Bücker Bü 131 Jungmann Bü 131B Dornier-Werke Altenrhein

In early 1936 Switzerland was looking for a suitable school aircraft for its novice pilots. After trials of several competing types, the choice fell clearly on the Bücker Bü 131B, the training biplane that Bücker Flugzeugbau had been building in series in Germany since 1934. According to the 1983 Air Britain Digest, Switzerland evaluated the Bü 131B and decided to buy it both for its military aviation and for the Aero Club. The first six machines were ordered directly from Bücker and handed to the service with the military serials A-1 to A-6. Given the uncertain international situation, it was decided to build the aircraft in the country itself, and the licence went to Dornier-Werke AG of Altenrhein, on the shore of Lake Constance, later known as Doflug. By the end of 1936 ten Swiss-built Jungmanns had already flown: seven for the Aero Club and three for the military.

The Altenrhein aircraft were standard Bü 131Bs: a biplane with a steel-tube fuselage, wooden wings and fabric covering, powered by a Hirth HM 504 A-2 four-cylinder inverted in-line air-cooled engine fitted with a carburettor for inverted flight. The sources give it as a 105 hp engine; the retired-equipment record of the Swiss Air Force lists a nominal output of 112 PS and a two-blade laminated wooden propeller of 2.00 m diameter. The same record gives the Swiss version a span of 7.40 m, a length of 6.62 m and a height of 2.37 m, 400 kg empty and 670 kg take-off weight, a top speed of 173 km/h, a climb rate of 3.8 m/s, a ceiling of 3500 m, a range of 400 km and an endurance of about three hours. It had dual controls, wheel brakes and parachutes, and carried no armament.

How many were built is where the sources disagree most. Swiss military aviation history pages number the licence-built aircraft A-7 to A-84, that is 78 Altenrhein Jungmanns for the military, and state that ten more were requisitioned from the aero clubs in 1942; one of them puts the total at 95, and the retired-equipment record speaks of 84 plus 10 aircraft acquired and says Dornier built "roughly one hundred" Bü 131s in all. The German Wikipedia gives 84 military aircraft, three of them imported and 81 licence-built, plus 46 for civil customers, built between 1936 and 1943; the Air Britain Digest credits Dornier with 84 Jungmanns for the Air Force, and the English Wikipedia speaks of 88 built by Dornier out of the 94 operated by Switzerland. This census therefore sets no single figure.

Today's civil registrations make it possible to follow individual aircraft. A-63 was delivered to the military on 11 August 1939; A-68, construction number 81, left Altenrhein on 19 October 1939. Through the war and after it the Jungmann served as an initial trainer, aerobatic trainer and liaison aircraft. In 1943 A-87 and A-88 were equipped for blind-flying instruction, in 1950 A-43 was experimentally fitted with an autopilot with remote control, and five aircraft received hooks for glider towing.

In the late 1950s and early 1960s the Pilatus P-2 gradually replaced the Jungmann, but the biplane stayed in service until 1971, when all remaining aircraft were withdrawn because, lacking radio and blind-landing equipment, they no longer met requirements. The released aircraft were eagerly sought by flying clubs and private owners, and a tradition of modifications grew around them. In 1962 FFW, successor to Dornier-Werke, fitted a 170 hp Lycoming to HB-UTH, in which Albert Ruesch took second place that year in the British Lockheed International Trophy. FFW and Pilatus converted others to a 180 hp Lycoming, and the Pilatus-modified HB-URN received from Max Dätwyler & Co. a new wing with an improved section designed by the engineer Fritz Dubs: this version was named Lerche ("lark"). The final batch of 25 aircraft was donated to the Swiss Aero Club, which had Ateliers de Précision Morand (APM) re-engine them with the Lycoming IO-320-E2A and Hoffman propellers, on condition that they be sold only to Swiss buyers.

A-63 illustrates that path: struck off charge on 31 December 1971, it received a Lycoming IO-320-E2A, entered the civil register on 22 May 1973 as HB-UUH, crashed at Dittingen on 1 September 1973, was rebuilt and returned to the register on 16 May 2000; in 2009 it changed hands. A-68 passed to the Swiss Aero Club and has carried the registration HB-UUT since 1977; it still had an original 1939 Hirth of 105 hp until it was badly damaged on approach to Grenchen on 5 July 2006. Dornier-Werke also built at Altenrhein the Bü 133 Jungmeister, a different Bücker model.