Advancing Blade Airfoil (Rotor) Angle of Attack Angle of Incidence Area (Blade) Area (Rotor) Autogiro

Blade (Rotor)

Blade Track Blade Tracking


Center of Gravity (Chordwise C.G.)

Center of Gravity (Spanwise G.G.)

Chord Line

(Horizontal Axis)

Coning Angle Damper Lead-Lag

A Glossary of Autogiro Terms

The blade that is moving into the oncoming airstream caused by forward flight of the aircraft.

The profile of the rotor blade that would be present if the blade was sliced through from leading edge to trailing edge.

The angle made by the intersection of a line drawn parallel with the chord line of the rotor airfoil and a line drawn parallel with the relative wind.

The angle made by the intersection of a line parallel with the chordline of the rotor airfoil and the horizontal (flapping) pin.

The actual area, in square feet included within the airfoil section of one blade, not including blade attach fittings and devices.

The area in square feet included within a circle drawn using the length of one blade from center of rotation to the tip, as the radius.

When spelled with a capital" A" denotes an aircraft, supported in flight by a rotor which is turning by the principle of autorotation, and produced by Sr. Juan de la Cierva or one of his licensees. When spelled with a lower case "a" it is intended to mean an autogiro-type aircraft built by persons other than Cierva licensees.

One of the elements in a rotor system that produces lift (in early days called rotor vanes).

The actual tip path of all blades in a rotor system.

The adjusting of the flight of each blade in the rotor system so that each blade follows the same path for smooth flight.

The top and bottom curvature of an airfoil.

The distance, in inches and hundredths of an inch, from the leading edge of a rotor blade at which the blade would balance chordwise.

The distance, in inches and hundredths of an inch from the center of rotation toward the tip, at a point where the blade would balance span-wise.

A line running from the leading edge of an airfoil to the trailing edge.

The flapping angle that the blade assumes as it revolves into the relative wind and with the relative wind. There is no mechanical stop to limit the up-flapping of the blades. The centrifugal force tries to pull the blade away from the center of rotation and lift tries to raise the blade straight up. The combination of the lifting force and centrifugal force causes the blade to have an angle above the horizontal,

A mechanical device that restricts the lead-lag motion of a rotor blade. Usually a viscous or friction method. The stationary part may be attached to the hub. The active part to the blades.

Diameter (Rotor)

Disc Loading Drag

Droop Cable

Droop Stop Flapping Hinge Flapping Link

Ground Resonance (Ground Instability)

Gyro copter

Gyroplane Hub (Rotor)

A great circle using as the radius the length of one blade in the system from the center of rotation.

The percentage of the design gross weight carried on each square foot of the rotor "disc" area expressed in pounds per square foot.

An aerodynamic force that resists the motion of objects being moved through the air. As the speed of the air over the object increases or the speed of the object increases through the air.

The older, 1920-1930's autogiro supported the blades while on the ground or at low rotational speeds with a cable attached to the blade about 1/3 of the distance out from the huh and to a "cone" or "tower" on the center of rotation.

A positive mechanical stop to restrict the down-flapping of the rotor blade on autogiros that weren't equipped with droop cables.

The mechanical joint including the flapping or horizontal pin which permits the freedom of motion for the blade tip to move up and down.

An attachment between the inboard (root) end of the rotor blade and the hub. The inboard end receives the flapping pin. The outboard end usually has the accommodation for the lead/lag pin.

An undesirable dynamic condition that usually happens in three blade rotor systems that have shock absorbing landing gear and/or pneumatic tires, with lead/lag hinges in their rotor systems.

A proprietary name belonging to Dr. Igor Bensen and describing auto-rotating rotary wing aircraft constructed by him or constructed from kits or from parts supplied by him. The craft may be a motorless towed glider type or a powered craft,

A rotary wing craft which may or may not resemble the autogiro type.

The element at the center of rotation of the rotor to which the blades are attached.

Interblade Cables Early 1920,1930's autogiros had lead-lag dampers installed in the blades a bit more that 1/3 of the distance from the center of rotation to the tip. Cables connected the damper actuating arm from one blade to the next.

Jump Takeoff

Lead-Lag Hinge Power Loading Retreating Blade

A vertical takeoff made by temporarily increasing the incidence of all blades in the rotor system simultaneously. The autogiro rises straight up, 5 to 20 feet; the incidence is reduced to normal and the autogiro flics away. No mechanical power is used to make the jump.

The mechanical joint, including the lead-lag pin which would permit the freedom of motion for the blade tip to move forward or backward.

Calculated same as a fixed wing type by dividing the design gross weight by the horsepower expressed in pounds per horsepower.

The blade that is moving with the oncoming airstream caused by the forward flight of the aircraft.

Re treating Blade Stall

Aerodynamic stalling of a rotor blade as it turns from nose to tail. This is caused when the forward speed of the aircraft is high enough that when this air speed is subtracted from the air speed caused by the rotation of the blade, the relative wind speed on the retreating side is so low that not enough lift is created on that side of the aircraft. The aircraft will roll to the retreating blade side; pitch up or both.

Running Takeoff Solidity Ratio

A takeoff made with the rotor prerotated to nearly cruising RPM while moving forward at full throttle.

The ratio of the total actual area of all blades in a rotor system to the total rotor area; expressed in percent.

Shear Pin

A pin made from soft metal or with a holethorugh its length or grooves cut around it or all these things to limit the power delivered to the rotor during prerotation. The pin will shear and interrupt the power train if more than design horsepower was applied to the prerotation drive system.

Taxi Takeoff

A takeoff made without the aid of a prerotating mechanism during which the rotor speed is brought up to takeoff speed by taxiing the craft along the ground while slowly and carefully increasing the taxi speed as the rotor speed increases because of autorotative force.

Tip Path Plane Tip Speed

An imaginary straight line connecting the lips of all blades when viewed from front, rear or either side.

The speed of the tip of the rotor blades of a rotor craft, usually expressed in feet per second.

Tilting Head

A rotor system in which the hub of the rotor system and all blades may be moved so that the rotating axis could be tilted fore and aft and side to side to accomplish lateral and Longitudinal control. A normal control stick furnished the motion.

Wing Loading

Calculated same as a fixed-wing type by dividing the design gross weight by the wing area (if a wing was used) expressed in pounds per square foot.

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