FTW98TA072

The helicopter was under contract by the New Mexico Game and Fish Department for the purpose of elk herd evaluation. The right front seat passenger said that they were flying northbound, approximately 180 to 200 feet above the ground, in an attempt to split a heard of elk, for counting purposes. He said that the helicopter was traveling at less than 10 knots, the pilot initiated a turn, and within 3 to 5 seconds, they rotated to the ground. The pilot stated that he thought they were traveling north at approximately 100 feet agl and approximately 30 knots when he initiated the right turn. He further stated that 'once the turn got started, I couldn't stop it, even with full left pedal.' The pilot reported that he believed the wind was from the west at approximately 5 to 10 knots (the density altitude was calculated to be 9,043 feet). He said that when the accident happened, 'I heard nothing unusual nor felt anything.' According to FAA AC 90-95, unanticipated right yaw can be brought about by low airspeeds, high power regimes, left crosswinds or tailwinds, and right turning maneuvers.

On December 18, 1997, approximately 1625 mountain standard time, a Bell 206B-III helicopter, N124DA, was substantially damaged during impact with the ground following loss of aircraft control near Reserve, New Mexico. The airline transport rated pilot received minor injuries and his two passengers were seriously injured. The helicopter was owned by MSI Helicopters Inc., Albuquerque, New Mexico, and operated by Aero West Management, Albuquerque, New Mexico, under Title 14 CFR Part 91 (see attached). Visual meteorological conditions prevailed for the local flight which originated from Reserve, New Mexico, approximately 2 hours before the accident. A company VFR flight plan had been filed.

The helicopter was under contract by the New Mexico Game and Fish Department for the purpose of elk herd evaluation. The field project began on December 10 when the helicopter was flown from Albuquerque to Reserve. During the next 8 days, approximately 58 hours of flight time was accrued accomplishing the project's goals. On the day of the accident, the first flight started at approximately 0800 from Apache Creek. The pilot and his passengers were finishing the third flight for the day when the accident occurred.

The right front seat passenger said that they were flying northbound, at approximately 180 to 200 feet above the ground for elk counting purposes. He said that the helicopter was traveling at less than 10 knots when the pilot initiated a turn (in an attempt to split a herd of elk) and within 3 to 5 seconds, they rotated to the ground. The pilot stated that he thought they were traveling north at approximately 100 feet agl and approximately 30 knots when he initiated the right turn. He further stated that "once the turn got started, he couldn't stop it, even with full left pedal."

The pilot reported that he believed the wind was from the west at approximately 5 to 10 knots (the density altitude was calculated to be 9,043 feet). He said that when the accident happened, "he heard nothing unusual nor felt anything." The helicopter impacted the ground and rolled onto its right side. Approximately 4 hours later, rescue teams reached their location.

According to FAA Advisory Circular 90-95, dated December 26, 1995, entitled "Unanticipated Right Yaw in Helicopters," it states that "all single main rotor helicopters at airspeeds less than 30 knots have a certain degree of vulnerability to unanticipated right yaw." This event can be brought about by low airspeeds flight regimes, high gross weights or high density altitudes (high power demands), left crosswinds or tailwinds, and right turning maneuvers (see attached).