Heinkel HD 25

Heinkel HD 25
HD 25 of the Japanese Navy
Type:	Maritime patrol
Design country:	German Empire
Manufacturer:	Heinkel / Aichi
First flight:	1925
Commissioning:	1926
Production time:	1925-1928
Number of pieces:	2 HD 25 16 Aichi type 2

The Heinkel HD 25 was a German airborne reconnaissance aircraft from the 1920s. The abbreviation HD stands for Heinkel Doppeldecker .

history

At the beginning of 1925, Ernst Heinkel received an order from the Japanese naval attaché in Berlin to develop two types of airborne aircraft, a two-seater reconnaissance aircraft and a single-seater fighter, along with an associated device for launching the aircraft from a ship. If it was successfully tested, it was offered the prospect of licensed series production in Japan. Heinkel then developed the HD 25 and the somewhat smaller HD 26 in the first half of 1925 at the record speed that was typical for him at that time . Two prototypes of both were built, the HD 25 were given the serial numbers 222 and 223. A special, 21.5 m long and 3 ° sloping runway made of wood was built for the deck launch. The aircraft was lifted onto a take-off car on it and then took off under its own power with maximum power against the wind. The construction was built on the Warnower Breitling near the Heinkelschen parent plant in Warnemünde, which offers the necessary wind conditions, and was successfully tested from June 1925. This enabled the HD 25 to take off successfully at a wind speed of 7 m / s with a take-off mass of up to 2400 kg. In the intended on-board operation, the ship should turn into the wind and create the required starting conditions through its own speed. 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 satisfactory conclusion of the tests, the two HD 25s and the HD 26 were shipped to Japan by ship. At the same time, Ernst Heinkel, chief designer Karl Schwärzler and test pilot Carl Clemens Bücker received an invitation to a presentation of the launching device and the aircraft in Japan, which was combined with a tour of Japanese and US aircraft factories and lectures on German aircraft construction in Japan. Heinkel and Schwärzler took advantage of this option and at the beginning of August 1925 went by ship via the USA to Japan, while Bücker chose the route with the Trans-Siberian Railway through the Soviet Union. When he arrived in Japan, he demonstrated the aircraft to the responsible representatives in the presence of Heinkel and Schwärzler, then, as was also the case in Germany, first with a launch device installed on land. However, the 222 broke due to a minor design flaw in its holding device. However, since this could be recognized and easily remedied, Bücker was able to continue the flights with the 223 and also to complete the scheduled take-offs. For this purpose, the runway was mounted on a turret of the battleship Nagato . The Japanese side was satisfied and, as announced, acquired the license rights for the HD 25 including the launch device. Series production began in 1926 at Aichi and ended two years later after 16 units, which were put into service with the Japanese Navy under the name Aichi Type 2 two-seater sea reconnaissance aircraft or also the Great Heinkel sea reconnaissance aircraft . The runway was successfully tested on the ships Furutaka and Nagara , but ultimately not put into production because Japan had meanwhile decided to use catapults on ships, to which Heinkel responded with appropriate developments, as already indicated. Three of the Japanese licensed aircraft were handed over to civilian owners in 1930, who converted them for passenger transport. One with the registration number J-BCOH was given an additional seat, while the other two ( J-BBEI and J-BBFI ) were given a cabin for three passengers, leaving out the observer 's stand . They were referred to as the Aichi Type 2 transport aircraft .

construction

The HD 25 is a semi- self-supporting , einstieliger biplane in wood construction .

Fuselage : The fuselage has a rectangular cross-section, arched in the upper area and tapering backwards into a vertical cutting edge. The frame consists of four Spruce longitudinal spars , light wooden transverse frames and load-bearing plywood planking . The firewall located between the engine and the tank is made of light metal. The engine mount is formed by a tubular steel frame that is clad with aluminum sheets up to the fire bulkhead.

Structure : The three-part upper wing and the lower wing are strongly staggered, equipped with two box spars and provided with spruce straps, plywood webs and wooden ribs. They are 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 are covered with plywood, all surfaces are covered with fabric. The upper outer wing and the lower wing are attached with hook joints and can therefore be easily dismantled by loosening a stem bolt. Only the upper wing has ailerons .

Tail unit : The fins of the tail unit consist of a wooden frame with plywood planking , with the side and keel fin being self-supporting, but the horizontal fin is supported by two struts on the fuselage. All oars are aerodynamically balanced and consist of a tubular steel frame with fabric covering.

Floating mechanism : The HD 25 has two single-stage floats made of wood and flat-bottomed in the front area and keeled in the rear . Several watertight compartments are integrated in them, which enable a reserve buoyancy of 75%. They are connected to the fuselage by W struts and to each other by longitudinal struts.

Technical specifications

Parameter	Data
crew	2
span	above 14.85 m below 14.15 m
length	9.6 m
height	4.46 m
Wing area	55.8 m²
Empty mass	1550 kg
Payload	950 kg
Takeoff mass	2500 kg
Engine	a liquid-cooled twelve-cylinder W-engine Napier Lion IV
Starting performance Combat and climbing performance Continuous performance	500 PS (368 kW) 450 PS (331 kW) on the ground 438 PS (322 kW) on the ground
Top speed	190 km / h near the ground
Landing speed	77 km / h
Rise time	3 min, 2 s at 1000 m 6 m, 11 s at 2000 m
Summit height	5800 m with maximum payload
Range	normal 800 km maximum 920 km
Flight duration	4.5 h
Armament	a movable 7.7 mm machine gun in the observer position four 30 kg bombs at lower wing stations

literature

• Volker Koos: Ernst Heinkel Flugzeugwerke 1922–1932 . Heel, Königswinter 2006, ISBN 3-89880-502-6 , p. 66/67 .
• Volker Koos: Ernst Heinkel . From the biplane to the jet engine. Delius Klasing, Bielefeld 2007, ISBN 978-3-7688-1906-0 , p. 60/61 .
• Ulrich Israel: “Flight deck clear!” German carrier aircraft until 1945. In: Fliegerrevue Extra . No. 2 . Möller, 2003, ISSN  0941-889X , p. 44/45 .
• Helmut Stützer: The German military aircraft 1919–1934 . E. S. Mittler & Sohn, Herford 1984, ISBN 3-8132-0184-8 , p. 35, 139 and 183 .

Web links

Commons : Heinkel HD 25  - collection of images, videos and audio files