Kokusai Ku-9-II Onmoraki
SwallowMeiyo Special Attack Unit, Home Defence Command, Chiba, Honshu, Japan
March, 1946
The Kokusai Ku-9 is a little known Japanese glider. Originally designed as a towed bomber interceptor, it was subsequently adapted for the ground-launched kamikaze mission. Over 900 were built, around 300 of which were used over the Kanto Plains following the Allied Y-Day invasion of Honshu.
In anticipation of Allied bomber raids against the Japanese Home Islands, Home Defence Command initiated a series of secret discussions with aircraft engine and airframe manufacturers in late 1943. They were seeking proposals for innovative, low cost air defence aircraft and weapons for employment in the 1945-46 period. These solicitations resulted in a range of production aircraft, including the Fuji Kaiken
Terry, Nippon Hikoki Bo-hiya
Elton, Kyushu Ya
Bruce and the Kokusai Ku-9
Swallow. Although similar in concept and often lumped in with these aforementioned types as product of Home Defence Command, the Rikugun Ki-89 Itsumade-Kai
Floyd originated as a project of the Imperial Japanese Army.
The Ku-9 was designed to be towed to altitude above a bomber stream by fighters, bombers or transport aircraft and released to make one or two slashing dive attacks before landing. Although largely built of wood, the cockpit was heavily armoured and ramming was an approved option. Although of wholly conventional construction, the Ku-9 did have one novel feature; expecting that the pilots would experience high G forces during the dive into the bomber stream, they lay prone on a cushioned bench instead of sitting in a seat. However, when the B-29 appeared over Japan, their combination of high speed and altitude, plus Japan's poor early warning capability, made the concept obsolete. Towed, the Ku-9 could neither make the altitude nor meet the response time necessary to attempt an intercept.
With over around 100 Ku-9s already built and production well established, the decision was made to turn the type into a ground-launched Special Attack and Special Transport type for use against the anticipated Allied invasion of the Home Islands. With minor adjustments (including the removal of the landing skid) existing Ku-9-Is were modified to Ku-9-II standard. For the interceptor role, the Ku-9-I was armed with wing root-mounted 20mm Ho-5 cannon, but these and their wing root fairings were removed to make room for rocket assisted take-off gear. New build aircraft for the battlefield role (distinguished by the absence of the nose-mounted tow cable connector) were designated Ku-9-III.
Onmoraki were ground launched using catapults or winches, assisted by rockets. Considered as pieces of ordnance, two types of rockets were used without any change of designation. Liquid fuel Toko Ro 3/KR11 rockets with used (as seen here), mostly for Special Attack missions. These were basically miniaturised versions of the Toko Ro.2 /KR10 motors used by the
Elton and
Bruce. The advantage that these rockets gave to the Special Attack role was that their fuel tanks retained an explosive quantum of propellants after motor burn out, adding to the type's lethality. For the Special Transport role, paired solid fuel rockets were preferred, these being the same type as as those strapped on to the outside of the
Elton.
When used in the kamikazi role, these “human artillery” aircraft were sent aloft across the battlefield for pilots to select targets of opportunity. Their small size, speed and fleeting flight time made them difficult to shoot down; a dozen were claimed shot down by ground fire and just 1 shot was shot down by an Allied fighter. Fortunately for the Allies, their small kinetic and explosive effect limited their lethal impact. A M4 Sherman is reported as having taken a direct hit and surviving, the Swallow disintegrating around the tank's armored hull. Also, their short range meant that they needed to be launched close to the front line and many aircraft and their launch sites were destroyed by bombing, strafing and artillery. Additional factors that limited their effectiveness included poor pilot training, limited pilot vision through the small cockpit windows and a lack of kinetic energy to allow sufficient height and fight time for meaningful target selection and maneuvering.
As the Allies moved across the Kanto Plains, they found hundreds of damaged Ku-9 airframes. Others, such as the one modeled here, were found complete and ready for action, but abandoned due to the Allies' swift advance following the break-out from the beach head; desperate for manpower, local commanders often commandeered the Ku-9 ground crews and pilots for infantry duty.
The US Army credited Ku-9 kamikaze missions with causing only 163 Allied casualties, including 19 deaths.
A less well known aspect of Japan's Glider Offensive is the use of the Ku-9 as a Special Transport type. Usually launched with the solid fuel rockets, these sorties were used to insert personnel behind Allied lines. Personnel included commandos and snipers (a handful of whom used Samurai bow and arrows instead of rifles), who were flown in at night to cause disruption in the Allies' rear.
More nefarious, and officially suppressed until the 1990s, was the use of the Special Transport role by Unit 731, which placed POWs into the gliders. These men were infected with diseases including typhoid and cholera, the idea being to spread these illness among the invading troops. There was also an additional psychological warfare aspect to the campaign, as it was hoped that Allied soldiers would become reluctant to shoot at the Ku-9s once they learnt that they might be “flown” by POWs. However, only about a dozen Unit 731 missions were mounted with the Ku-9 and the Allies quickly ascertained, controlled and suppressed both the spread of disease and of information.
The Onmoraki isnamed after a bird-demon created from the spirits of freshly-dead corpses. As a glider, the type received an Allied bird reporting name:
Swallow.
