NTSB CAROL · Event
Event FTW00LA137
Aircraft involved
Probable cause & findings
The company mechanic's failure to replace the bolt's cotter key properly and the subsequent loss of the nut, which then resulted in the tail rotor control disconnection and the pilot's inability to maintain aircraft control.
Factual narrative
On April 29, 2000, at 1810 central daylight time, a Bell 206L3 helicopter, N17237, sustained substantial damage during an emergency landing in the Gulf of Mexico near the Salt Marsh Island 61C offshore platform. The commercial pilot and his passenger were not injured. The helicopter was owned and operated by Chevron USA Inc., of New Orleans, Louisiana, under Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and a company VFR flight plan was filed for the local business flight. The helicopter departed the Salt Marsh Island 78B offshore platform at 1735. The 15,672-hour pilot reported that the helicopter lost tail rotor response when turning final to 61C. The pilot reported the problem to the operator and was informed that a rescue boat was dispatched to their area for assistance. After circling in the area for about 25 minutes, the pilot elected to make an autorotative emergency landing to the water. According to witnesses, the helicopter began the autorotation and proceeded to rotate to the left and "pitch nose down." The helicopter entered a steep descent, and the pilot reported that he could not control the helicopter. At approximately 100 feet above the ocean, the helicopter assumed level flight, the emergency floats deployed, and the helicopter subsequently impacted the water. Upon impact, the right float "broke," and the helicopter rolled to the right, coming to rest inverted in the water. According to the FAA inspector, a main rotor blade severed the tailboom. Both main rotor blades were shattered, and the fuselage sustained minor damage. According to the operator's maintenance superintendent, the loss of tail rotor control was a result of "a bolt falling out of a control rod in the tail rotor control system." The bolt (part number 20-057-4-22D) connected the control rod assembly to the control lever located at the rear of the tail rotor gearbox. The cotter key and castellated nut were not recovered. The bolt was recovered and showed no signs of distress. The helicopter underwent an approved aircraft inspection between March 21st and April 1st, 2000, 63 hours prior to the accident. During the inspection, the bolt was removed to facilitate the removal of another control tube for repair. During the re-assembly process, the cotter key was either not properly installed or was accidentally omitted. The discrepancy was not noticed by the mechanic, who was working the inspection, or the supervisor, who was inspecting the mechanic's work. The pilot reported that the helicopter lost tail rotor response while approaching an offshore platform. The pilot elected to make an autorotative emergency landing to the water. According to witnesses, the helicopter began the autorotation and proceeded to rotate to the left and 'pitch nose down.' The helicopter entered a steep descent, and the pilot reported that he could not control the helicopter. Prior to impacting the water, the helicopter assumed level flight and the emergency floats deployed. Upon impact with the water, the helicopter rolled right and came to rest inverted in the water. According to the operator's maintenance superintendent, a mechanic either omitted a bolt's cotter key or installed it improperly, which resulted in the disconnect of the tail rotor control rod assembly from the control lever located at the rear of the tail rotor gear box. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12
Verbatim from NTSB's published report. Source file
NTSB_2000_FTW00LA137.txt.
Findings + structured fields enriched from FAA avall.mdb.
Full investigation docket on
data.ntsb.gov ↗.
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Academic papers and agency reports matching this event's aircraft type or causal vocabulary (stall, maintenance). Sourced from NASA NTRS, NTSB Safety Studies, FAA CAMI, AOPA Air Safety Institute, Embry-Riddle Scholarly Commons, arXiv, and the Semantic Scholar academic graph.
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- Embry-Riddle Scholarly Commons 2026 · Journal article (IJAAA)
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- NASA NTRS 2026 · Conference Paper
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- Semantic Scholar 2025 · Article (Applied Sciences)
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- Embry-Riddle Scholarly Commons 2024 · Journal article (JAAER)
Low-Resource Automatic Speech Recognition Domain Adaptation – A Case-Study in Aviation Maintenance
With timeliness and efficiency being critical in the aviation maintenance industry, the need has been growing for smart technological solutions that optimize and streamline the different underlying ta…
- Embry-Riddle Scholarly Commons 2024 · Journal article (JAAER)
A New Trajectory in UAV Safety: Leveraging Reinforcement Learning for Distance Maintenance Under Wind Variations
In the field of aviation, safety is a critical cornerstone, and the operation of Unmanned Aerial Vehicle (UAV) systems is deeply connected with this principle.
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