The Heinkel He 45 was a light bomber produced in Germany in the early 1930s, one of the first aircraft adopted by the newly formed Luftwaffe. Its appearance was that of a conventional biplane and included seating for pilot and gunner in tandem, open cockpits. Developed in parallel with the He 46, it appeared in 1931 as a general-purpose biplane and was employed mainly as a trainer, but was also used by the Luftwaffe for reconnaissance and light bombing duties. Production of this plane totalled 512 aircraft, including those built under licence by Gotha, Focke-Wulf, and BFW.
The Albatros L 75 Ass was a German trainer biplane of the 1920s. Of conventional configuration, it seated the pilot and instructor in separate, open cockpits. The wings were single-bay, equal-span, and had a slight stagger. Production continued after Albatros was absorbed by Focke-Wulf.
The Arado W 2 was a two-seat twin-engine seaplane trainer developed for the DVS in 1928. It was a cantilever monoplane with a fabric-covered steel tube fuselage that accommodated the pilot and instructor in tandem open cockpits. The undercarriage consisted of two pontoons carried on steel struts.
The Breda A.9 was a biplane trainer produced in Italy in 1928 for the Regia Aeronautica. Conventional in design, it featured a single-bay, unstaggered wing cellule and fixed tailskid undercarriage. The student and instructor sat in tandem, open cockpits. A slightly smaller version, designated A.9-bis was developed for use in Italy's aeroclubs.
The Heinkel HD 42 50, later designated the Heinkel He 42 was a German two-seat biplane seaplane originally designed for the Deutsche Verkehrsfliegerschule, and later built for the German Luftwaffe. The aircraft was used until the end of World War II as a trainer for maritime pilots.
The Focke-Wulf S 2 was a trainer aircraft built in Germany in the late 1920s. It was a conventional parasol-wing monoplane with fixed tailskid undercarriage. The pilot and instructor sat side by side in an open cockpit. Only a single example was built.
The Fokker S.IV was a military trainer aircraft produced in the Netherlands in the mid-1920s. It was a conventional, single-bay biplane with staggered wings of unequal span braced with N-struts, essentially a radial-engined development of the S.III. The pilot and instructor sat in tandem, open cockpits and the undercarriage was of fixed, tailskid type with a cross-axle between the main units. The Royal Netherlands Army Aviation Group purchased 30 examples and used them right up to the German invasion of the Netherlands in 1940. On 14 May that year, a few surviving S.IVs escaped to France alongside some S.IX trainers, but never flew again.
The Hanriot H.41 was a military trainer aircraft produced in France in the 1920s. It was a further development in the family of aircraft that had commenced with the HD.14 in 1920, and incorporated a number of design features that had been developed for other members of that family. Like those other aircraft, however, it was a conventional, two-bay biplane with unstaggered wings of equal span.
The Heinkel HD 17 was a military reconnaissance aircraft produced in Germany in the late 1920s.
The Heinkel HD 22 was a trainer designed in Germany during the 1920s. It was a conventional single-bay biplane with staggered wings braced with N-type interplane struts. The pilot and instructor sat in tandem, open cockpits, and the main units of the fixed, tailskid undercarriage were linked by a cross-axle.
The Heinkel HD 35 was a trainer developed in Germany in the 1920s. It was a conventional single-bay biplane with staggered wings of equal span. The design was based on that of the HD 21, and like that aircraft, it had three open cockpits in tandem, although the most forward of these was usually faired over when not in use.
The Heinkel HD 37 was a fighter aircraft, designed in Germany in the late 1920s, but produced in the USSR for Soviet Air Force service. It was a compact, single-bay biplane with staggered wings of unequal span, braced by N-type interplane struts. The pilot sat in an open cockpit, and the main units of the tailskid undercarriage were linked by a cross-axle.
The Heinkel HD 40 was a special-purpose cargo aircraft developed in Germany in the 1920s to distribute the Berlin newspaper B.Z.. The success of Heinkel's previous design for the publisher, the HD 39, led to the order of a similar aircraft with greater capacity, and Heinkel responded with a machine of similar layout, but considerably enlarged. Like the HD 39, it was a conventional single-bay biplane with staggered wings of unequal span, and a fuselage that nearly filled the interplane gap. The pilot sat in an open cockpit, and the undercarriage was of fixed, tailskid type with divided main units. The wings were of wooden construction, while the fuselage was built from welded steel tube skinned in plywood.
The Aichi E3A was a reconnaissance seaplane developed in Germany as the Heinkel HD 56 to operate from warships of the Imperial Japanese Navy, which designated it the Type 90-1 Reconnaissance Seaplane. It was a conventional single-bay biplane with staggered wings braced by N-type interplane struts. The pilot and gunner sat in tandem, open cockpits.
The Morane-Saulnier MS.138 was a military trainer aircraft produced in France in the late 1920s,
The Heinkel Doppeldecker 43 was a prototype German fighter aircraft of the 1930s. A single-engined, single-seat biplane, the HD 43 was designed to meet a secret German Reichswehr requirement for a single-seat fighter. It had two-bay wooden wings with a steel-tube fuselage, and was powered by a 750 hp (600 kW) BMW VI engine. The single prototype flew in 1931.
The PWS 3 was a Polish sport aircraft, developed in 1927 by PWS, which remained a prototype.
The Heinkel HD 19 W was a biplane seaplane fighter developed by Ernst Heinkel Flugzeugwerke.
The Heinkel HD 27 was a mail-carrying transport built in Germany in the 1920s.
The Heinkel HD 34 was a reconnaissance bomber built in Germany in the late 1920s.
