The ULY factor described as the relationship between collective application and aircraft yaw is called:

• A. WEATHERCOOK STABILITY
• B. LEFT CROSS WINDS
• C. LOSS OF TRANSLATIONAL LIFT
• D. COLLECTIVE INDUCED YAW

Answer: (D)

The main idea here is that changes to the collective affect yaw due to torque balance. When you raise the collective, the rotor system produces more lift, which also increases the engine torque that drives the rotor. To keep the nose from swinging, the tail rotor must push harder in the opposite direction, which creates a yaw moment on the fuselage. Conversely, lowering the collective reduces the tail-rotor anti-torque demand and can allow the nose to yaw in the opposite direction if not stabilized with pedals. This coupling between collective input and yaw is what we call collective-induced yaw.

In hover or low-speed flight, this effect is most noticeable because tail-rotor authority and airflow over the tail rotor strongly influence how quickly yaw responds to collective changes. The other options describe different phenomena (like stability in a crosswind, environmental effects, or loss of lift due to translational motion) and do not capture the specific link between collecting input and yaw.