NTSB CAROL · Event
Event SEA99LA092
Aircraft involved
Probable cause & findings
The pilot's failure to maintain rotor RPM during an autorotation.
Factual narrative
On June 22, 1999, about 1430 Pacific daylight time, a Hughes 369D, N1089Y, registered to and operated by Olympic Air, Incorporated, was substantially damaged during landing following a practice autorotation. The accident occurred at Shelton Airport, Shelton, Washington. The commercial pilot, the sole occupant of the aircraft, was not injured. A company VFR flight plan was filed and visual meteorological conditions prevailed for this 14CFR91 flight. The flight originated from Rockaway, Oregon, approximately one hour prior to the accident. The pilot stated he was practicing autorotations from an altitude of approximately 200 feet above ground level (AGL) and an airspeed of approximately 50 knots. During the second practice autorotation, the pilot reduced power with throttle and used collective to adjust rotor speed to 410 RPM (minimum RPM for practice autorotations). The pilot stated the rotor RPM "quickly" decayed and the aircraft rapidly started to descend. Before the pilot was able to recover, the aircraft collided with the ground and rolled over. The aircraft sustained substantial damage to the main rotor blades, tail rotor, tail boom and fuselage. The pilot reported no mechanical failures or malfunctions with the aircraft at the time of the accident. The pilot was practicing autorotations from an altitude of approximately 200 feet above ground level (AGL) and an airspeed of approximately 50 knots. During the second practice autorotation, the pilot reduced power with throttle and used collective to adjust rotor speed to 410 RPM (minimum RPM for practice autorotations). The rotor RPM decreased below 410 RPM and the aircraft rapidly started to descend. Before the pilot was able to recover, the aircraft collided with the ground and rolled over. The aircraft sustained substantial damage to the main rotor blades, tail rotor, tail boom and fuselage. The pilot reported no mechanical failures or malfunctions with the aircraft at the time of the accident. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12
Verbatim from NTSB's published report. Source file
NTSB_1999_SEA99LA092.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 (icing). Sourced from NASA NTRS, NTSB Safety Studies, FAA CAMI, AOPA Air Safety Institute, Embry-Riddle Scholarly Commons, arXiv, and the Semantic Scholar academic graph.
- NASA NTRS 2026 · Contractor Report (CR)
Icing Physics Studies Using the 3D SIDRM Test Article: 2023 Icing Tests Analysis
In-flight icing is an important safety issue and is a factor that affects aircraft design and performance. Newer regulations are driving a need for improvements in airframe and engine icing simulation…
- arXiv 2025 · arXiv preprint
Multi-Agent Deep Reinforcement Learning for UAV-Assisted 5G Network Slicing: A Comparative Study of MAPPO, MADDPG, and MADQN
The growing demand for robust, scalable wireless networks in the 5G-and-beyond era has led to the deployment of Unmanned Aerial Vehicles (UAVs) as mobile base stations to enhance coverage in dense urb…
- Embry-Riddle Scholarly Commons 2025 · Journal article (JAAER)
A Mathematical Model on the Temporal Dynamics of Aviation Competitive Pricing
This study investigates the competitive dynamics of airport pricing using U.S. airport data to validate the findings. It employs linear and nonlinear ordinary differential equation models to analyze t…
- NASA NTRS 2025 · Presentation
NASA Icing Update – March 2025
This NASA Icing Update was prepared for presentation to the SAE International AC-9C Inflight Icing Technology Committee. This update includes the following topics: planned Rotational Icing Scaling tes…
- arXiv 2024 · arXiv preprint
An energy-stable phase-field model for droplet icing simulations
A phase-field model for three-phase flows is established by combining the Navier-Stokes (NS) and the energy equations, with the Allen-Cahn (AC) and Cahn-Hilliard (CH) equations and is demonstrated ana…
- NASA NTRS 2024 · Presentation
NASA Icing Update – Oct 2024
This presentation provides a status update on select NASA icing research activities for the SAE AC-9C Icing Technical Committee Meeting on Oct 21, 2024.
Browse the full corpus — academia portal ↗