NTSB Identification: ATL94LA079.
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Accident occurred Monday, April 11, 1994 in HAZEL GREEN, AL
Probable Cause Approval Date: 02/14/1995
Aircraft: CESSNA 150, registration: N11560
Injuries: 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.

UPON ARRIVING FROM A FORTY MINUTE LOCAL FLIGHT, THE PILOT ENTERED A TRAFFIC PATTERN FOR LANDING AT HIS PRIVATE SOD AIRSTRIP. WHILE ON FINAL APPROACH THE PILOT ELECTED TO GO AROUND BECAUSE SOMEONE WAS WALKING ON THE SOD STRIP. WHEN THE PILOT APPLIED POWER THE ENGINE FAILED TO DEVELOP FULL POWER AND HE HEARD A LOUD BACK FIRING SOUND COME FROM THE ENGINE. WITH REDUCED POWER, 1600 RPM, THE PILOT MADE A 270 DEGREE LEFT TURN AND MADE A FORCED LANDING IN A PLOWED FIELD ADJACENT TO HIS AIRSTRIP; AT TOUCH DOWN THE AIRPLANE NOSED OVER. EXAMINATION OF THE ENGINE ASSEMBLY DISCLOSED THAT, THE OUTER TOP OR HALF MOON SECTION OF THE INTAKE BOSS, ON NUMBER 3 CYLINDER HEAD, HAD SEPARATED FROM THE BOSS. THE HALF MOON SECTION OF THE BOSS ASSEMBLY WAS RECOVERED FROM INSIDE THE ROCKER COVER AND EXAMINED. THE EXAMINATION OF THE FRACTURE FACE REVEALED AREAS OF FATIGUE STRIATIONS, AND A POST-FRACTURE MARK ON THE OUTER RADIUS. THE EXAMINATION ALSO DETERMINED THAT THE FUNCTIONAL ABILITY OF THE CYLINDER WAS NOT EFFECTED UNLESS THE SEPARATED PIECE OF BOSS WAS WEDGED UNDER ONE OF THE MOVEABLE COMPONENTS OF THE CYLINDER HEAD.

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

THE LOSS OF ENGINE POWER WHEN THE FRACTURED PIECE OF THE ROCKER BOSS INTERRUPTED THE NORMAL OPERATION OF A MOVABLE COMPONENT UNDER THE VALVE COVER. A FACTOR WAS THE SOFT TERRAIN IN THE LANDING AREA.

Full narrative available

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