NTSB CAROL · Event
Event ANC93FA033
Aircraft involved
Probable cause & findings
INADEQUATE MAINTENANCE OF THE HYDRAULIC SERVO ACTUATOR WHICH LED TO THE FATIGUE FAILURE AND LOSS OF FLIGHT CONTROL. IN ADDITION, THE FLIGHTCREW DID NOT, OR WAS UNABLE TO, JETTISON THE EXTERNAL LOAD. FACTORS WHICH CONTRIBUTED TO THE ACCIDENT WERE: THE PILOT OPERATING THE HELICOPTER OVER MAXIMUM GROSS WEIGHT, THE OPERATOR'S CONTINUED AEROLOGGING OPERATIONS WITH AIRCRAFT EXCEEDING MAXIMUM GROSS WEIGHT, AND INADEQUATE SURVEILLANCE OF THE OPERATOR'S MAINTENANCE AND OPERATIONS ACTIVITY BY THE FEDERAL AVIATION ADMINISTRATION.
Factual narrative
THE HELICOPTER WAS HOVERING 200 FT AGL, WITH LOGS ATTACHED TO A 150-FT LONGLINE, WHEN IT WAS OBSERVED TO HAVE A LOSS OF CONTROL. THE LOGS WERE DRAGGED ALONG THE GROUND UNTIL CAUGHT IN STUMPS, PITCHING THE HELICOPTER INTO THE GROUND. THE LOWER PISTON ROD OF THE RIGHT DUAL HYDRAULIC SERVO ACTUATOR HAD FAILED IN FATIGUE; ALSO BEARING WEAR WAS INCONSISTENT WITH COMPONENTS OF COMPARABLE TIME. OPERATOR RECORDS SHOWED REGULAR OVERLOADING OF AEROLOGGING HELICOPTERS; ACFT OVERLOADED BY 2000 LBS PRIOR TO ACCIDENT. OPERATOR MAINTENANCE & FACILITY RECORDS INCOMPLETE. MAINTENANCE PERFORMED IN ALASKA WITHOUT FAA AUTHORIZATION. NO RECORDS OF OF FAA SURVEILLANCE OF OPERATOR EXTERNAL LOAD OPERATIONS IN ALASKA SINCE START OF OPERATIONS 4/91. THE EXTERNAL HOOK ELECTRICAL RELEASE MECHANISM WAS TESTED & FUNCTIONED NORMALLY. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12
Verbatim from NTSB's published report. Source file
NTSB_1993_ANC93FA033.txt.
Findings + structured fields enriched from FAA avall.mdb.
Full investigation docket on
data.ntsb.gov ↗.
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Related research
What the literature says.
Academic papers and agency reports matching this event's aircraft type or causal vocabulary (loss of control, 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.
- NTSB Aircraft Accident Reports 2002 · Accident report
Loss of Control and Impact with Pacific Ocean — Alaska 261
Alaska Airlines Flight 261 (MD-83) Pacific Ocean, January 31, 2000 — 88 fatalities. Definitive investigation of the Alaska 261 pitch-runaway-and-loss-of-control crash.
- Embry-Riddle Scholarly Commons 2026 · Journal article (IJAAA)
From Reactive to Predictive: A hybrid Trust-Mediated Adoption Framework for Data-Driven Maintenance in Distributed-Authority Aviation Environments
Modern aviation maintenance operates within increasingly data-intensive technological environments, yet the operational integration of predictive maintenance into routine decision-making remains incon…
- Embry-Riddle Scholarly Commons 2025 · Journal article (JAAER)
A Scoping Review of Aviation Loss of Control Inflight Research
Loss of control – inflight (LOC-I) contributes to aircraft accidents at unacceptably high rates. Significant industry efforts and research have aimed to improve LOC-I prevention, detection, and recove…
- Semantic Scholar 2025 · Article (Applied Sciences)
Decision-Making Framework for Aviation Safety in Predictive Maintenance Strategies
The implementation of predictive maintenance (PM) in aviation presents unique challenges due to strict safety requirements, complex operational environments, and regulatory constraints.
- SKYbrary (Eurocontrol) 2024 · SKYbrary article
Loss of Control In-Flight (LOC-I) — SKYbrary Knowledge Base
SKYbrary comprehensive knowledge-base entry on Loss of Control In-Flight — definitions, contributing factors, accident case studies (Air France 447, Colgan 3407), and prevention strategies.
- 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…
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