Why is Collective/Airspeed to Yaw mixing completely phased out when the airspeed exceeds 100 knots?

• A. Due to the efficiency of the tail rotor and cambered fin
• B. To prevent tail rotor overspeed
• C. Because tail rotor is hydraulically locked
• D. Because swashplate is electronically controlled

Answer: (A)

At low speeds, yaw control in a UH-60 relies on a mix of collective input and airspeed signals to modulate tail rotor thrust and keep the aircraft from yawing undesirably as torque changes. As airspeed climbs, the tail surfaces start doing more of the work themselves. The tail rotor becomes more effective in forward flight due to the relative wind, and the vertical fin with its cambered shape provides greater yaw stability (more directional damping) with increased dynamic pressure. Because of that, the mixed control path isn’t needed as much, and the system phases it out once you’re around 100 knots. This makes yaw control more stable and reduces unnecessary coupling between collective and yaw inputs.

The other options don’t fit because they describe failures or features unrelated to why the mixing is removed at higher speed: tail rotor overspeed isn’t the reason for the change, the tail rotor isn’t hydraulically locked, and swashplate electronic control isn’t what drives the need to phase out the mix.