Arado Ar 80 - Design and Development

Design and Development

With the Nazi rise to power in February 1933, a plan was put into place to dramatically expand the Luftwaffe. The new and highly-political Reichsluftfahrtministerium (RLM) demanded that the large industrial firms cooperate, keeping construction as secret as possible. Arado Flugzeugwerke, under the direction of Erich Serno and Felix Wagenführ, largely stopped being a designer of aircraft and increasingly became a production facility for other companies.

However, the company had just completed the Ar 65 biplane fighter. Several orders were placed for the Ar 65, and a follow-on Ar 68 model. This made Arado one of the few companies with actual fighter design experience, and they were considered for future developments

During 1933, the Technisches Amt, the technical department of the RLM, concluded a series of research projects into the future of air combat. One of these was Rüstungsflugzeug IV for an all-metal monoplane single-seat fighter aircraft, replacing the Ar 64 and Heinkel He 60 biplanes then in service. The plane needed to have a top speed of 400 km/h (250 mph) at 6,000 m (19,590 ft) which it could maintain for 20 minutes, while staying in the air for a total of 90 minutes. It was to be powered by the new Junkers Jumo 210 engine. It also needed to be armed with at least three machine guns with 1,000 rounds each, or one 20 mm cannon with 200 rounds. The plane needed to keep wing loading below 100 kg/m², which is a way of defining its ability to turn and climb. The priorities for the plane were level speed, rate of climb, and maneuverability, in that order. Hermann Göring sent out a letter in October 1933 asking for a "high speed courier aircraft" in order to start the work, and in May 1934, the actual R-IV request was sent out and made official. In addition to Heinkel and Arado, Focke-Wulf, and Bayerische Flugzeugwerk competed. They had to deliver three prototypes for head-to-head testing in late 1934.

Although Blume was officially the director of design at Arado, it was Rethel who did most of the early work on the design. Rethel was well aware of the advantages and disadvantages of the monocoque technique, but the company had never built such a design and was thus at a distinct disadvantage in relation to Heinkel who had used it on their He 70 Blitz design from 1932.

However he felt that he could not only design a successful monocoque aircraft, but in fact make one that was both lighter and easier to build than the techniques being used at other companies. His solution was to use two sets of skinning plates formed in long strips running front to back along the plane.

The first set of plates was formed roughly into the shape of a C, which a small flange at the open ends of the C where they could be easily riveted to the hoop bulkheads. Using this system he was able to eliminate one more piece of internal structure, the stringers that would normally run between the bulkheads. He used a second set of sheets that were flat, so they could easily bend front-to-back. They were cut into teardrop shapes, which exactly fit into the gaps between the main stringers. Not only did this system allow for the "perfect" aerodynamic shape, but in theory it was also lighter and easier to build. The system looked so hopeful that other parts of the aircraft's design were allowed to be heavier and less risky as the weight savings in the fuselage should compensate.

The rest of the plane was conventional. The forward fuselage and inner wings were formed up from steel tubing with removable aluminium sheeting over it, the outer wings were aluminium formers and skinned with aluminium on top and fabric on the bottom. Like the Heinkel designs, the wing included a reverse-gull bend to shorten the landing gear legs, but unlike the Heinkel it was almost straight on the leading and trailing edges instead of the more complex elliptical planform favoured by the Günter brothers.

In order to avoid cutting the outer wing formers with outward retracting gear, Rether decided to have the landing gear retract directly to the rear. To lie flat, the wheel would have to be rotated through 90° as it retracted. To do this, he put the main oleo strut inside a larger tube that was mounted to the pivot point on the lower leading edge of the box-spar. As the gear retracted a small arm would pull on a lever mounted to the oleo, turning the leg inside the larger tube.

In general terms, the resulting design was very similar to the Hawker Hurricane of roughly the same era.