Accident Description
A helicopter under contract by the New Mexico Game and Fish Department was conducting an elk herd evaluation flight when it experienced a loss of control and impacted the ground. The flight was intended to split a herd of elk for counting purposes. The helicopter was traveling at low speed when the pilot initiated a right turn, after which the aircraft rotated to the ground within seconds.
Pilot and Passenger Accounts
The right front seat passenger reported that the helicopter was flying northbound at an altitude of approximately 180 to 200 feet above ground level (AGL) and at a speed of less than 10 knots. He stated that the pilot initiated a turn, and within 3 to 5 seconds, the helicopter rotated to the ground.
The pilot provided a different account, stating that he believed they were traveling north at about 100 feet AGL and approximately 30 knots when he initiated the right turn. He noted that once the turn started, he could not stop it despite applying full left pedal. The pilot reported hearing nothing unusual nor feeling anything abnormal before the accident.
Meteorological Conditions
The pilot estimated the wind was from the west at 5 to 10 knots. The density altitude was calculated to be 9,043 feet, indicating high-altitude conditions.
Reference Materials
According to Federal Aviation Administration Advisory Circular (AC) 90-95, unanticipated right yaw can occur in helicopters at low airspeeds, high power regimes, and during left crosswinds, tailwinds, or right turning maneuvers. The advisory circular provides general guidance on this aerodynamic phenomenon.