On March 29, 1987, a Cessna 172L (registration N4211Q) was involved in an aviation accident near Plainfield, IL. Investigators recorded the probable cause as: Carbon monoxide asphyxiation due to an exhaust system defect (a 12-inch crack in the muffler) that predated the flight, combined with the pilot's decision to run the engine while occupying the aircraft on the ground. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot ran the engine of a parked aircraft to warm it up and turn the tires, but was found dead inside from carbon monoxide asphyxiation caused by an exhaust leak.
What happened
The pilot determined that weather conditions were not suitable for flight. Despite this assessment, he decided to run the engine while the aircraft remained on the ground, likely to warm the powerplant and rotate the tires. Other pilots later discovered him inside the cabin. He was pronounced dead at the scene due to carbon monoxide asphyxiation.
The investigation
Examination of the aircraft revealed a 12-inch crack in the muffler. A metallurgist analyzed the fracture and determined that the damage could not have occurred during the 1.1 hours since the plane's last annual inspection, indicating the defect existed prior to the incident.
Findings
The primary causal factor was carbon monoxide asphyxiation resulting from the exhaust leak. The pilot's decision to operate the engine in a confined or poorly ventilated area while remaining inside contributed directly to the fatal outcome.
Probable cause
Carbon monoxide asphyxiation due to an exhaust system defect (a 12-inch crack in the muffler) that predated the flight, combined with the pilot's decision to run the engine while occupying the aircraft on the ground.