Junkers Ju 52/3m

Development

Origins

The Ju 52 was designed starting in 1925, in two versions, a single engine version for freight transport (Ju-52/1m) and trimotor passenger version for 17 (Ju 52/3m), both as civilian versions. Both designs were overseen by the German aeronautical engineer Ernst Zindel, the design team being based at the Junkers works at Dessau. A driving force in the project was the commercial prospects presented by the German airline Deutsche Luft Hansa. Work on turning the design into a prototype started in 1928. The Ju 52 had numerous similarities to several previous Junkers aircraft, such as the previous Junkers W 33, noted for its crossing of the Atlantic in 1928, and the smaller Junkers W 34. Sharing features included the distinctive corrugated duraluminum exterior. According to aviation author J. Richard Smith, the Ju 52 directly drew upon the company's First World War-era Junkers J 1 - the world's first all-metal aeroplane.

On 13 October 1930, the first prototype, designated Ju 52ba, performed the type's maiden flight; it was initially powered by a single Junkers-built liquid-cooled V-12 engine, capable of generating up to 590 kW (800 PS). During the aircraft's extensive trials, it was reengined with a 555 kW (755 PS) BMW IV water-cooled inline-6 powerplant. The second prototype, designated Ju 52de, featured an increased wing span and was powered by the BMW IV engine at first; it was soon reengined with the 560 kW (750 hp) 14-cylinder twin-row air-cooled radial Armstrong Siddeley Leopard and re-designated Ju 52di. Later on, the Ju 52di was again reengined with the 550 kW (750 PS) Junkers Jumo 204 air-cooled inverted inline-6, after which it was re-designated Ju 52do. The third prototype, designated Ju 52ce, had a strengthened structure, a modified leading edge, and was fitted with both a wheeled and float undercarriages.

During May 1931, one of the prototypes, designated Ju 52cai, was written off after a crash. While these initial aircraft had been powered by a single engine, Junkers decided to develop the Ju 52 into a trimotor configuration. Accordingly, the Ju 52/3m (drei motoren—"three engines") was developed, being powered by an arrangement of three radial engines. According to Smith, the earliest known Ju 52/3m was delivered to Bolivian airline Lloyd Aéreo Boliviano during 1932. During its initial production years, airlines were the type's most common customers. By the mid-1930s, the Ju 52/3mce and Ju 52/3fe, were the two primary production variants, both being powered by the BMW 132 radial engine.

Militarized versions

During 1934, work commenced on a militarised model of the Ju 52/3m, designated Ju 52/3mg3e, on behalf of the then-secret Luftwaffe. This model could function as a medium bomber, being furnished with a pair of machine gun positions (an open dorsal position and a ventral "dustbin" position lowered by a hand crank), each with single machine guns and operated by a crew of four. Between 1934 and 1935, a total of 450 Ju 52/3mg3e aircraft were delivered to the Luftwaffe.

Wartime and postwar

Numerous improved models would be introduced prior to and during the Second World War. The dominant production model was the Ju 52/3mg7e, featuring advances such as an autopilot, enlarged doors to the cabin, and other general enhancements. It was configured as a pure transport aircraft, being capable of carrying up to 18 fully-equipped troops. Defensive armaments comprised a dorsal-mounted 13 mm MG 131 machine gun and a pair of beam 7.9mm MG 15 machine guns. Successive models saw other improvements, such as revised glazing, newer engines, undercarriage strengthening, and increased take-off weight. The final wartime model to be developed, designated Ju 52/3mg14e, featured improved armour protection for the pilot and a bolstered defensive armament.

From mid-1943 onwards, the Luftwaffe began to make less use of the Ju 52, interest having waned in the type. German officials were interested in procuring a successor to the type; at one stage, the Reich Air Ministry showed enthusiasm for the Junkers Ju 352, a larger transport aircraft somewhat resembling the Ju 52. Actions were taken to convert Junkers' Ju 52 production lines to instead manufacture Ju 352s; however, the conflict's end in May 1945 led to the effort being abandoned in an unfinished state. As such, German production of the Ju 52 was terminated during 1944; Smith claims that a total of 3,234 aircraft of various models were constructed during the conflict.

In the postwar era, manufacture of the Ju 52 resumed, albeit in foreign countries. It was constructed in France by Avions Amiot as the Amiot AAC.1 Toucan; it was also produced in Spain by Construcciones Aeronáuticas SA (CASA) as the CASA 352. A handful of captured wartime aircraft were also rebuilt by Short Brothers of Northern Ireland for civilian service.