The Bücker Bü 131 Jungmann was a biplane primary trainer that played an important role in the growth of the Luftwaffe, before seeing limited active service as a night harassment aircraft late in the Second World War.
The Bücker Flugzeugbau was founded in 1932 by Carl Clemens Bücker, with the Swede Anders J. Andersson as its chief designer. The Bü 131 was the new company's first product, and was an immediate success.
The Bü 131 was a conventional single bay biplane, carrying two people in tandem open cockpits. The wings had a fabric covered wooden framework. All of the wings carried ailerons, making the aircraft very manoeuvrable. Both upper and lower wings had dihedral and eleven degrees of sweepback. The upper and lower wings were interchangeable, making it easier to repair damaged aircraft.
The fuselage was made with a steel-tube fuselage, fabric covered for most of its length but using light alloy around the engine and cockpits. The prototype was powered by an 80hp Hirth HM 60R inline engine.
The aircraft made its maiden flight on 27 April 1934, and in the same year entered production as the Bü 131A Jungmann. Early aircraft went to the Deutscher Luftsportverband (German Air Sports Union), a civilian organisation that was used to train further Luftwaffe pilots. Direct deliveries to the Luftwaffe began in 1935, and the aircraft was used as the standard basic trainer until it was replaced with the Bücker Bü 181 Bestmann. The total number of aircraft produced is unknown, but probably ran to at least 3,000 before production was phased out in 1940-41.
The Jungmann did see some limited front line service when a number of aircraft were allocated to night harassment units operating on the Eastern Front. These aircraft were modified to carry 2.2lb and 4.4lb bombs and were used to keep up a constant stream of minor attacks on the Russian front lines.
The Jungmann was exported to eight European countries, starting in 1935. Spain received more than 100 German built aircraft, and then began licence built construction of the aircraft as the C.A.S.A. 1.131. The first 200 of these aircraft used imported Hirth engines, but these were then replaced by the Spanish ENMA Tigra G-IVA engine. The Swiss also began licensed production, at the Dornier-Werke. Bulgaria, Hungary, Sweden, Finland, France, Holland, Poland, Portugal and Romania also purchased the type. Outside Europe the aircraft sold in South Africa, Brazil, Uruguay and Chile. The largest export market was Japan, where both the Army and Navy ordered the aircraft into production, as the Ki-86A and K9W1 respectively (see below). The Bü 131 was also developed into the single seat Bü 133 Jungmeister aerobatic trainer.
The Bü 131A was the first production version of the aircraft, and was powered by the 80hp Hirth HM 60R engine. It was produced from 1934 until 1936.
The Bü 131B was the main production version, and used a 105hp Hirth HM 504A-2 engine. This was the last production version.
The Bü 131C was powered by a 90hp Cirrus Minor inline engine. A single prototype was built.
Some, but not all, sources mention a slightly improved Bü 131D that might have been introduced in 1938.
Kyushu Navy Type 2 Primary Trainer Model 11 (K9W1)
The Jungmann was produced under licence by two manufacturers in Japan. The first version was the Kyushu K9W1, of which 336 (or 217) were built for the Japanese Navy.
Kokusai Ki-86A Type 4 Primary Trainer
1,037 were produced by Nippon Kokusai Koku between 1943 and the end of the war, with the designation Kokusai Ki-86A Type 4 Primary Trainer
Tatra T 131
The Tatra Wagon Factory of Studenka, Czechoslovakia, obtained a licence to produce the Bü 131B, under the designation Tatra T-131. Ten were built in 1937.
This designation was given to twelve surviving Bü 131s taken over by the Czechoslovak Air Force after the end of the Second World War
Production was then resumed in Czechoslovakia, and around 260 were built as the Aero C 104, powered by a 105hp Walter Minor 4-III inline engine.
Stats: Bü 131B
Engine: Hirth HM 504A-2 inline engine
Wing span: 24ft 3 1/8in
Length: 21ft 8 5/8in
Height: 7ft 4 5/8in
Empty Weight: 860lb
Loaded Weight: 1,500lb
Max Speed: 114mph at sea level
Cruising Speed: 106mph
Service Ceiling: 9,840ft
Range: 404 miles
Bomb-load: None as standard, mix of 2.2lb and 4.4lb bombs as night harassment aircraft