How does excessive coning occur?

• A. High G-Maneuvers
• B. Turbulent Air
• C. Low RPM
• D. High Gross Weight

Answer: (C)

Excessive coning happens because lift on the rotor blades tends to bend them upward, but centrifugal force from rotation provides outward tension that stiffens the blades and resists that bending. When rotor speed is high, this centrifugal stiffening is strong, so the blades stay flatter and coning stays small. When rotor speed is low, the centrifugal stiffening is reduced, so the same aerodynamic lift bends the blades more, increasing the coning angle. So, the best explanation is low RPM—the reduced centrifugal support allows greater blade bow under lift, leading to excessive coning. Turbulence or heavier loads can affect loads, but the primary cause here is insufficient centrifugal stiffening from low rotor speed.