NTSB Identification: CHI97LA097.
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Accident occurred Tuesday, April 01, 1997 in DES MOINES, IA
Probable Cause Approval Date: 09/05/1997
Aircraft: Piper PA-28-235, registration: N9004W
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot reported that about 40 minutes after takeoff the tachometer started surging. The oil pressure gauge dropped to zero and the engine started knocking. The engine seized and the pilot landed the airplane in a soy bean field. During landing rollout the airplane hit some large ruts which collapsed the landing gear. The engine examination indicated the number six connecting rod had failed and knocked a hole in the top of the crankcase. The number three upper piston pin plug had deteriorated and was contaminating the engine with aluminum metal. The oil filter was opened and evidence of aluminum metal contamination was found. The cam shaft and tappets indicated various stages of spalling. Rust was noted inside all cylinder walls and all the connecting rods had surface rust on them. In addition to the separated number six connecting rod, the number four and five connecting rods were blued and not free to move. The pilot reported that the oil filter was not opened during the oil changes to inspect for metal contamination. The pilot was unaware that the engine oil filter indicated that the oil system was contaminated with metal particles.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: oil contamination and starvation due to the inadequate maintenance inspection of the pilot/owner. Factors included the deterioration of the piston pin plug, the connecting rod failure, and the unsuitable terrain for landing. Full narrative available
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