Incident
During landing, the aircraft bounced several times. After exiting the airplane, the pilot collapsed. Blood samples taken three hours after landing contained 22.1% carbon monoxide.
Investigation Findings
Examination of the aircraft revealed that the left engine muffler overboard tube had broken loose from the muffler at the weld joint. This separation allowed exhaust gas to enter the cockpit through the heater system. The overboard tube exhibited a 0.022-inch deep groove on the side where the crack originated, caused by rubbing against the engine cowling.
The muffler had been installed during the last 100-hour inspection, which occurred 68 flight hours prior to the incident. The source or manufacturer of the muffler could not be verified.