Accident Sequence
The airplane was en route when radar data from the last nine minutes of flight indicated a descent from 3,400 to 300 feet. Sixteen days after the aircraft was reported missing, search and rescue personnel located the airplane in a water inlet at a depth of 132 feet. Nineteen days later, the aircraft was recovered from the accident site.
Postaccident Examination
A postaccident examination of the engine and airframe revealed that the left exhaust muffler had separated at the forward seam. Sooting was noted on the scat hoses surrounding the area. The forward end cap and exhaust riser were separated from the main body of the muffler. Magnified examinations found that almost all of the fractures were blackened and severely oxidized.
Muffler Failure Analysis
The failure of the muffler was the result of undetected oxidation and cracking resulting from normal thermal degradation. The cracking would have allowed exhaust gases direct access to cabin air through the heater system.
Toxicological Testing
Toxicological testing of the pilot and his passenger revealed carbon monoxide levels of 45 percent and 46 percent, respectively.