Cyclogyro

The cyclogyro, or cyclocopter, is an aircraft design that uses cyclorotors as the principal source of lift, propulsion, and control. They are capable of vertical take off and landing and hovering performance like a helicopter, without the same disadvantages such as limited forward speed, very high noise and vibration levels, limited flight altitude etc. The biggest hope of Cyclocopter developers, which remains unrealised in any flying prototypes, is to achieve higher efficiency in terms of lift per engine horsepower (aka Power Loading) which would translate into higher lifting capability and longer flight range. Although a number of cyclogyros were built in the 1930s, none were known to have successfully flown until 2011. The cyclogyro should not be mistaken for Flettner airplanes, the unsuccessful and aerodynamically different aircraft designs using cylindrical wings which attempted to harness the Magnus effect.

The cyclogyro wing resembles a paddle wheel, with airfoils replacing the paddles. The airfoils' pitch (angle of attack) is adjusted either collectively (by means of a control ring with links to all blades, which is located eccentrically and variably relative to the rotor's axis of rotation) or the blades are individually adjustable in pitch and are adjusted continually by the control system as they move around the rotor's axis. In normal forward flight the airfoils are given a slight positive pitch at the upper and forward portions of their arc, producing lift and forward thrust. They are given flat or negative pitch at the bottom, and are "flat" through the rest of the circle to produce little or no lift in other directions. The pitch can be adjusted to change the thrust profile, allowing the cyclogyro to travel in any direction. Differential thrust between the two wings (one on either side of the fuselage) can be used to turn the aircraft around its vertical axis, although conventional tail surfaces are generally used as well.

Jonathan Edward Caldwell appears to have been the first to patent the concept, and invent the term. He filed a patent on the concept that was granted in 1927, but immediately moved on to an ornithopter design and then an autogyro. Several attempts to build a working cyclogyro were made by other designers. The earliest full-sized example appears to be the Schroeder S1 from 1930, which used the cyclogyro "wheels" for forward thrust only.Adolf Rohrbach of Germany designed a full VTOL version in 1933, which was later developed in the US and featured a tall fish-like fuselage to keep the wings well clear of the ground. Another early example was by Rahn Aircraft in 1935, which used two much larger chord wings instead of a multi-blade wheel driven by a 240 hp supercharged Wright Whirlwind In 1935 NACA carried out a series of wind tunnel experiments on the cyclogyro concept, and found that the power required to turn the wheels was much higher than expected. Theoretical tools of the era simply weren't useful for prediction on the highly asymmetrical lift profiles and the greatly simplified models they used varied dramatically from real-world results. Early experiments then ended.

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