CHI94LA314

The pilot reported a loss of engine power during his third aerial application swath run. During the subsequent forced landing, the airplane sustained substantial damage. Examination of the wreckage revealed the engine was seized and the case was fractured in the vicinity of the number one cylinder. No evidence of preimpact airframe malfunction was discovered. Examination of the engine revealed the crankshaft was fractured forward of the number one connecting rod journal. It was concluded that a fatigue fracture resulted from a misalignment after a recent overhaul which caused damaged to the number two crankshaft cheek.

On September 7, 1994, at 1600 central daylight time, a Cessna 188B, N731SV, operated by B D Flying Service of Virden, Illinois, sustained substantial damage during a forced landing near Oakdale, Illinois. The commercial pilot reported no injuries. Visual meteorological conditions prevailed for the 14 CFR Part 137 aerial application flight which originated in Sparta, Illinois, about 1530. No flight plan was filed.

The pilot reported a loss of engine power during his third aerial application swath run. He said he attempted to land in a field and the airplane slid sideways, breaking the landing gear. The airplane sustained substantial damage to both wings and the fuselage. The pilot reported the total engine time was 1863.6 hours and the engine had 1835.7 hours at the time of overhaul.

A Federal Aviation Administration (FAA) Inspector examined the wreckage and reported the engine was seized and the case was fractured in the vicinity of the number one cylinder. He reported no evidence of preimpact airframe malfunction.

The FAA inspector said the engine was overhauled 27.9 flight hours prior to the accident. He provided the NTSB with an overhaul invoice which listed the part numbers of multiple after market engine components from Superior Airparts, Inc. He also provided a copy of a "yellow tag" for the crankshaft dated April 6, 1994.

The engine was examined by the NTSB on November 18, 1995, at Teledyne Continental Motors, Mobile, Alabama. A large quantity of metallic debris was in the sump and oil screen. The crank case was fractured at the number one cylinder pad. The number one main bearing was severely galled. The number four and five rod bearings exhibited smeared metal deposits and discoloration.

The crankshaft was fractured forward of the number one connecting rod journal. Inspection of the fracture revealed beach marks originating at a point at the bottom center of the connecting rod journal. The origin was smeared and located near a circumferential gouge next to the front face of the connecting rod. Dye penetrant inspection of the crankshaft revealed multiple cracks in the bearing surfaces forward of the fracture.

An investigator from Teledyne Continental Motors concluded in his written report that "a misalignment problem existed after overhaul which resulted in damaging the number two crankshaft cheek just above the journal fillet. The damaged area initiated a fatigue fracture that progressed until separation."