Loss of tail-rotor effectiveness
Loss of tail-rotor effectiveness (LTE) occurs when the tail rotor of a helicopter is exposed to wind forces that prevent it from carrying out its function—that of cancelling the torque of the engine and transmission. Any low-airspeed high-power environment provides an opportunity for it to occur. Causes. Environmental factors which can lead to LTE include higher operating-density altitudes or temperatures, and high winds. A high gross weight can also create an LTE-conducive situation. Causative wind-directions may include: Indications of onset. Many factors affect the onset of LTE, but  no matter which way it occurs, the clues are present: Recovery. Recovery from an unexpected yaw movement is initiated by applying forward cyclic control to increase airspeed, and reducing power if at a safe altitude. If these measures are not effective, an entry into an autorotation may be necessary, applying full opposite rudder until rotation stops.