In February 1932 design work was begun at the Heinkel factory on a high-speed mailplane which could also carry four passengers. A top speed of 285 km/h (177 mph) was required by Deutsche Lufthansa who issued the specification. The Heinkel team, were inspired into setting their sights higher by the appearance in May that year of the Lockheed Orion, operated by Swissair. Maximum speed now required to compete with this aircraft was 322 km/h (200 mph).
The result was a low-wing monoplane, tapered in chord and thickness and were of spruce construction, planked with plywood, having a retractable undercarriage, and it flew for the first time on December 1, 1932. It had an all-metal oval semi-monocoque fuselage, elliptical wings of wooden construction, and small rounded tail surfaces. The powerplant was a 469.5kW / 637hp BMW VI liquid-cooled engine. When the Blitz was officially presented at Tempelhof field - its speed of 362 kilometers per hour - made it not only the fastest commercial airplane of the time, but also faster than contemporary foreign fighters. An immediate production batch was ordered and 14 aircraft went into service with Lufthansa on domestic express routes during 1932-33 accommodating a pilot, navigator and four passengers. Early in 1933 the aircraft also captured a number of international speed records. Further commercial developments of this model were the He 70B and the G-1, with lengthened fuselage; some variants were fitted with a 559kW / 750-hp BMW VI engine.
Actual production of the passenger-carrying variants was 28.
The military potential of the He 70 was recognized by the embryonic Luftwaffe, and nine He 70B-0s, and an initial production batch of D-Is, were delivered for high-speed military communication and liaison duties. They retained the shorter fuselage, but were fitted with the uprated engine. The three-seat E-1 light bomber, developed from the D series, could carry up to 300 kg (660 lb) of bombs and was armed with one rear-mounted MG 15 machine-gun. Only limited E-1 production took place before the appearance of the three-seat F-1, F-2 and F-3 series long-range reconnaissance -bombers. Eighteen He 70F-2s were used by the Legion Kondor in Spain from late 1936. An additional 12 were transferred to the Spanish Nationalist forces.
The production total of nearly 300 military He 70 included 18 He 170A exported to Hungary during 1937-38, each of these powered by a 678kW Gnome-Rhone 14K Mistral Major radial engine and armed with two 7.8mm Gebauer machine-guns for defence.
Engine: 1 x BMW VI 7.3, 559kW
Max take-off weight: 3640 kg / 8025 lb
Empty weight: 2530 kg / 5578 lb
Wingspan: 14.80 m / 48 ft 7 in
Length: 11.70 m / 38 ft 5 in
Height: 3.25 m / 10 ft 8 in
Wing area: 36.51 sq.m / 392.99 sq ft
Max. speed: 360 km/h / 224 mph
Ceiling: 5485 m / 18000 ft
Range: 1250 km / 777 miles
Span: 14.8 m (48 ft 61 in)
Length: 12 m (39 ft 41 in)
Gross weight: 3460 kg (7630 lb)
Maximum speed: 360 kmlh (224 mph).