Operation Shō-gō (Battle of Leyte Gulf)
Sunset of the carrier fleet – Cape Engāno. 25–26 October 1944
At the massive sea/air battle of Leyte Gulf the once proud Japanese carrier fleet was reduced to the status of ‘live bait’ due to the appalling aircraft losses it had taken during the Philippine Sea encounter. Admiral Jisaburo Ozawa’s Northern Force sortied out with his one operational fleet carrier, Zuikaku, as his flagship, accompanied by the three light carriers Zuihō, Chiyoda and Chitose. Having been totally destroyed 601 Kōkūtai had to be re-built from scratch between July and October and 3 Kōkū-sentai no longer existed and they became 1 Division. 601 was re-established from scratch under 3 Fleet, mainly with pilots straight from training units and even so had a strength of only two Hikōtai, 161 under Lieutenant Hōhei Kobayashi, and 162 led by Lieutenant Sanyuki Hida, each with forty-eight A6M5s. With a few dive-and attack-bombers Ozawa had embarked aboard the four Japanese carriers a total of just 108 aircraft.
Two old battleships, Hyūga and Ise, were added to his force as 4 Kōkū sentai. They had both been partly converted as intended hybrids, keeping many of their main guns but able to carry a limited number of aircraft. However, after many attempts to organize an agreed ratio of suitable types, no aircraft actually proved available and they sailed into battle with none aboard. They were escorted by three light cruisers and nine destroyers. Ozawa was not found until late on the afternoon of 24 October.
Halsey duly swallowed the bait and set off after the Northern Force with overwhelming fire power, having five fleet carriers, five light carriers, six battleships, two heavy and six light cruisers and destroyers. In the American carriers no fewer than 600–1,000 were embarked.
Early on the 25th Halsey sent Vice-Admiral Willis A. Lee’s six modern battleships of Task Force 34 on ahead at high speed, with the aim of being positioned to finish off with their seventy-two 16-inch guns any of Ozawa’s ships that survived the coming days air strikes. Ozawa made his air attack at dawn that day, launching fifty-six aircraft, which comprised thirty A6M5s, nineteen A6M5bs, two Suisei dive-bombers and five B6Ns Tenzans.
Nearly all were overwhelmed by the CAP and ships gunfire with just a few surviving to land at airfields on Luzon, including six of the A6Ms, five attack and one dive-bomber. They had inflicted no damage on Halsey’s ships.
Mitscher’s counter-strike was rather more effective, his 180-strong force crushing the Japanese thirteen-plane CAP under Lieutenant Kobayashi with ease, although the A6Ms claimed twelve kills. Some 527 American sorties were conducted that day and the carriers Zuihō and Zuikaku, along with a light cruiser were all sunk.
While these air strikes were being exchanged the beleaguered Admiral Kinkaid’s 7th Fleet was continually calling for assistance having being in danger of being overwhelmed by the powerful surface forces of Admiral Nishimura in the Surigao Strait. Halsey recalled Lee’s battleships, which were just about to sink the crippled carriers, and after refuelling them, sent them south in two sections, but they were again, too late and Kurita escaped. This left Halsey’s carriers with no heavy ships to protect them and when the Japanese sent their two battleships south another crisis seemed imminent but no contact was made here either and the battle petered out on the 26th by which time Ozawa’s carrier force was all but destroyed by further air attacks but not before the carrier Chitose was sunk with all hands and the destroyer Hatsuzuki, which had earlier rescued Lieutenant Kobayashi and some of his other ditched fighter pilots, had also been sent to the bottom by shelling, both by Rear-Admiral Lawrence T. DuBose’s cruiser squadron led by the Santa Fe. None of the rescued pilots survived.
Zero versus Hellcat
In examining the factors involved in aerial combat, on paper at least, the Grumman F6F was superior to the A6M in acceleration, climb, dive, roll rate, top speed, hit damage survivability, and engine power. The Japanese fighter, with her low wing loading × lift coefficient, retained her edge on slow speed turning (via her smaller turning circle and higher turning rate), and visibility and could outperform the Hellcat in climb rate and manoeuvrability, while the improved 20mm cannon of the later Zero models packed a more powerful punch and had greater range than the F6F .50 Browning machine-guns. Given the reputation of the A6M the general tactic adopted by the American pilots was to gain superior altitude, dive down – fire and then zoom away and climb again. However, that required the twin advantages of surprise and height to be successful. If the surprise part of the factor was lost, then the height factor rapidly went also for the A6M could climb at a rate of 3,050ft/min (929.63m/min), outperforming both the US Army Curtis P-40 and the Navy’s F4F. In a close turning duel at low altitude it was still suicidal to tangle with the A6M, although, as the quality of the Japanese pilots began to be seriously diluted, the danger was less and the American fighters were able to sustain heavier hitting.
But that was on paper. Saburo Sakai used his six years of front-line combat savvy and skill to out-fight no fewer than fifteen F6F Hellcats in his A6M even though he was blinded in one eye and exhausted. The standard of the A6M pilots certainly and undisputedly fell sharply as the war continued, but the rookie American pilots coming out of much longer training schedules, during which they had been carefully trained to conduct aerial deflection shooting, were hardly supermen either and had the advantage of hugely numerical superiority as well. Despite that, on 24 June 1945, Sakai, having already shot down two F6Fs already, took on the whole fifteen and routed them totally, causing some to flee and totally out-flying the others before landing back on Iwo Jima without a mark on his aircraft. In the end, no matter how good the aircraft, it was often the man who counted.
By 1943 the war in the Pacific was fast slipping away from Japan. The massive ship-building programme of the United States Navy dwarfed the Imperial Japanese Navy and its own new construction. The new classes of Essex Class carriers and Independence Class light carriers were now finally joining the fleet and were being joined by hordes of brand-new battleships, cruisers and destroyers and this new build fleet easily replaced any losses that the Japanese could hope to inflict. Matching the new ships was a similar enormous output of military aircraft from newly constructed plants all over the USA entirely free of any threat of bombing or retaliation. A huge pilot training programme matched the tens of thousands of aircraft and, with regard to fighter types, the overwhelming numbers churned out were also new types, many of which obviously much outclassed the hitherto dominant A6M. The Grumman F6F Hellcat and the Chance-Vought F4U Corsair were both large and powerful new Navy and Marine Corps heavy fighters of high-speeds. The A6M weighed 5,500lb, the F4F 7,500lb, the F6F an astonishing 12,000lb.
In addition converted General Motors East Coast automobile plants, as Eastern Aircraft Division, were building updated and improved versions of the F4F Wildcat as the new General Motors FM-1 of which more than a thousand were produced in 1942–43. These were pretty much straight copies of the F4F-4s, with reduced gun armament of four .50 calibre machineguns. These were clearly inferior but were mainly employed on second-line duties with small escort-carriers (CVE or ‘jeep’ carriers) used by the US and Royal Navies in both the Atlantic and Pacific. More challenging to the A6M was the new Grumman XF4F-8, of which Eastern Aircraft built no fewer than 4,000 of under the designation FM-2. This aircraft featured the 1,350hp Wright R-1820-56 Cyclone single-row radial engine, and this power upgrade was coupled with a re-designed and much lightened build overall, 8,271lb, and a re-working of the vertical tail to increase stability. The result was a faster (332mph at 28,800ft) and more agile Wildcat taking on some of the attributes of its main opponent including improved range, speedier climb rate, longer range and being far more agile than the old F4F. The armament was unchanged but the extra range was superfluous however, as again they were operated from CVEs as close-in fighter support for the island-hopping campaign’s many landing operations but, as such, they often came up against the improved A6M.
A6M5 Model 52
By the summer of 1943 the Americans in the Pacific were introducing several new fighter types that would eventually simply overwhelm the Japanese, producing huge, rugged machines with 2,000hp+ engines and heavy gun armaments, such as the Grumman F4F Hellcat, Chance-Vought F4U Corsair and Lockheed P-38 Lightning, which were churned out by the tens of thousands from factories totally immune from attack. In a futile attempt to match these new American fighters and also to speed their own production, which was lagging far behind demand due to casualties, the A6M was subjected to a range of improvements and modifications and in the summer of 1943 appeared in a new guise on the combat zone. This was the A6M5 Model 52, which was destined to be the most prolific of all Zero marks. The wings were of the shorter 36ft 2in (11 metre) span, with the clipped wings abandoned and rounded tips re-adopted. The ailerons were lengthened out to the tips of the wings and the flaps were also elongated accordingly to obviate any space in between. In order to improve the known weakness of its poor dive qualities the wings were thickened up with heavier gauge material and this resulted in a 410mph (659.83km/h) diving speed, while overall maximum speed was increased to 351mph (564.88km/h) in level flight by introducing individual exhausts, which protruded aft from notched flaps in the engine cowling (five to port, six to starboard, each vent requiring its own individual fuselage heat shield patch), instead of a single centralized exhaust collector ring. The range of the Type 22 having proved key, the two 12-gallon (45.42 litres) wing tanks were retained in this model giving a range of 1,194 miles (1,921.6km). The power unit remained the 1,130hp Sakae-21 and armament reverted to two 20mm cannon and two 7.7mm machineguns. Production problems at home had seen the introduction of large, tail-finned 66-gallon (300-litre) wooden drop tanks replacing the original under-belly type and the introduction of 33-gallon (150-litre) under-wing drop tanks. The Type 3 Mark 1 radio was installed to replace the Type 98Ku Mark 1 set and the new installation could be detected by a much shorter antenna mast, but the reputation for unreliability apparently continued, the main problem being the unshielded ignition systems, exacerbated by the effect of humid tropical conditions as well as hindered by the difficulty of access for proper maintenance in the field on jungle airstrips. There was also a persistent shortage of copper for the wiring and it was not until 1945 that the Second Research Institute was established to improve electronics in the fleet’s aircraft. Some land-based units were reputed to have discarded their radios completely, although, of course, they were a vital necessity for carrier-based A6Ms who did not abandon them as some have claimed.
A prototype was converted from a Model 22 machine and made its debut in August 1943 achieving a maximum speed of 351.07mph (565km/h). This seemed to satisfy the Navy but this aircraft proved to be less agile than the Model 21, while the endurance was far inferior, three hours against eight. If it were expected that this would render the concept null-and-void this proved not to be the case and production was immediately ordered as the urgent need from the front predominated over any reservations. Although problems were encountered with the new engine exhaust venting design, which meant early models had to go to war without them, Mitsubishi eventually produced a total of 747 in the numerical range #3904 to #4650. These were rushed into service due to the worsening situation.
A further adaptation of the A6M5 was the Model 52 KO (a). The 20mm 100-round drum-fed cannon were upgraded to the Model 2-4, which was belt-fed, each carrying 125 rounds. Further thickening of the wing construction pushed the dive speed up still further, to around 460mph (740.3km/h). Mitsubishi produced 391 of this sub-type but they did not begin to enter front-line service until March 1944. They still lacked armour protection however, but the need to get them into battle quickly dominated. To address this latter problem another variant, the Model 52 OTSU (b) appeared in April 1944. The pilot was given a measure of protection with the introduction of an armoured glass plate almost 2 inches (45mm) thick. To try and solve the notorious tendency of the A6M to burn easily the internal main fuel tank was fitted with a CO2 fire-extinguishing system. These defensive measures were matched by an increase in offensive power and range. The 7.7mm machine-gun mounted in the starboard wing was deleted and a more powerful 13-mm Type 3 machine gun was substituted. This weapon was a licence-built version of the German Rheinmetall-Borsig Maschinengewer MG-131 weapon, and weighed 37lb (17kg). It had a rate of fire of 900 rpm, was belt-fed and was of the percussion-ignition variant, which the IJN apparently considered more suitable for Pacific climate conditions. This enabled a smoothing of the wing under-surface and required an addition fairing where the cannon protruded from the leading edge of the wing. Ammunition access points were also modified. A number of OTSU aircraft also had provision for a pair of 33-gallon (150-litre) under-wing drop tanks. Both Mitsubishi and Nakajima production runs involved the OTSU, 470 being built by the former but no figures seem to be available for the latter plants output.
Subsequently further changes along these lines were progressively introduced to the A6M5, which resulted in the Model 51 HEI (c). The pilot was finally given protection on the scale that Allied flyers had long been used to as standard by the insertion of a sheet of one-third of an inch (8mm) thick armoured plate to the rear of his seat, with over 2 inches (55mm) of armoured glass sheet emplaced to protect his head from above. This added considerable weight but there was more for to further increase internal fuel stowage a 37-gallon (140-litre) fuel tank was inserted directly astern of the pilot, and this tank was made self-sealing. The armament was subject to further drastic revision. The type 13mm machine-gun, with 240rpg, was now fitted to both wings, beyond the wing-mounted cannon; the 7.7mm machine-gun mounted in the nose was eliminated while the 13mm fuselage-mounted weapon remained. Some of this sub-type later had their underwing hard-points for 30–60kg (66–132lb) air-to-air bombs replaced by an air-to-air rocket carrier. Wooden drop-tanks with stabilizer fins and four-point support became the norm. These aircraft began to enter front-line service in November 1944.
Night-fighters (Heisen)
Despite the continuing western article of faith that the Japanese avoided night-fighting (Savo Island and other examples to the contrary notwithstanding) night fighter (Heisen) adaptations were in use both in the south-west Pacific and later in the defence of the home islands. One early attempt to use the A6M in this capacity had been made by the 4 Kōkūtai, which was established on 10 February 1942 at Truk under the command of Captain Gashi Moritama with twenty-seven Type 96 fighters and moved into Vunakanau airfield at Rabaul shortly afterward. American bombers were subjecting this area to nuisance night bombings with some frequency at this time. Three A6Ms arrived on 28 January and attempts were made at interceptions in conjunction with the bases searchlights, but this embryo effort proved futile.
It was not until of the advent of A6M5s properly equipped for night work that real progress was made. The selected Zeros were converted to this mission type by adding a fixed, angled Type 99 Mark 2 Model 4 20mm cannon firing obliquely upward and forward from the rear of the cockpit over the pilots head. This required a modification of the panelling of the after greenhouse, which was plated over astern for strength from the recoil. An additional Type 3 Sight was emplaced on top of the forward windshield frame.
Another ‘in-the-field’ adaptation was the fitting of some A6M5, A6M5a and A6M5bs with a fixed Type 99-2 Model 4 20mm cannon mounted in the aircraft fuselage behind the pilot. This weapon was angled to fire 30° forward and 30° to port when first installed. Later variations had an oblique firing angle of 10° to port and in both cases the barrel of the gun barrel pierced the aircraft’s fuselage. Another modification resulted in the same cannon being recessed into the cockpit canopy rather than the fuselage itself. All methods found some disfavour with the pilots due to the weight penalty this involved and the difficulty in lining up the target. Units that experimented with this type of fixture were not dedicated only to night interceptions of course and among such was the 302 Kōkūtai at Atsugi, near Tokyo, whose experienced commander, Yasuna Kozono, was apparently somewhat fixated on the use of slanted cannon, having successfully deployed it with 251Ku earlier, even considering it useful in fighter duelling (an enthusiasm not generally shared by his pilots or his superiors). Originally organized for the defence of Tokyo on 1 March 1944, with twenty-four night fighters, the 302 Kōkūtai moved to Atsugi to replace the 203-Ku, which had shifted up to the Kuriles. Containing many experienced aviators, including redundant seaplane pilots, reinforced by university student cadets, the unit was given intensive training in the use of oblique-firing cannon. The A6M5s thus equipped, under Lieutenant Kushichirō Yamada and later Lieutenant Hiroshi Morioka, the unit’s strength between January and March 1945 was never more than twenty strong. The additional weight of the emplaced cannon also detracted from the A6M5’s climb performance, which meant that actual interceptions were rare and success almost non-existent. After participating in the defence of Okinawa the force was reduced to ten A6M5s. Along with its other aircraft types the unit was dispersed to be husbanded in readiness for the Allied invasion and flew its last mission on 15 August, when eight A65Ms joined a fight with six F6Fs over their airfield, losing six of their own number to just one Hellcat. When the order came to lay down their arms, the fanatical Kozono refused to accept the inevitable and vowed to carry on the fight regardless. He began to gather aircraft to organize an attack, but was restrained and confined to a mental ward and the disbandment of his unit under a new commander was undertaken.
Other units that specialized in oblique armed fighters, were the 332 Kōkūtai at Iwakuni, in Yamaguchi Prefecture, southern Japan, and on 6 November eight A6M5s equipped with this weapon moved to Atsugi for one month undertaking air defence of the Kantō region. The 131 Kōkūtai was re-organized as a night fighter outfit in March 1945, and based at Kanoya, Kyūshū, under Lieutenant-Commander Tadashi Minobe, flying their first night interceptions on 4 April. After sixty such missions the unit moved to the secret Iwakawa airbase on 20 May with ten A6M5 night fighters, in order to avoid continuous enemy bombing.
Engine boost system
While the Zero herself had been steadily improved, lack of a really powerful engine continued to restrict just what improvements could be made to the existing airframe, which these additions had now increased by 700lb (317.5 kg) additional weight with the same power plant. Mitsubishi requested the Navy Air Arsenal allow them to fit the more powerful Mitsubishi Kinsei-62 radial to this aircraft, but the request was rejected outright. The Navy’s solution was to insist on fitting the existing Sakae-21 with a water-methanol injection system to boost its output for short bursts during combat. However, such was the slow pace of development of this system that the HEI had to go into combat without it. Eventually one trial aircraft appeared late in 1944 fitted with the Sakae 31a radial. It was a far from successful prototype; the injection system was still in its experimental stage and was plagued with continual problems, while the modified engine generated less power not more. The A6M5c sub-type was built at the Nakajima Koizuma Plant, and attained a maximum speed of 346mph (556.83km/h) but only ninety-three ever appeared before the whole project was cancelled in the increasingly frenetic situation the Navy found itself that final winter of the war. Production was complex and still mired by problems, maintenance of the temperamental power plant in the field difficult.
Work on the water-methanol injection system continued, however, utilizing the Nakajima Sakae-31 engine, which was a fourteen-cylinder, aircooled radial, which was rated at 1,130hp (831.11kW) for take-off, 1,100hp (809kW)at 9,350ft (2,850m) and 980hp (720.79kW) at 19,685ft (6,000m). With this power plant the climb rate to 26,250ft (8,001m) was 9 minutes 53 seconds. It provided a service-ceiling of 33,300ft (10,150m), and a maximum range of 956 miles (1,538.5km) at a cruising speed of 230 mph (370.15km/h). These aircraft had a wingspan of just over 36ft (10m), an overall length of almost 30ft (9.118m), a height of 11ft 6in (3.505m) and a wing area of 229.27ft2 (21.300m2). Weights were 4,519lbs (2,049kg) empty, 6,614lb (3,000.59kg) loaded. The armament comprised a single 13mm Type 3 machine-gun in the upper fuselage decking, two wing-mounted 13mm Type-3 machine-guns and two wing-mounted 20mm Type 99 cannon. Provision was also made for eight 22lb (10kg) rockets or two 132lb (60kg) rockets carried beneath the wings. For the first time the A6M was fitted with a CO2 fire-suppression system.
A direct comparison was done later in the war between the A6M5 Model 52 (‘Zeke-52’), the F4U-1D, F6F-5 and the FM-2, which makes for interesting reading. With regard to speed the A6M5 was overall speedier, with the top speeds recorded being 335mph (539.13km/h) at 18,000 feet (5,486m) for the A6M5, against 321mph (516.6km/h) at 13,000ft (3,962.4m) for the FM-2. At sea level the FM-2 was marginally faster than the Zeke-52 by 6mph (9.66km/h) but as the altitude increased the A6M5’s superiority became more and more marked, being 4mph (6.44km/h) faster at 5,000ft (1,524m); 12 mph (19.31 km/h) faster at 10,000ft (3,048m); 8mph (12.87km/h) faster at 15,000ft (4,572m), 19mph (30.58km/h) faster at 20,000ft (6,096m), 22mph (35.41km/h) faster at 25,000ft (7,620m) and 26mph 41.84km/h) faster at 30,000ft (9,144m). To get to those altitudes the two machines were evenly matched, with, at sea-level, the FM-2 exceeding the A6M5’s rate of climb by 400ft/min (2.03m/s). However, at an altitude of 4,000ft (1,219.2m) the two aircraft were level, the FM-2 being 500ft/min (2.54 km/h) superior at 8,000ft (2,438.4m), with the rate of climb equalling out again at 13,000ft (914.49m). The A6M5’s best climb speed was 105 knots (120.832mph) compared with the FM-2’s 120 knots (138.094 mph).
In the field of combat that the A6M had hitherto made her own, the roll rate was found to be equal to the FM-2 at less than 160 knots (184.125mph), but the margin was with the FM-2 at high speeds, which was put down to high control forces. The Japanese fighter could still out-turn the Wildcat gaining one turn in eight at an altitude of 10,000ft (3,048m). In the dive, unexpectedly, the heavier American machine showed no great excess over the A6M5, the latter in fact being better in the initial acceleration and on a par afterward, with zooms following dives also being similar. With regard to pilots’ all-round vision, the A6M5 excelled, notably rear-vision. The manoeuvring of the A6M5 was recorded as ‘remarkable’ at speeds under 175 knots (201.386mph), but this edge lessened as the speed factor went up, again due to high control forces, and above 200 knots (230.156mph/370.4 km/h) the FM-2 was considered to have a marginal advantage
The final suggested tactics for FM-2 pilots tangling with the Zero fighter remained, as they had for the previous three years, quite simple: ‘DO NOT DOG-FIGHT WITH THE ZEKE 52.’ Other advice was to maintain altitude advantage but, should a Zero appear on your tail, to ‘… roll and dive away into a high speed turn’. The A6M5’s maximum safe dive speed was around 350mph, but she lost her roll agility.
Return to China
Three years after the last A6M units had departed from the Chinese mainland they returned again in a combat rôle. As early as May 1943, following heavy Allied bombing raids, nine A6Ms were once more based at San Ya airfield on Hainan Island to provide limited defensive air protection over the Hainan and Canton airspace. In October this section was beefed up with the establishment of 245 Wing based on Haikou, Hainan Island, with twenty-four A6Ms plus four Kates. Some of the A6Ms were detached for similar duties to Yangzi. Finally, in February 1944, 256 (Air Defence) Unit was established at Longhua airfield, Shanghai, with a strength of twenty-four A6Ms and eight Kates.
With the war drawing ever closer to the home islands and the (perceived) success of the suicide method of attack, a bakusō version of the once nimble A6M became the last combat variant and was termed by some the Kamikaze variant, the A6M7 Model 62/63. Designed for the job instead of being retro-fitted conversions of earlier models, the power plant was the 1,130hp (831.11kW) Sakae-31-KOH water-methanol injected radial, designated as Model 62. Others using the same engine but without the injector boost equipment fitted to it, were termed the Model 63. The injection gear necessitated the enlargement of the engine cowling to accommodate it. Further increases in weight to aid diving capability were incorporated by using heavier-gauge material in the tail assembly. Armament was generally as the Model 52c, with the Type 4 gun-sight, but in many the 13mm cannons were removed. The centre wing section was beefed up also to enable a 550lb (250kg) bomb to be carried on a recessed ventral rack instead of the 37-gallon (168.2 litres) drop-tank, and to compensate a 33-gallon (150-litre) drop tank could be accommodated under each wing or alternately air-toair rocket bombs. Introduced as a means of bringing down the hordes of American four-engined bombers laying waste to her cities, the Japanese Navy introduced two type of Tekkō-dan (armour-piercing) rocket bombs toward the end of the war. The Type 3 No. 25 Mk 4 (I-Gou) weighing 315kg appeared as early as 1943 and had a launch speed of 100m/sec with a 3.5kg bursting charge. This was found to be inefficient for the job and was replaced from February 1945 onward by the more practical and efficient Type 3 No. 6 (6-Gou) air-to-air rocket bomb. Weighing just 145lb and with a velocity of 270m/sec, it was in three sections and had a rocket motor with a 5.5lb incendiary shrapnel warhead, consisting of 140 metal pellets embedded with white phosphorus, affixed. The warhead became activated by a clockwork adjustable-delay time fuse, which ejected them in a 60-degree cone. This weapon appeared shortly after the first A6M7 Model 63 appeared in the spring of 1945. In the chaos of the final days of the Pacific War, and also by the deliberate destruction of some records, it is difficult to ascertain exactly how many of this variant were built. However, an entire Model 63 (#82729) has been on exhibition at the Arashiyama Museum, Kyoto City, having been brought up from the cold waters of freshwater Lake Biwa, north of Kyoto in 1976, in relatively good condition.
Training conversions
The A6M was a ‘hot ship’ and, although her reputation had outlived her undisputed merits by 1943, she continued to soldier on to the very end of the war. Like all such fighters the need to train increasing numbers of fresh young pilots, who had already qualified in the primary and intermediate training course, in the face of ever-mounting casualties, finally saw the modification of early types for which little combat value remained. The Model 21 survivors in particular were deemed particularly apt to have their now surplus airframes converted to the training (Tsukuba) role but it was not until March 1944 that they first appeared on the scene becoming the A6M2-K. The Naval Aeronautics Arsenal quickly did the necessary design work, following which the Hitachi Kokuki was allocated the mission of carrying out the task and eventually 273 conversions were carried out. The elongated cockpit canopy was extended aft to accommodate the instructor and dual-controls were emplaced, while the front cockpit for the trainee had an open canopy, accessible from both sides. The radio mast was moved to a middle position between pupil and instructor or even removed altogether. For added stability, an elongated running strake extended from the new rear end of the greenhouse to just before the horizontal stabilizers of the tail fin and the fire wall was shifted aft. To compensate for the additional weight the aircraft were stripped down; the 20mm cannon were removed from the wings but the nose-mounted 7.7mm machine-guns were retained to provide rudimentary gunnery training; the main landing gear doors likewise and the rail wheel was made permanently fixed in the landing position further forward, doing away with the covers, and making for easier maintenance, and with the tail cone often being deleted as well. A thicker tyre was substituted.
Plans were also being considered for a similar derivative of the Model 52, known as the A6M5-K, Interim Type O Training Model 22. The concept basically followed that of the A6M2-K but with the entire nose armament deleted. The Ohmura-based 21 Aircraft Arsenal actually produced a prototype conversion in 1945 but the war terminated before production could get underway at Hitachi. All of these trainers were able to offer less and less air time. By 1 January 1945 the average pilot training hours flown had fallen to a mere 275 hours for the entire fleet. Fresh-faced Imperial Navy pilots were being sent from the training cadres with about forty hours flying time; in contrast the US Navy combat pilots usually had more than 500 hours to their credit. There was no longer much question of teaching the rookies complex dog-fighting techniques; lack of fuel, lack of facilities and, above all, lack of time meant that many were sent off to face the enemy with just the sheer basics. Inevitable also, in those final days, was the sacrifice of numbers of even these training aircraft in Kamikaze missions.
Belated realization that all the many ‘improvements’ had, in general, added weight but slowed down the original concept until it was no longer able to catch, let alone destroy, many opponents, meant a reversion was made to shed some of the excess and get back to basics. The basis was the adoption of the new Mitsubishi Kinsei 14-cylinder air-cooled radial, which developed 1,560hp (1,163.76kW), which was still far less than contemporary American fighter engines of course. This power plant had a bigger diameter (more than 4 inches larger, at 103mm) than its predecessor and therefore entailed a corresponding enlargement of the cowling and the nose guns were deleted, resulting in a bigger profiled but smoother, forward profile. As a consequence the pilot’s windshield was slightly modified to suit. This aircraft was designated as the Model 64, but only two examples were ever completed. Testing of the prototype in April 1945 revealed a maximum top speed of 349.83mph (563km/h), with a climb rate of 19,685ft (6,000m) in just under seven minutes.
