NTSB CAROL · Event
Event WPR11FA348
Aircraft involved
Probable cause & findings
The fatigue failure of the aluminum air intake duct, which resulted in material being ingested into the engine cylinders and a subsequent loss of engine power during cruise flight.
Factual narrative
HISTORY OF FLIGHT
On July 22, 2011, at 1225 mountain daylight time, a Cessna 210-5, N8427Z, sustained substantial damage following a loss of engine power and subsequent forced landing near Darby, Montana. The airplane was registered to the pilot and operated under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot and passenger sustained minor injuries. The flight departed Lemhi County Airport, Salmon, Idaho, at 1155, with a planned destination of Chamberlin, Idaho. Visual meteorological conditions (VMC) prevailed and no flight plan was filed for the cross-country flight. The pilot reported that the airplane was in a cruise flight configuration when the engine began to run rough and eventually lost power. The pilot maneuvered the airplane towards a nearby open valley and gravel road. The pilot positioned the airplane to land downwind to the road and prepared for a short/soft field landing. He reported that the airplane touched down on the gravel road about 200 feet beyond a cattle guard and began to skid. The pilot reduced braking pressure and crossed a second cattle guard. During the landing rollout, the airplane's left wing impacted a tree and the airplane pivoted approximately 90-degrees to the left before it came to an abrupt stop. The airplane sustained substantial damage to the left wing and forward fuselage.
AIRCRAFT INFORMATION
The accident airplane (serial number 205-0427) was manufactured in 1963. The single engine airplane was equipped with a Continental IO-470 S engine and constant-speed propeller manufactured by McCauley. The most recent annual inspection of the airplane, engine, and propeller was completed on January 9, 2011. At the time of the accident, the airplane had accumulated 7,343 total hours and the engine had accumulated 475 total hours since new. The airplane had accumulated approximately 56 hours between the annual inspection and the accident.
TESTS AND RESEARCH
The NTSB conducted a postaccident examination of the engine and airframe after the airplane was transported to a storage facility in Phoenix, Arizona. The examination revealed a dark residue that covered the left side of the engine accessory section (aft) and associated baffling and hoses. The residue was concentrated in the area of the outboard engine air intake duct assembly, just aft of the bracket air filter. The air filter, bracket assembly and aluminum air intake duct were removed. A large hole (approximately 4.25 inches by 1.75 inches) and material loss was noted on the bottom side of the duct. The circumference of the hole was an irregular shape with both jagged and smooth edges/fracture surfaces. A dark residue was noted to the face of the fracture surfaces. A weld repair was noted adjacent to the hole. A section of fuel pump baffle tubing was routed adjacent to the hole in the outboard intake duct. Rub marks and dark residue was noted along the baffle tubing, concentrated in the area of the hole in the duct. Material loss and deformation was noted to the baffle tubing in the area adjacent to the hole in the intake duct. Internal borescope examination of the piston cylinders revealed mechanical etching to the No. 4 and No. 6 combustion chambers and associated valve heads. The corresponding spark plugs were removed and mechanical damage was noted. The ground electrodes were bent down onto the insulators and center electrodes. The examination of the airframe and engine revealed no additional findings or anomalies. Additional examination notes are located in the public docket associated with this case file. A senior NTSB metallurgist examined the engine air intake duct and reported that the fractures were consistent with fatigue and possibly the result of vibration. Although there was evidence that a weld repair had been performed near this area, it was not determined if it contributed to the hole and loss of material. A review of the airplane’s maintenance records showed no recent modifications or repairs to the engine air intake duct. The pilot reported that, while in a cruise flight, the engine began to run rough and eventually lost power. The pilot subsequently initiated a forced landing to a gravel road, and the airplane collided with a tree during the landing roll. Postaccident examination of the engine found a 4-inch by 2-inch hole and material loss on the bottom side of the aluminum air intake duct assembly. The circumference of the hole was an irregular shape with both jagged and smooth edges/fracture surfaces. The fractures were consistent with fatigue and were possibly the result of vibration. Internal borescope examination of the cylinders revealed mechanical etching to the No. 4 and No. 6 combustion chambers and associated valve heads. The corresponding spark plugs were removed and mechanical damage was noted. The ground electrodes were bent down onto the insulators and center electrodes. No other mechanical failures were noted with the engine or airframe. It is likely that the missing aluminum duct material was ingested into the cylinders, which resulted in a loss of engine power. Although there was evidence that a weld repair had been performed on the air intake duct near the area of the hole, it could not be determined if it contributed to the hole and loss of material. A review of the airplane’s maintenance records showed no recent modifications or repairs to the engine air intake duct. Source: NTSB Aviation Accident Database Retrieved: 2026-02-12
NTSB Findings
Hierarchical cause / factor breakdown from the FAA bulk avdata database. Each finding tagged C (Cause) or F (Factor).
- C Aircraft-Aircraft power plant-Power plant-Air intake-Fatigue/wear/corrosion - C
- C Aircraft-Aircraft power plant-(general)-(general)-Failure - C
Verbatim from NTSB's published report. Source file
NTSB_2011_WPR11FA348.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 (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.
- 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…
- 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.
- 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.
- Embry-Riddle Scholarly Commons 2024 · Journal article (IJAAA)
Just Culture in Aviation: A Metaphorical Study on Aircraft Maintenance Students
Just Culture, a sub-dimension of safety culture, has been a prominent and debated topic in aviation safety in recent years.
- Embry-Riddle Scholarly Commons 2024 · Journal article (IJAAA)
Performance PRISM: A Comprehensive Framework For Performance Measurement In Aircraft Maintenance
Aircraft maintenance is governed by rigorous safety requirements and high operational complexity, demanding robust performance measurement frameworks to ensure optimal maintenance practices.
Browse the full corpus — academia portal ↗