Accident Overview
Moments after takeoff, the tower controller observed flames from the left engine and inquired if the flight was experiencing a problem. The crew affirmed, and the controller cleared them to land on any runway. The aircraft began a left turn at the departure end of the runway and continued turning at low altitude until it struck utility poles and crashed through the roof of a warehouse approximately two miles from the airport. A witness reported the aircraft at an altitude of about 100 to 150 feet above ground level, with the left propeller feathered and the right engine at full power.
Examination
Examination of the left engine revealed that the #14 cylinder was missing a spark plug from the front spark plug hole. The spark plug lead and 'b' nut were attached to the ignition harness, but no plug was attached to the lead. The threads of the spark plug hole and b-nut were undamaged. A white deposit was found inside the cylinder spark plug threads and outside the cylinder near the hole. The deposit contained high concentrations of lead and bromine, likely formed from exhaust gases and fuel during cylinder operation. A company mechanic had reportedly worked on the plugs the previous day.
Probable Cause
The official findings identify three occurrences. Occurrence #1: loss of engine power (partial) due to mechanical failure/malfunction—the spark plug was loose, maintenance was improper by company personnel, and the spark plug separated; the pilot performed propeller feathering. Occurrence #2: loss of control in flight—the reason for loss of control is undetermined, airspeed was not maintained, directional control was not maintained, and climb was not possible. Occurrence #3: in-flight collision with object—the light condition was dark night, and the objects were a utility pole and a nonresidential building.