Heinkel HD 28

Heinkel HD 28
Type:	Maritime patrol
Design country:	German Empire
Manufacturer:	Heinkel
First flight:	August 27, 1927
Commissioning:	-
Production time:	1927
Number of pieces:	1

The Heinkel HD 28 is a German floatplane developed in the second half of the 1920s by Heinkel-Flugzeugwerke in Warnemünde . The abbreviation HD stands for "Heinkel Doppeldecker".

development

The HD 28 was created in 1927 on behalf of the Japanese aircraft manufacturer Aichi as a sea ​​reconnaissance aircraft for the Japanese Navy and was intended to form the basic model for any license production in Japan. For reasons of disguise, in Germany at that time the construction of military aircraft was still prohibited by the Versailles Treaty , the type was officially declared as a travel and sport aircraft or simply as a "sea biplane". As an alternative to the conventional wooden construction floats, Heinkel also produced floats made of stainless steel for the first time. The first flight of the only model built with the serial number 259 took place on August 27, 1927 and the subsequent flight test under observation of the DVL was completed without incident. The HD 28 was then shipped to Japan and handed over to Aichi, who presented it to the Japanese Navy as the “Heinkel three-seater sea reconnaissance aircraft” or “Heinkel 2 sea reconnaissance aircraft”. However, this criticized the insufficient visibility and rejected the aircraft because of this and also due to engine problems, so that the planned series production was also omitted. Instead, Aichi's project engineer Tetsuo Miki made some changes to the HD 28. He shortened the lower wing, moved the main tank from the fuselage to the upper wing, and staggered the structure . A Japanese Nakajima license build of the British Jupiter engine was used as the drive . Retrofitted in this way, the HD 28 served as the initial sample for the AB-5 and AB-6 types later built by Aichi .

construction

The HD 28 is a non -staggered, single-leg braced double - decker in a composite construction . The fuselage consists of a fabric-covered tubular steel frame with a rectangular to almost oval cross-section , because it is strongly curved at the top, and aluminum planking in the engine area. Any form frames and strips are made of wood. The engine mount is attached to the fuselage with only four bolts and can therefore be easily removed. Behind it is the fire bulkhead made of sheet steel and the main tank with 1280 l capacity. This is followed by the cabin for the pilot and behind it two other cabins that can be used as cargo hold or equipped with two additional seats, double steering and radio. The stern ends in a vertical cutting edge.

The three-part wings of the same span consist of a fabric-covered wooden construction with two spars , consisting of spruce belts and plywood webs , as well as wooden ribs and tubular steel inner struts. The upper middle section, in which there is another 95 l drop tank, is made of steel tubing. The upper and lower wings are connected to each other by double I-stems and wire crossing in two levels. Further N-struts run to the fuselage. The outer wings can be folded backwards

The tail unit is formed from a welded tubular steel frame with fabric covering. Rudder and elevator are aerodynamically balanced and have a horn compensation, the horizontal fin is supported towards the fuselage by I-struts and the fin is designed as a keel fin. Ailerons are located in both the upper and lower wings and are connected to one another by rods.

The two parallel floats are either made of wood, each with a volume of 4000 l and 108% reserve buoyancy, or of stainless steel , each with 3800 l. They are single-step , keeled and connected to each other and to the fuselage by tubular steel struts. Since the appropriate fittings are available, the HD 28 can be converted into a land plane after removing the floating mechanism by adding a rigid wheel chassis and a tail spur.

Technical specifications

Parameter	Data
crew	3
span	15.0 m
length	11.0 m
height	4.62 m
Wing area	59.5 m²
V shape	above o ° below 2.5 °
Empty mass	2365 kg
Payload	1485 kg
Takeoff mass	3850 kg
drive	a water-cooled 18-cylinder four-stroke cycle - V-engine
Type	Lorraine-Dietrich 28 III with four-blade metal propeller and 11:17 reduction
Starting performance Combat performance Continuous performance	720 PS (530 kW) at 2200 rpm 650 PS (478 kW) at 2000 rpm 600 PS (441 kW) at 1900 rpm
Fuel supply	1375 l
Top speed	198 km / h near the ground
Cruising speed	172-175 km / h
Landing speed	96 km / h
Rate of climb	4.1 m / s
Rise time	4.1 min at 1000 m altitude 9.6 min at 2000 m altitude 17.7 min at 3000 m altitude
Range	1250 km
Summit height	4500 m with maximum payload
Flight duration	7 h
Armament	two fixed 7.7 mm machine guns one movable 7.7 mm machine gun 220 kg bombs

literature

• Volker Koos: Ernst Heinkel Flugzeugwerke 1922–1932 . Heel, Königswinter 2006, ISBN 3-89880-502-6 , p. 72/73 .
• Volker Koos: Aviation between the Baltic Sea and Breitling . Warnemünde sea and land airfield 1914–1945. Transpress, Berlin 1990, ISBN 3-344-00480-8 .
• Helmut Stützer: The German military aircraft 1919–1934 . E. S. Mittler & Sohn, Herford 1984, ISBN 3-8132-0184-8 .

Web links

Commons : Heinkel HD 28  - Collection of images, videos and audio files