# NTSB CHI00LA277: Bell 47G-2, N67083, Spring Brook, WI, August 31, 2000 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 31, 2000, 09:30 local (14:30 UTC) - Place: Spring Brook, WI - Coordinates: 45.940654, -91.679077 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.9407&lon=-91.6791&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report May 18, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 50148 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI00LA277 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/50148/pdf - Page: https://openairdocs.org/ntsb/CHI00LA277 ## Probable cause A fatigue failure of the tail rotor drive gear shaft. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, maneuvering - aerial application - rotor drive system,tail rotor drive shaft - failure,total (cause) - rotor drive system,tail rotor drive shaft - fatigue (cause) - aircraft control - not possible, pilot in command - In flight collision with terrain/water, descent - uncontrolled ## Analysis The helicopter impacted the terrain following a loss of tail rotor effectiveness. The pilot reported he just completed a turn in order to begin a swath run when he experienced a loss of tail rotor effectiveness. He attempted to control the helicopter, however it continued to rotate until it impacted the terrain in a clearing in a wooded area. Post accident examination revealed a failure of the tail rotor drive gear assembly. The drive gear shaft was fractured at the underside of the bevel gear. Metallurgical examination revealed fatigue was found over 90 to 95 percent of the shaft cross sectional area. The fatigue cracking origin was on the cylindrical portion of the shaft surface, adjacent to the keyway slot. ## Factual narrative 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. ## Aircraft - Registration: [N67083](https://openairdocs.org/deregistered/N67083-2005-11-15), registration cancelled 2005-11-15, S/N 2280, built 1958 (OpenAirDocs) - Reported make and model: Bell 47G-2 - Registry model: [Bell-Agri Helicopter 47G-2](https://openairdocs.org/model/bell-agri-helicopter-47g-2) (registry code 1180822) (OpenAirDocs) - Category: Helicopter - Serial number: 2280 - Airframe hours: 5558 - Engines: Lycoming O-435-A1F HC 265 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Registered owner: Scott Helicopters - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, August 20, 2000, 117 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 31; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: front; flight hours: 820 total, 400 in this make and model, 756 as pilot in command, 450 in the last 90 days, 148 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 190° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 68 °F ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20000831012529A](https://openairdocs.org/incident/20000831012529A), Aug 31, 2000: Bell 47G2, Springbrook, WI, No damage. (-23) Pilot was preparing to spray a potato field. He overflew the field on a northerly direction in order to approach field from the south. Said when he… ## Other investigations on N67083 (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB CHI80DER52](https://openairdocs.org/ntsb/CHI80DER52), Jul 5, 1980: Bell OH-13 (N67083), Bixby, MN, substantial damage From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.