Arado Ar 80

Arado Ar 80
	; Two-seat Ar 80 ( D – IPBN )
Type:	Fighter plane
Design country:	German Empire
Manufacturer:	Arado aircraft works
First flight:	July 6, 1935
Commissioning:	-
Production time:	1935-1936
Number of pieces:	3

The Arado Ar 80 was the pre-war development of a fighter aircraft from Arado Flugzeugwerke . It was designed for the Luftwaffe's first tender for fighter aircraft before the Second World War , but it did not perform well and also suffered from numerous problems. The tender was finally won by the Messerschmitt Bf 109 and the prototypes of the Ar 80 ended up as test aircraft.

background

Arado was one of the few German companies that already had experience with the construction of modern fighter aircraft at the time of the tender. The Arado Ar 65 , which at its time was the best fighter aircraft in the Air Force, was already in series production and the Arado Ar 68 was created as its successor . This made them one of the candidates for the construction of the future fighter plane.

The tender

In 1933 the Technical Office of the Reich Aviation Ministry (RLM) decided on a series of research projects for the future of air combat . As a result, four basic designs for aircraft of the future air force emerged:

Armaments aircraft I for a multi-seat medium bomber
Armaments aircraft II for a tactical bomber
Armaments aircraft III for a two-seat heavy fighter
Armaments aircraft IV for a single-seat fighter

The armaments aircraft IV should be a single-seat fighter in the form of an all-metal monoplane , which should replace the biplanes in use at the time . Although the future aircraft should be able to beat everyone else in flight, the requirements were not set too high.

With the new Junkers Jumo 210, the aircraft should reach a top speed of 400 km / h at an altitude of 6000 m and hold it for 20 minutes. It should be able to fly for a total of 90 minutes. At least three machine guns with 1000 rounds each or one 20 mm cannon with 200 rounds should be used. To ensure high maneuverability, the wing loading should be less than 100 kg / m². The priorities were in the following order: flight speed, rate of climb and maneuverability.

These specifications were not laid down in isolation; they were based on the private developments at Heinkel and Arado for a monoplane fighter, which began in 1933 . Only the best properties of both types were selected and summarized in a specification. In October 1933, Hermann Göring initially requested a so-called "high-speed courier aircraft" from these companies. The final and official tender for the fighter followed in May 1934.

In addition to Heinkel and Arado, the tender also went to Focke-Wulf . Each was supposed to deliver three prototypes for direct comparison in the course of 1934. A few months later, the Messerschmitt Bf 108 of the Bayerische Flugzeugwerke (BFW) flew , which was created due to the demand for a "sports aircraft". Because of the advanced construction, BFW was then also offered to participate.

Development history

Although Walter Blume was officially head of the design team, most of the preparatory work was done by Walter Rethel . He knew the advantages and disadvantages of the shell construction, but Arado had no other experience with it. The competition at Heinkel had already been able to gain experience in shell construction with the Heinkel He 70 in 1932 and thus had an advantage.

Nevertheless, Rethel believed that he would not only be able to successfully build a shell-type aircraft, but also a structure that was lighter and easier to build than that of other companies. His solution was to wrap two sets of metal rails lengthways around the hull.

The first set was shaped roughly in the shape of a "C" - with narrow flanges at the open ends of the C that could easily be riveted to the bulkheads. In this way he could save the otherwise usual longitudinal ribs between the frames. When applying long, parallel strips to a cigar-shaped surface, it becomes clear that the distance between the strips becomes smaller and smaller towards the ends. To fill in these gaps, Rethel used a second set of metal rails that were cut in the shape to exactly cover the gaps. This system not only enabled a “perfect” aerodynamic shape, but was theoretically also lighter and easier to build. The system appeared so advantageous that it was believed that other parts of the aircraft could be made heavier and more stable.

The rest of the plane was more conventional. The front fuselage and the inner wings were built from steel tubes with attached aluminum panels, the wing ends were made from molded aluminum parts, which were also planked with aluminum on the top and covered with fabric on the underside. As with the Heinkel constructions, a " gull wing " was used in order to be able to use a shorter landing gear. However, while Heinkel chose an elliptical wing shape, the one chosen by Arado had a straight shape.

In order not to have to cut open the molded parts of the outer wing to accommodate an outwardly retractable landing gear, Rethel decided to retract the landing gear directly to the rear, whereby the wheel should turn 90 degrees.

Test sample

Since Rethel switched from Arado to Willy Messerschmitt in 1934 before the Ar 80 was completed, the design was continued by Blume.

The aircraft was to be equipped with the Junkers Jumo 210 engine and a non-adjustable wooden two-bladed propeller. However, since this engine had not yet been completed by the time it was compared, a replacement engine had to be procured. Coincidentally, Arado had already bought a Rolls-Royce Kestrel VI to be used in the Arado Ar 67 . This engine did not have a good compressor, which led to poor performance in the Ar 67; with this, however, the aircraft could at least be flown once, as long as the Jumo engines were not available.

On July 6, 1935, the V 1 took off on its maiden flight. It was one of the first aircraft in the competition that was even capable of this. However, just a few weeks later, one of the test pilots lost control of the aircraft and it was destroyed.

In these few weeks, the chassis turned out to be a real problem. When it was pulled in, it kept getting stuck in the semi-closed state, but luckily it could be extended again for landing. Several attempts to solve this problem were unsuccessful. When the aircraft was jacked up in the hangar, the landing gear worked perfectly. Finally, it turned out that the air flow acting on the shock absorber in flight caused it to tilt in its tube in such a way that the wheel could not be turned to retract.

Another problem that arose during construction was that Rethel's strip construction turned out to be significantly heavier than expected. The main problem was that it required significantly more rivets than expected. In the end, the plane became too heavy overall.

The V2 was built in a big hurry, but the Jumo engine was still not available. In order to be able to give the competition participants a somewhat realistic engine, the RLM exchanged one He 70 for four Rolls-Royce Kestrel Vs. The Kestrel V, while basically the same engine as the VI, had a much better compressor and was the most powerful engine available at the time. Companies fought hard to get this engine for their prototypes. The future result was probably already becoming apparent, because BFW received two engines, Arado and Heinkel one each and Focke-Wulf none at all.

In autumn 1937 the V 2 with the Kestrel was completed and testing began. Again the chassis turned out to be a problem. Blume blamed Rethel for these difficulties and said that he was skeptical of the construction from the start. He decided that the performance disadvantage of a fixed undercarriage would be offset by its lower weight and gave the Ar 80 such a landing gear - similar to what the double-deckers had already had. Several months were lost for the change.

However, the fixed undercarriage did not save as much weight as expected and with a curb weight of 1630 kg the aircraft was still 16% heavier than intended. When fully loaded, it weighed 2100 kg. So it was underpowered with the Kestrel V. The air resistance was also higher than expected. In the end, it came as no surprise that the plane only performed disappointingly and only reached 410 km / h.

At the beginning of 1936 the Jumo 210 finally came. Although it had less take-off power than the Kestrel, the performance was comparable in flight. The speed could be increased with increasing altitude, but the performance near the ground and the climbing performance fell significantly. Arado believed that installing a controllable pitch propeller could improve both and increase the top speed to 425 km / h. However, no such attempts were made until the comparison flight.

Although the Arado actually flew as one of the first aircraft in the competition, it was one of the last to fly due to the persistent problems with the landing gear and the engine. It was delivered to Travemünde on February 8, 1936 and relocated to Rechlin in March . There it was shown that the Ar 80 had no chance against the competition from Heinkel and BFW.

Further test samples

At this point in time, the V 3 had already been completed. To save weight, the gull wing was replaced by a straight one, which necessitated a slightly longer landing gear. In addition, a Jumo 210C with a controllable pitch propeller was installed, which resulted in a speed of 410 km / h. At that time, the RLM had already rejected the design and the V 3 stayed in the hangar with Arado.

In 1937 the V 3 was reactivated as a flying test stand for various experiments. A second seat for an observer was installed behind the pilot's seat and supplemented by a hood. This aircraft was the first to fire a 20 mm cannon through the hollow propeller shaft. This made the Ar 80 the first German aircraft with a motor cannon (MK) - an armament that later became standard in many fighter planes; so also with the Messerschmitt Bf 109 , which finally won the comparison flight.

In 1938 the V 3 was rebuilt again to test new Fowler flaps for the Arado Ar 198 and Arado Ar 240 . The tests showed that these flaps were so effective that the lift distribution on the wing changed radically. Therefore, an additional modification was made by which the ailerons were lowered together with the flaps. The attempts finally led to the "Arado landing flap" and new ailerons.

conclusion

The Arado 80 was apparently a victim of its own success. It was Arado's own designs that determined the specification of the tender for the R-IV aircraft. At the same time, it was also the oldest of the designs submitted. Due to the speed with which aircraft development advanced in the 1930s, the last aircraft developed was almost certainly the best - and it was exactly the same when the Bf 109 won.

The sum of Arado's lack of experience building clamshell airplanes and Blume's inability to solve the retractable landing gear problem predictably resulted in that plane never standing a chance. Since only three prototypes were built, it's not surprising that it is hardly known today.

Technical specifications

Parameter	Data (Ar 80 V2)
crew	1
span	11.80 m
length	10.10 m
height	2.75 m
Wing area	21.00 m²
Wing extension	6.6
Empty mass	1,645 kg
Payload	455 kg
Takeoff mass	2,100 kg
drive	a liquid-cooled twelve-cylinder - V-engine Jumo 210 C with 610 hp (450 kW)
Top speed	360 km / h near the ground, 425 km / h at an altitude of 4,000 m, 410 km / h at an altitude of 6,000 m
Landing speed	96 km / h
Rise time	9.5 min at an altitude of 6,000 m
Service ceiling	10,000 m
Range	600 km
Armament	-

literature

Jörg Armin Kranzhoff: Arado. History of an aircraft factory . 1st edition. Aviatic, Oberhaching 1995, ISBN 3-925505-27-X .
Volker Koos: Arado Flugzeugwerke 1925–1945 . Heel, Königswinter 2007, ISBN 978-3-89880-728-9 .
William Green: Warplanes of the Third Reich . Galahad Books, 1990.

Web links

Commons : Arado Ar 80 - collection of images, videos and audio files

Thomas Wilberg: Arado Ar 80 V2. The Virtual Aviation Museum, accessed on March 31, 2015 .
Arado Ar 80 Source: FliegerWeb.com