Heinkel He 70

https://en.wikipedia.org/wiki/Heinkel_He_70

The Heinkel He 70 is 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.

The Heinkel He 70 Blitz (lightning) was designed in the early 1930s to serve as
a mailplane for Deutsche Luft Hansa in response to a request for an aircraft
faster than the Lockheed Vega and 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, twin propellers driven by a single
engine, and small, rounded control surfaces.

In order to meet the demanding speed requirements, the design minimised drag,
with flush rivets giving a smooth surface finish, and a retractable landing
gear. It was powered by a BMW VI V12 cooled by ethylene glycol rather than
water, allowing a smaller radiator to further reduce drag. The pilot and radio
operator were seated in tandem, followed by a cabin seating four passengers in
twos 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 (222 mph).


Role
Mail plane, Passenger

National origin
Germany

Manufacturer
Heinkel Flugzeugwerke

First flight
1 December 1932

Introduction
1933

Retired
1954 Spanish Air Force

Primary users
Luft Hansa
Luftwaffe
Royal Hungarian Air Force

Number built
324 + license-built in Hungary

Military use

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.

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.

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.

Specifications (He 70F-2)

General characteristics
Crew: 3 (pilot, radio operator and dorsal gunner)
Length: 11.70 m (38 ft 4? in)
Wingspan: 14.80 m (48 ft 6?.75 in)
Height: 3.10 m (10 ft 2 in)
Wing area: 36.50 m² (392.9 sq ft)
Empty weight: 2,360 kg (5,203 lb)
Loaded weight: 3,386 kg (7,450 lb)
Max. takeoff weight: 3,500 kg (7,700 lb)
Powerplant: 1 × BMW VI 7.3 Z water-cooled V12 engine, 750 PS (552 kW)
Propellers: metal, two-bladed

Performance
Maximum speed: 360 km/h (195 knots, 224 mph) at sea level
Cruise speed: 295 km/h (159 knots, 183 mph)
Range: 2,100 km (1,135 nmi, 1,305 mi)
Service ceiling: 5,300 m (17,390 ft)
Climb to 1,000 m (3,300 ft: 2.5 min
Climb to 4,000 m (13,125 ft): 15 min

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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