Ellsworth, NE, USA
N84580
AERONCA 7AC
The private pilot departed for a local personal flight on a winter day with an outside air temperature of about 6°C. About 1 hour after takeoff, the pilot's brother saw the airplane maneuvering near his home, which was in a rural area about 31 miles from the departure airport. The airplane did not return to the departure airport, and the accident site was located in an open field 2 days later, about 4 miles from the pilot's brother's home. Examination of the accident site revealed wreckage and impact signatures consistent with the pilot losing control of the airplane. Examination of the engine's exhaust muffler revealed cracks in several locations, and the muffler's shroud contained a layer of exhaust residue. Six months before the accident, the pilot and the mechanic who had previously performed an annual inspection on the airplane became aware of a crack in the muffler near a weld that the pilot had performed. The pilot had purchased a replacement muffler, but it was not installed before the accident. A carbon monoxide detector was not on board the airplane. Toxicology testing of the pilot's blood revealed a carbon monoxide level of 40%, which was more than enough to severely impair the pilot. The carbon monoxide likely entered the airplane's cabin because of the cracked engine exhaust muffler. The toxicology testing also revealed several non-impairing medications and two potentially impairing medications (temazepam and buspirone). According to the pilot's medical records, he was being treated for anxiety with temazepam and buspirone, and he may have been fatigued from insufficiently treated sleep disorders (insomnia and obstructive sleep apnea). However, it could not be determined whether the pilot's anxiety, the medications used to treat it, or fatigue contributed to his poor judgment in flying the airplane with known cracks in the exhaust muffler.
HISTORY OF FLIGHTOn March 20, 2016, about 1110 mountain daylight time, an Aeronca 7AC airplane, N84580, impacted terrain near Ellsworth, Nebraska. The private pilot sustained fatal injuries, and the airplane was destroyed. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations (CFR) Part 91 as a personal flight. Day visual meteorological conditions prevailed for the local flight, which departed without a flight plan from Alliance Municipal Airport (AIA), Alliance, Nebraska. At 1000, an airport surveillance camera captured the airplane departing from AIA. About 1100, the pilot's brother observed the airplane maneuvering near his home, which was in a rural area about 31 miles northeast of AIA. After concerned family members reported the pilot missing, the accident site was subsequently located on March 22, 2016, about 4 miles southwest of the pilot's brother's home. PERSONNEL INFORMATIONThe pilot, age 68, held a private pilot certificate with an airplane single-engine land rating. The pilot was last issued a Federal Aviation Administration (FAA) third-class medical certificate on July 7, 2005. The pilot held a valid driver's license. The Aeronca 7AC is defined by the FAA as a light sport aircraft (LSA). Pilots flying LSAs are only required to possess a valid driver's license and comply with 14 CFR 61.53(b), which states that no person may act "as pilot in command, or in any other capacity as a required pilot flight crewmember, while that person knows or has reason to know of any medical condition that would make the person unable to operate the aircraft in a safe manner." A review of the pilot's logbook showed that the pilot had accumulated 355 flight hours of which 3 flight hours were in the last 30 days. The pilot's most recent flight review was completed on February 22, 2016. AIRCRAFT INFORMATIONThe airplane, serial number 7AC-3289, was manufactured in 1946 and registered to the pilot on September 10, 2013. It was a two-place, tandem, high-wing monoplane equipped with a Lycoming O-235-C1 engine, rated at 115 horsepower at 2,600 rpm. Review of the maintenance records showed that the most recent annual inspection was completed on July 25, 2015, at a total time of 1,848.2 hours. At the time of the accident, the airplane had accumulated 7 hours since the annual inspection. Although the airplane held a standard airworthiness certificate, it met the definition of an LSA as contained in 14 CFR Part 1.1. The mechanic who performed the last annual inspection stated that he and the pilot became aware of an engine exhaust muffler crack in September 2015. The crack was located near a weld that the pilot had performed. The pilot had intended to replace the muffler; a new muffler was in the pilot's hangar when the accident occurred. METEOROLOGICAL INFORMATIONAt 1053, the weather observation station at AIA, located about 27 miles southwest of the accident site, reported the following conditions: wind variable at 6 knots, 10 miles visibility, clear skies, temperature 6°C, dew point minus 12°C, and an altimeter setting of 30.23 inches of mercury. AIRPORT INFORMATIONThe airplane, serial number 7AC-3289, was manufactured in 1946 and registered to the pilot on September 10, 2013. It was a two-place, tandem, high-wing monoplane equipped with a Lycoming O-235-C1 engine, rated at 115 horsepower at 2,600 rpm. Review of the maintenance records showed that the most recent annual inspection was completed on July 25, 2015, at a total time of 1,848.2 hours. At the time of the accident, the airplane had accumulated 7 hours since the annual inspection. Although the airplane held a standard airworthiness certificate, it met the definition of an LSA as contained in 14 CFR Part 1.1. The mechanic who performed the last annual inspection stated that he and the pilot became aware of an engine exhaust muffler crack in September 2015. The crack was located near a weld that the pilot had performed. The pilot had intended to replace the muffler; a new muffler was in the pilot's hangar when the accident occurred. WRECKAGE AND IMPACT INFORMATIONThe aircraft impacted rolling terrain on a southeasterly heading. The main wreckage came to rest upright on a northerly heading, about 340 ft from the initial impact point. The left and right wings separated from the fuselage with the front and rear wood spars of both wings fractured near the wing roots. Both spars of the right wing were also fractured near the wing tip. The right wing was about 210 ft northwest of the main wreckage, and the left wing was about 5 ft to the right of the main wreckage. The propeller separated from the engine and came to rest about 180 ft northwest of the main wreckage. The flight control surfaces remained attached to their respective airframe surfaces. The elevator, rudder, and elevator trim tab cables had normal continuity with their respective cockpit controls. The aileron flight control cable was fractured in four locations. The fractures had a broomstraw appearance consistent with overload. Both aileron bellcrank connecting rods were fractured adjacent to the bellcranks, and the fracture surfaces were consistent with overload. No preimpact anomalies were noted with the flight control system. The engine remained attached to the airframe. The top Champion REM40E spark plugs were removed from the cylinders. All displayed a normal worn condition when compared to the Champion Aviation Service Manual (AV-27). A borescope inspection of the four cylinders was conducted, which revealed no anomalies with the pistons, cylinder barrels, cylinder heads, valves or valve seats. Both magnetos were rotated by hand and produced spark at all leads. The carburetor float bowl was removed with no anomalies noted. Both propeller blades were significantly twisted and curled aft with chord-wise polishing. The engine and propeller exhibited damage consistent with operation at impact. The cabin heat control was in the "off" position. The left muffler shroud was removed, and the muffler was found rusted and cracked in several locations. The muffler shroud contained a layer of exhaust residue. A carbon monoxide detector was not located in the wreckage. MEDICAL AND PATHOLOGICAL INFORMATIONThe pilot had reported no chronic medical conditions and no medications during his last FAA medical exam in 2005. However, according to his personal medical records, he had been treated for prostate cancer in 2000 and had intermittently been treated for hypertension. In 2009 and 2011, he underwent a series of interventions (angioplasty and stenting) for severe coronary artery disease. Since 2013, he had been treated for stress, insomnia, and anxiety with two antianxiety medications, temazepam and buspirone; both of these drugs carry warnings about behavior changes. In 2011, he had been diagnosed with obstructive sleep apnea and instructed to use a continuous positive airway pressure machine. A physician's review in 2016 revealed that he was not using his machine to the desired extent (at least 4 hours/night). As of February 18, 2016, the pilot was taking the following medications that are not generally considered impairing: aspirin (an antiplatelet drug to decrease the risk of recurrent heart attack), finasteride and tamsulosin to treat symptoms from his prostate gland (known also as Proscar and Flomax, respectively), simvastatin (a cholesterol lowering drug also known as Zocor), metoprolol (a blood pressure medication that also decreases the risk of recurrent heart attacks), and clopidogrel (an antiplatelet drug used to prevent clots in coronary stents, also known as Plavix). As previously mentioned, the pilot was also taking the potentially impairing anti-anxiety medications buspirone and temazepam. Finally, the pilot used nitroglycerin as needed for chest pain. According to the autopsy performed by the Regional West Medical Center, Western Pathology Consultants, P.C., Pathology Departmentin Scottsbluff, Nebraska, the pilot's cause of death was blunt force trauma, and the manner of death was accident. The autopsy also identified coronary artery disease with a 50% stenosis in the proximal left anterior descending artery. Toxicology testing performed by the FAA's Bioaeronautical Sciences Research Laboratory identified carbon monoxide (carboxyhemoglobin) at 40% in subclavian blood. In addition, metoprolol, buspirone, and temazepam (0.123 ug/ml) were identified in subclavian blood. These drugs and clopidogrel, diazepam, oxazepam, and ranitidine (a heartburn medication) were identified in urine. The finding of diazepam and oxazepam only in urine and not in blood was consistent with their presence as metabolites of temazepam. Carbon monoxide is an odorless, tasteless, colorless, nonirritating gas formed by hydrocarbon combustion. Carbon monoxide 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%. The pilot was not a smoker. Carboxyhemoglobin levels between 10% and 20% can result in confusion, impaired judgment, and difficulty concentrating. The primary effects of acute carbon monoxide poisoning are on the brain and heart and include headache, arrhythmias, confusion, coma, and death. ADDITIONAL INFORMATION FAA Advisory Circular 91-59A, Inspection and Care of General Aviation Exhaust Systems, emphasizes the safety hazards of poorly maintained exhaust systems and highlights points at which exhaust system failures occur.
The pilot's impairment due to carbon monoxide poisoning from a known cracked engine exhaust muffler, which resulted in a loss of aircraft control. Contributing to the accident was the pilot's decision to continue flying the airplane without properly repairing the exhaust muffler.
Source: NTSB Aviation Accident Database
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