NTSB Identification: LAX98LA214.
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Accident occurred Saturday, June 27, 1998 in FLAGSTAFF, AZ
Probable Cause Approval Date: 06/23/2000
Aircraft: Cessna 172, registration: N7188A
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 stated that the preflight and run-up were conducted with no anomalies noted. After takeoff, the airplane experienced a loss of engine power followed by a loss of altitude and collision with terrain. The airplane came to rest inverted in a sewage pond near the airport. After the power loss, the pilot made an unsuccessful attempt to restart the engine utilizing the emergency checklist. The engine was inspected and mechanical continuity of the engine was established. The crankcase was separated and it was noted that the bearings, pistons, and cylinders exhibited heat discoloration. The number 4 main bearing exhibited evidence of rubbing on the crankshaft and a section of that bearing insert was severely worn, heat distressed, and had flowed over the edge of the crankcase bearing journal. The number 6 connecting rod bearing insert exhibited an unidentified metal substance in the oil port. The remaining crankcase oil journals were found to be clear. The oil pump was disassembled and revealed a nick on one of the driven gear teeth, which corresponded to circumferential scoring on the oil pump housing. The oil filter and suction screen were clean. No further discrepancies were noted with the engine. Review of the maintenance records revealed that an annual inspection, which included an oil change, had been completed approximately 1 hour prior to the accident flight.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Oil system contamination with an unidentified metal substance that traveled through the oil system and blocked the number 4 main bearing and number 6 connecting rod bearing oil ports, resulting in oil starvation and failure of the engine. The source of the contamination is undetermined.

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