Glossary of Gyroplane Terms

 

Termos utilizados na giroaviação de âmbito internacional , para discutir , analisar e elucidar.

 

           http://www.magnigyro.com/USA/feature_articles/GyroTerms.pdf

 

 

Angle of Attack – AOA:

The angle between the chord line of an airfoil (rotor blade) and the relative wind or airflow acting on that airfoil. The AOA and airspeed on an airfoil determine the lift and drag of that airfoil. AOA may be positive or negative – positive refers to an AOA that creates an upward lift on the airfoil. Sometimes AOA can also refer to the angle between the longitudinal axis of an object (aircraft, enclosure, etc.) and the relative wind.

 

Angle of Incidence – AOI:

The angle between the chord line of an airfoil and the angle of the airframe. AOI typically refers to the angle at which an airfoil is mechanically mounted on an airframe.

 

Autorotation:

A self sustaining rotational mode of a rotor wherein flight RPM is sustained from the air passing up though the rotor disk. For autorotation, the AOA of the rotor blades are reduced to near zero so that an unstalled condition exists on most of the rotor blade length. An inner portion of each rotor blade produces lift in a direction that tends to drive the rotor forward, and portions nearer the tips produce lift in a direction that tends to retard the rotor. The “driving” and “driven” forces exactly match at the operating RRPM and sustain rotation. Autorotation requires no power to the rotor and is the mode employed in gyroplane rotors to provide lift. Autorotation is utilized in helicopters when power to the rotor is lost. See also “Driving Area,” and “Driven Area.”

 

Center of Drag – CD:

The point within an aircraft or aircraft component where all of its drag can be considered to act. I.e.: CD is the point on an airframe where there is equal drag above and below. The CD of a rotor acts through the spinning center of the rotor. See also “Center of Lift” and “Center of Pressure.”

 

Center of Lift - CL:

The point on an airfoil, on an aircraft, or on any aircraft component where all its forces of lift can be considered to act with no resulting pitching moment. On a rotor blade, the center of lift exists as a line, usually about 25% back from the leading edge. On a complete rotor, the CL is approximately at the spinning center of the rotor. On an airframe, the CL is a complex function of all the surfaces on that airframe that often result in a pitching moment about the aircraft CG.

 

Centerline Thrust – CLT:

A gyro configuration which has the propeller thrust passing through or very near the vertical center of gravity (VCG) of the aircraft. This minimizes the static pitching moments on the aircraft due to propeller thrust.

 

Horizontal Stabilizer – HS:

A horizontal flying surface placed on the tail of an aircraft to provide a stabilizing moment tending to keep the aircraft aligned in pitch with the relative wind upon disturbance. The HS adds dynamic stability in pitch in the form of more precision and reduced overshoot in control response. The Horizontal Stabilizer serves to dampen the natural oscillatory pitch tendencies of the aircraft. A horizontal stabilizer on an aircraft is normally arranged to provide a down force or negative lift to balance the CG forward of the lift vector so as to provide airspeed stability. A horizontal tabilizer on a gyro is normally rigged for the same purpose but is also arranged so that the down force on the tail maintains the VCG forward of the Rotor Thrust Vector for pitch stability. The effectiveness of the HS is a function of its size, its moment arm from the CG of the aircraft, its airfoil shape efficiency, and any enhancement from the effect of propwash immersion. A HS can be arranged to react to both Free Airflow and accelerated airflow from propwash. See also“Damping,” “Horizontal Tail Volume,” Airspeed Stability,” Vertical CG,” “Rotor Thrust Vector,”“Moment,” “Stabilizer,” “Embedded” and “Free Air.”

Low Propeller Thrustline:

Propeller thrust which acts on a line or “Vector” passing below the center of gravity of the gyroplane, tending to a nose-up pitching moment on the airframe. A low propeller thrustline tends to move the longitudinal CG forward with the nose-up tendency when power is applied – improving stability when power is applied. The larger the propeller offset, the larger horizontal stabilizer moment is required to compensate for the nose-up moment from propeller thrust. See also “Centerline Thrust” and “High Propeller Thrustline.”