Nakajima Ki.44
During the 30s, the Western powers that constrained the Japanese territorial expansion were developing four engine heavy bombers. The Tupolev TB.3, capable of reaching Tokyo taking off from Soviet territory, flew for the first time in 1930. In 1932 the French Farman 222 also performed its first flight; although ugly as all of its kind, it was very effective to control navigation in the area to the south of Formosa, operating from Saigon. The Boeing B-17 prototype was on the air in 1935 and the British Sunderland and Stirling prototypes, capable of transatlantic flights, followed in 1938 and 1939. Even the Dutch worked on a four engine version of the Fokker T-IX, named T-VI /115.
The B-17 had a 2,000 miles range, turbocharged engines and such a powerful armament that allowed this airplane autonomous defence. When the IJA was aware of these excellent performances, they realized that the American bomber was above the interception capabilities of the standard fighter Ki.27 and possibly exceeded its successor Ki.43, that had not yet entered service.
Given the potential threat that the B-17s based in Philippines could represent, the IJA requested Nakajima the design of the Ki.44, a point defence interceptor with high climb rate and twice the armament of the
Oscar. Realities of war showed that this effort would not be enough though, since the US industry was able to design, test and mass-produce a new aircraft in the third time than the Japanese.
On November 1, 1944, the first American bomber flew over Tokyo, but it was not the expected B-17 but a giant B-29 F-13 42-93852, of the 3rd Photo Recon Sqn, ironically named ‘Tokyo Rose’. When the Ki.44-II-Otsu of the 47th Sentai tried to intercept it, they discovered that the Superfortress flew so high and fast that they could not reach it. It turned out that the Japanese plane used for the intended interception, equivalent to the Starfighter of the time and with an astonishing climb rate of 5,000 m in four minutes, was not good enough to do the work for which it had been designed.
The psychological impact caused by this realisation on the Japanese pilots had important consequences. The IJA needed interceptors equipped with turbo superchargers, but the Japanese industry was unable to build them or even replicate enemy bombers that had been shot down. They also needed more powerful weapons with wider range, whose usefulness was not foreseen until it was too late.
In 1944, the Luftwaffe had two types of guns of 30 mm to fight against the B-17 and B-24:
The MK 103, a potent and heavy weapon, with great effective range and low rate of fire, difficult to install in single engine fighters given its powerful recoil that damaged the airframes.
The MK 108, light and with high rate of fire, but with low effective range that forced the fighters to come dangerously close to the self-defence formations of American bombers.
Across the world, the Japanese interceptors fighting against the B-29 had similar problems with their weapons. The IJA had the Ho-203 cannon of 37 mm, weighted 89 kg, and had a rate of fire of 120 rpm and an effective range of 1,000 m. As was the case with the German Mk 103, this gun was difficult to integrate in the fragile airframes of the Japanese fighters because of their excessive recoil. The alternative seemed to be the new Ho-301 of 40 mm, weighing about half of what the Ho-203 weighs, had a moderate recoil and increased rate of fire of 450 rpm, although only 150 m range because the ammunition used was propelled by small spin-stabilised rockets.
It was determined during its design that the warhead should at least contain 65 grams of High Explosive (HE) to be effective against the B-29s, but this could only be achieved by reducing the amount of rocket propellant and thus the range of the weapon. The manufacturing of the Venturi nozzles at the base of this type of rockets, that generated both propulsion and spin, required an accuracy that the Japanese industry could not achieve for large production runs. As a consequence, the trajectory of the rockets was not precise enough for air-to-air combat.
Under pressure from the bombings and the proven futility of the weapons of 12.7 and 20 mm, the IJA decided to carry out a series of operational tests with two Ho-203 guns, with belt magazines of 25 rounds installed in the wings of some Ki.44-II-Hei of the 70th Sentai, based in Manchuria.
On September 8, 1944, ninety B-29s from the 58th BW made an attack on the Showa Steel Works at Anshan. The aircraft of the70th Sentai attempted interception, but the extra weight of the guns prevented them to reach the flight altitude of the bombers in time. Meanwhile, the aircraft of the 59th and 104th Sentai, equipped with standard armament, could only manage to damage three B-29s, after losing in combat eleven
Tojo to the powerful American defensive fire.
Some tests were also carried out with the Ho-301, using some Ki.44-II-Otsu of the 1st Field Reserve Squadron, without suffering any structural damages. Afterwards, some Ki.44s of the 47th Sentai were transformed to test these 40mm cannons in combat. The 47th was an elite squadron whose pilots have had some success fighting against the Liberators at a medium altitude.
But the flight altitude of the B-29 made the extra weight of the Ki.44 difficult to manoeuvre. Above 8,000 m the small wings generated little lift and the plane uncontrollably fell several hundred meters when trying any combat manoeuvring. Its only effective tactic was diving at 45 degrees, frontally attacking the ‘bomber box’ to avoid the dangerous effect of the 20mm cannon at the B-29 tail, firing against the vulnerable bomber cockpit and then increasing the falling angle to avoid collision.
These manoeuvres were already difficult with the
Tojo standard, but with the extra weight of the guns, the flight controls barely responded due to the low air density at high altitude. It is therefore possible that some registered rammings were actually accidental collisions. After shooting, the two aircraft crossed just a few meters away, with a combined speed of 1,000 kph. Considering the limited range of the Ho-301, the Japanese pilot could either shoot four rounds and escape, or shoot six rounds and die.
The
Ta-Dan bombs used by the IJA for air-to-air bombing were also not effective. Some pilots as Capt. Yasuro Masazaki, of the 47th Sentai, developed a special skill using these weapons and achieving some hits. However, their experience was not transferable and generally speaking the
Ta- Dan only proved useful in combat at lower altitudes.
On February 4, 1945, the Ki.44 of the 70th Sentai destroyed the B-29 42-24608 over Kobe and six days later the 42-24867 over Ota, using air-to-air bombing tactics. Some Ki.43 and Ki.44 of the 1st Field Reserve Squadron based in Singapore were used in experiments with the new spin stabilised rockets
Ro-San Dan that proved to have too erratic flight paths for use in air-to-air combat. Three types of spin-stabilised rockets were built for the IJA during World War II:
Ro-San Dan (Ro-3) of 10 cm and 10 kg
Ro-San Dan (Ro-5) of 20.2 cm and 76 kg
Ro-Sichi Dan (Ro-7) of 30.3 cm and 280 kg
All stabilized in flight rotating at 3,600 rpm thanks to the spin effect produced by six 25 degrees angled nozzles, had incendiary and shrapnel warheads, time fuses and percussion primers and could be fired from simple iron tubes. Some tests were also performed with an unknown type of fin stabilised rocket, possibly a modified Ro-3, using a Ki.43 with underwing rails, but there is no record that it were used in combat as happened with the efficient German R4M.
After all these failures, only the
Tai-Atari (head-on ramming) tactics remained, using the plane as a weapon to destroy the B-29 in deliberate collision course. On September 26, 1944, a
Tojo of the 9th Sentai piloted by Sgt Mamoru Taguchi rammed the first B-29 during a raid against Showa Steel Works in Manchuria. In November 1944, a group of pilots of the humiliated 47th Sentai began to make rammings against the B-29 on a volunteer basis.
These practices were widespread until December 5, when the IJA ordered the creation of a
Shinten Seiku Tai (Air Superiority Company) built into every Sentai of fighters. They were initially formed by four planes stripped of weapons, armour and any other unnecessary equipment for ramming, in order to improve manoeuvrability at high altitude. The number of
Shinten fighters was increased up to eight per each Sentai of air defence during the last months of the war.
The
Shinten pilots received special training in the 1st Advanced Training Unit where tail and belly approaches to the B-29s were not recommended. On November 24, 1944, hundred and eleven B-29's of the 73rd BW attacked the Nakajima-Tokyo factory flying at an altitude between 9,100 and 8,200 m. They were intercepted by the Ki.44-II-Otsu of the 47th Sentai, with the ‘Lucky Irish’ 42-24622 being destroyed after its ramming by the
Tojo of Yoshio Mita.
On December 7, the B-29 ‘Humpin’ Honey’ 42-6299 was rammed over Manshu-Mukden by the Ki.44-II-Hei of Sgt. Tadanori Nagata and the 42-6390 by the Yoshihiro Akeno airplane, both of them from the 104th Sentai. On December 22, during a raid over Nagoya, ‘The Dragon Lady’ 42-63425 was rammed by the Ki.44 of Yoshi Hirose, from the Akeno Flying School, but the B-29 managed to return to its base despite resulting severely damaged in the tail section.
On January 9, 1945, two B-29 bombers were rammed over Tokyo by fighters of the 47th Sentai, during a new attack to the Nakajima factories. ‘Miss Behavin’ 42-24655 was rammed in engine No. 2 by a Ki.44-Otsu piloted by Masumi Yuki. ‘Tail End Charlie’ 42-24772 was rammed by Takashi Awamura airplane. On the 27th, the B-29 repeated the attack with the ‘Irish Lassie’ 42-65246 being rammed by the Ki.44 of Isamu Sakamoto and the ‘Shady Lady’ 42-24619 resulting rammed by the airplane of Kiyoshi Suzuki, both from the 47th Sentai. On February 10, during the bombing of the Nakajima-Ota factory, the B-29 ‘Battlin' Betty’ 42-24760 was rammed by a Ki.44-II of the 47th Sentai piloted by Heikichi Yoshizawa.
There are no records indicating the assignment of the Ki-44 to any Tokko unit as these aircraft were considered indispensable for air defence of the Japanese mainland. The structure of the Ki.44-II-Ko only supported the installation of a 150 kg bomb fixed for close-range attacks, instead of a centreline 200 litres fuel tank. The Ki.44 of the following series could transport two fuel tanks under the central section of the wing, in a rather rear position, to not interfere with the deployment of the landing gear. Under the outer wings, it could carry two
Ta-Dan bombs of only 52 kg.
At the end of 1944 there were three Sentais in the Philippines, the 22nd, 29th and 246th equipped with Ki.44-II-Otsu fighters. They were used for air defence of Clark and Nicholls airfields as well as to carry out escort missions of the Ki.43 suicide and Ki.46 reconnaissance airplanes that tried to locate the Allied Task Forces. During the Battle of the Philippines, the Ki.44 suffered heavy casualties in air and ground combat because of the TF-38 attacks. The 246th Sentai lost all its aircraft.
On 28 November, two Ki.44s in strafing mission over San Pedro Bay were shot down by the naval AA and one of them voluntarily impacted against the destroyer USS Ross (DD-563). During the Battle of Okinawa, on April 13, 1945, the British fleet reported the presence of a
Dinah escorted by
Tojos on a reconnaissance mission. On May 12, a Ki.84
kamikaze of the 120th Sei squadron escorted by a Ki.44, attacked the battleship USS New Mexico (BB-40) off Yomintan