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Senkaku Sentinels - Air War over the East China Sea

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apophenia:
Senkaku Sentinels - Part 5: "Snakes follow the way of serpents" [1]

In Japanese Air Self-Defence Force (JASDF) planning, both the manned Mitsubishi F-2A fighter and the LM/Mitsubishi A-16AJ were to be armed with domestically-produced ASM-3 Kai anti-shipping missiles. The Mitsubishi ASM-3 Kai has a hybrid rocket motor/ramjet engine - the missile reaching high speed on its rocket before the burned-out rocket chamber was transformed into a combustion chamber for the sustaining, air-breathing ramjet. That hybrid engine allows the ASM-3 Kai to reach speeds over Mach 3. Details of the ASM-3 Kai warhead remain classified but, at the speeds reached, the impact of the missile body alone would impart considerable kinetic energy.

The operational concept for the ASM-3 Kai was straightforward but had two variations. In the first, a low-flying launch aircraft would loose its missile just outside the opposing force's radar detection range. The ASM-3 Kai would then hug the waves until reaching its target ship. In the second, a launch aircraft at either low- or medium-altitude would launch its ASM-3 Kai which would immediate pop up to higher altitude using its rocket motor. Upon reaching the opposing SAM defence range perimeter, the missile would then dive steeply. Pulling up at the last moment, the ASM-3 Kai would skim the surface to its intended target.

Unfortunately, production of the original ASM-3 had to be cancelled in order to rework the design. But the results were worthwhile. The ASM-3 Kai's range was almost doubled, allowing manned Mitsubishi F-2A fighters to launch these missiles from safer distances. However, the delayed deployment meant that there were insufficient ASM-3 Kai missiles to equip the A-16AJ UCAVs during the Senkaku Incident. Instead, the A-16AJ Baipa had to be armed with the older, slower, much-shorter-range ASM-2 (Type 93) missile which the ASM-3 Kai had been meant to replace. [2]

"A serpent is a serpent, and none the less a viper"

The A-16AJ Baipa was intended to be a high-risk partner to the manned Mitsubishi F-2A fighter. During the Senkaku Incident, those risks were pushed even higher. The unmanned aircraft needed to go in closer to launch the slower, shorter-range ASM-2s. For obvious reasons, the manned F-2As were assigned the faster, longer-range ASM-3 Kai missiles. As a result, losses of A-16AJs were disproportionately large - but far better to lose matériel than pilots!

There was an unexpected benefit to this mix of anti-ship missile types. Operational experience revealed that joint missions greatly increased the success rate of the missile strikes. The most successful missile impacts were recorded with ASM-3 Kai missiles. In some cases, however, ASM-2s struck targets when the supersonic ASM-3 Kai missiles (loosed at the same time) had succumbed to Chinese anti-air defences. JASDF planners concluded that success was increased when both ASM-3 Kai and ASM-2 missiles were launched during the same attack. Apparently, forcing the East Sea Fleet to counter two disparate threats simultaneously, meant that one or the other of the two missile types could get through. In other words, two different incoming missile types would often overwhelm PLA-Navy close-in weapon system defences.

"There were many beautiful vipers in those days ..."

The LM/Mitsubishi A-16AJ conversions did everything that was asked of them - and more - during the Senkakus Incident. Lessons were also learned in the process. In some mission profiles, emphasis on automatic versus remotely-piloted control was the reverse of that expected. This required rapidly-introduced changes to operating program files. In many cases, changing options was built into the core program. In others, thousands of lines of new code were needed. Fortunately, no major bugs were introduced. Programming errors may account for some A-16AJ combat losses. But the Baipa conversions were based on fairly elderly airframes so simple mechanical failures are a more probable explanation of unaccounted for A-16AJ losses.

The overall A-16AJ Baipa loss rate approached 50% of the available fleet (if three training and orientation losses are included in the count). A number of minor tweaks were made to control systems - both onboard and in the Mitsubishi Electric CKK-16-01 (Chijo kanseikyoku 16-01) Ground Control Stations. Other improvements had to wait until the Senkakus conflict was over - for example, improved data link communications infrastructure plus updated INS and SATCOM equipment. There was also a call for an optional separation between visual inputs for piloting and targeting but this was not realized (since it demanded fairly major changes to the Subaru Remote-Pilot Vision Centre and probable replacement of the Fujitsu electro-optical turret).

"He that has been bitten by a snake is afraid of a rope" - Chinese proverb

The effectiveness of the A-16AJ Baipa in combat was now proven. More difficult for Japanese strategists to assess was the degree to which surprise played a part in that success. PLA-Navy air defence crews and PLAAF fighter pilots all tackled the Baipa assuming that it was a manned fighter-bomber. That worked in the JASDF's favour. But, now the Chinese were aware of the true nature of the A-16AJ. Would the Baipa UCAV [3] be viable in the next conflict when its unmanned nature was known from the outset? The A-16AJ loss rate had increased noticably towards the end of the Senkakus Incident. Had the Chinese got the measure of the Baipa? Or were the A-16AJs simply being employed more aggressively?

In the aftermath of the Senkakus Incident, the future of the A-16AJ - or potential UCAV follow-ons - was anything but secure. But no-one could question the Baipa's combat record over the Senkaku Islands. The reputation of the A-16AJ Baipa was secure.

Image: '608' is an LM/Mitsubishi A-16AJ Baipa (Viper) of 207 Hiko-tai, Kokujieitai. [4] The 2-tone blue scheme is identical to that on manned Mitsubishi F-2A fighters. On the vertical tail is the 207 HT unit marking - the Shachihoko (Fish-Tiger), a mythical sea monster. [5] Note belly-mounted LM Sniper Extended Range (XR) targetting pod.

Inset: ASM-2 (Type 93) missile on outboard under-wing pylon (left). Larger view of 207 HT's Shachihoko emblem (right).

(To be continued ...)

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[1] The expression ja no michi wa hebi is actually intended to mean something akin to 'it takes one to know a one'.

[2] Likewise, Kawasaki P-1 patrol aircraft had to make do with ASM-1C and AGM-84 Harpoon anti-ship missiles during the conflict. P-1 missile strikes were responsible for sinking three minor Haijing vessels (and a North Korean 'spy ship' thought to be penetrating Japanese territorial waters on behalf of Beijing). Of necessity, however, most P-1 operations were focused on PLA-N submarine detection. Fortunately for Japan, most East Sea Fleet submarines had been redirected into the Taiwan Strait or South China Sea.

[3] The JASDF preferred the term UTA (Unmanned Tactical Aircraft) over Unmanned Combat Aerial Vehicle. In English, the Baipa would routinely be described as a UCAV. But in Japanese usage, the A-16AJ was always a Mujin Senjutsu Kokuki (MSK)

[4] The 207 HT is part of the JASDF's 9th Air Wing. The original 207th Tactical Fighter Squadron was disbanded - appropriate to the A-16AJ home base - at Naha in March 1986. The revived 207 HT is never referred to by role - only as a 'Squadron'.

[5] Considered appropriate to the A-16AJ's maritime strike role, this emblem was actually inherited from the 102nd Tactical Fighter Squadron. The disbanded 207 TFS featured a plum blossom motive but this was associated with that squadron's original founding base of Hyakuri (Ibaraki Prefecture).

All operational A-16AJs were assigned to the 207 Hiko-tai, home-based at Naha Air Base on Okinawa. However, a major 207 HT detachment was deployed to a Forward Operating Location at Ishigaki Air Base further south in the Ryukus. A JASDF Type-3 airfield (shared with F-15EXJ interceptors in troubled times) is 170 km flying distance from the Senkakus. A second A-16AJ detachment rotated through Shimoji Air Base (a part of Miyako Shimojishima Airport, SHI) on Shimoji-shima, 115 km ENE. Both airfields have long runways but, for safety, Shimoji must be closed to commercial traffic when A-16AJs were being operated. In both cases, direct mission control was secluded 'off base'.

apophenia:
Senkaku Sentinels - Part 6: The Mitsubishi F-2A Update Program

The Mitsubishi F-2A fighter had evolved from the F-16 - being, in effect, the Japanese take on General Dynamics' proposed US F-16 Agile Falcon with its 25% larger wing. [1] Whereas the F-16 has four underwing pylons, the 'big wing' F-2A has six. By comparison with the F-16 - or, indeed, the A-16AJ - an F-2A also had larger horizontal tailplanes and a larger engine air intake. As one of the 'stars' of the Senkaku Incident, there were no complaints about F-2A performance. However, even before the outbreak of fighting, the Japanese Air Self-Defence Force had been finalizing its plans for an F-2A Mid-Life-Upgrade (MLU). Service and industry reviews of the A-16AJ program caused some rethinking of this F-2A MLU. With a modicum of extra effort, this MLU would be able to incorporate the best features of the A-16AJ onto an updated F-2A fleet.

From the outset, it had been intended that the Mitsubishi F-2A fighter be the primary carrier of the supersonic ASM-3 anti-ship missile. As previously recounted, the Mitsubishi fighter was an outstanding success in that role. That success would also colour the planners' view of other JASDF fighter aircraft and their potential as anti-shipping missile launch platforms.

Improving the Breed - "Every great story seems to begin with a snake"

The revised F-2A MLU adopted the A-16AJ's Conformal Fuel Tanks (CFTs) along with the Diverterless Supersonic Inlet (DSI). With its six underwing pylons, the F-2A did not really require the extra carrying space allowed by the CFTs. Rather the conformal tanks were adopted primarily for their weight savings while loaded and their drag reduction. The DSI was adopted primarily for its marginally-reduced radar signature. The DSI actually reduced top speed slightly but, with a new emphasis on the attack role for the F-2A, this was deemed acceptable. As modified and refurbished, the upgraded F-2A was redesignated by the JASDF as the Mitsubishi F-2M Kai.

The A-16AJ's wingtip ECM pods were also briefly considered for the mid-lifed F-2 but objections to this plan eventually won out in favour of load-out flexibility. A typical load-out for the upgraded F-2M Kai was (from inboard): 2 x ASM-3 Kai anti-ship missiles; 2 x AAM-4 (Type 99) medium-range missiles (or AGM-88E HARM anti-radiation missiles); 2 x ASM-3 Kai anti-ship missiles, and 2 x wingtip AAM-5 (Type 04) short-range missiles. For ultra-long-range missions, 2 x 2,270 litre drop tanks could be substituted for the pair of inboard ASM-3 Kai missiles. More commonly, longer-range was made possible by inflight refuelling - which was simplified by the arrival of the first Mitsubishi KC-3A Tanchō medium-range tankers. [2]

"It was like looking for a needle in a haystack full of vipers" - Samuel Beckett

At the start of the Senkaku Incident, the Japanese Air Self-Defence Forces had three on-going air-launched anti-shipping missile programmes. Two were subsonic US missiles - the Joint Strike Missile (JSM, US AGM-184A) [3] and Long Range Anti-Ship Missile (LRASM, US AGM-158C). [4] Neither JSM or LRASM played much of a role in the Senkaku Incident - primarily because their carrier aircraft were assigned other roles as priorities. In both cases, the F-35 and F-15 fighters (JASDF carriers of the JSM and LRASM, respectively) were employed almost exclusively in interceptor roles during the conflict.

By contrast with the US missiles, [3] the hybrid-powerplant ASM-3 Kai could exceed Mach 3. To employ an old cliché, the only problem with the ASM-3 Kai was that there just weren't enough of them. In a few cases, the F-2As carried four ASM-3 Kais but the commonest load during the conflict was twin drop tanks (2,270 or 1,400 litre) and a pair of ASM-3 Kai missiles (along with the usual self-defence missiles). Towards the end of the Senkaku Incident, consideration was given to F-2As carrying JSMs as ASM-3 Kai stocks ran low. Fortunately, that substitution never became necessary. However, stocks of the ASM-2s fired by the A-16AJs were now entirely depleted. In any future conflict, a new 'mix' of anti-shipping missile would be needed.

Image: Post-MLU Mitsubishi F-2M Kai strike fighter carrying ASM-3 Kai anti-shipping missiles and 600 US gallon underwing tanks. For self-defence, '563' carries AAM-5 (Type 04) short-range IR missiles on its wingtip rails.

Inset: Mitsubishi F-2M Kai carrying four AGM-184A Joint Strike Missiles on its underwing racks. For self-defence, '539' carries the older AAM-3 (Type 90) IR missiles on its wingtip rails. Here, the centre underwing pylons are empty but these pylons could be loaded twin self-defence AAM-4 (Type 99) missiles or AGM-88E HARMs.

(To be continued ...)

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[1] For the Japanese FS-X contest (which led to the F-2A), Mitsubishi was partnered with General Dynamics. Two of GD's concept submissions - SX-2 and SX-3 - featured the larger Agile Falcon wing but few construction details were provided. As a result, an entirely new wing of mainly composite construction was designed for the F-2A by Mitsubishi engineers.

[2] With AAR demand increasing, the JASDF's six KC-46A Pegasus tankers were overstretched. The shoot-down of a new PLAAF Xian Y-20 tanker during the Senkaku Incident also showed the vulnerability of larger tanker aircraft in the regional airspace of the East China Sea (Higashi shina kai). As a result, it was decided to complete three Mitsubishi SpaceJet prototype airframes as KC-3A inflight refuelling tankers.

[3] The Joint Strike Missiles (JSM) were integrated into the F-35 (Block 4 software fit) in 2022. A Lightning II can carry one JSM within each of the fighter's internal bays - which restricts the missile's size. Despite this, the JSM has a respectable maximum range of 565 km (although this would be much reduced if operated at low level). The JSM's carries a relatively modest 125 kg warhead.

[4] The externally-carried LRASM has a more substantial 450 kg warhead. Maximum range is 480 km - although ~370 km is more realistic on low-level missions. Had they been available in larger numbers and the F-15s not otherwise engaged, the LRASM would have been valuable assets during the Senkaku Incident.

elmayerle:
Going to be interesting to see if this prompts Japan to order some F-15EJ aircraft to carry both ASM-3-Kai and LRASM.

apophenia:
Thanks Evan. All will be revealed in the post after this one ;)
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Senkaku Sentinels - Part 7: The Future and Further UCAVs?

In the aftermath of the Senkaku Incident, JASDF planning attention turned to replenishment and upgrades. The first conclusion was that, if fighter-sized UCAVs were to be restocked, these unmanned aircraft would have to be new, stealthier designs. A request for Expressions of Interest (EOI) issued to industry received three proposals in reply. The first was from Lockheed-Martin for an 'optionally-piloted strike fighter' derivative of the F-35A. [1] The other two EOI submissions came from Japan's traditional keiretsu conglomerates - Mitsubishi, Kawasaki, and Subaru.

The proposal from Mitsubishi Heavy Industries was fairly straightforward. While waiting for the sixth-generation Mitsubishi F-X (aka F-3) stealth fighter to deploy in 2030, MHI would develop an interim UCAV. The airframe design would be relatively conservative, allowing a proof-of-concept demonstrator to be created from Mitsubishi's X-2 stealth prototype. As proposed, the X-2 would remain piloted - with a YDK Technologies UCAV control system mounted in the former rear cockpit. The major change would be the replacement of the existing tailplane group with new V-configured 'tailerons'. This rearrangement was intended to further reduce radar signature and the resulting reduction in manoeuvrability was considered acceptable for a strike UCAV.

The fully-developed UCAV concept was dubbed the Mitsubishi XA-2 Mizuchi (Watersnake). [2] MHI intended that Mitsubishi Electric would create replacements for the A-16AJ's YDK Technologies UCAV control system and Subaru Remote-Pilot Vision Centre. Primary armament would be four pylon-mounted ASM-3ER missiles - an extended-range derivative of the advanced ASM-3C anti-ship missiles then in development. For self-defence, the XA-2 Mizuchi would carry two AAM-5 IR missiles (one each in enclosed, fuselage-side bays). All fuel was to be carried internally.

Image, bottom Mitsubishi X-2FTB (Flying Test Bed) proof-of-concept modification proposal for the Mitsubishi XA-2 Mizuchi (Watersnake) UCAV. Note: this image illustrates the earliest proposed stage of X-2FTB testing (hence the exhaust nozzle manoeuvring 'paddles' not being fitted here).

The third proposal was a joint submission by Subaru Aerospace and Kawasaki Heavy Industries. This approach was not the norm in Japanese practice, but it allowed each firm to focus on one major aspect of their joint submission. Subaru Aerospace was to focus on developing the UCAV airframe (largely because of Subaru predecessor Fuji's experience with composite construction). The airframe layout was clearly influenced by the Northrop/MDC YF-23 prototype fighter design - although the Subaru FXS UCAV would be considerably smaller than that US fighter). The offensive armament was to be a single, hypersonic anti-shipping missile which, unusually, would be mounted on the UCAV's back. As such, the two airframes - UCAV and missile - had to be highly integrated.

KHI designers took great pains to ensure that their missile design would not unduly compromise the low-observable features of the Subaru UCAV. The anti-shipping missile's propulsion was very similar to that of the ASM-3 Kai - in other words, it was a rocket motor booster which turned itself into a sustaining ramjet engine. But there the similarity with the in-service missile ended. The Kawasaki XASM-5 Kobanzame (Remora) missile body was effectively a scaled-down and tailless version of the UCAV itself. However, the approach to flight stability and attitude control was quite different. On launch, attitude control was handled by drooping wingtips (which could act asymmetrically for yaw/roll control). As the air-breathing ramjet took over, the wingtips 'straightened' to reduce radar signature. At this point, all flight control was handled by asymmetrical operation of vectoring jet nozzles.

Image, top The Subaru Aerospace AXS UCAV concept along with the operating phases of the Kawasaki Heavy Industries XASM-5 Kobanzame (Remora) anti-shipping missile. The AXS shows the Kobanzame missile in its stowed position atop the AXS fuselage. Top right shows the XASM-5 launching and igniting its hybrid rocket booster motor. Top left shows the Kobanzame with air-breathing ramjet propulsion (note the missile's wingtip position and vectoring nozzles).

(To be continued ...)
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[1] This optionally-manned 'F-35 OPSF' was an updated version of LM's original 2006 optionally-manned F-35 concept. Experience with the jointly-developed A-16AJ Baipā helped firm up the 'F-35 OPSF' design.

[2] The Mizuchi is actually a legendary Japanese serpent-like creature or dragon. The mythical Mizuchi was to be found in aquatic habitats, which made it a suitable namesake for a maritime strike UCAV.

elmayerle:
Be interesting if Japan used this incident to persuade the US government to let them purchase all IP rights to the AGM-137A/BGM-137B TSSAM and recruite NGC personnel to continue development.  Combining aspects of the two versions would give you, among other things, a ship- or ground-launched all-aspects stealthy ASM in addition to the main air-launched variants.  Yeah, it's subsonic but they won't see it coming until way too late.

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