NTSB Identification: LAX91LA255.
The docket is stored on NTSB microfiche number 44937.
Accident occurred Saturday, June 08, 1991 in THERMAL, CA
Probable Cause Approval Date: 03/31/1993
Aircraft: CESSNA 172N, registration: N6230D
Injuries: 2 Minor,2 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.

A CESSNA 172N NOSED OVER IN SOFT SOIL DURING LANDING ROLL AFTER A FORCED LANDING. THE PILOT INDICATED THAT THE ENGINE WAS RUNNING ROUGH AND LOSING POWER. THE PILOT LANDED THE AIRPLANE ON AN AIRPORT, BUT WAS UNABLE TO MANEUVER THE AIRPLANE TO A RUNWAY. THE AIRPLANE DECELERATED TO ABOUT 20 MPH DURING THE GROUND ROLL ON DIRT. THE AIRPLANE NOSED OVER AFTER THE NOSE GEAR STRUCK A 15 TO 18 INCH HIGH DIRT BANK. THE ENGINE WAS EXAMINED BY AN A&P MECHANIC. THE A&P FOUND THE NUMBER THREE CYLINDER INTAKE VALVE WAS 'TULIPED.' ACCORDING TO THE AIRPLANE'S MAINTENANCE RECORDS, THE ENGINE HAD ACCRUED 2,850 HOURS OF OPERATION WITHOUT OVERHAUL. FORTY FOUR HOURS OF OPERATION BEFORE THE ACCIDENT, THE ENGINE'S CYLINDER COMPRESSION CHECKED 'OK' DURING A LEAK TEST. THE ENGINE MANUFACTURER RECOMMENDED TIME BETWEEN OVERHAULS IS 1,500 HOURS. DURING OVERHAUL THE VALVES ARE REMOVED AND VISUALLY CHECKED FOR WEAR.

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

THE PARTIAL FAILURE OF THE ENGINE/POWERPLANT FROM A WORN INTAKE VALVE AND THE FAILURE OF COMPANY/OPERATOR MANAGEMENT TO PERFORM AN OVERHAUL ON THE ENGINE WITHIN THE TIME FRAME RECOMMENDED BY THE ENGINE MANUFACTURER.

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