The Heinkel HD 23 was a carrier-borne fighter biplane designed in Germany at Heinkel Flugzeugwerke in the 1920s, for export to Japan. Two examples were delivered to Aichi as pattern aircraft in 1927. Aichi added rudimentary flotation capability and built two further examples as the Type H Carrier Fighter, but full-scale production was not started.
The Albatros L 65 was a German two-seat reconnaissance fighter biplane first flown in 1925.
The Hütter Hü 211 was a German prototype long-range reconnaissance and heavy night fighter commissioned by the Reich Air Ministry in late 1944. The project stopped after an air raid destroyed the prototypes before they were finished.
The Arado SD I was a fighter biplane, developed in Germany in the 1920s. It was intended to equip the clandestine air force that Germany was assembling at Lipetsk. The layout owed something to designer Walter Rethel's time with Fokker. Of conventional configuration, the SD I featured a welded steel tube frame, metal-covered ahead of the cockpit, and fabric-covered aft of it. The wooden sesquiplane wings were braced with N-type interplane struts, without any wires - a typical Fokker feature.
The Arado SD II was a fighter biplane developed in Germany in the 1920s. Like the preceding SD I, it was intended to equip the clandestine air force that Germany was assembling at Lipetsk and was hoped to overcome the shortcomings of that type. Although it shared the same basic configuration, the SD II was an all-new design. A considerably larger and heavier aircraft, it had wings of less stagger, braced with conventional wires. The landing gear and tailplane were of far stronger construction.
The Arado SSD I was a biplane fighter seaplane developed in Germany in 1930, intended to be launched from catapults on warships. This was an all-new design from Walter Rethel, sharing nothing with his other fighter designs for Arado of the late 1920s. It was a conventional unequal-span, staggered biplane, with the slightly gulled top wing attached to the upper fuselage. It was equipped with a single, large float under the fuselage and two outrigger floats near the wingtips. After evaluation at Travemünde, the floats were removed and a simple, wheeled undercarriage was fitted for competitive evaluation with the Heinkel HD 38 at Lipetsk. The Heinkel was selected, and the SSD I was relegated to trainer duties with the LVS in 1932.
The Fokker D.XIII was a fighter aircraft produced in the Netherlands in the mid-1920s. It was a development of the Fokker D.XI with a new powerplant and considerably refined aerodynamics, and had been designed to meet the requirements of the clandestine flying school operated by the German Army at Lipetsk in the Soviet Union. Like its predecessor, it was a conventional single-bay sesquiplane with staggered wings braced by V-struts. The pilot sat in an open cockpit and the undercarriage was of fixed, tailskid type. The wings were made of wood and skinned with plywood, and the fuselage was built up of welded steel tube with fabric covering.
The Gotha Go 149 was a military aircraft developed in Germany in the mid-1930s for training fighter pilots. It was a conventional low-wing cantilever monoplane with tailwheel undercarriage, the main units of which retracted inwards. The wing was wooden, while the monocoque fuselage was metal. Two prototypes were constructed, and an armed version was also proposed as a light home-defence fighter (Heimatschutzjäger) armed with two 7.92 mm (.312 in) MG 17 machine guns, but the Luftwaffe did not purchase either version of the design, and no further examples were built.
The Heinkel HD 17 was a military reconnaissance aircraft produced in Germany in the late 1920s.
The Heinkel HD 21 was a trainer built in Germany during the 1920s. It was a conventional single-bay biplane with staggered wings braced with N-type interplane struts. The main units of the fixed, tailskid undercarriage were linked by a cross-axle, and the aircraft had three open cockpits in tandem, although one of these was typically faired over. The HD 29 of 1925 was essentially similar, but was purely a two-seater.
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 36 was a trainer developed in Germany in the 1920s at the request of the Swedish Air Force, which was in search of a new trainer aircraft. The newly formed air force had previously evaluated the HD 35, found it to be underpowered, and asked Heinkel to address this problem. Heinkel's response was a development of the HD 35 modified to use the Mercedes D.III engine instead. The HD 36 also dispensed with the third cockpit that had been a feature of the HD 35 and HD 21 before it, but otherwise the design was largely the same. The single example built by Heinkel was tested by the Air Force, and found still not quite satisfactory, was modified by CFM until the problems had been largely eliminated. Once this had happened, CFM built two batches of 10 aircraft, delivering them in 1928 and 1930 as the Sk 6.
The Heinkel HD 26 was a reconnaissance seaplane developed in Germany during the 1920s for production in Japan. It was intended as a smaller, single-seat counterpart to the HD 25, to provide a spotter aircraft for warships, to take off from a short ramp. The HD 26 was a conventional biplane with staggered wings, twin float undercarriage, and an open cockpit.
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 He 49 was a German single-bay, single-seat biplane of mixed construction armed with two machine guns. Four variants were made, the He 49a, He 49b, He 49c and He 49d.
The Junkers J 21 was a reconnaissance aircraft designed in Germany in the early 1920s and produced in the Soviet Union at the Junkers plant at Fili for use by the Soviet Air Force.
The Hanriot HD.7 was a French fighter prototype of the 1910s.
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 Albatros L 76 Aeolus was a military reconnaissance aircraft built by Albatros Flugzeugwerke in 1927. The plane had wooden dual-spar wings with plywood skins supported by N-type struts and a fabric-covered fuselage made of welded steel tubing. The aircraft was used for testing, as well as the training of the Soviet Air Force. It was difficult to fly, and killed many people, including Emil Thuy, who crashed near Smolensk on June 11, 1930, and Paul Jeschonnek, who crashed near Berlin on June 13, 1929. As a result, it had to be improved, leading to the production of the Albatros L 77v, designed by Ernst Heinkel Flugzeugwerke.
The Heinkel HD 34 was a reconnaissance bomber built in Germany in the late 1920s.
