The design of the autogyro greatly affects the outcome of the machine. A poorly designed gyro can result in disaster, just like any great invention. First we will discuss the parts of an autogyro.

Obviously the most important piece is the rotor. Every autogyro has one to create lift. The rotor has two or more blades which are attached to the mast axis by several hinges. Essentially what theses hinges do is prevent aerodynamic forces from interacting with the mast and fuselage too much. Also there must be a propeller for thrust. Also, if the rotor is not pitch variable, meaning that the rotor can be controlled by a joystick to change direction, there must also be a rudder and ailerons. These essentially do the same thing, by changing the direction of flight.

As the rotor wings fly into the wind, they create more lift than the blade flying away from the wind. If not corrected, this can set the lift of the machine off balance and the autogyro could possibly tilt. This is what happened with Cierva's early autogyros. As was aforementioned, he fixed this by added hinged rotors. This allowed the front blade to lift while the back blade dropped. Refer to figure F1 for reference. This type of hinge was called the flapping hinge.

Flapping Hinge

Picture courtesy of huizen.dds.nl/~w-p/bookaut

When a hinge is in its flapping motion, it is slightly more toward the center of rotation in relation to its original position. This is because the blades have lifted. When this happens, the moment of inertia decreases, which causes the angular velocity of the blade to increase exponentially. To compensate for this increase in velocity, lead-lag hinges are used to allow the blades to "lag" back, so that not as much stress is put upon the blades. This is shown in figure F2.

Lead-lag Hinge

Picture courtesy of huizen.dds.nl/~w-p/bookaut

Certain newer autogyros, and all modern helicopters, have a new kind of hinge called the feathering hinge. This is used to change the pitch of the blades for vertical lift-offs. Basically, this changes the angle that the blade flaps into the wind, therefore changing the angle of lift. These hinges generally aren't used on light or ultra-light autogyros, because they aren't necessary unless you want to accomplish a vertical take-off. This type of hinge can be seen in figure F3.

Feathering Hinge

Picture courtesy of huizen.dds.nl/~w-p/bookaut

The mast is also a central part of the aircrafts system in that it is basically what holds up the rotor. This is all a matter of weight. When you get out of the light and ultra-light range, the rotor becomes too heavy for just the cabin roof to hold up itself. This is where the mast comes in to help hold the rotor. Also the flexibility of the mast helps to reduce the large changes in the moment of inertia from the blades flapping, much like the lead-lag hinges.

The fuselage keeps everything together. Sometimes it has a nice aerodynamic shape to keep the drag at a moderate level and to keep the pilot out of the air stream if he is exposed. Small wings called canards can be fitted if you want to reduce the drag even more.