After the Battle of the Coral Sea in May 1942 the IJN admitted the need to have a ground based fast reconnaissance airplane. Little afterwards, the Naval Air Arsenal at Yokosuka received the specification 17 Shi to design an aircraft that could fly at 666 kph at an altitude of 6,000 m. Under the project name Y-30, it was assigned to two teams that would study the different possibilities of a single or a twin engine airplane.
The R1Y1 Seiun would have had a classic airframe and been propelled by a Mitsubishi 24 cylinder, liquid cooled, 2,500 hp experimental engine. The R1Y2 Gyoun would be an evolution from the Ginga with two Mitsubishi Mk10A (Ha-214) 2,400 hp radial engines.
The Seiun engine did not prove to be acceptable on the medium term and the estimated performance of the Gyoun showed that it did not comply with the conditions of the 17 Shi. Dr. Masao Yamana, of Kugisho, suggested the use of German technology inline engines, paired inside of the fuselage, to build the R2Y1 Keiun with a single nose propeller and long power shaft. The formula did not work and the team of Kugisho proposed to the IJN its transformation into a suicide fast bomber with two Ne-30 turbojets.
The opportunity to have these new engines reactivated the Gyoun, using a Ginga as a prototype, propelled by the two turbojets in under wing nacelles position. The final model was known as Tenga and would have probably been propelled by two Ne-130 turbojets with a power equivalent to that of a German Jumo 004. The Tenga could have just been built as suicide bomber within the Kokoku Heiki No.2 programme, carrying an anti ship bomb inside. The most important modifications compared to the Ginga series included the adoption of a solid nose cone and the installation of the main undercarriage legs between the engines and the fuselage. This single seat aircraft also included the usual Kokoku Heiki complements of machine guns in the nose and rockets launchers under the wings.
Technical data
Type suicide bomber
Airframe light alloy and steel
Wingspan 20 m
Length 15 m.
Height 4.30 m
Wing area 55 sq.m
Maximum weight 10,500 Kg
Engines two Ne-30 centrifugal turbojets with 850 kgf peak thrust or two Ne-130 axial turbojets with 900 kgf peak thrust
Estimated maximum speed 700 to 750 kph
Estimated service ceiling over 10,000 m
Crew one
Armament two type 3 machine guns of 13 mm in the nose, four under wing I.S.R. 12 cm decoy rocket launchers, one number 30 Model 2, 807.5 kg anti-ship bomb.
