Conning
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As a helicopter develops lift during takeoff and flight, the blade tips rise above straight-out position and assume a coned shape. This coning occurs due to the combined effects of centrifugal force from blade rotation, which adds rigidity, and developing lift from the collective. Some coning is normal, but excessive coning can cause problems like decreased lifting area and blade stress due to factors like low RPM, high gross weight, turbulence, or high-G maneuvers reducing centrifugal force or requiring more lift.
Conning
- 1. Coning As the helicopter develops lift during takeoff and flight, the the blade tips rise above the straight-out position and assume a coned position. Primary forces involved: Centrifugal Force: The force which tends to make rotating bodies move away from the center of rotation Centrifugal force adds rigidity to the rotor blade, causing it to assume a straight-out position Lift: As the collective is increased and lift develops, the blades respond by rising above the straight-out position
- 2. Coning Resultant: The combined effects of centrifugal force and lift cause the blades to assume a coned position. The angle between the straight-out position and the path flown by the blades is the coning angle. Some amount of coning is normal, however, excessive coning can create problems t u ltan Res Lift Centrifugal Force
- 3. Causes of excessive coning •Low rotor RPM = Loss of centrifugal force •High gross weight = More lift required •High “G” maneuvers = More lift required •Turbulence = Updrafts increase angle of attack, which increases coefficient of lift which increases lift
- 4. Effects of excessive coning •Decreased rotor area and useful lift •Stress on blades and blade roots Resultant or effective lifting area Lift Centrifugal Force