Bücker Bü 131 Jungmann Bü 131A

The Bü 131A is the configuration in which the Jungmann was born and the first production version of Bücker Flugzeugbau. The company had been founded in 1932 by Carl Clemens Bücker, who had served in the Imperial German Navy and was returning from Sweden with a young SAAB engineer, Anders J. Andersson, who became his chief designer. The new firm was housed in the premises of Ambi-Budd Presswerke at Berlin-Johannisthal —the Air Britain Digest dates that move to October 1933— and within six months it had its first aircraft flying.

The requirement came from the Deutscher Luftsportverband (DLV), a nominally civilian sporting organisation, ultimately answerable to Hermann Göring, that concealed pilot training while the Luftwaffe still existed clandestinely. It called for a trainer that was cheap to operate and easy, simple and inexpensive to build, yet fast, light and strong; hence the decision to fit an efficient 80 hp engine from the outset. The prototype, registered D-3150 and powered by a Hirth HM 60R, made its maiden flight on 27 April 1934 with Joachim von Köppen, a test pilot of the Deutsche Versuchsanstalt für Luftfahrt (DVL), at the controls.

It was a conventional single-bay biplane with two open cockpits in tandem and fixed landing gear. The wings had a fabric-covered wooden framework, carried ailerons on all four panels —making the aircraft very manoeuvrable— and both upper and lower wings had dihedral and eleven degrees of sweepback; the upper and lower wings were also interchangeable, which made damaged aircraft easier to repair. The fuselage was a steel tube structure, fabric-covered for most of its length but skinned in light alloy around the engine and cockpits. The HM 60R was an 80 hp (60 kW) four-cylinder inverted air-cooled inline engine. The whole design was intended for basic instruction, yet sturdy enough for aerobatics.

That same year, 1934, the aircraft entered production as the Bü 131A: it was the firm's first type to reach series production and would prove to be the last biplane manufactured in quantity in Germany. Orders from the DLV for its flying schools soon outgrew the Johannisthal workshop; according to the Bücker museum at Rangsdorf, the Jungmann was built at Johannisthal in 1934 and 1935 and from 1935 at the new, larger factory at Rangsdorf, south of Berlin. Historyofwar dates production of the A series from 1934 until 1936. The German Wikipedia records that 223 aircraft with the HM 60 engine, i.e. the A series, were delivered against orders from the Reich Air Ministry (RLM), compared with 1,356 with the HM 504 of the B and D series; this is a figure for RLM deliveries, not the total number of A-series aircraft built, which none of the sources consulted gives.

The first deliveries went to the DLV in 1934, and direct deliveries to the Luftwaffe began in 1935. That "civilian" organisation was the first school for most of the German pilots who would later make their names in the Second World War, and the Jungmann was their training mount: docile and easy for the student, yet robust enough to tolerate their mistakes.

Its replacement came quickly. In 1936, after the Luftwaffe chose the Jungmann as its primary trainer, the 105 hp Hirth HM 504 became the standard engine of the B series. According to the Air Britain Digest, the change brought an increase of about 8 mph (some 13 km/h) in maximum speed and a much better rate of climb: the B reached 1,000 metres in 5.2 minutes, against 7 minutes for the Bü 131A.

The A also reached export customers; exports began in 1935 and were mostly in small quantities. The Air Britain Digest notes that of the 119 Jungmann ordered by Hungary, one went to Count Festetich and was a Bü 131A. In Spain, the Fundación Infante de Orleans relates that the first Legion Condor forces, arriving on 6 November 1936, brought the first three of the ninety-five Bü 131s that would be received; some had the 80 hp Hirth and most already the 105 hp engine, and they were initially assigned to the elementary flying school at El Copero (Seville). Another source speaks of a hundred Bü 131As arriving that year, a figure that does not match the former.

The A-series powerplant remains the reference point for modern replicas: the FK131 Jungmann built by B&F Technik with Podešva Air uses an 82 hp Walter Mikron, almost exactly the power of the Bücker 131A.