Kawanishi Baika
Would Japan have not surrendered after the atomic attacks over Hiroshima and Nagasaki in August 1945, the Allies would have been forced to land on the Japanese home islands. There were plans to carry out the invasion in two phases. The first step, known as ‘Operation Olympic’, aimed to occupy the south of Kyushu Island and should start on November 1st. The second one, ‘Operation Coronet’, would have consisted of landings on Honshu Island, to control the Tokyo plain, and it was planned for March 1946. The whole plan, ‘Operation Downfall’, required 5,000,000 men, 3,000 ships, 66 aircraft carriers, loaded with 2,649 aircraft, and all the airplanes in the 7th, 8th and 10th Army Air Forces. Casualties were expected to be extremely heavy. A study requested by U.S. Navy Secretary estimated that conquering Japan would cost between 1.7 and 4 million casualties including 400,000 to 800,000 fatalities and the destruction of 800 Allied ships.
The defensive plan of the Japanese High Command (Operation
Ketsu-Go) included the use of the 12,725 airplanes available in one single and uninterrupted attack with the purpose of collapsing the defences of the Allied fleet. A force of 2,000 IJA and IJN Japanese fighters would battle to control the skies over Kyushu Island. While the Allied fleet would still be in open sea and approaching Japan, the warships of the Task Force would be attacked by 330 IJN suicide bombers, then a group of 825 IJA and IJN suicide airplanes would try to sink the troop transports. Once the invasion ships got close to their proposed anchorages, another 2,000 suicide aircrafts would be launched hour after hour in nonstop attacks which the Japanese hoped could be sustained for 10 days. Thirty five camouflaged airfields and nine seaplane bases had been built in Kyushu to that purpose. The Japanese also had 20 suicide take off strips with underground hangars, from where the Ki.115
Tsurugi and
Baika Model 1 could operate.
The
Ohka 43-Otsu would use some straight railway sections and rocket-propelled trolleys to operate. It was very effective but had the handicap of using the new Ne-20 turbojet of which just a few units were available. The Ki.115 could use several types of second hand conventional engines but it required 80 octane gasoline which was almost non-existent in Japan due to the naval blockade. On the other hand, the Ne-20 could work with a mixture of wood turpentine and charcoal, although the battered Japanese industry could not manufacture them in high numbers on time for
Ketsu-Go.
The Japanese scientists found the solution to this situation with the mass production of pulsejet engines based on the Argus As 109-014 scale drawings that the I-8 submarine had brought from Germany in 1943. The Japanese version, known as
Maru Ka-10 was designed by professors Ichiro Tami and Taichiro Ogawa of the Aeronautical Institute of Tokyo Imperial University in 1944. The
Maru Ka-10 was 3,750 mm long, had 550 mm of diameter and weighted 153 kg, producing 360 kg of thrust at 740 kph. It used Benzol as fuel during the flying tests, although it could also work with low quality oil or heavy kerosene. It was expected that the operational version would burn 1,600 lt of crude pine root oil that the local chemical industry produced as
ersatz fuel.
The Japanese did never receive the blueprints for the V-1 missile or for their manned variant
Reichenberg as the German submarine carrying them was sunk. They were forced to design their own version based in a general description of the German model. The result was a small low wing monoplane made out of wood and steel, given the scarcity of aluminium. By the beginning of 1945 their mass production was ordered to the Kawanishi Kokuki K.K. firm, under the
Baika denomination. The plan was to manufacture three different versions.
The first one was the Kawanishi
Baika model 1 that took off from a conventional aerodrome reaching the ignition speed of the pulsejet (360 kph) thanks to the thrust of its three
Toku-Ro.1 Type 2 rockets with 600 kg of thrust, located in the wing roots and in the fuselage centreline. Its main undercarriage (from a Ki.115) and the rockets (from an
Ohka 43) were jettisoned after take-off. The high rate of fuel consumption of the pulsejet allowed a range of just 204 km at the cruise speed of 556 kph and sea level. The model 1 could only operate against troops transports located near the southern coast of Kyushu. To that purpose they planned to have a Type 97 warhead with 150 kg of Torpex H.E. (from a Type 91 mod.1 airborne torpedo) to impact under the ship waterline.
The Kawanishi
Baika model 2 was the second version. During the WWII the Japanese used 46 submarines with capacity to carry different types of airplanes in deck watertight hangars. By August 1945 they still kept six of them: The I-14 (AM class) with a hangar of 4.2 x 21 m. able to house two
Seiran bombers, the I-36 (B1 class) and the I-58 (B3 class) with a hangar of 1.4 m high, 2.4 m. wide and 8.5 m long where they could transport a Watanabe reconnaissance floatplane and the I-400, I-401 and I-402 of the
Sen-Toku Class that had a hangar of 4.2 m. of diameter and 31 m long with capacity for two
Saiun or three
Seiran or four
Ohka type 43-Ko.
These submarines were ideal to transport specialized suicide airplanes that could attack the enemy fleet in their bases of Ulithi, Pearl Harbour, the west coast of USA or even when they were crossing the Panama Canal. They could be refuelled during the trip by the I-402, specially modified as tanker to that purpose. The I-400 could even reach New York and Washington going round South America from the south in a four months journey. Would the Allies have used poison gas against Iwo Jima in February 1945, New York could have been attacked in June using Type 7 bacteriological bombs, launched from six
Seiran airplanes carried by the
Sen-Toku submarines.
To compete against the O
hka type 43-Ko, the Kawanishi firm designed a
Baika model 2 version to be launched from submarines. To facilitate their storage it was considered convenient to reduce their length in 63 cm moving forward the support structure of the pulsejet. The clear cockpit opened sliding forward. The wings were built in such a way that could be folded backwards, like in the
Seiran, and put back in flying position very quickly using a hydraulic mechanism connected to the submarine. The warhead was a general purpose 250 kg bomb with nose priming plug and rear impact fuse.
The
Baika model 2 used the same launch system than the
Ohka type 43-Ko. It was positioned over a launch cart of 700 kg at the end of a catapult (26 m length, 116 cm track and 3º30’ pitch) shot by a 90-150 kg/sq. cm compressed air device coming from the torpedo launch system of the submarine. A buffer cable was used for decelerating the launch cart that was quickly stored under the deck. The four airplanes of a
Sen-Toku could be launched within 20 minutes. The time required was of 6 min 23 sec for each from the oldest submarines.
The last version of the
Baika was the model 3. One of the main reasons of the operational failure of the
Ohka model 11 was the excessive weight of their warhead which had been designed for the single shot destruction of major warships.
To cover this gap, the Kawanishi firm designed an air launched variant of the
Baika. Instead of solving the problem of integration with the
Ginga by reducing the wingspan, so that it could be housed between the main undercarriage legs, the manufactured airplane weighted half the weight of an
Ohka 11 and could be installed in a more rearward position within the
Ginga bomb bay. To allow the ignition of the pulsejet during flight, it should be exposed to the air stream outside the carrier airplane. Its original location was therefore moved to below the fuselage centreline of the
Baika. Although the cruise speed of the model 3, when launched from 6,100 m, was of just 481 kph, it started a shallow dive at 556 kph until being intercepted by the fighters flying at 600 kph. It then increased the dive angle until reaching 740 kph passing under the fighters screen and going to the target at sea level, impacting under the waterline, or climbing at 450 m to go down over the ship deck in a 75º dive, depending on the type of warhead used.
At this point of time the Japanese were no more interested in sinking the big heavily armoured warships. The political circumstances were more favourable to the kind of war that caused a high number of casualties to the Allies. It was better to try and destroy the little protected troop transports with a warhead of just 250 kg.
Technical data
Type suicide bomber
Phase project
Wings wood structure with plywood covering (foldable in Mod. 2)
Fuselage steel structure and cladding
Tail surfaces wood structure with plywood covering
Engine one
Maru Ka-10 pulsejet with 300-360 kg thrust
Fuel tank one of 600 litres behind the pilot
Warhead a Type 97 torpedo warhead with 150 kg of Torpex H.E.or a 250 kg G.P. bomb with Trinitro-Anisol H.E. and nose priming plug
Wingspan 6.6 m
Length (Mod. 1) 7.63 m; (Mod. 2) 7 m; (Mod. 3) 6.84 m.
Wing area 7.6 m2
Wing load 188.2 kg/sqm
Overall weight 1430 kg
Empty weight 750 kg
Max speed dive 740 kph
Max speed level 556 kph at sea level and 481 kph at 6,000 m
Launch speed 360 kph
Stall speed 111 kph
Ceiling 6,000 m (Mod. 3)
Range 280 km (Mod. 3); 204 km (mod. 1 & 2)
Endurance 22 min (Mod.1)
![image_thumb[3].png](/data/attachments/293/293278-36c13b8518aa1a10be5208b5db3afc01.jpg)
