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Heinkel / Aichi HD 23

Shipborne Biplane Fighter Prototype

The Japanese were not impressed with the Heinkel HD 23 shipborne biplane fighter of Germany - leading to just four examples being built in total.
Authored By: Staff Writer | Edited: 4/3/2017
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Year: 1926
Manufacturer(s): Ernst Heinkel Flugzeugwerke (Heinkel) - Germany / Aichi - Imperial Japan
Production: 4
Capabilities: Fighter; Navy/Maritime; X-Plane;
Crew: 1
Length: 24.77 ft (7.55 m)
Width: 35.43 ft (10.8 m)
Height: 12.47 ft (3.8 m)
Weight (Empty): 3,241 lb (1,470 kg)
Weight (MTOW): 4,564 lb (2,070 kg)
Power: 1 x BMW VIa 12-cylinder water-cooled inline piston engine developing 660 horsepower and driving a two-bladed propeller at the nose.
Speed: 155 mph (250 kph; 135 kts)
Ceiling: 25,919 feet (7,900 m; 4.91 miles)
Operators: Imperial Japan (cancelled)
Ernst Heinkel Flugzeugwerke (Heinkel) of Germany began operations in the aviation business during December of 1922. From a Japanese Empire government request, their first single-seat, single-engine fighter became the "HD 23", a traditionally-arranged biplane intended for shipborne (catapult-launched, crane-recovered) operations. Following a first-flight in 1925-1926 and delivery of two prototypes from Germany in 1927, Aichi of Japan made some local modifications to the aircraft and built a further two more examples. Beyond these offerings, the GD 23 - known to the Japanese as the "Type H Carrier Fighter" - was not adopted for service after being evaluated at length by Imperial Japanese Navy (IJN) authorities.

As built, the HD 23 seated one pilot in an open-air cockpit positioned high over the nose section. The wing mainplanes were of equal span and included an upper and lower wing section joined by a network of support struts (N-style) and cabling. The lower fuselage incorporated a boat-like hull and held flotation bags for on-water landings in case of emergency. The undercarriage was wheeled at the two main leg members and fixed during flight. Dimensions included a length of 24.8 feet, a wingspan of 35.4 feet and a height of 12.4 feet. Empty weight was 3,240lb against an MTOW of 4,560lb.

The original German prototype (HD 23a) was powered by the BMW VIa 12-cylinder, water-cooled engine delivering 600 horsepower and the second followed with a Hispano-Suiza 12Ha engine of 450 horsepower. In-service aircraft were to carry 2 x 7.92mm machine guns synchronized to fire through the spinning propeller blades.

Once available to Aichi engineers in Japan, workers installed a jettisonable undercarriage for on-water operations (landing and take-off) as well as wing-based slats for better control. In testing the aircraft was found to possess poor qualities for a shipborne fighter - it was underpowered and heavy and exhibited inadequate control. In testing the HD 23a reached a speed of 160mph and a service ceiling of 26,000 feet.


2 x 7.92mm machine guns mounted over the nose, synchronized to fire through the spinning propeller blades.

Graphical image of an aircraft medium machine gun

Variants / Models

• HD 23 - Base Series Designation
• HD 23a - Initial prototype form; two completed in Germany, two completed in Japan.
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