Cyclogyro

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Concept drawing of a 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.[citation needed] Although a number of cyclogyros were built in the 1930s, none were known to have successfully flown until 2011.[citation needed] The cyclogyro should not be mistaken for Flettner airplanes, the aerodynamically different aircraft designs using cylindrical wings which attempted to harness the Magnus effect.

Function

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.[1] 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.[2]

Animation of cyclogyro wing mechanics.

History

Early designs

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.[3] 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.[citation needed] Adolf Rohrbach of Germany designed a full VTOL version in 1933,[4] which was later developed in the US and featured a tall fish-like fuselage to keep the wings well clear of the ground.[5] 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[6] 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.[citation needed] 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.[citation needed] Early experiments then ended.

Recent advances

The concept has recently been applied to smaller unmanned aerial vehicle designs, where the hovering capability would be particularly useful.[7][8][9] Several of these designs have produced flying prototype models:

  • In 2007 a team at the University of Singapore built a working model of cyclogyro, although it has only flown in tethered flight. Their cycloidal model was a modified helicopter, with the rotor replaced with two sideways cycloidal rotors, each with three blades sticking out of them in the perpendicular.[10]
  • InAugust 2011 a team at Northwestern Polytechnical University in China flew a free flying Cyclogyro. This design used two cycloidal rotors for the generation of lift and small conventional head and tail rotors to stabilize the craft and provide control of its horizontal position and direction of flight.[citation needed]
  • In December 2011 a team at the University of Maryland successfully built and tested a micro Cyclocopter. Their design does not require a head rotor in addition to the usual tail rotor.[citation needed]
  • The Austrian company Innovative Aerodynamic Technologies (IAT) premiered a 4 rotor cyclogyro at the Paris Air Show in June 2011.[11]
  • A team at the Seoul National University has built and in December 2012 successfully demonstrated a stable, mostly hovering flight of a 4 rotor Cyclocopter.[citation needed]
  • In Israel, OptiVector Ltd. has conducted Computational Fluid Dynamics (CFD) studies of these rotors in hovering flight using various elliptic blade trajectories, observing power loadings in excess of 16 kgf/hp.[citation needed]
Animation of the Heligyro wing deformation.

A European Seventh Framework Programme consortium, the CROP, also studied cycloidal rotors with the optic of optimizing their performance.[12] Within this project, various possible aircraft configurations were considered. One of those is the Heligyro, for which a conceptual aeroelastic study rendering is shown. A 3-meter demonstrator is expected to fly in 2016 along with the 20 kg D-DALUS.[13]

Future developments

Future developments, such as a variable cycloidal rotor, with optimized and elongated blade trajectory instead of the circular one, may improve the cyclogyro design. The dynamic counterbalancing of the blades radial movements would then be used to keep the rotor balanced for non-symmetric trajectories. However, oncoming flow severely disrupts the operation of a cycloidal rotor. Potential developments include shielding or partially enclosing the rotor, varying the blade elliptic orbit by means of inclining the blade trajectory positioning track so that its projection on the blades plane of operation changes, and variable shape trajectory tracks.

See also

References

  1. ^ The Development of cyclogyro
  2. ^ The Cyclogyros, Planned paddle-wheel aeroplanes
  3. ^ "The Fantastically Flighty Gray Goose"
  4. ^ Shackleton, W.S. (November 2, 1933), "The Rohrbach Rotating Wing Aeroplane", Flight, XXV (1297): 1087–1090
  5. ^ "Rohrbach Cyclogyro"
  6. ^ Rahn Aerofiles.
  7. ^ Aerodynamics of the Cyclogyro aps.org
  8. ^ The research on the performance of cyclogyro aiaa.org
  9. ^ Development of a Cyclogyro-based Flying Robot with Variable Attack Angle Mechanisms ieee.org
  10. ^ Simonite, Tom (2008-02-22). "Flying 'paddleboat' may finally take off". NewScientist.com news service.
  11. ^ IAT (2012-10-11). "D-DALUS Website". http://iat21.at/. {{cite news}}: External link in |publisher= (help)
  12. ^ CROP (2014-11-10). "CROP Project Website".
  13. ^ http://www.janes.com/article/54330/dsei-2015-iat21-showcases-cyclogyro-helicopter-for-improved-lift-and-increased-efficiency

Further reading

  • "The Cyclogyro", Vertiflight, The American Helicopter Society, 2005, Vol. 51; No. 2, pages 16–19

External links

Media related to Cyclogyro at Wikimedia Commons

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