Heinkel HD 26

Heinkel HD 26
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Type:	Airborne fighter aircraft
Design country:	German Empire
Manufacturer:	Heinkel
First flight:	1925
Commissioning:	-
Production time:	1925
Number of pieces:	2

The Heinkel HD 26 was a German airborne fighter from the 1920s developed by Ernst Heinkel Flugzeugwerke in Warnemünde on behalf of the Japanese Navy . The abbreviation HD stands for Heinkel Doppeldecker .

history

In early 1925, the Japanese naval attaché in Berlin, Kojima, commissioned Ernst Heinkel to develop two types, a reconnaissance aircraft and a fighter with a floating mechanism , which were supposed to take off and operate from ships. The construction of a starting device necessary for this was also included in the requirement. In the event of a successful test, series production under a Japanese license was planned. As a reaction, Heinkel developed the HD 25 reconnaissance aircraft and the somewhat smaller HD 26 model, designed as a hunter, in what was known as the "Heinkel Tempo", which is typical for him, in the first half of 1925. Two prototypes were made of both types built. The two HD 26s with the serial numbers 224 and 225 were designed as conventional double-deckers and were powered by an HS-42 8Fb - V-engine with 300 hp. For the start of the ship's deck, Heinkel constructed a special, 21.5 m long and 3 ° sloping runway made of wood, which was successfully tested on the Warnower Breitling , which offered the necessary wind conditions, near Heinkel's main plant in Warnemünde from June 1925. The aircraft was lifted onto a take-off vehicle on it and then took off under its own power with maximum power against the wind. According to the calculations, an aircraft with a takeoff mass of 2,400 kg was able to take off in this way with a prevailing headwind of 7 m / s. This assumption was confirmed with the HD 25; the tests with the much lighter HD 26 were also successful, as expected. When operating on board, the required wind speed should be generated by turning the ship into the wind. This runway can be viewed as the forerunner of the ship's own aircraft catapult , the first type of which, the K-1, was also developed by Heinkel and successfully tested in 1927.

After the start attempts and flight tests were completed, the HD 26s were shipped to Japan together with the two HD 25s. At the same time, Ernst Heinkel, his chief designer Karl Schwärzler and test pilot Carl Clemens Bücker received an invitation to Japan as a thank you for the quick implementation, which, in addition to the presentation of aircraft and launch equipment, also for a series of lectures on German aircraft construction in Japan and for visits to Japanese and US American aircraft factories should be used. Heinkel agreed and at the beginning of August 1925 drove with Schwärzler by ship via the USA to Japan, Bücker traveled via the Soviet Union on the Trans-Siberian Railway . There the demonstrations took place from the battleship Nagato and the heavy cruiser Furutaka , where the runways had been set up for this purpose. The Japanese side was satisfied and, as announced, acquired the license rights for the HD 25 and HD 26 including the launching device. The four aircraft were taken over by the Aichi Tokei Denki KK and tested further, with the HD 26 being referred to as the “Type 2 single-seat sea reconnaissance aircraft” or the “Little Heinkel sea reconnaissance aircraft”. One of the two HD 26s was tested with a more powerful British 420 HP radial engine Jupiter VI , built under license by Nakajima . With this drive, the aircraft reached a top speed of 211 km / h and the climb time to 3000 m in 7.5 minutes was reduced by almost half compared to the HS-42 with a take-off mass of 1500 kg. Nevertheless, no further copies of the HD 26 were built, in contrast to the HD 25, of which Aichi launched a smaller series.

construction

The HD 25 was a semi- self-supporting , einstieliger biplane in wood construction . The fuselage had a rectangular cross-section, arched in the upper area and tapering backwards into a vertical cutting edge. The framework consisted of four Spruce - longitudinal beams , light wooden transverse frames and supporting Sperrholzbeplankung . The engine was installed in an easily removable tubular steel frame , which was clad with aluminum sheets up to the fire bulkhead. This was located between the engine and the fuel tank and was made of light metal. Another tank was housed in the middle section of the upper wing.

The three-part upper wing and the lower wing were staggered and consisted of two box spars , spruce straps , plywood webs and wooden ribs . They were connected to each other by V-struts and to the trunk by N-posts. With the exception of the undersides of the wing between the spars, which were covered with plywood, all surfaces were covered with fabric. The upper outer wing and the lower wing were attached with hook joints and could therefore be easily dismantled by loosening a stem bolt . Only the upper wing had ailerons .

The tail unit of the HD 25 consisted of wooden fins with plywood planking , whereby the side and keel fin were self-supporting, but the horizontal fin was supported by two struts on the fuselage. All rudders had an aerodynamic compensation and consisted of a tubular steel frame with fabric covering. The aircraft had two single-stage wooden floats that were flat-bottomed in the front and keeled in the rear . They were connected to the hull by W struts and to each other by longitudinal struts and were designed in such a way that they could be detached from the float frame in a very short time. Several watertight compartments were located inside them, which enabled a reserve buoyancy of 84% if necessary.

Technical specifications

Parameter	Data
crew	1
span	11.8 m
length	8.3 m
height	3.53 m
Wing area	37.84 m²
Preparation mass	1100 kg
Payload	577 kg
Takeoff mass	1677 kg
drive	a water-cooled eight-cylinder - V-engine Hispano-Suiza 8 Fb with zweiblättriger Holzluftschraube
Starting power nominal power continuous power	345 PS (254 kW) 300 PS (221 kW) 270 PS (199 kW)
Fuel volume	600 l
Top speed	185 km / h
Landing speed	77 km / h
Rate of climb	4.2 m / s
Rise time	4.0 min at 1000 m altitude 8.5 min at 2000 m altitude 14.0 min at 3000 m altitude
Service ceiling	5200 m
Range	900 km
Flight duration	5.0 h

literature

• Volker Koos: Ernst Heinkel Flugzeugwerke 1922–1932. Heel, Königswinter 2006, ISBN 3-89880-502-6 , pp. 68/69.
• Volker Koos: Ernst Heinkel. From the biplane to the jet engine. Delius Klasing, Bielefeld 2007, ISBN 978-3-7688-1906-0 , pp. 60/61.
• Ulrich Israel: “Flight deck clear!” German carrier aircraft until 1945. In: Fliegerrevue Extra No. 2, Möller, Berlin 2003 p. 44/45.
• Helmut Stützer: The German military aircraft 1919–1934. E. S. Mittler & Sohn, Herford 1984, ISBN 3-8132-0184-8 , pp. 36, 140 and 183.