Germany (1943)
Experimental Circular Wing Aircraft – 1 Prototype Built
History
Prior to the war, Germans were prohibited from developing and building military aircraft. The Germans simply bypassed this prohibition by instead focusing on gliders, but also on civilian aircraft which if needed would be quickly converted for military use and conducted secret experiments. They especially took great care in the development and investment of manned gliders, but also scale model-building competitions and organizations. While this may seem like a waste of time and money, it actually helped gain initial and valuable experience in aircraft development which proved vital for the later Luftwaffe.
One such model competition was the National Contest of Aero Models with combustion engines, held in late June 1939 at Leipzig-Mockau. Here, aviation enthusiast Arthur Sack presented his model of an unusually circular-wing-shaped aircraft named AS-1. It is sadly unclear why Sack pursued the design of such an unusual aircraft design. Due to engine problems, the AS-1 was unable to take off from the ground, so the small model had to be launched by hand instead. The Air Minister (Reichsluftfahrtministerium RLM) Ernst Udet, who was present at the event, seemed to be impressed with this design and advised Sack to continue its development.
With the order secured, Sack initiated the construction of a prototype. He named this aircraft the AS-6 V1 (Versuchs – version). As he had no proper workshop to build the aircraft himself, the glider manufacturer Mitteldeutsche Metallwerke was tasked with this instead. The initial work for the assembly of the aircraft began in the autumn of 1943. It took nearly half a year to complete the working prototype. Interestingly, due to the general shortage of materials, the AS-6 was constructed by utilizing a considerable amount of salvaged components from other damaged aircraft. For example, the cockpit canopy and parts of the interior were taken from a Bf 109B. Once the prototype was ready, it was allocated to the Luftwaffe for initial tests in early 1944.
![](https://i0.wp.com/plane-encyclopedia.com/wp-content/uploads/2022/05/Sack-AS-6-3.jpg?resize=604%2C453&ssl=1)
Technical Characteristics
The cockpit canopy and its interior, as already mentioned, were taken from a Bf 109B. The cockpit was slightly elevated above the fuselage and provided the pilot with an excellent all-around view. The landing gear was also salvaged from a Bf 109B, but in the case of the AS-6, it was fixed. Initially, a landing skid was used on the rear, which was later replaced with a landing wheel instead.
![](https://i0.wp.com/plane-encyclopedia.com/wp-content/uploads/2022/05/Sack-AS-6-7.jpeg?resize=600%2C338&ssl=1)
Testing the Prototype
Initial evaluation tests of the AS-6 prototype were conducted at the Luftwaffe Brandis Airbase. The flight tests were conducted by Rolf Baltabol Junkers test pilot. While several short take-offs were made, there were no attempts to actually take the aircraft to the sky. The test pilot noted that the aircraft had an overall poor design and was difficult to control. He urged that the control surfaces and rudder be completely redesigned. The engine was also deemed too weak. During the last short take-off, one of the two landing gear assemblies was damaged.
The AS-6, following its unsuccessful start, spent several weeks in repairs and received a number of modifications in an attempt to improve its performance. These included adding an additional 70 kg of weight to the rear, installation of brakes taken from a Ju 88, and repositioning the landing wheels to the rear by about 20 cm. Sack proposed moving the landing wheels further back, but the test pilot Rolf simply refused to fly it if this change was implemented. He argued that placing the landing gear to the rear would imbalance the aircraft potentially leading to tipping forward during a take-off. For this reason, the modification was not implemented. While the engine was underpowered, there were simply no alternatives available at that time.
The fate of the AS-6
Following the unsuccessful testing, the AS-6 was stored at the Brandis airfield. In the summer of 1944, this airfield became the main operational base for the experimental Me 163 rocket-powered aircraft. The pilots of the I./JG 400 (charged with testing the Me 163) found the AS-6. One of its pilots, Franz Rossle, expressed a desire to attempt flying the unusual plane. But when the ground crew was preparing the aircraft for take-off, one of its landing gear units simply broke due to rough terrain, effectively preventing the test flight to be conducted. After this, it was once again stored at Brandis. It would remain there until early 1945 when it was lost in an Allied bombing raid.
The AS-7 project
While not clear when (possibly during early 1945), Sack approached Messerschmitt company with a proposal to use his circular-wing design on the Bf 109K-4 aircraft. The aircraft marked as SA-7 would be powered by a DB 605 2,000 hp engine. Fitted with circular wings it was theorized that it would be capable of carrying more armament inside the wings. It is believed (but not clear) that Messerschmitt was interested in this proposal and designated the project Me 600. Due to the war’s end, nothing really came from this project.
Conclusion
While certainly an unusual and interesting design, due to poor quality and salvaged materials used during its construction, the AS-6 performed poorly and never actually achieved flight. We will never know if the AS-6 circular-wing design offered any major advantage over more conventional wing designs. It appears that Arthur Sack did not continue with his idea after the war and passed away in the mid-1960’s. While his work was never implemented in mass production, his unusual design was often mistakenly taken as some advanced and secret German World War II project, which ironically, it never was.
AS-6 Specifications |
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Wingspan | 16 ft 5 in / 5 m | |
Length | 21 ft / 6.4 m | |
Wing Area | 19.62 ft² / 211 m² | |
Engine | One 240 hp Argus As 10C-3 engine | |
Maximum Take-off Weight | 1,984 lbs / 900 kg | |
Crew | 1 pilot | |
Armament |
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Gallery
Illustration by Ed Jackson
Credits
- Written by Marko P.
- Edited by Henry H. & Blaze
- Illustrated by Ed Jackson
Sources
- B. Rose and T. Butler (2006) Secret Projects Flying Saucer Aircraft, Midland Publishing
- J. Dennis G.G. Lepage (2009) Aircraft of the Luftwaffe 1935-1945, McFarland and Company
- Duško N. (2008) Naoružanje Drugog Svetsko Rata-Nemacka. Beograd.
- http://www.luft46.com/misc/sackas6.html