Bücker Bü 131 Jungmann CASA 1.131

CASA 1.131 is the factory designation given by Construcciones Aeronáuticas, S.A. (CASA) to the Bücker Bü 131 Jungmann licence-built in Spain. This entry covers the first generation of that production, the aircraft fitted with the German Hirth HM 504 engine, which some sources call the CASA 1131H; the later versions with the Spanish Tigre engine, the CASA 1.131E and CASA 1.131L, have their own entries and their figures are not included here.

The Jungmann reached Spain before local manufacture began. According to the Spanish-language Wikipedia, the first three Bü 131s arrived with the Condor Legion in November 1936 and Germany eventually supplied up to ninety-five aircraft; the Bücker history translated by Steve Beaver says the Nationalist forces received more than 100 from the German factory. They were first assigned to the elementary flying school at El Copero, near Seville, which had been set up because Tablada airfield was congested, and later to the other training centres. The type proved so satisfactory that, before the civil war was over, licence production was decided upon.

Manufacture was assigned to CASA's plant at Puntales, near Cádiz, which since 1927 had built Dornier Wal flying boats. According to Defensa.com, the first aircraft ordered were designated CASA 1131H and began to be built in 1938; the first batch of 50 was delivered between 1940 and 1941 with the 100 hp Hirth HM.504 engine, and three further series of 50 aircraft were then ordered. The early dates differ between sources: Beaver places the appearance of the first Spanish-built examples in 1938, the Spanish-language Wikipedia and the Fundación Aérea de la Comunidad Valenciana give 14 March 1941 as the first flight of the CASA 1.131, and Defensa.com states that the first aircraft was delivered on 20 May 1940.

In Spanish Air Force numbering the aircraft was identified as the E.3B, and each airframe received an individual E.3B number; Defensa.com explains that the Bückers entered the newly created Ejército del Aire as EE.3 (Escuela Elemental 3, elementary school) and later under the E.3 notation. The four Hirth-engined series add up to two hundred aircraft: the Spanish-language Wikipedia states that two hundred were built with the German engine before the switch to the Tigre, Beaver places the engine change 'from the 201st aircraft onwards', and Beaver also describes the later 1.131E as an improvement of the Bü 131 D-2, of which CASA had previously built 200 under licence.

Technically the CASA 1.131 was the German Jungmann: a two-seat tandem open-cockpit biplane with a steel-tube fuselage, fabric-covered wooden wings and fixed landing gear. Skytamer's data for the CASA-built version give a 7.4 m span, 6.62 m length, 2.25 m height, 13.5 m² wing area, 380 kg empty and 670 kg gross weight, with the four-cylinder inverted Hirth HM 504 of 75 kW (100 hp), a two-bladed fixed-pitch propeller, a maximum speed of 183 km/h, a cruising speed of 170 km/h and a range of 650 km. These are the same figures published for the German Bü 131B, so they should be read as type data rather than measurements specific to the Spanish series. Defensa.com notes that gross weight rose from 670 kg to 720 kg with the Tigre version, which supports the 670 kg figure for the Hirth-engined aircraft.

The engine brought the Hirth series to an end. With German engines no longer available, the new aircraft were fitted with the 125 hp Elizalde (later ENMASA) Tigre G-IV A, and the aircraft built this way were designated CASA 1.131E. According to Defensa.com the first Tigre series was ordered in 1948, and the Spanish-language Wikipedia says deliveries of Tigre-powered aircraft began in 1950. Beaver adds that all existing older versions were later brought up to 1.131E standard; Defensa.com mentions 30 of the first aircraft being re-engined with the Tigre, while the Spanish-language Wikipedia speaks of thirty original Bückers converted. The CASA Jungmann Research Team report (Karli, Rivas and Comstedt, 2023) explains that airframes converted from Hirth to Tigre carry two manufacturer's plates on the rear fuselage tube, and its list of survivors includes airframes with low E.3B numbers and two dates, such as E.3B-153 (now G-BPTS, 1943/57) and E.3B-198 (now EC-MCP, 1944/57).

The Hirth-engined CASA 1.131s served in the post-war elementary schools: besides El Copero and Las Bardocas, the air force used Alcantarilla air base (Murcia), a new school at El Palmar and, from 1945, the Academia General del Aire at San Javier. In those years of isolation, Defensa.com says, the little Bückers did almost everything, including night flying. CASA's overall production, which lasted into the 1960s, made the Jungmann the most numerous aircraft in the Spanish Air Force, which kept it as its primary basic trainer until 1968. Total production figures vary between sources and cover all versions, not just the Hirth-engined series.

Not found in the sources consulted: the construction number and military serial of the first CASA 1.131, the year-by-year breakdown of the 200 aircraft, delivery dates for the second to fourth series, and the retirement date of the last aircraft still fitted with the Hirth engine.