Flight Details
A night cross-country flight was conducted at flight level 250 (FL250). During the flight, the pilot elected to leave the cockpit area and move to the rear of the aircraft to attend to physiological needs. While supplemental oxygen was available in the cockpit, it was not available in the rear of the aircraft.
Pressurization Deficiency
The aircraft was operated with a known pressurization system deficiency that limited the airplane to flight at 17,000 feet mean sea level (MSL) while maintaining a cabin altitude of 10,000 feet. Despite this limitation, the flight continued at FL250.
Loss of Radio Contact
After 2 hours and 10 minutes, air traffic control (ATC) declared the flight to be 'no radio.' The aircraft continued without communication.
Descent and Impact
At 3 hours and 57 minutes after departure, radar plotted the airplane in a descending left turn, which continued to ground impact. Fuel starvation resulted in power loss to the left engine. Propeller signatures indicated that the right propeller was producing power at the time of impact.
Findings
The pilot's body was found in the aft cabin area against the aft cabin bulkhead. The aircraft had departed with a known pressurization issue that restricted its maximum operational altitude.