Heinkel HD 17

Heinkel HD 17
The first built HD 17 with the serial number 216
Type:	Reconnaissance plane
Design country:	German Empire
Manufacturer:	Heinkel
First flight:	1924
Production time:	1924, 1926
Number of pieces:	9

The Heinkel HD 17 was a German reconnaissance aircraft from the Ernst Heinkel Flugzeugwerke . The abbreviation HD stands for "Heinkel Doppeldecker".

development

The HD 17 was developed in 1923/1924 on behalf of the US aircraft manufacturer Cox-Klemin . Although the construction of armed military aircraft was strictly forbidden in Germany at the time, two examples with different engines were built in the Heinkel factory in Warnemünde in 1924, the number 216 with a Napier Lion and the number 217 with a Liberty engine. This ban also results in the false statement that can be found repeatedly in the literature that the aircraft were made by the Swedish company Svenska Aero , as this was always stated in official documents for reasons of obscurity. The Heinkel sister company from Lidingö also appeared as an exporter in the delivery papers with which the two HD 17s were shipped to the USA in the same year.

When they arrived in the USA, Cox-Klemin declared them as own products with the designations CO-1 and CO-2. In this way, they were then registered by the company for a competition which the US Army carried out to select an army reconnaissance officer in the summer of 1924 at McCook Field in Dayton . There the two HD 17s received the military test license plates P-377 and P-379 . Ernst Heinkel himself took advantage of this opportunity in November of the same year for a business trip to the USA in order to be able to conclude further deals on site if the construction was possibly successful. This hope was not fulfilled, the two aircraft were subjected to thorough testing by the Army's flight test department, but were judged to be the worst of the competition aircraft after the Atlantic AO-1 and the two aircraft of the Engineering Division (CO-5 and CO-6) returned to Cox-Klemin. A series order was not placed either for Cox-Klemin or for the other competitors. Instead, the HD 17 seem to have been sold to civilian owners afterwards. At least the serial number 217 flew from December 1926 with the registration 1189 for the General Airways airline and was transferred to the Sky Signs of America company in October 1927 . It was last recorded in the summer of 1929, when it was badly damaged during a storm in Wichita , but was rebuilt; their further whereabouts are unknown.

In 1926 a small series of seven more HD 17s with the serial numbers 239–245 was launched on behalf of the Reichswehr . They differed from the specimens built two years earlier in that they had a fin with a sloping edge instead of a rounded edge, a rudder with horn compensation and the use of N instead of I stems as a connection between the upper and lower wings. The Napier Lion engine was adopted as the drive. On April 16, 1926, the first model carried out a few test flights in Warnemünde in front of representatives of the aviation department of the Reichswehr and revealed some minor weaknesses in controllability, which were easy to eliminate. The remaining HD 17s, which were completed in the following month, could not be flown in for the time being, as the associated Napier engines could not be officially procured due to the Allied restrictions, but had to reach Warnemünde via detours. Whether a license production of the model was also considered by Arado Handelsgesellschaft , as already happened in the case of the HD 21 and HD 32 , can only be assumed, since such a project was not carried out. When the engines were finally available, all HD 17s were delivered to the Secret Aviation School and test site of the Reichswehr in the Soviet Union and flown there for the training of observers and bomber pilots. One of them broke in a failed landing on October 7, 1927, of the remaining six were still in use in 1929 and four in May 1933.

construction

The HD 17 is a single-legged, cantilevered double-decker with a strong positive staggered structure in a composite construction with a tail landing gear .

hull

The fuselage is formed by a tubular steel frame consisting of four longitudinal spars and a cross frame and braced on the inside with steel wire and strands. It has a square cross-section with a curvature on the top and ends in a vertical tail cutting edge. The engine mount, which is also made of tubular steel, is clad in sheet aluminum with the tank behind it up to the fire bulkhead in front of the first seat, the rest of the fuselage is covered with fabric.

Structure

The wings are in two parts and consist of a wooden frame with two box spars and plywood ribs. The upper wing is continuous and staggered towards the lower wing. The undersides are covered with plywood from the wing nose to the rear spar, the rest of the surface is covered with fabric. The wings are connected to each other with either I or N posts and are not braced. The canopy connection consists of tubular steel struts. The ailerons and other fuel tanks are housed in the upper wing, which together with the fuselage tank can hold around 690 liters.

Tail unit

The tail unit is self-supporting in a normal construction. The vertical fin and rudder as well as the elevator are tubular steel constructions covered with fabric, the horizontal fin is made of wood and is adjustable in flight. In the 1926 version, the rudder is equipped with a horn compensation.

landing gear

The HD 17 has a rigid main landing gear with a continuous axle and rubber suspension. There is also a rubber-sprung grinding spur at the rear.

Technical specifications

Three-sided view

Parameter	HD 17 (1924)	HD 17 (1926)
crew	2	2
span	above 12.80 m below 11.40	above 12.90 m below 11.43 m
length	9.18 m	9.30 m
height	3.25 m	3.6 m
Wing area	40.6 m²	39.02 m²
Preparation mass	1380 kg	1369 kg
Payload	820 kg	779 kg
Takeoff mass	2200 kg	2148 kg
drive	a liquid-cooled, twelve-cylinder - four stroke - W motor
Type	Napier Lion XI
fuel	≈ 690 l
Starting power	575 hp (423 kW)
Continuous output	450 hp (331 kW)
Top speed	220 km / h at an altitude of 1000 m	225 km / h at an altitude of 1220 m
Cruising speed	200 km / h
Landing speed	90 km / h	140 km / h
Rate of climb	4.8 m / s	k. A.
Rise time	3.5 min at 1000 m altitude 12.0 min at 3000 m altitude	11.0 min at 3000 m altitude
Range	k. A.	k. A.
Service ceiling	6500 m	6360 m

literature

• Volker Koos: Ernst Heinkel Flugzeugwerke 1922–1932 . Heel, Königswinter 2006, ISBN 3-89880-502-6 , p. 46-48 .
• 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. 55 ff .
• Helmut Stützer: The German military aircraft 1919–1934 . E. S. Mittler & Sohn, Herford 1984, ISBN 3-8132-0184-8 , p. 34, 136 and 179 .

Web links

Commons : Heinkel HD 17  - collection of pictures, videos and audio files

Individual evidence

1. ↑ Directory of the P codes of McCook Field
2. ^ ^{A b} American Planes of the 20th Century
3. ^ Volker Koos: Ernst Heinkel . From the biplane to the jet engine. Delius Klasing, Bielefeld 2007, ISBN 978-3-7688-1906-0 , p. 56/57 .