What happened
Shortly after departure, the flight crew heard a loud noise and observed sparks emanating from the right side of the right engine. They attempted to feather the propeller on that engine, but it remained unfeathered. Unable to maintain altitude due to the asymmetric thrust, the aircraft descended into trees before striking the roof of a house. The plane burst into flames approximately five to ten minutes after the initial impact. A responding police officer who had climbed onto the roof was reportedly thrown off by an explosion and sustained minor injuries.
The investigation
Examination of the right engine revealed that one blade of the HC-82XG propeller did not feather and was free to move. The retaining clamp on this blade was cracked with a portion missing. A metallurgical examination determined that the clamp had failed due to high cycle fatigue.
Findings
The failure was linked to an older model retaining clamp. Hartzell Propeller Service Bulletin No. 126, dated December 9, 1980, recommended replacing this old clamp with a new improved type. No other preimpact failures were found in the aircraft.
Safety message
Adherence to manufacturer service bulletins regarding propeller component upgrades is critical to preventing in-flight engine failures.