Bücker Bü 131 Jungmann Kokusai Ki-86A

Japanese interest in the Jungmann began in 1938, when Bücker demonstrated a Bü 131 and a Bü 133 Jungmeister in Japan. The Navy bought first: after trials it ordered twenty more aircraft and eventually acquired a licence to build the type as the Kyūshū K9W1. According to History of War, the K9W1's performance impressed the Army, but the intense rivalry between the two services meant it would not use the Kyūshū aircraft. Production was instead given to another company, Nippon Kokusai Kōkū Kōgyō (Kokusai). The Japanese Wikipedia dates the Army's order to Kokusai for licence production of the Bü 131, separate from the Navy's, to 1942; History of War gives 1943 as the year the Army began its own licence production.

According to the Japanese Wikipedia, Kokusai began adapting the design for domestic production in November 1942. The first prototype was completed in July 1943, and the aircraft was officially adopted in April 1944 as the Army Type 4 Basic Trainer (四式基本練習機), with the project number Ki-86. It kept the German nickname "Jungmann", and the Allies gave it the code name "Cypress". The designation Ki-86A distinguishes this production version from the wooden Ki-86B.

The Ki-86A kept the Bü 131's structure: a two-seat biplane with a fabric-covered metal framework. It was powered by the Hitachi Ha47 11, an air-cooled inverted four-cylinder inline engine rated at 100 hp nominal and 110 hp for take-off (about 82 kW). The Ha47 was the Army version of the Hitachi Hatsukaze engine, whose first model was a licence-built Hirth HM 504; the Navy used the GK4 version in its K9W1. The Army's long designation was "Army Type 4 110hp Air Cooled Inline", and its later unified designation was Ha-11 model 11.

History of War describes it as very similar to the standard Jungmann. Its wingspan was two inches narrower than the Bü 131B's, its top speed nine miles per hour higher and its service ceiling around 3,000 ft higher. That source gives it a span of 7.34 m, a length of 6.61 m, an empty weight of 409 kg, a loaded weight of 639 kg, a top speed of 180 km/h, a cruising speed of 121 km/h at 3,280 ft (1 km), a ceiling of about 3.9 km and a range of 600 km. The Japanese Wikipedia gives slightly different figures: length 6.62 m, span 7.35 m, height 2.25 m, empty weight 401 kg, normal weight 631 kg, maximum speed 180 km/h, cruising speed 120 km/h and a normal range of 470 km (600 km overloaded).

The Japanese Wikipedia, citing Yōji Watanabe, lists its strengths: it was easy to handle, used little fuel and could run on low-grade 70-octane petrol. Its weaknesses were engine trouble caused by spark plugs that fouled easily, a lack of power that gave it a poor rate of climb, and a weak undercarriage. Because the cylinders pointed downwards, an engine that faltered in flight would sometimes recover if the aircraft was rolled inverted.

With two on board, the instructor or assistant instructor sat in front and the trainee behind. When flown solo, the pilot sat in the rear seat to balance the weight of the engine. The aircraft was easy to take off and land and handled well in the air. According to the same source, trainees reached the skill needed to fly solo after about nine and a half hours on average, five or six fewer than on earlier primary trainers, and some were cleared to fly solo after as little as six and a half hours of dual instruction. History of War says the Ki-86 replaced the Tachikawa Ki-17 as the Army's standard basic trainer. In April 1945, because of fuel shortages, the Army Air Academy moved around 500 aircraft to Manchuria to continue training there.

The most widely cited figure is 1,037 aircraft. It is given by History of War, the English and German Wikipedias, the May-June 1983 Air Britain Digest article reproduced by sbeaver.com and the English Wikipedia entry on the Ha47 engine. History of War specifies that they were built between 1943 and 1945 and that the total includes one Ki-86B. The Japanese Wikipedia instead breaks production down by fiscal year: 260 aircraft in 1943, 763 in 1944 and 7 in 1945, a total of 1,030. Either way, this was far more than the Navy's 339 K9W1s.

Material shortages led to trials of an all-wooden Ki-86B (乙型). History of War says one was completed in February 1945 and did not enter production; the Japanese Wikipedia mentions one prototype and six pre-production aircraft, with no official adoption.

According to the text reproduced by sbeaver.com, none of the nearly 2,000 Japanese Jungmann survive. One Ki-86A outlived the war and was taken to Britain for evaluation, but it was burned in the mid-1950s during a fire-fighting exercise at RAF Station Wroughton in Wiltshire.