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Autogyro

An autogyro, or autogiro, sometimes called a gyroplane or Gyrocopter (TM), is an aircraft that has an unpowered rotary wing, or rotor, and looks similar to a helicopter. It is moved through the air by either an engine-powered propeller or a tow cable.

General characteristics

Autogyros can take off and land in short fields compared to conventional fixed-wing aircraft. They can even land straight down. When they have a jump start feature, they can jump vertically and then start flying forward so avoiding a take off run (but this does not give them a hovering ability); but this feature adds weight, complexity and expense so it is not common. If they have a variable-pitch rotor, they can flare to a soft vertical landing, using excess momentum in the rotor to perform a soft landing; this is related to the way the jump start feature is implemented.

Autogyros are notably safe. If the engine should fail, the autogyro does not stall or spin. Instead, it begins to settle like a parachute. The pilot can usually maintain some directional control by slipping the rotor.

Autogyros are neither efficient nor fast. Fixed-wing aircraft use less fuel over the same distance.

They are more maneuverable than fixed-wing aircraft, but cannot hover as a true helicopter can. When helicopters became practical, autogyros were neglected for nearly thirty years. Yet they were used extensively by major newspapers to move information from city roof top to roof top.

As the infastructure for service, repair, training and building increases the number of gyrocopter users may increase. NASA is said to be exploring the use of these sporty flying machines to encourage personal air transportation for everyone.

History

Juan de la Cierva, a Spanish aeronaut, invented the autogyro sometime around 1923. His craft used a tractor-mounted forward propeller and engine, a rotor mounted on a mast, and a vertical stabilizer. His first three designs the C.1, C.2, and C.3, constructed by Parnall were unstable. His fourth design, the C.4, was successful.

The C-11 and some of his later designs had a power-coupling to the rotor, the so-called "jump" feature. The rotor would be sped up before the take-off roll. The coupling would be disengaged during the the take-off as the airflow began to power the rotor. This allowed the craft to take off with almost no roll at all.

The C-19 was licensed to a number of manufacturers, including Harold Pitcairn in the U.S. (in 1928) and Focke-Angelis of Germany. In 1931 Amelia Earheart flew a Pitcairn PCA-2 to a then world altitude record of 18,415 feet.

In World War II, Germany pioneered very small gyrogliders towed by submarines safety and short-field ability of an autogyro.

Since Bensen, a number of improved designs have been constructed. Two FAA-certified designs have been commercial failures, despite performing well.

Modern autogyros are quite frisky on the ground, and versions with brakes and tied rotors have been driven successfully in heavy automobile traffic.

Bensen's design

The Bensen Gyrocopter (TM), the protoype of modern gyroplanes, actually consists of three versions, the G-6, G-7 and G-8. All three were designed in both unpowered and powered forms.

The two-bladed rotor is 20 to 21 feet (6.4m) in diameter (models have slight variations) with a 7" (17.8cm) width and 2 degree angle of attack.

Rotor loading is roughly 1.5lbs/square foot (7.3Kg/sq. m).

The gross vehicle size is 5ft (1.5m) wide by 6ft (1.8m) tall by 6 to 7ft (2m) long.

Payload is 250 to 300 lbs (110 to 135Kg), depending on the frame material and engine. The payload is usually a single pilot.

Dry unloaded weight varies from 155lbs (70Kg) (for an unpowered gyroglider) to 254lbs (115Kg) depending on the model, presence and type of engine.

Gross take-off weight is approximately 550lbs (250Kg).

Ceiling is 15,000 feet (4500m) on a good day with high-octane fuel.

Maximum speed is 75 to 100mph (125-165Kph). Cruising speed is 65mph (110Kph).

Endurance is usually one to two hours, limited by the gas tank and pilot endurance.

As of 2002, Wing Commander Ken Wallis, an enthusiast who has built several a major rise in the use of gyrocopters for herding range animals. One gyrocopter 'cowboy' holds the worlds record for total hours in the air each week.

The basic design is a simple frame of square aluminum or galvanized steel tubing, reinforced with triangles of lighter tubing. It is arranged so that the stress falls on the tubes, or special fittings, not the bolts. All welds or soldered sructural joints should be inspected.

The rotor is on the top of the vertical mast. The outlying fixed wheels are mounted on an axle (of tubing). The front-to-back keel (more tubing) mounts the forward wheel (which casters), seat, other tubes, engine and a vertical stabilizer. Some versions mount seaplane-style floats and successfully land and take off from water.

It is common for the vertical stabilizer to drag on the ground unless it is cut away. This is also why many frames have a small wheel mounted on the back end of the keel.

The rotor is not symmetric as in a helicopter. It has a true wing shape. Most light gyroplane rotors are made from aluminum.



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