Cirrus SR22 N729SR

The instrument-rated private pilot, along with two passengers, departed on an instrument flight rules (IFR) cross-country flight. The pilot requested to climb to 10,000 feet and was cleared to do so. Shortly thereafter, the pilot reported that he was level at 10,000 feet. Approximately 33 minutes later, air traffic control (ATC) radioed the pilot with a frequency change; however, the pilot did not respond. Repeated attempts to contact the pilot were unsuccessful as the airplane continued flying a straight course, while at 10,000 feet, towards its intended destination. One hour and 33 minutes after the last pilot contact, the autopilot equipped airplane made a rapid descending right turn before radar contact was lost. In the area of the last radar contact, several fishermen reported observing the accident airplane descending nose down and impacting the surface of a reservoir. The airplane's wreckage came to rest about 40 feet below the surface of the water. Calculations revealed that if the pilot maintained full throttle and did not switch fuel tanks during the flight, the selected fuel tank would have been nearly empty by the time it reached the area near the crash site; thus a loss of engine power could have occurred. Multiple dives were conducted in an attempt to recover the wreckage. The ballistic parachute was found in its storage bag and had not been deployed. The fiberglass fuselage and wings were not located. In addition, the avionics equipment with nonvolatile memory, that would have recorded the accident flight, was not located. Maintenance records revealed that in the previous year and a half, the airplane’s number six exhaust header was found to be cracked and was replaced three separate times; however, the exhaust system was not recovered and therefore could not be examined to see if possible carbon monoxide leaks were present. The airplane was not equipped with a factory installed carbon monoxide detector, and investigators were unable to determine if an aftermarket unit was installed. Due to the limited remains that were recovered, an autopsy could not be accomplished on the pilot or passengers. In addition, adequate specimens were not recovered to perform toxological testing for the presence of carbon monoxide or cyanide. No reported radio communications with the airplane for the hour prior to the accident, straight and level flight consistent with flying with an autopilot with no deviations, estimated fuel calculations indicating that the airplane could have exhausted all its fuel by the time it reached the accident location, a repeated history of exhaust leaks, no evidence of an on-board carbon monoxide detector, and radar showing the airplane in an unarrested descent prior to impact, suggest that the pilot and passengers may have been incapacitated during the last portion of the flight. However, due to the limited recovery of airplane wreckage and human remains to test for carbon monoxide, incapacitation could not be confirmed and the reason for the unarrested descent into the lake could not be determined.

Quoted verbatim from the NTSB record.