|Role||Mail plane, Passenger|
|First flight||1 December 1932|
|Retired||1954 Spanish Air Force|
|Primary users||Deutsche Luft Hansa|
Royal Hungarian Air Force
The Heinkel He 70 Blitz ("lightning") was a German mail plane and fast passenger monoplane aircraft of the 1930s designed by Heinkel Flugzeugwerke, which was later used as a bomber and for aerial reconnaissance. It had a brief commercial career before it was replaced by larger types. The He 70 had set eight world speed records by the beginning of 1933.
The Heinkel He 70 Blitz (Lightning) was designed in the early 1930s 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 had a cantilever low-wing monoplane, with an aerodynamically efficient elliptical wing and retractable undercarriage, and a single, nose-mounted engine.
To meet the demanding speed requirements, care was taken to minimize drag, with flush rivets giving a smooth surface, and fully retractable main landing gear. The tail wheel was not retractable. It was powered by a 470 kW (630 hp) BMW VI V-12 engine cooled with ethylene glycol rather than water. This allowed a smaller radiator to be used, 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.
The first prototype flew on 1 December 1932, and proved to have excellent performance, setting eight world records for speed over distance, and reaching a maximum speed of 377 km/h (234 mph).
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 between Cologne and Hamburg.
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.
Remaining aircraft were transferred to the Luftwaffe in 1937.
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 to use 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 given the RLM number: He 170) was a fast reconnaissance airplane export variant used by the Hungarian air force. Powered by a Gnome-Rhône Mistral Major radial engine, the engines were built under license in Hungary as the WM-K-14, but the air frame and final assembly were in Germany. The new engines raised the top speed of the aircraft from 360 to 435 km/h (224 to 270 mph). 18 were used by the Royal Hungarian Air Force from 1937 to 1942.
A major weakness of the He 70 in military use was the fire risk. Parts 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 210-litre (47-imperial-gallon) fuel tank, which may have further added to the aircraft's reputation for catching fire. Other problems included poor defensive armament, short range and poor view from the cabin, all of which led to the Hungarian He 170A fleet being prematurely retired and replaced with obsolescent Heinkel He 46 parasol-wing monoplanes, until Focke-Wulf Fw 189 "Uhu" medium altitude observation aircraft could be introduced.
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 some of the bombers involved in the Battle of Britain.
The He 70 is known mainly as the ancestor to the Heinkel He 111, which had similar elliptical wings and streamlined fuselage in a twin-engined configuration. 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 – in the early years of World War II.
The He 70 was essentially scaled down to produce the He 112 fighter which lost out on competition against the Messerschmitt Bf 109, but was nonetheless built in small numbers.
An He 70 was exported to Japan for study and inspired the Aichi D3A ("Val") carrier-launched light bomber. This aircraft shared the He 70's distinctive, low-mounted elliptical wing.
Beverley Shenstone, R.J. 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.
The Günther brothers had already used an elliptical wing 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.
Data from The Beautiful Blitz
Aircraft of comparable role, configuration, and era