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GOT: The Arado Ar 80

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#1 Romantic Technofreak

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Posted 02 December 2004 - 01:23 AM

Since the original links were dead, and the Wikipedia article in English language is not too complete, I translated the German one for you. Nowadays I use Google translate for the basics aund could use some sentences one to one, but had to do a lot of improving work still. Now please enjoy reading about


The Arado Ar 80

The Arado Ar 80 was a pre-war fighter development of the Arado Flugzeugwerke. It was designed for the first Luftwaffe fighter contest before the Second World War but showed no convincing performances and was additionally hampered by numerous problems. The contest was finally won by the Messerschmitt Bf 109 for good reasons, and the prototypes of the Ar 80 ended up as test aircraft.

Background

Arado was one of the few German companies that by the time of the contest already had experience in the design of modern fighter aircraft. The Arado Ar 65, which in this time had been the best fighter aircraft of the Luftwaffe, was already produced in series, and the Arado Ar 68 emerged as successor to it. For this, Arado became one of the candidates for the construction of the future fighter aircraft.

The contest

In 1933, the Technical Office of the Reich Air Ministry (RLM) decided a number of research projects for the future of air combat. The results were four basic designs of the future Luftwaffe aircraft:

"Rüstungsflugzeug I" (= "armed aircraft I") for a multi-seated medium bomber
"Rüstungsflugzeug II" (= "armed aircraft II") for a tactical bomber
"Rüstungsflugzeug III" (= "armed aircraft III") for a two-seated heavy fighter
"Rüstungsflugzeug IV" (= "armed aircraft IV") for a single-seated fighter aircraft

The Rüstungsflugzeug IV had to be a single-seated fighter in the form of an all-metal monoplane, which would replace the set of contemporary biplanes. Although the future aircraft should be able to beat all others in flight performances, the requirements were not set too high.

Equipped with the new engine Junkers Jumo 210, the aircraft should be able to reach a top speed of 400 km/h at 6000 m and to keep it for 20 minutes. It should have been able to fly a total of 90 minutes. At least three machine guns with 1000 rounds each, or a 20-mm cannon with 200 rounds should be used. To ensure a high maneuverability, the wing load was to be less than 100 kg /m². The priorities were laid out in the order: airspeed, rate of climb and maneuverability.

These specifications were not established in isolation, they were rather based on private developments, which had started in 1933 by Heinkel and Arado for a fighter aircraft in monoplane configuration. Only the best features of both types were selected and brought together in a specification. Hermann Göring initially demanded in October 1933 a so-called "high-speed courier aircraft" from these companies. In May 1934, the final and official contest for the fighter followed.

The invitation went out to Heinkel, Arado and also Focke-Wulf . During the year 1934, everyone should deliver three prototypes for a direct comparison. A few months later flew the Messerschmitt Bf 108 of the Bayerische Flugzeugwerke (BFW), which arose due to the demand for a "light aircraft". Because of the advanced design BFW was then also offered to participate.


Development history

Although officially Walter Blume was head of the design team, most of the preliminary work, however, was contributed by Walter Rethel. He knew the pros and cons of the monocoque design, but otherwise Arado had no experience with it. The competitor Heinkel had in 1932 already gained experience in shell construction for the Heinkel He 70 and thus was at an advantage.

Nevertheless, Rethel believed that he would not only be able to successfully build an airplane in shell construction, but also a lighter and easier-to-build construction than the other companies. His solution was to put two sets of metal rails along the fuselage.

The first set was roughly shaped in form of a "C" - with narrow flanges on the open ends of the C, on which they could easily be riveted to the frames. In this way he was able to save the usual longitudinal ridges between the ribs. When attaching long, parallel stripes on a cigar-shaped surface it is clear that the distance between the stripes gets smaller toward the ends. To fill these gaps, Rethel used a second set of metal rails that were cut in form in a way it could accurately cover these gaps. This system should not only allowed a "perfect" aerodynamic shape, but was theoretically even easier and simpler to be built. The system seemed so advantageous that it was believed to be possible to build other parts of the aircraft heavier and more stable.

The rest of the aircraft was rather conventional. The front body and the inner wing were made of steel tubes with attached aluminum panels, the wing ends came from aluminum moldings, which were at the top also clad with aluminum and at the bottom were covered with fabric. Like in the Heinkel designs, a gull wing was used to get a shorter undercarriage. But while Heinkel chose an elliptical airfoil shape, Arado chose a straight shape.

In order for not needing to open the form parts of the outer wing to accommodate a retractable landing gear, Rethel decided to directly retract the landing gear to the rear, the wheel then should be rotated by 90 degrees.


Test samples

Since Rethel in 1934 even before the completion of the Ar 80 transferred to Willy Messerschmitt, the construction was continued by Blume. The aircraft was to be equipped with the Junkers Jumo 210 engine and a non-adjustable wooden two-blade propeller. Coincidentally, Arado already had bought a Rolls-Royce Kestrel VI engine for use in the Arado Ar 67 (this aircraft was +/- an Ar 65 with little changes, constructed for the only purpose to test the RR Kestrel in Germany, RT). This engine had indeed no good compressor, resulting in the Ar 67 in poor performances; but the aircraft was able to be flown at least, as long as the Jumo engines were not available.

In spring 1935, the V 1 took off for the first flight. Thus, it was one of the first aircraft in the competition to be already able to. A few weeks later, however, one of the test pilots lost control of the aircraft and it was destroyed.

Already in these few weeks, the undercarriage proved to be a real problem. During retraction, it always stuck in the semi-closed state, but fortunately could be extended again for landing. Several attempts to solve this problem proved unsuccessful. While the aircraft was jacked up in the hangar, the landing gear worked fine. In the end it was discovered that in flight the air flow acting on the shock absorber made it jam in such a way in its tube, so the wheel could not be rotated to retract.

Another trouble arising during construction was that Rethel's stripe design turned out to be much heavier than expected. The main problem was that many more rivets were needed than had been expected . In the end, the aircraft was too heavy overall.

The V 2 was built in a big hurry, but the Jumo engine was still not available. To give the contestants a reasonably realistic engine, the RLM traded a He 70 for four Rolls-Royce Kestrel Vs. Basically, the Kestrel V was indeed the same engine as the VI, but had a much better compressor and represented at the time the strongest available engine. The companies fought hard to get this engine for their prototypes. Presumably the future results now already showed, because BFW received two engines, one each Arado and Heinkel, and Focke-Wulf none.

In autumn 1935, (originally 1937, but this must be a mistake, RT) the V 2 was completed with the Kestrel, and testing started. Once again, the undercarriage proved to be a problem. Blume blamed Rethel for these problems and said that he was sceptical about the design from the very beginning. He decided that the performance penalty of a fixed landing gear would be offset by its low weight and gave the Ar 80 an undercarriage of this kind - similar to that which the biplanes had already possessed. Several months were lost for the change.

But the solid undercarriage did not save so much weight as expected and the aircraft at 1630 kg empty weight still was 16% heavier than planned. Fully loaded, it weighed 2100 kg. Also with the Kestrel V it was underpowered. Furthermore, the air drag was higher than expected. In the end it was not surprising that the aircraft produced only a disappointing performance and reached only 410 km/h.

In the beginning of 1936 the Jumo 210 finally came. It had not so much starting power as the Kestrel, but in flight the performance was similar. The speed could be increased with increasing altitude, but the performance close to the ground and climb performance dropped off significantly. Arado had the opinion that the installation of a variable-pitch propeller could improve both, and may increase the top speed to 425 km/h. But until to the comparative flights no more attempts to this were made.

Although the Arado was actually one of the first aircraft which flew in the competition, due to the ongoing problems with the undercarriage and the engine it arrived as one of the last for the comparison. On 8 February 1936 it was delivered in Travemünde and in March transferred to Rechlin. There it showed that the Ar 80 had no chance against the competition from Heinkel and BFW.


Further trial samples

At this time the V 3 was already completed .To save weight, the gull wing was replaced by a straight one, needing a slightly longer undercarriage. Also, a Jumo 210C with a variable pitch propeller was installed, which resulted in a speed of 410 km/h. At this time, the RLM already had rejected the design, and the V 3 remained at Arado's in the hangar.

In 1937, the V 3 was reactivated as a flying test bed for various experiments. Behind the pilot's seat, a second seat for an observer was installed and completed by a canopy (there is no picture available showing this configuration in complete, RT). For the first time, in this aircraft shooting took place through the hollow propeller hub with a 20-mm gun. Thus, the Ar 80 was the first German aircraft with engine cannon (MK) - an armament, which later became the standard for many fighters, so with the Messerschmitt Bf 109, which eventually won the flight competition.

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


Conclusion

The Arado 80 apparently was a victim of its own success. At the same time it was also the oldest of the submitted designs. Because of the speed at which the aircraft development progressed in the 1930s, the recently developed aircraft was almost certainly the best - and that's how it was with the victory of the Bf 109.

The sum of Arados lack of experience in the construction of monocoque aircraft and Blume's inability to solve the problem with the retractable landing gear predictably led to the fact that this aircraft never had a chance. Since only three prototypes were built, it is not much surprising that it is hardly known today.

End of the Wikipedia article. Please look the original article http://de.wikipedia....iki/Arado_Ar_80 for souces and the net for pictures.


Regards, RT


Edited by Romantic Technofreak, 04 August 2013 - 03:45 PM.


#2 Romantic Technofreak

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Posted 05 January 2013 - 08:42 AM

Just to show that changes were done. Please look above!

Regards, RT

#3 GregP

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Posted 22 January 2013 - 05:42 AM

Hi Holger!

Thanks for the research. It was a neat if obscure type and most people never heard of it. I'd love to fly one ...

Robin, Bob, and Joe say "Hi!"

- Greg





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