Accident Sequence
The pilot reported being level at 6,000 feet and no further radio transmissions were received. Radar data indicated that after five minutes of cruise flight, the ground speed began to decrease. As the speed reached 85 knots—the minimum control speed (VMC) being 83 knots—the aircraft executed a rapid left turn, and the speed dropped to 74 knots. Radar contact was then lost.
Witnesses reported hearing and seeing the aircraft with an engine sputtering and then quitting, at which point no engine noise was audible. The engine subsequently restarted, and the aircraft was observed initiating a climb after the engine start. The engine then regained near full power, but shortly thereafter the sound of impact was heard.
Investigation Findings
Examination of the left engine fuel servo revealed contamination with corrosion and dirt, which prevented fuel flow to the engine. The fuel strainer for this engine had been installed backwards, allowing unfiltered fuel to enter the engine. The left propeller was not feathered and showed no signs of rotation under power. The right engine fuel servo also contained corrosion and contamination. Additionally, the aircraft did not have a current annual inspection. All five occupants were killed.
Probable Cause
The official probable cause was determined to be the pilot's failure to feather the propeller to maintain altitude following a loss of power of the left engine. The power loss was due to an improperly maintained fuel system. Furthermore, the right engine lost power for undetermined reasons.