Loss of tail rotor effectiveness, commonly referred to as LTE, is when the ability to provide anti-torque thrust from the tail rotor is ineffective or highly unreliable.
Notwithstanding mechanical problems, there are several wind conditions that impact the tail rotor’s ability to provide anti-torque thrust: main rotor disc interference, tail rotor vortex ring state, and weathercock stability. Main rotor disc interference may occur when there is a wind between 285-310-degrees. From this angle, the main rotor vortices can be blown into the tail rotor, making the tail rotor operate in turbulent air. A tail rotor ring state may occur when the wind is from 210-330 degree as there is the potential for the wind to blow tail rotor’s vortices into the tail rotor and the tail rotor can end up in a vortex ring state. When the wind is from 120-240 degrees, the helicopter will want to weather vane into the wind, making it operate in extremely turbulent air.
When there is pilot discretion to approach a landing site with left or a right cross wind, a right crosswind minimizes the likelihood of LTE. Often, a pilot has the discretion on the approach to a landing site, so the wind should be considered, particularly on final where tail rotor use increases.
FAA-H-8083-21A – Helicopter Flying Handbook pg. 11-17
Principles of Helicopter Flight, 2nd Edition, pg. 69