Heinkel HD 37

Heinkel

Industry	Aerospace
Founded	1920s
Headquarters	Germany

The Heinkel HD 37 was a fighter aircraft originally designed in Germany during the late 1920s but manufactured within the USSR to serve the Soviet Air Force. This compact biplane featured a single-bay wing configuration with staggered wings of differing spans, supported by N-shaped interplane struts. The pilot operated from an open cockpit, while the conventional tailskid undercarriage incorporated main landing gear units connected by a cross-axle.

Design and development

Initially developed for the covert air force training program of the Reichswehr at Lipetsk, the HD 37 was ultimately declined by German authorities, who opted instead to acquire the Fokker D.XIII.

Facing an urgent need to replace its aging primary fighter, the Polikarpov I-5, the Soviet Air Force found no suitable domestic successor available. Upon request, Heinkel offered the HD 37 as a potential solution, and two prototypes were transported to Moscow for evaluation in early 1928. Test flights yielded mixed feedback; although the fundamental design appeared viable, Soviet pilots identified numerous handling shortcomings. Consequently, Heinkel received an extensive list of required modifications. The company responded with the development of the Heinkel HD 43, but Soviet test pilots expressed even greater dissatisfaction with this model compared to the HD 37. By late 1929, focus returned to refining the earlier design. In early 1930, the Soviet government secured a three-year license to produce the aircraft domestically, compensating Heinkel with 150,000 Marks. Production responsibilities were assigned to TsKB (Tsentrahl'noye konstrooktorskoye byuro - central design bureau) and Polikarpov, who designated the aircraft as I-7.

Incorporating many enhancements derived from the HD 43 alongside additional adjustments, the I-7's initial flight tests in summer 1931 showed promising results. Despite ongoing challenges sourcing materials, a total of 131 units were manufactured by 1934. Most of these aircraft were briefly deployed within units stationed in Belarus, yet by the time production concluded, the model had already become outdated.

Variants

HD 37a

A single unit was manufactured.

HD 37b

Only one example was produced.

HD 37c

This third iteration, constructed under licence by Polikarpov following modifications by TsKB (Tsentrahl'noye konstrooktorskoye byuro – central design bureau), saw over 132 units built.

Polikarpov I-7

The HD 37c model, licence-produced and modified by TsKB, featured a Mikulin M-17F engine, equipped with PV-1 machine guns and Soviet radio systems.

Operators

Template:USSR

• Soviet Air Force