Which ULY factor includes tailwinds that can accelerate an established yaw rate to the left or to the right?

Which ULY factor includes tailwinds that can accelerate an established yaw rate to the left or to the right?

• A. WEATHERCOOK STABILITY
• B. LEFT CROSS WINDS
• C. LOSS OF TRANSLATIONAL LIFT
• D. MAIN ROTOR / TAIL ROTOR INTERACTION

Answer: (A)

Weathercock stability describes the helicopter’s tendency to align its fuselage with the direction of the relative wind. When a tailwind is present, the wind pushes on the tail and fuselage in a way that tends to rotate the nose into the wind. If you already have an established yaw, this wind-driven moment can quickly speed up that rotation, making the yaw rate grow to either the left or the right depending on the wind direction. The other factors don’t capture this wind-induced yaw acceleration: cross winds are about side forces and sideslip, loss of translational lift relates to rotor efficiency in hover, and main rotor / tail rotor interaction concerns rotor aerodynamics rather than wind alignment.

Weathercock stability describes the helicopter’s tendency to align its fuselage with the direction of the relative wind. When a tailwind is present, the wind pushes on the tail and fuselage in a way that tends to rotate the nose into the wind. If you already have an established yaw, this wind-driven moment can quickly speed up that rotation, making the yaw rate grow to either the left or the right depending on the wind direction. The other factors don’t capture this wind-induced yaw acceleration: cross winds are about side forces and sideslip, loss of translational lift relates to rotor efficiency in hover, and main rotor / tail rotor interaction concerns rotor aerodynamics rather than wind alignment.