Japan’s naval officers, in the summer of 1944, were faced with the almost sure knowledge that their country’s defeat was simply a matter of time. Even before Vice Admiral Ohnishi ordered the creation of the Kamikaze Special Attack Force in October 1944, some naval officers were seeing suicide attacks as the only way to defeat the Allied fleets. One of these men was a transport pilot of the 405th Kokutai, Ensign Mitsuo Ohta. He conceived the idea of a rocket-propelled suicide attack plane, and with the aid of personnel from the University of Tokyo’s Aeronautical Research Institute, he drafted preliminary plans for his brainchild. In August 1944 he submitted his drawings to the Naval Air Technical Arsenal at Yokosuka. The Navy decided that Ensign Ohta’s idea had merit, and so the Arsenal was instructed to prepare a set of detailed blueprints – the engineers involved were Masao Yamana, Tadanao Mitsugi, and Rokuro Hattori. The Ohka (Cherry Blossom) was, in effect, a manned anti-shipping cruise missile of the Pacific War.
The MXY7, as the design was named, was intended as a coastal-defense or anti-invasion weapon, launched by a “parent” aircraft. Once released by its “mother” ship – usually a G4M twin-engined bomber – the MXY7 would glide downwards, and once the pilot had selected a target, the weapon would accelerate to attack speed using the power of three solid-fuel rockets mounted in the tail. These rockets could be fired one at a time or all three simultaneously. Theoretically, when it was at its terminal velocity, the MXY7 would be virtually impossible to stop, and only pilot error could cause it to miss. This small but lethal aircraft was to be built of wood and non-critical metal alloys, utilizing unskilled labor, and as it would be flown by pilots with only limited aerial experience, flight instruments were to be kept to a bare minimum and good maneuverability was required to achieve accuracy in flying and aiming the “manned missile”.
The actual aircraft itself looked like a torpedo to which wings and twin tail surfaces had been added. Barely 20 feet long, and with wings spanning just over 16½ feet, its sliding canopy was hump-backed. In front of the canopy was a ring sight, with a bead sight in front of that, for precise aiming when in the terminal dive on a target. The Ohka was built by unskilled workers using as much non-strategic material as possible. The fuselage was a standard aluminium structure, but the wings were made of moulded plywood covered in fabric. Cockpit instrumentation consisted of only four instruments: a compass, an airspeed indicator, an altimeter and an inclinometer for turn indication.
Ten MXY7s were completed by the end of September 1944. Unpowered flight trials began at Sagami the following month, and in November the first powered flight was made at Kashima. The MXY7 was accepted for Navy service under the name Navy Special Attacker Ohka Model 11. It was powered by a battery of three Type 4 Mark 1 Model 20 rockets, which produced 1,764 pounds of thrust, combined, for 8 to 10 seconds of powered flight. Performance measured during an unmanned flight at Kashima in January 1945 indicated that the Ohka could reach a top unpowered speed of 288 mph and a top powered speed of 403 mph, both speeds being attained at a height of 11,485 feet.
The Imperial Navy didn’t bother to wait for all test results to come in; production began with the first ten Ohka Model 11s in September 1944, and 755 were built by the end of March 1945, when production of this variant ceased. One hundred and fifty-five were built by the Naval Air Technical Arsenal at Yokosuka, and 600 more by the First Naval Air Arsenal at Kasumigaura; Nippon Aircraft Ltd. and Fuji Aircraft Ltd were subcontractors for the wings and tail units. But barely a hundred of them were actually used in operations.
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