Bellanca 14-19-3A N11RC accident near Boerne, Texas

Probable cause

A defective exhaust system that allowed carbon monoxide to enter the cabin and impair the pilot, rendering him unable to control the airplane.

NTSB analysis

The pilot was returning to his home airport. A review of radar data showed the accident airplane in a straight-line descent from cruise flight at a rate of nearly 2,900 ft per minute. The descent resulted in a loss of 8,100 ft in less than 3 minutes until the airplane disappeared from radar in the vicinity of the accident site.

Disassembly of the airplane's cabin heat shroud, which provided heated air to the cabin, revealed evidence of cracks and holes in the muffler wall and exhaust gas penetration into the interior of the shroud. According to the autopsy report, the pilot died as a result of thermal injuries and smoke inhalation, with soot present in the upper airway and 37% carbon monoxide found in his blood postmortem. Based on the lack of soot in the lower airway and the elevated carbon monoxide levels, the majority of the carbon monoxide in the pilot's blood was likely from inhalation during the flight at levels that would have impaired his ability to safely fly the airplane. Although cetirizine, also known as Zyrtec® (used to temporarily relieve allergy symptoms and could cause drowsiness), was also detected in the pilot's urine and blood, the detected level indicated that impairment from the drug was unlikely.

Text from the NTSB. Open the NTSB docket for CEN14FA024 for the full record.