Heinkel HD 23

Heinkel HD 23
Type:	Airborne fighter aircraft
Design country:	German Empire
Manufacturer:	Heinkel
First flight:	1926
Commissioning:	-
Production time:	1926
Number of pieces:	1 (+ possibly 2 Japanese replicas)

The Heinkel HD 23 is the first fighter in Germany specially designed for use on ships and was created in the mid-1920s. The abbreviation HD stands for Heinkel Doppeldecker .

history

In April 1926, the Japanese Navy turned to the companies Aichi , Mitsubishi and Nakajima to develop a new carrier fighter to replace the Type 10 that had been in use until then . The desired performance parameters were extremely demanding. Particularly difficult to meet was the requirement of a take-off distance of only 10 meters, which should be enough to get the aircraft into the air with a headwind of 20 knots (about 37 km / h) and without jump start. This point was due to the design of the first two Japanese aircraft carriers Kaga and Akagi at the time, which, in addition to the normal main deck used by the bombers stationed on board, also included one or two sub-decks below, which were intended for the fighter launch and had a runway from 10 to 15 meters. Aichi himself did not take part in this order, but passed it on to Ernst Heinkel, taking into account the good experiences made with the Heinkel works in Warnemünde in the previous cooperation . He reacted with the speed that was typical for him and appreciated by his business partners and developed the HD 23 in the same year. For the intended use of the carrier , the model was equipped with some details that were not generally common for that time. The hull was given an unusual boat shape, which should facilitate emergency landings on the water. For this reason it was also possible to lock the two-bladed propeller in a horizontal position. In order to ensure a long buoyancy, both the fuselage and the wing center section were made waterproof and provided with floating tanks. A rollover during a water landing should be avoided by a main landing gear designed to be released.

The first and only prototype with the serial number 257 was completed in 1926. It received a Hispano-Suiza engine with 450 hp, but this turned out to be too weak during the tests that began shortly afterwards, as the many innovations made the HD 23 heavier than planned, which is why it relied on the newly developed BMW-VI Engine with 660 hp was used. The tests carried out from 1926 onwards confirmed the suitability of some innovations. For example, the spoilers built into the leading edges of the wings were able to cause a targeted stall during the landing phase and shorten the lift-out distance by 25% from 160 m to around 120 m. The HD 23 reached a speed of almost 250 km / h during testing, which made it the fastest German aircraft at the time. A curious accompanying phenomenon was a police order for "gross nonsense and deafening noise", which was imposed on the Heinkel pilot Wolfram Dick for his speed measurement flights carried out on February 3, 1927 in Warnemünde. The ability to swim was also demonstrated on the Breitling's water , but only with the engine removed, the weight of which was simulated by sandbags. The dropping of the landing gear was also successfully tested on the HD 23 suspended from the ceiling in the workshop, one day before the Japanese acceptance commission was due to arrive in Warnemünde. However, there was a momentous incident when a tether came loose and the aircraft hit the ground and broke in the middle of the fuselage. The repair, which was then carried out under stressful time pressure, was completed on time and the sample was presented to the Japanese representatives the next day. In August 1927, the HD 23 reached Japan by ship. There it was also subjected to a number of tests under the designation Test Carrier Fighter Airplane Type H , which were generally favorable, but also revealed some defects. The Japanese side complained about the insufficient maneuverability and a certain top-heaviness. The high weight mentioned at the beginning also spoke against the HD 23. Although Aichi is said to have produced two Type Hs , it ultimately remained at the prototype stage. Instead, the Navy opted for the Nakajima Type 3 based on the British Gloster Gambet .

construction

The HD 23 is a einstieliger, staggered biplane in wood construction .

Hull : The hull consists of a wooden frame with plywood planking with an underside designed as a keeled boat hull. Swimming cells are installed inside, which should enable the aircraft to swim for 24 hours. There are side-mounted coolers ( ear coolers ) behind the cockpit , as conventional attachment to the forehead or underside of the bow is not possible due to the boat design. There are four catapult fittings on the fuselage for use with the carrier.

Structure : The wings consist of a wooden frame with two box spars and plywood planking, whereby the lower wing is watertight and has floating cells in the middle part. The upper wing is in one piece and connected to the fuselage with a canopy . The lower wing consists of the central piece, which forms a unit with the fuselage, and two outer wings, which are connected to the upper wing by N-stems. Both upper and lower wing leading edges are to shorten the landing distance slats used.

Tail unit : The wooden tail unit consists of a vertical and horizontal fin, the latter being supported with an I-post on each side towards the fuselage. Ailerons are in the upper wing.

Landing gear : The HD 23 has a main landing gear with a split axle and oil-dampened front struts. It is designed to be dropped so that it can land on the water without problems in the event of danger. There is a spring-loaded leaf spur at the stern.

Technical specifications

The values ​​given in brackets refer to the version with Hispano-Suiza engine.

Parameter	Data
span	10.8 m
length	7.55 m
height	3.89 m
Wing area	36.0 m²
Empty mass	1470 kg (1275 kg)
Payload	600 kg
Takeoff mass	2070 kg (1830 kg)
Engine	a liquid-cooled twelve-cylinder V-engine BMW VIa ( Hispano-Suiza 12 HA )
power	485 kW (659 PS) (331 kW (450 PS))
Top speed	249 km / h (217 km / h) close to the ground
Landing speed	88 km / h (87 km / h)
Rise time	1.6 min at 1000 m 5.8 min at 3000 m 18.4 min at 6000 m
Summit height	7900 m (6500 m)
Range	k. A.
Armament	two 7.7 mm machine guns above the engine, two 30 kg bombs at underwing stations
crew	1

literature

• Volker Koos: Ernst Heinkel Flugzeugwerke 1922–1932 . Heel, Königswinter 2006, ISBN 3-89880-502-6 , p. 60-62 .
• Ulrich Israel: “Flight deck clear!” German carrier aircraft until 1945. In: Fliegerrevue Extra . No. 2 . Möller, 2003, ISSN  0941-889X , p. 45/46 .
• Helmut Stützer: The German military aircraft 1919–1934 . E. S. Mittler & Sohn, Herford 1984, ISBN 3-8132-0184-8 , p. 47, 138 and 186 .

Web links

• HD – 23rd Retrieved September 6, 2016 (Russian, history, dates, and photos). 

Individual evidence

1. ^ Volker Koos: Ernst Heinkel . From the biplane to the jet engine. Delius Klasing, Bielefeld 2007, ISBN 978-3-7688-1906-0 , p. 70 .