Accident Details
A commercial certificated pilot was conducting scheduled passenger flights. On the flight preceding the accident, passengers reported a smell that the pilot suspected might be exhaust. After landing, the pilot inspected the engine for exhaust leaks but found none, and subsequently continued with the return flight. While departing the airport, a loud bang was heard, the passenger cabin began to fill with smoke, and the pilot observed fire at his feet. He reduced the throttle and landed the airplane on the runway. In his haste to evacuate, the pilot did not turn off the fuel supply and left the electric fuel boost pump running. After exiting, he noticed a large pool of fuel forming beneath the airplane, and smoke continued to emanate from the passenger cabin door. The pooled fuel ignited, burning the airplane. Passengers reported first noticing smoke in the rear of the passenger cabin, and that the smoke propagated forward until they could no longer see the pilot.
Examination Findings
During the airplane examination, the NTSB investigator found that approximately a 4-by-6-inch piece of the right side exhaust manifold at the rear of the engine was missing. The edges of the manifold at the missing section exhibited scalloped fractures and long straight tears, consistent with fatigue fractures and failure. Additional fractures were found in other areas of the exhaust system. The hot exhaust gases burned a hole in the heater shroud at the point where it attaches to the scat tubing, which provides heated air to the vents in the rear of the passenger cabin. The hot exhaust gases were deflected by the firewall onto the engine fuel line attached to the engine-driven fuel pump mounted on the left rear of the engine, burning the fuel line through. The electric fuel boost pump provided pressurized fuel to the engine-driven pump, resulting in fuel continuing to flow and pooling on the ground.
Inspection Records
According to airplane records, the exhaust system had been inspected in accordance with the operator's approved inspection program 2.9 flight hours prior to the accident.