the tank empty, the IRST becomes, in essence, a giant sensor the size, weight, and drag of a fuel tank!  If the tank can’t be used for fuel or only in partial load conditions, one has to wonder at the wisdom of placing the unit in a centerline fuel tank to begin with as opposed to a wing or nose mounted location.  On the other hand, DOT&E points out that the flight restrictions may not be significant.

“Given the rate at which fuel is consumed from the centerline fuel tank, these restrictions are effective for only a short period at the beginning of the mission profile and should not have an operational impact.”

The under-the-fuselage location also restricts the field of view of the sensor.  Obviously, it can’t see anything above the aircraft.  Thus, it’s only 50% effective to begin with, even if it worked perfectly for the lower field of view.

Reliability is also an issue.

“Demonstrated reliability is below what was expected at this point in the flight test program. As of the time of DOT&E’s OA 2 report, the cumulative Mean Time Between Operational Mission Failure (MTBOMF) was 4.1 hours; the reliability after incorporating known fixes was 19.5 hours. The MTBOMF requirement is 40 hours and the system was expected to have a projected reliability of 38 hours when entering IOT&E.”

DOT&E’s report concludes with this criticism of the Navy and admonishment to learn a lesson.

“Many of the Block I system’s difficulties with detection and tracking seen in OA 1 and OA 2 did not require flight testing to uncover them, but could have been discovered earlier via analysis and modeling and simulation. The Navy expects that the Block II configuration (which includes sensor and aircraft hardware and software), will provide improved capability. This assumption should be tested as early as possible, prior to major decisions …,”

Unfortunately, the Navy seems determined to ignore this lesson, having already scheduled Block II production.

Please don’t read this post as being against fielding an IRST.  ComNavOps believes that a fully functional IRST would be a relatively cheap and highly effective combat aid and is well worth pursuing.  Successful and functional IRST units apparently exist around the world and there is no reason to believe that the Navy and its manufacturing partners cannot produce a functional unit.  However, we need to go about this intelligently.

I would recommend that the Navy reconsider the under-the-fuselage location.  Perhaps there is a good reason why the unit can’t be wing or nose mounted but it would be worth some extraordinary effort to do so.  The actual sensor is small and should be able to be mounted in a more advantageous position.

I also recommend that the Navy stop making production plans for an unproven and, thus far, unsuccessful unit.  By all means, continue development but set production plans aside and remove that artificial deadline from consideration.  Take the time needed to field a fully functioning unit.

IRST

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.