Summary
On August 31, 2000, a Bell 47G-2 (N67083) was involved in an incident near Spring Brook, WI. All 1 person aboard were uninjured. The aircraft sustained substantial damage.
The National Transportation Safety Board determined the probable cause of this incident to be: A fatigue failure of the tail rotor drive gear shaft.
On August 31, 2000, at 0930 central daylight time, a Bell 47G-2, N67083, collided with the terrain following a loss of control while maneuvering during an aerial application flight in Spring Brook, Wisconsin. The pilot was not injured and the helicopter was substantially damaged. The 14 CFR Part 137 flight was operating in visual meteorological conditions. The flight originated in Spring Brook, Wisconsin, at 0925 central daylight time.
The pilot stated he was going to spray a field and had just made a turn to enter his first swath run when he experienced a loss of tail rotor power. He stated his attempts to return to normal flight were unsuccessful resulting in rotation of the helicopter and airspeed dropping to zero.
This incident is documented in NTSB report CHI00LA277. AviatorDB cross-references NTSB investigation data with FAA registry records to provide comprehensive safety information for aircraft N67083.
Accident Details
Probable Cause and Findings
A fatigue failure of the tail rotor drive gear shaft.
Aircraft Information
Registered Owner (Historical)
Analysis
On August 31, 2000, at 0930 central daylight time, a Bell 47G-2, N67083, collided with the terrain following a loss of control while maneuvering during an aerial application flight in Spring Brook, Wisconsin. The pilot was not injured and the helicopter was substantially damaged. The 14 CFR Part 137 flight was operating in visual meteorological conditions. The flight originated in Spring Brook, Wisconsin, at 0925 central daylight time.
The pilot stated he was going to spray a field and had just made a turn to enter his first swath run when he experienced a loss of tail rotor power. He stated his attempts to return to normal flight were unsuccessful resulting in rotation of the helicopter and airspeed dropping to zero. He reported the helicopter settled into a clearing in a wooded area at the end of the field. The helicopter impacted some small trees and the terrain, which resulted in the separation of the main rotor and substantial damage to the helicopter.
Post accident inspection of the helicopter revealed a failure of the tail rotor drive gear assembly. The assembly was removed from the helicopter and sent to the NTSB Materials Laboratory in Washington, D.C. The metallurgical inspection of the drive gear assembly revealed the drive gear shaft was fractured at the underside of the bevel gear. The examination revealed, "The fracture surface was on a flat transverse plane and contained crack arrest positions over most of the fracture, indicative of fatigue cracking." The metallurgist's report also stated, "The origin area was located on the cylindrical portion of the shaft surface, directly adjacent to the keyway slot. The origin area contained a single ratchet mark, indicating initiation from at least two origin sites in the origin area. Fatigue crack features visible on the scanning electron microscope extended from the origin area through about 90 percent to 95 percent of the shaft cross sectional area." The report defined a ratchet mark as a small step in the fracture surface that separates fatigue origin areas on slightly offset planes.
Data Source
Data provided by the National Transportation Safety Board (NTSB). For more information on this event, visit the NTSB Records Search website. NTSB# CHI00LA277