On August 31, 2000, a Bell 47G-2 (registration N67083) was involved in an aviation accident near Spring Brook, WI. Investigators recorded the probable cause as: A fatigue failure of the tail rotor drive gear shaft. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced a loss of tail rotor effectiveness after a turn for a swath run, resulting in an uncontrolled rotation and impact with terrain. Post-accident examination revealed a fatigue fracture in the tail rotor drive gear shaft.
Accident Description
The helicopter impacted terrain in a wooded area after the pilot lost control during a swath run. According to the pilot's account, he had just completed a turn to initiate a swath run when the helicopter began to experience a loss of tail rotor effectiveness. Despite his attempts to maintain control, the helicopter continued to rotate uncontrollably until it struck the ground in a clearing within a wooded environment.
Post-Accident Examination
A post-accident examination of the helicopter revealed a failure of the tail rotor drive gear assembly. The drive gear shaft was found fractured at the underside of the bevel gear. Metallurgical analysis determined that fatigue cracking was present over 90 to 95 percent of the shaft's cross-sectional area. The origin of the fatigue cracking was located on the cylindrical portion of the shaft surface, adjacent to the keyway slot.
What happened in the 31 Aug 2000 Bell 47G-2 accident near Spring Brook, WI?
A helicopter experienced a loss of tail rotor effectiveness after a turn for a swath run, resulting in an uncontrolled rotation and impact with terrain. Post-accident examination revealed a fatigue fracture in the tail rotor drive gear shaft.
What aircraft was involved and where did it happen?
The accident on 31 Aug 2000 involved a Bell 47G-2, registration N67083, at Spring Brook, WI.
What was the probable cause of the accident?
A fatigue failure of the tail rotor drive gear shaft.
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