Heinkel HD 37

Heinkel HD 37
Soviet license version I-7
Type:	Fighter plane
Design country:	German Empire
Manufacturer:	Heinkel GAS No. 1 Moscow
First flight:	April 1928
Commissioning:	1931
Production time:	1927-1928 (HD 37) 1931-1934 (I-7)
Number of pieces:	2 HD 37 + 131 I-7

The Heinkel HD 37 was a German fighter aircraft designed by Ernst Heinkel for the Soviet air force in the late 1920s . In the Soviet Union it was built under license under the designation I-7 . HD stands for "Heinkel double-decker", I for "Istrebitel" (Russian for fighter plane).

history

Under the impression of the hunter HD 17 , which had been tried and tested at the secret test site of the Reichswehr near Lipetsk from 1926 , the Soviet military command gave Heinkel the order to create a successor model with a BMW VI drive. Two copies were planned, which should be extensively tested. If the results were positive, the purchase of the manufacturing license was planned. Construction of the two test models began at the end of 1927, disregarding the arms restrictions of the Versailles Treaty and was followed by Soviet specialists. The first flight took place in April 1928 by the head of the DVL Joachim von Köppen on the grounds of the Heinkel works in Warnemünde. Subsequent tests were carried out from April 19 by the Swedish test pilot Nils Söderberg. He complained about the high angle of attack , which had a negative effect on takeoff and landing. On his advice, the rudder and elevator were increased a little. At the end of the month, Söderberg carried out a few more measurement flights, during which he reached a speed of 327 km / h on a 3 km route. The day before a Soviet commission arrived to inspect the aircraft, it reached a peak altitude of 9,800 m, which was a national record. The HD 37 also achieved an impressive rate of climb for the time.

In April the two HD 37s were flown in front of the Soviet delegation by Söderberg, among other things with a dive at maximum speed. The Soviet side was satisfied and took over both aircraft, which were immediately transferred to the USSR. At the request of the buyer, the height record reached by Söderberg was not made public and therefore not recognized. In July, the test flights of the first machine began in the Soviet Union with the pilots I. F. Koslow and W. O. Pissarenko. When attempting a spin , the plane got out of control on July 20 and crashed; Pissarenko was able to jump off with the parachute. Heinkel then sent the Prodzynski factory pilot to investigate the incident. It turned out that some passages of the German operating manual had not been translated into Russian. Von Prodzynski began testing the second HD 37 on August 14, 1928 and completed it without further incident.

As a result of the incident, the Soviet side submitted some suggestions for changes to improve the spin characteristics. Heinkel therefore developed the HD 43 with a modified wing profile , tail and landing gear and wing surface . There were also two copies that went into trials from the end of 1929 and were again tested by Nils Söderberg, among others. Contrary to all forecasts, the HD 43 had poorer flight characteristics than its predecessor, and so the HD 37 was finally approved for series production. Heinkel received ℛℳ 150,000 for the sale of the license .

Production began in 1931 under the designation I-7 with the BMW VI licensed engine M-17 in Moscow Plant No. 1, after Plant No. 39 was rejected. During production, changes were made to suit local possibilities. This applied, for example, to the radiator arrangement and the bonnet. Since the domestic industry was not in a position necessary for the fuselage of molybdenum - steel pipes to customize, they had to be imported. The licensed aircraft had poorer performance data than those built by Heinkel. This mainly concerned the speed and the climbing performance. Since the native Polikarpov I-5 produced around the same time achieved nearly the same data, it eventually became the standard fighter of the WWS in the first half of the 1930s. Production of the I-7 was discontinued in 1934 after only 131 copies, which were also withdrawn from the first line after a very short time.

construction

The HD 37 / I-7 was a braced biplane . The hull consisted of a molybdenum steel tube frame and was planked with aluminum from the bow to the cockpit ; behind it it was covered with fabric and partially covered with plywood . The wings of different spans consisted of a wooden structure with fabric covering and were connected to each other and to the fuselage by N struts. Thanks to the “camel hump” fuselage rising towards the cockpit and the low-set upper wing, the pilot had an extremely good view. The tail unit was conventional and braced and braced with I-stems. The main wheels of the chassis were rigid and had no connecting axis between them. There was a grinding spur at the stern . As with most Soviet aircraft of the time, the I-7 had a ski landing gear for the winter.

Technical data of the HD 37

The values ​​in brackets refer to the license model I-7

Parameter	Data
crew	1 pilot
length	7.00 m
span	10.00 m
height	3.45 m
Wing area	26.71 m²
Empty mass	1267 kg
Takeoff mass	1685 kg (1808 kg)
Engine (s)	a liquid-cooled twelve-cylinder - V-engine BMW VI 7,3Z (M-17)
Starting power nominal power continuous power	750 PS (552 kW) 650 PS (478 kW) at an altitude of 1000 m 500 PS (368 kW) at a height of 700 m
Top speed	312 km / h near the ground, unofficially 327 km / h (279 km / h) 285 km / h at 5000 m altitude
Marching speed	273 km / h
Landing speed	96 km / h
Rise time	4:50 min at 2000 m altitude 10.2 min at 5000 m altitude (11.2 min)
Duration of a full curve	12 s (12 s)
Summit height	8700 m, unofficially 9800 m
Range	k. A.
Flight duration	5.5 h
Armament	two synchronized machine guns

See also

• Rapallo Treaty

literature

• Dimitri Alexejewitsch Sobolew: German traces in Soviet aviation history . Mittler, Herford 2000, ISBN 3-8132-0675-0 .
• Helmut Stützer: The German Aircraft 1919–1934 . Mittler, Herford 1984, ISBN 3-8132-0184-8 , pp. 58, 143 and 197 .

Web links

Commons : Heinkel HD 37  - Collection of pictures, videos and audio files

• Heinkel HD 37 at airwar.ru, in Russian, illustrated

Individual evidence

1. ↑ Volker Koos: Aviation between the Baltic Sea and Breitling . Transpress, Berlin 1990, ISBN 3-344-00480-8 , pp. 97 ff .
2. ^ Andrei Alexandrow, Gennady Petrow: The German Aircraft in Russian and Soviet Services, Vol . 1 1914–1951 . Flugzeug Publikations GmbH, ISBN 3-927132-43-8 , p. 31 .
3. ^ Lennart Andersson: German-Swedish secret projects between 1921 and 1935 . In: Flieger Revue Extra . No. 18 , 2007, p. 17 .