NTSB Identification: BFO94LA010.
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Accident occurred Sunday, November 14, 1993 in STERLING, MA
Probable Cause Approval Date: 10/20/1994
Aircraft: GULFSTREAM AMERICAN AA-5B, registration: N28215
Injuries: 4 Minor.

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 THE AIRPLANE WAS AT 2000 FEET MSL WHEN A SEVERE VIBRATION DEVELOPED ON THE AIRPLANE. HE STATED THAT THE AIRPLANE WAS DESCENDING AT 200 FEET PER MINUTE WITH THE THROTTLE FULL FORWARD, AND 1700 RPM ON HIS GAGE. HE STATED THAT THE NEAREST AIRPORT WAS ABOUT 6 MILES AWAY, SO HE RADIOED THE AIRPORT OF HIS SITUATION AND ENTERED THE TRAFFIC PATTERN ON THE BASE LEG. HE STATED THAT HE WAS HIGH ON THE APPROACH, BUT HE RECALLED FROM HIS TRAINING THAT IT WAS BETTER TO BE HIGH AND FAST THAN LOW AND SLOW. THE AIRPLANE TOUCHED DOWN ABOUT HALF WAY DOWN THE 3100 FOOT LONG RUNWAY AND EXITED INTO A SIX FOOT CULVERT WHERE IT NOSED OVER. AN EXAMINATION OF THE ENGINE BY THE FAA REVEALED A LEAK WHEN A COMPRESSION TEST WAS COMPLETED. THE CYLINDER WAS REMOVED AND SENT TO THE NTSB LAB IN WASHINGTON, DC. A METALLURGICAL EXAMINATION REVEALED THE EXHAUST VALVE SEPARATED AS A RESULT OF FATIGUE CRACKING THAT INITIATED IN THE RADIUS BETWEEN THE STEM AND THE HEAD OF THE VALVE.

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

SEPARATION OF THE NUMBER ONE EXHAUST VALVE DUE TO FATIGUE CRACKING WHICH RESULTED IN LOSS OF ENGINE POWER. OTHER RELATED FACTORS WERE MISJUDGMENT OF ALTITUDE AND AIRSPEED BY THE PILOT RESULTING IN ON GROUND COLLISION WITH THE TERRAIN AND SUBSEQUENT NOSE OVER.

Full narrative available

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