NTSB CAROL · Event
Event LAX96TA298
Registry · N499DF
FAA Aircraft Registry record.
Make / Model
BELL UH-1H
Seats / Engines
15 seats · 1 engine
ADS-B equipped
Yes — Mode-S A631D8
Registrant of record
USDA FOREST SERVICE FEPP
Source: FAA Aircraft Registry (releasable master file).
Aircraft involved
Probable cause & findings
the commercial/student pilot's improper/abrupt use of aft cyclic during the flare, and the instructor's inadequate supervision of the flight.
Factual narrative
On August 7, 1996, at 0900 hours Pacific daylight time, a Bell UH-1H, N499DF, collided with the runway while performing a practice autorotation at Ukiah Municipal Airport, Ukiah, California. The aircraft sustained substantial damage; however, neither the flight instructor nor his commercial student was injured. The aircraft was being operated as an instructional flight by the California Department of Forestry. The flight originated in Willits, California, at 0745. Visual meteorological conditions prevailed and a company VFR flight plan had been filed. According to the statements of both pilots, after first practicing a few confined area and slope landings, they flew to the Ukiah Airport. At Ukiah the instructor conducted emergency procedure training, which consisted mainly of autorotations terminating with power recoveries. He felt that the pilot had been having difficulty maintaining situational awareness during the previous confined area operations. The training continued with a series of straight in autorotations, with the touchdown point planned to be about midfield on runway 15. During the first three or four autorotations, the instructor pilot had to take control of the collective because she allowed the N2 to overspeed. She was also having problems with aircraft control, primarily during flare, initial pitch application, and recovery. The instructor estimated they had performed 10 to 15 straight in autorotations prior to the accident. During the final autorotation, the instructor described her flare as "very gradual." She had allowed the aircraft to descend to approximately 10 feet agl, with the aircraft was still in a near level attitude, when she began a power recovery. As she was rolling on the throttle, she inadvertently made an abrupt aft cyclic control movement. The stinger and tail rotor struck the ground before the instructor could regain control. After the tail rotor strike, the instructor stabilized the aircraft at a 3- to 4-foot hover. When he checked the controls he noticed a vibration and realized the aircraft had been damaged. He had hovered off the east side of runway 15 and was setting the aircraft down when the vibration became worse. During the aircraft shutdown, the tail rotor and tail rotor gearbox separated from the tailboom. The crew exited the aircraft without further incident. Fresh scrapes and gouges were observed on the runway surface. The left- and right-hand synchronized elevator, as well as the tail boom vertical fin and spar, had structural damage. The second stage power turbine wheel exhibited foreign object damage (FOD) on two blades. A tail rotor control tube and a synchronized elevator control tube also exhibited damage. The pilot had previously received 5.4 hours of initial training from the instructor between June 25 and June 27, 1996. On June 28, 1996, the pilot received a check ride from the CDF air operations officer. A pilot qualification card was issued with the provision that she receive additional training and a reevaluation check ride. The pilot then went on 2 weeks active duty for training (ADT) with the California Army National Guard at Los Alamitos AAF where she received additional training in the UH-1H helicopter. A telephone conversation between the CDF safety officer and her National Guard instructor pilot indicated that the pilot continued to have difficulties with aircraft control. The helicopter was being used on a training flight with a commercial rated (student) pilot and a flight instructor (CFI) aboard. During a straight-in autorotation, the student made a 'very gradual' flare and allowed the helicopter to descend to approximately 10 feet agl before she began rolling on the throttle. As she rolled on the throttle, she inadvertently made an abrupt aft cyclic control movement. The tail rotor and stinger then struck the ground before the CFI could regain control. The CFI stabilized the helicopter in about a 3 to 4 foot hover and noticed a vibration. As he was setting the helicopter down, the vibration became worse. During shutdown the tail rotor and tailrotor gearbox separated from the tailboom. The commercial (student) pilot's current qualification card had been issued with the provision that she receive additional training and take a reevaluation check ride. After the accident, the pilot spent 2 weeks with the Army National Guard, where she received additional training in the UH-1H helicopter. A conversation between the CDF safety officer and the National Guard instructor pilot indicated that the student continued to have difficulty with aircraft control. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12
Verbatim from NTSB's published report. Source file
NTSB_1996_LAX96TA298.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 2019 · Technical Memorandum (TM)
Analysis of a Hovering Rotor in Icing Conditions
A high fidelity analysis method is proposed to evaluate the ice accumulation and the ensuing rotor performance degradation for a helicopter flying through an icing cloud.
- 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…
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