During Tail Rotor Vortex Ring State, if yaw rate is allowed to build, into which region can the helicopter rotate?

During Tail Rotor Vortex Ring State, if yaw rate is allowed to build, into which region can the helicopter rotate?

• A. Weathercock Stability
• B. Downwash region
• C. Autorotation zone
• D. Coning region

Answer: (A)

The main idea here is weathercock stability: a helicopter tends to yaw back toward aligning its longitudinal axis with the oncoming wind, producing a restoring effect that dampens yaw disturbances. In Tail Rotor Vortex Ring State, the tail rotor loses anti-torque effectiveness and yaw can become unstable, but if you let the yaw rate build, the fuselage’s aerodynamic forces act to rotate the helicopter toward a wind-aligned orientation, i.e., into the weathercock stability region. The other regions described don’t describe this damping into a wind-aligned attitude: the downwash region is about tail-rotor inflow effects, the autorotation zone concerns rotor RPM during loss of collective, and the coning region relates to rotor disc coning effects.

The main idea here is weathercock stability: a helicopter tends to yaw back toward aligning its longitudinal axis with the oncoming wind, producing a restoring effect that dampens yaw disturbances. In Tail Rotor Vortex Ring State, the tail rotor loses anti-torque effectiveness and yaw can become unstable, but if you let the yaw rate build, the fuselage’s aerodynamic forces act to rotate the helicopter toward a wind-aligned orientation, i.e., into the weathercock stability region. The other regions described don’t describe this damping into a wind-aligned attitude: the downwash region is about tail-rotor inflow effects, the autorotation zone concerns rotor RPM during loss of collective, and the coning region relates to rotor disc coning effects.