Heinkel He 70

The Heinkel He 70 was a mail plane and fast passenger aircraft of the 1930s designed by German aeronautics firm Heinkel Flugzeugwerke, which was also used in auxiliary bomber and aerial reconnaissance roles. It had a relatively brief commercial career before it was replaced by types which could carry more passengers. The He 70 was a leading design for its day, setting eight world speed records by the beginning of 1933.

He 70
Role Mail plane, Passenger
National origin Germany
Manufacturer Heinkel Flugzeugwerke
First flight 1 December 1932
Introduction 1933
Retired 1954 Spanish Air Force[1]
Primary users Luft Hansa
Luftwaffe
Royal Hungarian Air Force
Number built 324 + license-built in Hungary

Design and development

The Heinkel He 70 Blitz (Lightning) was designed in the early 1930s to serve as a mailplane for Deutsche Lufthansa in response to a request for an aircraft faster than the Lockheed Model 9 Orion (used by Swissair) to service short routes.

It was a low-wing monoplane, with the main characteristics of its design being an aerodynamically efficient elliptical wing, a two-bladed propeller driven by a single engine.

In order to meet the demanding speed requirements, the design endeavored to minimise drag, with flush rivets giving a smooth surface finish, and retractable main landing gear. The tail wheel was not retractable. It was powered by a BMW VI V12 engine of 630hp cooled by ethylene glycol rather than water. This allowed a smaller radiator which also retracted at high speed to further reduce drag. The pilot and radio operator were seated in tandem, followed by a cabin seating four passengers in pairs facing each other.[2] and proved to have excellent performance, setting eight world records for speed over distance, and reaching a maximum speed of 377 km/h (222 mph).[3]

Operational history

Luft Hansa operated He 70s between 1934 and 1937 for a fast flight service which connected Berlin with Frankfurt, Hamburg and Cologne, as well as on the Cologne/Hamburg route.

He 70s were flown abroad from Stuttgart to Seville between 1934 and 1936. The route was part of the South America mail service provided by Luft Hansa that continued via Bathurst, The Gambia to Natal, Brazil, using Junkers Ju 52/3m and Dornier Wal flying boats.[4]

Remaining aircraft were transferred to the Luftwaffe in 1937.

Military use
Royal Hungarian Air Force He 70Ks

The Luftwaffe operated He 70s from 1935, initially as a light bomber and reconnaissance aircraft. As soon as purpose built designs became available, it was relegated as a liaison and courier aircraft.

Twenty-eight aircraft were sent in the late 1930s to Spain with the German-manned Legion Condor, where they were used during the Spanish Civil War as fast reconnaissance aircraft. There they were known as the Rayo, Spanish for "lightning".

The He 70K (later He 170) was a fast reconnaissance airplane variant used by the German air force. Fitted with a new WM-K-14 radial engine, it was used by the Royal Hungarian Air Force as the He 170A early in World War II during 1941–42.

The main weakness of the He 70 in military use was that crews considered it a fire risk. Elements of the airframe were made out of an extremely flammable magnesium alloy called "Elektron", though the majority of the monocoque fuselage was Duralumin. Elektron is very light yet strong, but burns readily when ignited and is difficult to extinguish. Moreover, each wing contained a non-self-sealing 47-gallon fuel tank, which may have further added to the aircraft's reputation for catching fire. A single hit from a light machine gun is reputed to have often set the entire aircraft ablaze. The Hungarian He 170A fleet was retired for this and other reasons, including poor defensive armament, short range and poor view from the cabin, and replaced with vintage, high-wing He 46 monoplanes, until modern Bf 109 fighter-reconnaissance and specialized Fw 189 "Uhu" medium altitude observation aircraft could be introduced.

Influence

While the He 70 saw only limited service in training capacities during World War II, it was the Luftwaffe's first Schnellbomber and served as the antecedent for the majority of bombers involved in both the Battle of Britain and the attack on Pearl Harbor.

German designs

The He 70 is known mainly as the direct ancestor of the Heinkel He 111, which had the distinctive elliptical wings and streamlined fuselage in a twin-engine configuration. One can also see the close similarity of the designs in the tail section and cockpit of the early He 111. The He 111, which began service with the Luftwaffe in 1936, went on to become the most numerous bomber type of the Luftwaffe – with just over 5,600 examples produced during the war in total[5] – in the early years of World War II, before the growing numbers of Junkers Ju 88 bomber variants (the -A and -S subtypes) overtook it later in World War II.

Heinkel's pioneering design was also a model for the He 112 fighter which competed unsuccessfully against the Messerschmitt Bf 109 to become the Luftwaffe's first monoplane fighter. The He 112 was nonetheless built in small numbers, and its performance proved once again the strength of the He 70's original design.

Japanese designs

The He 70 was exported to Japan for study and inspired the Aichi D3A ("Val") carrier-launched light bomber.[6] This aircraft shared the He 70's distinctive low-mounted elliptical wing and was one of several collaborations between Heinkel and the Japanese aviation industry.

British designs

It has been said that the He 70 was an inspiration or influence for the Supermarine Spitfire's elliptical wing.

In a letter to Heinkel, written after seeing the aircraft perform with the Rolls Royce Kestrel engine fitted, R. J. Mitchell said:

We, at Supermarine Aviation, were particularly impressed, since we have been unable to achieve such smooth lines in the aircraft that we entered for the Schneider Trophy Races.... In addition to this, we recently investigated the effect that installing certain new British fighter engines would have on the He 70, We were dismayed to find that your new aircraft, despite its larger measurements, is appreciably faster than our fighters. It is indeed a triumph.

However, Beverley Shenstone, RJ Mitchell's aerodynamic advisor denied that the Spitfire wing was copied from the He 70. Shenstone said:

It has been suggested that we at Supermarine had cribbed the wing shape from that of the He 70 transport. This was not so. The elliptical wing had been used on other aircraft and its advantages were well known. Our wing was much thinner than that of the Heinkel and had a quite different section. In any case it would have been simply asking for trouble to have copied a wing shape from an aircraft designed for an entirely different purpose.[7]

The Günther brothers had already used an elliptical wing design for the Bäumer Sausewind sports aircraft before they joined Heinkel.

Shenstone said that the He 70's influence on the Spitfire design was limited to use as a benchmark for aerodynamic smoothness.

Variants
He 70a
First prototype.[8]
He 70b
Second prototype with the crew of 2 and 4 seats for passengers.
He 70c
Third prototype armed with machine gun for trials of versions for light bomber, reconnaissance and courier duties.
He 70d
Fourth prototype built in 1934 for Luft Hansa, powered by BMW VI 7,3 engine.
He 70e
Fifth prototype built in 1934 for Luftwaffe as light bomber, powered by BMW VI 7,3 engine.
He 70A
Passenger version for Luft Hansa.
He 70D
Passenger version for Luft Hansa, 12 examples built.
He 70E
Light bomber version for Luftwaffe, later converted to F version.
He 70F
Reconnaissance / courier version for Luftwaffe.
He 70F-1
Long-range reconnaissance version.
He 70F-2
Similar to the He 70F-1
He 70G
Passenger version built for Luft Hansa, after 1937 converted to F versi on.
He 70G-1
One aircraft fitted with a 604 kW (810 hp) Rolls-Royce Kestrel piston engine.
He 70K (He 170A)
License-built Hungarian fast reconnaissance variant equipped with a licence-made 746 kW (1,000 hp) WM-K-14 radial engine.
He 270 V1 (W.Nr. 1973, D-OEHF)
Prototype with DB-601Aa inline engine.

Operators

Civil operators
 Nazi Germany
  • Deutsche Luft Hansa received the first two prototypes in 1933 and 1934 as well as three He 70D in 1934 and 10 He 70G in 1935.
 Japan
  Switzerland
  • Swissair received a few Heinkel He 70s for express trans-alpine flights between Zurich and Milan in 1934.
 United Kingdom
  • Rolls Royce acquired one He 70G from the RLM in exchange for 4 Kestrel engines. It was used as an engine test bed.
Hungarian pilots with a He 70K

Military operators
 Nazi Germany
Hungary
 Spanish State

Specifications (He 70F-2)
Heinkel He 70 3-view drawing from L'Aerophile April 1933

Data from The Beautiful Blitz[9]

General characteristics

  • Crew: 3 (pilot, radio operator and dorsal gunner)
  • Length: 11.7 m (38 ft 5 in)
  • Wingspan: 14.8 m (48 ft 7 in)
  • Height: 3.1 m (10 ft 2 in)
  • Wing area: 36.5 m2 (393 sq ft)
  • Empty weight: 2,360 kg (5,203 lb)
  • Gross weight: 3,386 kg (7,465 lb)
  • Max takeoff weight: 3,500 kg (7,716 lb)
  • Powerplant: 1 × BMW VI 7.3 Z V-12 liquid-cooled piston engine 750 PS (740 hp; 550 kW)
  • Propellers: 2-bladed variable-pitch metal propeller

Performance

  • Maximum speed: 360 km/h (220 mph, 190 kn) at sea level
  • Cruise speed: 295 km/h (183 mph, 159 kn)
  • Landing speed: 105 km/h (65 mph; 57 kn)
  • Range: 1,820 km (1,130 mi, 980 nmi)
  • Service ceiling: 6,000 m (20,000 ft)
  • Time to altitude:
  • 1,000 m (3,281 ft) in 2 minutes 30 seconds
  • 4,000 m (13,123 ft) in 15 minutes

Armament

  • Guns: 1 × 7.92 mm (.312 in) MG 15 machine gun aimed from rear cockpit
  • Bombs: 6 × 50 kg (110 lb) or 24 x 10 kg (22 lb) bombs internally
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See also

Related development

Aircraft of comparable role, configuration and era

Related lists

References

Notes
  1. "Historical Listings: Spain, (SPN) Archived 2011-07-20 at the Wayback Machine."] World Air Forces. Retrieved: 10 June 2011.
  2. Smith and Kay 1972, p.234.
  3. Donald 1999, p.494.
  4. "Transatlantic". Flight. 1934-12-10. pp. 1349–1350. Retrieved 2011-05-18.
  5. Regnat, Karl-Heinz (2004). Black Cross Volume 4: Heinkel He 111. Hersham, Surrey, UK: Midland Publishers. p. 74. ISBN 978-1-85780-184-2.
  6. Mark Peattie, Sunburst: The Rise of Japanese Naval Air Power, 1909–1941, p. 94
  7. Price 1977, pp. 33–34.
  8. "Landing Wheels Vanish Into Wings During Take Off" Popular Science, June 1933
  9. Green and Swanborough Air International January 1991, p. 28.

Bibliography
  • Donald, David (ed.) The Encyclopedia of Civil Aircraft. London:Aurum Publishing. 1999. ISBN 1-85410-642-2.
  • Green, William and Gordon Swanborough. "The Beautiful Blitz". Air International, January 1991, Vol 40 No 1. Stamford, UK:Key Publishing. pp. 25–33. ISSN 0306-5634.
  • Nowarra, Heinz. Heinkel He111 A Documentary History. Jane's Publishing Co Ltd. 1980. ISBN 0-7106-0046-1.
  • Smith, J.R. and Kay, A.L. German Aircraft of the Second World War. London: Putnam. 1972. ISBN 0-85177-836-4.
  • Price, Alfred. Spitfire: A Documentary History. London: Macdonald and Jane's, 1977. ISBN 0-354-01077-8.
  • Townend, David, R. Thunderbolt & Lightning—The History of Aeronautical Namesakes. AeroFile Publications. 2009. ISBN 978-0-9732020-2-1.
  • Green, William. "Warplanes of the Second World War – Bombers and Reconnaissance Aircraft, Volume Nine" Macdonald: London, 1967.
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