Bowling Green, OH, USA
N4635V
VARGA AIRCRAFT CORP. 2150A
The private pilot was performing a visual flight rules cross-country flight after purchasing the airplane. After flying for about 1 hr 20 minutes, the airplane suddenly entered a spiraling descent from cruise flight. Witnesses observed the airplane flying erratically at low altitude before it impacted an open field; they stated that the engine was running until impact. Toxicological testing of specimens taken from the pilot found 55% carbon monoxide saturation of blood. At carbon monoxide levels above 40%, people typically experience incapacitating symptoms such as severe confusion, agitation, seizures, loss of consciousness, and death. Examination of the airplane's heat exchanger showed that the outside casing had either previously been repaired or had been originally constructed of metals with different properties. About one-half of the casing was discolored and exhibited varying signs of corrosion (the other half did not). Small holes were found where corrosion had occurred in the casing material. The holes from the corrosion provided a means for carbon monoxide to enter the cockpit from the exhaust system. Federal guidelines for annual aircraft inspections require an inspection of the exhaust systems for cracks, defects, and improper attachment during each 100-hour or annual aircraft inspection. Maintenance logbooks indicated that the airplane's most recent annual inspection was completed less than 1 month before the accident. The available maintenance logbooks did not contain any record of repairs or replacement of the heat exchanger. However, the condition of the heat exchanger is indicative of an insufficient annual inspection that did not detect and correct the corroded heat exchanger. It is likely that impairment caused by acute carbon monoxide poisoning led to the pilot's loss of airplane control. The corrosion in the heat exchanger allowed carbon monoxide to enter the cabin.
HISTORY OF FLIGHT On June 1, 2017, at 1157 eastern daylight time, a Varga 2150A airplane, N4635V, was destroyed when it impacted terrain near Bowling Green, Ohio. The private pilot was fatally injured. The airplane was privately owned by the pilot, and he was operating it under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91. Visual meteorological conditions prevailed for the personal flight, which originated from Tri-City Airport (3G6), Sebring, Ohio, and was en route to Conklin Airport (OI92), Bowling Green, Ohio. The pilot had recently purchased the airplane and was relocating it to a private airstrip near his home. GPS data recovered from an onboard device showed that the airplane departed 3G6 about 1034 and flew northwest toward OI92. The airplane maintained consistent groundspeeds and headings until 1156, when it entered a left-turning spiral descent. (See figure.) Figure: Final GPS Data (oriented Northeast up, times are depicted in UTC) Witnesses observed the airplane flying erratically at low altitude before it impacted terrain. One witness stated, "the airplane was flying very low to the ground and turned to the east almost turning sideways and upside down. The plane flew south and then turned … the plane was nose down, heading north." Each witness reported that the engine was running before impact. The accident location was about 6 miles southeast of the destination airport. PERSONNEL INFORMATION AIRCRAFT INFORMATION The airplane was manufactured in 1977. The airframe maintenance logs located during the investigation were annotated "Logbook #2, 10/2/92." The first work documented in the engine log was an engine overhaul dated June 11, 1992. The first work documented in the propeller log was an annual inspection dated June 23, 2014. The aircraft log recorded 15 annual inspections between 1992 and 2017. The last annual inspection occurred on May 5, 2017. METEOROLOGICAL INFORMATION WRECKAGE AND IMPACT INFORMATION Wreckage and impact signatures were consistent with the fixed-tricycle gear, tandem-seat airplane impacting terrain left-wing-low in an attitude that exceeded 70° nose-low. The impact point and wreckage debris field were contained within an area about 200 ft in diameter. All airplane and engine components were accounted for at the accident location. The propeller was found separated from the engine. Leading edge gouges and chordwise scratches were present on both propeller blades. The fuel selector was found in the "BOTH" position. The left wing and fuel tank were destroyed by impact forces. The right-wing fuel tank contained an undetermined amount of fuel and the tank displayed evidence of hydraulic deformation. Fuel was present in the fuel selector valve and inside the remnants of the engine-driven fuel pump. The flap selector was found at the second notch (extended) position and the flaps were also found in an extended position. No pre-impact anomalies were noted with the airframe or engine during examination at that time. The NTSB investigator-in-charge conducted an additional examination of the engine on November 1, 2017. Portions of the engine exhaust system, heat exchanger, and associated scat tubing were removed and examined. No nonimpact-related anomalies were identified with the exhaust system or the scat tubing. The heat exchanger was impact-damaged. The examination also revealed that the outside casing was comprised of metals with different properties. About one-half of the casing was constructed of a material similar to stainless steel that was discolored but showed no indications of corrosion. The remainder of the casing was discolored and exhibited varying signs of corrosion. Small holes were found where corrosion had occurred in the casing material. There were cracks in the casing in areas affected by impact damage. It could not be determined if the cracks were present before impact or resulted from impact forces. Review of the maintenance logbooks revealed no entries regarding repairs or replacement of the heat exchanger. MEDICAL AND PATHALOGICAL INFORMATION The Lucas County Coroner's Office, Toledo, Ohio, conducted an autopsy of the pilot. The cause of death was blunt force trauma. The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology testing and identified 55% carbon monoxide in cavity blood. No other tested-for substances were identified. Carbon monoxide (CO) is an odorless, tasteless, colorless, nonirritating gas formed by hydrocarbon combustion. CO binds to hemoglobin with much greater affinity than oxygen, forming carboxyhemoglobin; elevated levels result in impaired oxygen transport and utilization. Nonsmokers may normally have up to 3% carboxyhemoglobin in their blood; heavy smokers may have levels of 10 to 15%. Acutely, low levels of CO may cause vague symptoms like headache and nausea but increasing levels (40% and above) lead to confusion, seizures, loss of consciousness, and death. ADDITIONAL INFORMATION Title 14 CFR Part 43, Appendix D states, in part: (d) Each person performing an annual or 100-hour inspection shall inspect (where applicable) components of the engine and nacelle group as follows:… (8) Exhaust stacks - for cracks, defects, and improper attachment.
The pilot's loss of control due to impairment from carbon monoxide poisoning. Contributing to the accident was the corrosion of the heat exchanger and the failure of maintenance personnel to adequately inspect and repair or replace the exchanger during the most recent annual inspection.
Source: NTSB Aviation Accident Database
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