What happened
During cruise flight, the pilot of a Cessna (registration not provided) experienced an explosion while the combustion heater was operational. Following the explosion, smoke entered the aircraft cabin and the pilot experienced a loss of electrical power. The pilot subsequently diverted the aircraft and performed a landing without further incident.
The investigation
An examination of the aircraft revealed that the combustion heater had sustained both heat and fire damage. Investigators identified that the fuel pump supply line, which connected the fuel pump to the heater, was loose and cracked at the inlet of the fuel pump housing. The surfaces of the fracture were found to be dull and covered in carbon build-up.
Review of the aircraft logbooks showed that the combustion heater had been removed, rebuilt, and reinstalled on December 1, 1993, when the aircraft had a total time of 3,932.2 hours. The aircraft's most recent annual inspection occurred in September 2001, at 5,213.5 hours. At the time of the event, the aircraft had accumulated 5,231.9 total hours. No records were found indicating compliance with a 20-year-old Airworthiness Directive intended to prevent hazardous conditions caused by deterioration of this specific combustion heater model.