Heinkel HD 15

Heinkel HD 15
Type:	Catapultable reconnaissance flying boat
Design country:	German Empire
Manufacturer:	Heinkel
First flight:	June 28, 1927
Commissioning:	-
Production time:	1927
Number of pieces:	1

The Heinkel HD 15 was the first flying boat produced by the Heinkel works and at the same time the first catapult aircraft developed in Germany . A copy was created. HD stands for Heinkel double decker .

development

In 1927 Ernst Heinkel received an order from the Reich Ministry of Transport to develop a catapult that could be used on ships, along with the aircraft that went with it. The actual client in the background, however, was the German Reichsmarine , which wanted to gain experience with the operation of airborne aircraft as part of a secret armaments program bypassing the Versailles Treaty . The work began immediately and was completed in the same year. The design of the type designated as HD 15 came from Heinkel's chief designer Karl Schwärzler . For a long time it was assumed that Schwärzler was also responsible for the construction of the K 1 catapult. However, it can be assumed that its developer was Wilhelm Stein , who had started a position as technical director at Heinkel around the same time. Stein had already submitted similar plans to the Reichsmarineamt in 1916 , according to which a test construction was built and tested in October 1918 at the Danzig shipyard with a W.29 . On July 29, 1928, Stein also registered a patent for the inventor of a Heinkel catapult.

The HD 15 with the serial number 265 began its factory trials with Wolfgang von Gronau in Warnemünde on June 28, 1927 . In the course of this, anti-splash water strips were attached to the right and left of the bow because of the strong bow wave that formed while rolling. Attempts were made to increase the climbing performance, which was perceived as too low, by reversing the upper wing twice. Various propellers were also tested.

The K 1 was also completed in 1927. It was operated with compressed air and was the first aircraft catapult built by the Heinkel works. It had a length of 21.50 m and a weight of 15 t. The 0.4 t take-off sled was designed for 2.5 t and accelerated the HD 15 to the required take-off speed of 105 km / h over a length of 11.85 m. A pulley system provided the necessary 1: 4 ratio. The acceleration forces were 4.9  g . The sled was then braked to 2.2 m, with the aircraft disengaging from the catapult. A special floating dock from Lübeck's Flender-Werke , which had been put into operation on the Pötenitzer Wiek in Travemünde in November 1927, was used for the spin tests . It was anchored on the Breitling of Warnemünde and installed the catapult on it. The trials were without exception successful and ended in the late summer of 1928. The dock was then transferred back to Travemünde together with the catapult and used by the sea ​​trial site. Heinkel developed other devices of this type based on the K 1.

On September 12, 1927, the HD 15, marked D-1237 , was handed over to Severa GmbH , an officially civil service company that was operated in secret by the Reichsmarine. The following year a serious incident occurred during a visit to the factory in Warnemünde when the propeller was dismantled on April 27 during a flight at a height of 2000 m. The pilot Hermann Becker was able to land unharmed, but the engine broke out of its holder when ditching . The HD 15 was repaired at Aero-Sport GmbH Warnemünde and then flew for Severa until August 1929. Then, like the catapult before, it was incorporated into the See trial site, which it used in Travemünde for several years for experiments.

construction

The HD 15 is a strained , einstieliges biplane - flying boat in wood construction .

hull

The hull is made up of four longitudinal spars and frames made of wood with plywood cladding. It has a cruciform bow, is double-keeled and designed in two stages. Its trapezoidal cross-section with a rounded upper part ends in a vertical cutting edge towards the rear. The three separate crew cabins are open. The pilot sits in the front area in front of the wing under the engine nacelle. Behind it is the main fuel tank with motor pump, to which the cabins for the two remaining crew members are connected. Swimming stability on the water is ensured by two stepless wooden support floats with plywood planking, which are attached to the lower wing on each side by struts in the area of ​​the N-posts.

Structure

The upper and lower wings of the HD 15 are staggered and have a slight V-position. They consist of two box spars with spruce straps, plywood webs and ribs and tubular steel struts between the spars. The leading edges of the wings are covered with plywood, the rest of the panels are covered with fabric. The lower wing of the smaller span is connected to the fuselage directly at its upper edge, the two-part upper wing is placed on it and connected to the structure through the tombstone and N-shaped legs in the upper area. There is an additional fuel tank in its middle section. In front of it, the engine is housed in a streamlined aluminum nacelle, which is supported by steel struts towards the fuselage and upper wing. Both the upper and lower wings have ailerons, which consist of steel frames with fabric covering and are connected to each other on each side by pull cables.

Tail unit

The horizontal stabilizer and all the rudders are made from a tubular steel frame covered with fabric. The free-standing fin is made of wood and clad with plywood. The horizontal stabilizer is supported by V-struts towards the fuselage and adjustable in flight. Both the elevator and rudder have horn compensation.

Technical specifications

Parameter	Data
crew	2-3
span	above 12.37 m below 11.88 m
length	10.8 m
height	4.25 m
Wing area	44.0 m²
Empty mass	1450 kg
Payload	900 kg
Takeoff mass	2350 kg
drive	an air-cooled nine-cylinder four-stroke radial engine with a rigid two-bladed wooden propeller
Type	Gnome et Rhône Jupiter VI 9 Af
fuel	a total of 635 l in the main fuselage and auxiliary wing tanks
Starting power nominal power continuous power	540 PS (397 kW) 500 PS (368 kW) on the ground 482 PS (355 kW)
Top speed	172 km / h near the ground
Landing speed	85 km / h
Rise time	3.6 min at 1000 m 8.8 min at 2000 m
Summit height	4300 m
Flight duration	5 h
Radius of action	850 km

literature

• Volker Koos: Ernst Heinkel Flugzeugwerke 1922–1932 . Heel, Königswinter 2006, ISBN 3-89880-502-6 , p. 42/43 .
• Helmut Stützer: The German military aircraft 1919–1934 . E. S. Mittler & Sohn, Herford 1984, ISBN 3-8132-0184-8 , p. 52, 136 and 192 .

Web links

• Heinkel HD.15. www.airwar.ru, accessed March 12, 2018 (Russian, photos). 

Individual evidence

1. ↑ Matthias founder: German Atlantic connections - faster than the competition. Spin starts . In: Aviation Classics . No. 4/2012 , p. 52 .
2. ^ Volker Koos: Ernst Heinkel . From the biplane to the jet engine. Delius Klasing, Bielefeld 2007, ISBN 978-3-7688-1906-0 , p. 78 ff .
3. ↑ Koos, Heinkel 1922–1932 , p. 143
4. ↑ Christian König: First at the enemy. On-board aircraft and coastal reconnaissance aircraft Heinkel He 60 . Helios, Aachen 2017, ISBN 978-3-86933-187-4 , pp. 9 .