Heinkel HE 31

Heinkel HE 31
Type:	Maritime reconnaissance and fighter aircraft
Design country:	German Empire
Manufacturer:	Heinkel
First flight:	October 1928
Commissioning:	-
Number of pieces:	1

The Heinkel HE 31 was a German floatplane developed by the Warnemünder Heinkel-Flugzeugwerke in the 1920s .

history

The aircraft was created at the request of the Reichsmarine for a two-seater sea chase with seaworthiness up to seas 2 to 3 and two rigid machine guns as offensive armament and a movable machine gun for defense in the observer stand , similar in the design of the successful Hansa-Brandenburg W.29 , the Ernst Heinkel had already designed in the First World War . Use as a reconnaissance vehicle was also considered. Heinkel developed the HE 31 as an improved successor to the proven HE 5 from 1926 in a similar design as a two - seater low- wing aircraft , but with improved wings with decreasing profile thickness. One example was built that, for the first time in the company's history, was given two floats with a rounded top , because it was hoped that it would reduce air resistance and thus increase speed. An American Packard engine with 840 hp served as the drive . The only HE 31 with the serial number 310 was produced in 1928 and approved in October for Severa GmbH , a front company of the Reichsmarine D–1522. After testing by Severa, Deutsche Luft Hansa (DLH) incorporated it into its coastal flight department in February 1929 , but in June 1929 it was transferred to the German Aviation Research Institute (DVL) in Adlershof , with the testing center of the Reich Association of the German Aviation Industry (RDL) in Travemünde acted as holder. In October 1931 the aircraft was fitted with a British Lion-XI-a engine with 576 hp and was finally taken over by the RDL, which subjected it to a number of tests in its sea test site. Series production was not considered, as the HE 31 was only seen as an intermediate step from the HE 5 to the HE 9 as the successor and the Reichsmarine preferred the latter in their procurement planning from 1929 due to their domestic BMW engine.

construction

The U 31 was a semi- cantilever low-wing aircraft in composite construction designed. The fuselage consisted of a welded tubular steel frame designed as a truss with a rectangular cross-section , a curved top and a stern that ended in a vertical cutting edge. In the engine area it was planked with duralumin sheets up to the rear edge of the observer's cabin and covered with fabric behind it. Between the engine and the front cabin was a firewall from sheet steel .

The HE 31 had two-spar , rectangular wings with elliptical edge arches and a V-position of 2.5 °. They were made in two parts, had inner struts made of tubular steel and straps made of Spruce between the spars . In the area of ​​the wing nose they were planked with plywood and otherwise covered with fabric. The connection with the trunk was ensured by hook joints. On the underside there were N-braces at half the span , which supported the wing towards the swimmers.

The components of the tail unit consisted of fabric-covered tubular steel frames, the vertical and horizontal tail fins were braced with wire. The rudder was aerodynamically balanced. The HE 31 was equipped with two semicircular wooden floats with stepped floors made of duraluminium, each with a volume of 1560 liters.

Technical specifications

Parameter	Data
crew	2
span	16.80 m
length	12.20 m
height	4.74 m
Wing area	47.9 m²
Wing loading	65.8 kg / m²
Empty mass	2255 kg
Preparation mass	2505 kg
Payload	645 kg
payload	95 kg
Takeoff mass	3150 kg
drive	a water-cooled twelve-cylinder - four cycle - V-type engine with a rigid four-bladed Holzluftschraube
Type	Packard 3A 2500 5.1
Starting power nominal power continuous power	840 PS (618 kW) at 2000 rpm 700 PS (515 kW) at 1920 rpm 560 PS (412 kW) at 1800 rpm
Top speed	250 km / h
Landing speed	95 km / h
Rate of climb	6.7 m / s
Rise time	2:30 min at 1000 m altitude
Service ceiling	5200 m
Range	500 nm (926 km)
Flight duration	3.5 h

literature

• Volker Koos: Ernst Heinkel Flugzeugwerke 1922–1932. Heel, Königswinter 2006, ISBN 3-89880-502-6 , p. 78/79.
• Volker Koos: Aviation between the Baltic Sea and Breitling. Warnemünde sea and land airfield 1914–1945. Transpress, Berlin 1990, ISBN 3-344-00480-8 , pp. 103 and 127.
• Helmut Stützer: The German military aircraft 1919–1934. E. S. Mittler & Sohn, Herford 1984, ISBN 3-8132-0184-8 , pp. 61, 141 and 197.

Individual evidence

1. ^ Hans-Jürgen Becker: Seaplanes - Flying Boats, Amphibians, Float Plane. In: German aviation. Bernard & Graefe, Bonn 1994, ISBN 3-7637-6106-3 , p. 144
2. ↑ Bruno Lange: Type manual of German aviation. In: Die deutsche Luftfahrt, Volume 9 , Bernard & Graefe, Koblenz 1986, ISBN 3-7637-5284-6 , p. 158.
3. ^ Karl Ries: Research on the German aviation role. Part 1: 1919-1934. Dieter Hoffmann, Mainz 1977, ISBN 3-87341-022-2 , p. 113.