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On Wednesday, September 8, 1993, at about 1215 eastern daylight time, a Cessna 402B, N4504B, operated by Freight Runners Express Inc., of Milwaukee, Wisconsin, lost total power from the left engine during cruise flight and sustained substantial damage during the subsequent forced landing in a field in Eau Claire, Pennsylvania. The pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed at the time of the accident. The cross country positioning flight originated from Harrisburg, Pennsylvania, and was destined for Milwaukee, Wisconsin. An instrument flight rules flight plan was filed for the flight. The flight was conducted under 14 CFR Part 91.
The pilot reported that while in cruise "...the left engine started to develop engine vibrations." He stated he started to look for an airport to land when he heard a "bang" from the let side of the airplane. He said he looked over to the left wing and saw an engine cylinder depart the engine from the "out board side of the engine cowling..." and go over the wing. He stated he turned the airplane around and headed towards the Clarion Airport which he had passed a few minutes earlier. The pilot stated that due to the damage incurred by the engine, the propellers would not feather and that the drag of the left engine would not allow sustained flight. He stated that he put the flaps and gear down and made a forced landing in a field.
The pilot reported that during the landing roll the left main gear sheared and the nose gear collapsed. He stated that the field was hilly and the terrain was soft and uneven.
The left engine was removed from the airplane and sent to G & N Aircraft, Inc., located in Griffith, Indiana, for examination. (See TESTS AND RESEARCH section of this report for engine examination results.)
The left engine was remanufactured and had been overhauled by AeroSmith Engines of Springdale, Arkansas, in December, 1991. At the time of the accident, the engine had accrued about 302 flight hours since the overhaul. The engine had a 100 hour inspection on July 20, 1993, at a tach time of 1904, 14 hours prior to the accident.
TESTS AND RESEARCH
The examination revealed that the number four cylinder and piston were gone from the engine case. A hole larger than the cylinder base was noted in the case half. Pieces of piston were throughout the casing. The number four connecting rod was attached to the crankshaft. The piston pin end of the connecting rod was intact but caved inward.
Material from the piston, a counterweight bushing, and piston rings were found in the oil sump. The oil pump housing and gears were not contaminated.
The cam shaft was not damaged except for some marring near the number four cylinder. The crankshaft was not damaged. The 4th order counterweight was damaged and a section of it was missing near the dampener counterweight pin hole.
The left half of the engine case with three studs and two through bolts were sent to the Safety Board's Materials Laboratory Division for further examination. The examination revealed extensive fatigue cracking in the engine case, through bolts and studs. Three of the six studs were not recovered. The initial failure was not determined. (See attached Metallurgist's Factual Report for details.)