Primary finding
Probable cause
the failure of the tail rotor drive shaft hanger bearing, which resulted in the separation of the tail rotor drive shaft. A contributing factor was the lack of suitable terrain for the forced landing.
Investigator assessment
Analysis narrative
The helicopter pilot was spraying a cotton field at 4 feet agl, when he felt a vibration followed by a "pop" with a loss of tail rotor control. Subsequently, during the forced landing to the cotton field, the main rotor blades struck the tailboom separating it from the fuselage. Examination of the helicopter, by an FAA inspector revealed that a tail rotor drive shaft hanger bearing had failed, and the tail rotor drive shaft had separated.
Source record
Factual narrative
On September 3, 2001, at 1610 central daylight time, a Hiller UH-12D agricultural helicopter, N2770, was substantially damaged during a forced landing following a loss of directional control near Lubbock, Texas. The helicopter was registered to the pilot and operated by Aero Management, Inc., of Olton, Texas. The commercial pilot, sole occupant, was not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 137 aerial application flight. The local flight originated from the Town and Country Airpark Airport, Lubbock, Texas, at 1515. The pilot reported to the FAA inspector that while spraying a cotton field, at 4 feet agl, he felt a vibration followed by a "pop" with a loss of tail rotor control. Subsequently, during the forced landing to the cotton field, the main rotor blades struck the tailboom separating it from the fuselage. Examination of the helicopter by the FAA inspector, who responded to the accident site, revealed that a tail rotor drive shaft hanger bearing had failed, and the tail rotor drive shaft had separated.