On September 3, 2001, a Hiller UH-12D (registration N2770) operated by Aero Management, Inc. was involved in an aviation accident near Lubbock, TX. Investigators recorded the probable cause as: 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. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced a tail rotor drive shaft hanger bearing failure while spraying a cotton field at 4 feet AGL, leading to loss of tail rotor control and a forced landing where the main rotor blades struck the tailboom.
Event Details
A helicopter pilot was conducting agricultural spraying operations over a cotton field at an altitude of approximately 4 feet above ground level (AGL). During the flight, the pilot felt a vibration in the aircraft, followed by a distinct "pop" sound accompanied by an immediate loss of tail rotor control. The pilot initiated a forced landing to the cotton field. During the descent and touchdown, the main rotor blades struck the tailboom, causing the tailboom to separate from the fuselage.
Examination Findings
Following the accident, an inspector from the Federal Aviation Administration (FAA) examined the helicopter. The examination revealed that a tail rotor drive shaft hanger bearing had failed. As a result of this bearing failure, the tail rotor drive shaft had separated. The failure of the bearing and subsequent separation of the drive shaft are consistent with the loss of tail rotor control reported by the pilot.