# NTSB DEN01LA012: Bell 206L-1, N613, Mesa Verde, CO, October 30, 2000 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: October 30, 2000, 11:30 local (17:30 UTC) - Place: Mesa Verde, CO - Coordinates: 37.179656, -108.490409 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.1797&lon=-108.4904&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report May 18, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 50609 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN01LA012 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/50609/pdf - Page: https://openairdocs.org/ntsb/DEN01LA012 ## Probable cause The manufacturer's use of improper materials, and inadequate quality control of the tail rotor blades during the manufacturing process, which resulted in fatigue failure of the blade. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, approach - vfr pattern - final approach - rotor system,tail rotor blade - fatigue - rotor system,tail rotor blade - failure,partial - inadequate quality control, manufacturer (cause) - material inadequate,improper, manufacturer (cause) ## Analysis During approach to land on a helipad at the completion of a seeding flight, the helicopter began, what the pilot described as, an unusual vibration. The pilot conducted a normal landing and during inspection following shutdown, the pilot found that one tail rotor blade had shed the trailing edge counterweight and trailing edge skin. He also found that three of the four mounting points for the tail rotor gearbox had fractured. Both tail rotor blades, which had accumulated approximately 30.8 hours since new, were sent to the NTSB Materials Laboratory for examination. The helicopter was repaired and when the shipping container containing new tail rotor blades was opened and the blades unpacked, the repair station rejected one blade for visual abnormalities in the area of the trailing edge counterweight. The rejected blade was also sent to the laboratory for examination. The laboratory examination provided evidence the tail rotor blade failed due to fatigue in the inboard and outboard skins initiating at the root near the trailing edge counterweights. The fatigue initiated due to buckling deformation of the inboard skin, which was found to be thinner than that specified in the manufacturer's drawings. The rejected tail rotor blade examination provided evidence of uneven bonding of the inboard counterweight and deformation due to the riveting process. Deformation was also noted on the outboard counterweight. Composite Structures, LLC, Monrovia, California, manufactured all the tail rotor blades. ## Factual narrative On October 30, 2000, at 1130 mountain daylight time, a Bell 206L-1 helicopter, N613, sustained substantial damage when a tail rotor blade failed during approach to a helicopter landing pad at Mesa Verde National Park, Colorado. The airline transport certificated pilot, the sole occupant, was not injured. The flight was a public use flight operating under Title 14 CFR Part 91 and no flight plan was filed. Visual meteorological conditions prevailed. The flight originated from the pad about 0930. According to information provided by the Department of Interior, Office of Aviation Services, the flight was on approach to land at the completion of a seeding flight when the pilot noted an increase in vibration level. The pilot landed the helicopter without incident. An examination following shut down of the helicopter provided information that a counterweight and part of the trailing edge had separated from one tail rotor blade. The resulting vibration fractured three of the four tail rotor gearbox mounts. The tail rotor blades had accumulated approximately 30.8 hours time in service since new. All failed parts were recovered at the accident site. Following the accident, repairs to the helicopter were made. New tail rotor blades were required and when one of the two blades was unpacked from its shipping container, the repair station noted what appeared to be a faulty counterweight attachment. They rejected the blade. The failed tail rotor blade, its mate, and the new rejected blade were sent to the National Transportation Safety Board's Materials Laboratory for examination. Their report of the examination is attached and provides evidence that the failed tail rotor blade failed due to fatigue in the inboard and outboard skins initiating at the root near the trailing edge counterweights. The fatigue initiated due to buckling deformation of the inboard skin which was found to be thinner than that specified in the manufacturer's drawings. The rejected new tail rotor blade examination provided evidence of uneven bonding of the inboard counterweight and deformation due to the riveting process. Deformation was also noted on the outboard counterweight. According to information provided by the Federal Aviation Administration, Rotorcraft Directorate, Composite Structures, LLC, Monrovia, California, manufactured all the tail rotor blades. ## Aircraft - Registration: [N613](https://openairdocs.org/deregistered/N613-2014-10-10), registration cancelled 2014-10-10, S/N 45287, built 1979 (OpenAirDocs) - Reported make and model: Bell 206L-1 - Registry model: [Bell Helicopter Textron 206L-1](https://openairdocs.org/model/bell-helicopter-textron-206l-1) (registry code 1182107) (OpenAirDocs) - Registry engine: [Allison 250 SER 400HP](https://openairdocs.org/engine/allison-250-ser-400hp) (registry code 03013, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 45287 - Airframe hours: 10006 - Engines: Allison C30P 650 horsepower turbo shaft - Damage: Substantial damage - Flight: Public aircraft, Part 91 - Operator: U.S. Bureau Of Reclamation - Registered owner: U. S. Dept. Of Interior - Airworthiness certificate: Standard, Normal - Last inspection: Annual, October 23, 2000, 31 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 51; flight instructor, airline transport; airplane ratings: single-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--w/ waivers/lim; seat: right; flight hours: 15,237 total, 3,009 in this make and model, 14,237 as pilot in command, 140 in the last 90 days, 71 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 180° at 10 knots - Lowest ceiling: none - Temperature: 50 °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 20001030035619A](https://openairdocs.org/incident/20001030035619A), Oct 30, 2000: Bell 206L1, Mesa Verde, CO, No damage. (-23)On October 30, 2000, at 1230 MDT, a Bell BHT-206-L1 helicopter, N613 sustained substantial damage when a tail rotor blade failed during approach to a… 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.