OT-but cool.

[Hauksbee 103]

 

falkeeins.blogspot.com/2011/11/arthur-sack-as-6-flugplatz-brandis.

Arthur Sack Kreisflügler Sack AS 6 Flugplatz Brandis - flying disc design tested by JG 400 Me 163 Komet pilot

Over in 72 Land Kevin Callahan has finished his Special Hobby Sack AS 6. I happened to see this at the same time as Tom GF was reviewing Stephen Ransom's brief history of Brandis airfield "Zwischen Leipzig und der Mulde" at his German Aviation 1919-1945 blog Like all of Tom's recommendations this little booklet is well worth tracking down - especially as amazon.de re-sellers have copies on offer for under 10 euros. The connection is Ransom's treatment of the Sack AS 6 on page 61 of his Brandis history. He provides some fascinating information..

 

Circular wing aircraft planforms were all the rage in America in the 1930s and for a time post war. In fact the American "flying flapjack" flew well enough, but these designs were ultimately no more than aeronautical cul-de-sacs. The Luftwaffe 'sponsored' a similar concept - although their machine was dreamt up in his barn by a farmer, Arthur Sack from Mackern in Saxony (north-east of Leipzig). Sack was an aero-modeller who had entered his flying model in a contest in Leipzig in 1939 and where he had apparently met Ernst Udet who had encouraged him to continue his 'design' work. By early 1944 Sack had built his first piloted Kreisflügler circular wing design 'aircraft', since designated the Sack AS 6 (or the Sack AS 6 V1 according to Special Hobby). Sack then apparently persuaded the Kommandant of his local airfield to allow some developmental work to go on at his airfield - only in this case the local airfield was Flugplatz Brandis, where later that year highly secret and state-of-the-art designs such as the rocket-powered Messerschmitt Me 163 point interceptor and the amazing forward-swept wing Junkers Ju 287 jet bomber were being test flown and operated!

 

 

Despite the presence of such a 'design' at a 'secret' test base like Brandis, the Sack AS 6 was as far removed aeronautically from these futuristic machines as it was possible to be - a plywood circular wing powered by an old Messerschmitt Bf 108 Argus engine utilising cockpit parts from a crashed Bf 109. Ground taxiing tests were performed during February 1944, with the first test proving that the rudder was not strong enough and the landing gear not fit for purpose - some structural damage ensued. Five takeoff runs were made during the second test on the 1200 metre Brandis runway during April 1944 with ATG Leipzig test pilot Baltabol at the controls. Testing continued that summer -presumably on a very ad-hoc basis - with a pilot who had some experience of tail-less aircraft trying his hand - Oblt. Franz Rösle, Staffelkapitän of 3./JG 400. These were apparently flight tests although it is doubtful whether the Sack AS 6 ever got airborne - other than a short hop - since it was clear that the 'aircraft' was under-powered. In addition the control surfaces of the flying 'beer mat ' were hopelessly inadequate since they were masked by the circular wing. Based on eye witness reports Ransom concludes that the Sack AS 6 never flew and the 'aircraft' was later broken up on the airfield for fire wood. Of course it is entirely possible that the main legacy of the Sack AS 6 was the host of rumours and myths post-war regarding German 'disc' aircraft and flying saucers...

 

Edited November 29, 2011 by Hauksbee

[Von Paulus 8]

The Germans, must have tested all kind of airplane shapes in WW2.

This one was unknown to me.

Thanks for sharing.

[UK_Widowmaker 571]

The TRUE UFO's

 

Little green men from Mars?...yeah, right

[Hauksbee 103]

The TRUE UFO's

Little green men from Mars?...

Why not? It's a little green plane.

[Hauksbee 103]

There's been a lot of attempts to make a flying disc. It's the Siren's Call of aeronautics. It turns out that discus shaped airfoils just don't want to work. As the air comes up and over the the mid-point and moves toward the trailing edge, it spills away in a large, turbulent vortex to each side. There's not enough 'clean air' lift to make up for the dead weight drag of the aft end. In the Sack AS6, the cone of turbulence would start next to the canopy and spiral out across the ailerons, rendering them useless, even if the Sack did manage to lift of. Then there was the U.S.Navy's XF5U-1 "Flying Pancake". [The following is from Wikipedia] A developed version of the original V-173 prototype, the XF5U-1 was a larger aircraft. Of all-metal construction, it was almost five times heavier, with two 1,600 hp (1,193 kW) Pratt & Whitney R-2000 radial engines. The configuration was designed to create a low aspect ratio aircraft with low takeoff and landing speeds but high top speed. The XF5U looks like it should not be able to fly, as its wing area looks so small. Normally, a wing with such a low aspect ratio will suffer from very poor performance due to the degree of induced drag created at the wingtips, as the higher pressure air below spills around the wingtip to the lower-pressure region above. In a conventional aircraft, these wingtip vortices carry a lot of energy with them and hence create drag. The usual approach to reducing these vortices is to build a wing with a high aspect ratio, i.e. one that is long and narrow. However, such wings compromise the maneuverability and roll rate of the aircraft, or present a structural challenge in building them stiff enough. The XF5U overcomes the tip vortex problem using the propellers to actively cancel the drag-causing tip vortices.^[3] The propellers are arranged to rotate in the opposite direction to the tip vortices, which retains the higher-pressure air below the wing. Since this source of drag is eliminated, the aircraft will fly with a much smaller wing area, and the small wing yields high maneuverability with greater structural strength. The propellers envisioned for the completed fighter were to have a built-in cyclic movement like a helicopter's main rotor, with a very limited ability to tilt up and down to aid the aircraft in maneuvering. An ejection seat was fitted to allow the pilot to clear the massive propellers in the event of an in-flight emergency. Although the prototype was unarmed, a combination of machine guns and cannons would have been installed under the nose. Testing and evaluation The XF5U design was promising: specifications given at the time promised the ability to hover like a helicopter while having an airspeed range of 0 to 550 mph (885 km/h). However, it came at the time when the United States Navy was switching from propeller driven to jet propelled aircraft. By 1946, the XF5U-1 project was already long over its expected development time, and well over budget. With jet aircraft coming into service the Navy finally canceled the project on 17 March 1947 and the prototype aircraft (V-173) was transferred to the Smithsonian Museum for display. Although two aircraft were constructed, a lone XF5U-1 underwent ground runs but never overcame vibration problems. Taxi trials at Vought's Connecticut factory culminated in short "hops" that were not considered true flights. The only completed XF5U-1 proved to be so structurally solid that it had to be destroyed by a wrecking ball.[

Edited November 30, 2011 by Hauksbee