What happened
During the landing phase of flight, the aircraft bounced several times on the runway. Shortly after exiting the aircraft, the pilot collapsed.
Following the incident, blood samples were taken from the pilot three hours after landing. The results indicated a carbon monoxide level of 22.1%.
The investigation
Investigators examined the left engine muffler and discovered that the overboard tube had broken loose from the muffler at the weld point. This failure allowed exhaust gases to enter the cockpit via the aircraft's heater system.
The investigation revealed a .022 inch deep groove on the overboard tube, caused by it rubbing against the engine cowling. This abrasion was located on the same side where the crack originated. The muffler had been installed during a 100-hour inspection 68 hours prior to the event. The manufacturer of the muffler could not be verified.