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Kyushu K9W1 Momiji

In 1939, the Kaigun Koku Hombu’s 14-Shi called for a training aircraft capable of rivalling the German Bücker Bü 131B Jungmann, which had been operational in-flight schools since 1938 as the KXBu1tag, with twenty units in service.

Watanabe Tekosho K.K. with their K9W prototype and Hitachi Kokuki K.K. with the K9G prototype responded to the call.

However, both prototypes underperformed in tests, with the original German Jungmann, the KXBu1, emerging as the clear winner.

Consequently, the Navy dispatched a commission to Germany, resulting in the purchase of documents and licensing rights for the Jungmanns to be produced in Japan.

Watanabe commenced production in August 1942, while Hitachi initially provided only the Hitachi GK4A Hatsukaze engines, inspired by the German Hirth engine.

Later, Hitachi also began producing complete aircraft, delivering a total of 61 units.

The Naval Air Force adopted the K9W1 aircraft as the “Navy Type 2 Trainer Model 11,” which was similar to its German counterpart except for the engine’s cooling air intake.

The Japanese Army Air Force (Rikugun Koku Hombu) chose the German Jungmanns as well, which were commissioned in 1944 as the “Army Type 4 Primary Trainer” and labelled Ki-86a in the Kitai system.

In contrast to naval aviation, the Army Air Force pursued additional development.

In one prototype (Ki-86b), metal tubes in the aircraft’s structure were substituted with wooden slats.

Unfortunately, this modification was unsuccessful; the added weight prevented the aircraft from achieving take-off.





6.62 m (21 ft 9 in)


7.4 m (24 ft 3 in)


2.25 m (7 ft 5 in)

Wing area

13.5 m2 (145 sq ft)


NACA 3410.5

Empty weight

380 kg (838 lb)

Gross weight

670 kg (1,477 lb)


Hitachi GK4A Hatsukaze 11,

81 kW (100 hp)


2-bladed fixed-pitch propeller


Maximum speed

183 km/h (114 mph, 99 kn)

Cruise speed

170 km/h (110 mph, 92 kn)

Landing speed

82 km/h (51 mph; 44 kn)


650 km (400 mi, 350 nmi)

Service ceiling

4,300 m (14,100 ft)

Time to altitude

1,000 m (3,300 ft) in five minutes and12 seconds

2,000 m (6,600 ft) in 12 minutes

3,000 m (9,800 ft) in 23 minutes

4,000 m (13,000 ft) in 45 minutes

Wing loading

46.3 kg/m2 (9.5 lb/sq ft)


0.120 kW/kg (0.073 hp/lb)


Japanese Aircraft of the Pacific War-R J Francillon.

Japanese Military aircraft illustrated-Bunrin Do.

Japanese Aviation-R Firsov.

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