Event Description
During a low-level flight, the pilot of a helicopter was following a hog up the side of a rocky ridgeline at an altitude of approximately 25 feet above ground level. As the helicopter began to overtake the hog, the pilot pulled the aircraft into a hover to avoid overflying the animal. The pilot reported that the helicopter encountered "dirty air" and experienced a loss of tail rotor effectiveness (LTE).
Pilot Actions and Outcome
The pilot stated that he "added left pedal and increased power, but the helicopter didn't respond." He further noted that he "had no altitude, or airspeed to make a recovery." Subsequently, the helicopter spun to the right and settled into the side of the ridge, coming to rest on its left side.
Background on Loss of Tail Rotor Effectiveness
According to the Federal Aviation Administration's Advisory Circular 90-95, loss of tail rotor effectiveness (LTE) is a critical, low-speed aerodynamic flight characteristic that can result in an uncommanded rapid yaw rate. The advisory states that this yaw rate does not subside on its own and, if not corrected, can lead to loss of aircraft control. It emphasizes that LTE is not related to a maintenance malfunction and may occur in varying degrees in all single main rotor helicopters under certain conditions. Conditions conducive to LTE include high power setting, low airspeed, and a tailwind or left crosswind.