NTSB Identification: CHI95LA187.
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Accident occurred Monday, June 19, 1995 in ELKHORN, WI
Probable Cause Approval Date: 03/06/1996
Aircraft: BELL 47J2A, registration: N470RA
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.

THE PILOT REPORTED THAT HE WAS CRUISING AT ABOUT 1,000 FEET WHEN THE ENGINE LOST POWER. AN AUTOROTATION WAS INITIATED. DURING THE LANDING PHASE (CYCLIC FLARE), THE MAIN ROTOR STRUCK THE TAILROTOR DRIVE SHAFT. AN EXAMINATION OF THE ENGINE REVEALED THAT THE NUMBER TWO CYLINDER INTAKE VALVE HAD FAILED IN THE TOP RADIUS (NECK AREA) OF THE VALVE KEEPER RECESS, CAUSING DAMAGE TO THE CYLINDER COMBUSTION CHAMBER AND PISTON. AN INSPECTION OF THE ENGINE LOGBOOKS INDICATED THAT AN IDENTICAL FAILURE HAD OCCURRED EIGHT HOURS PREVIOUSLY. FURTHER INSPECTION REVEALED THAT THE MAJOR ENGINE OVERHAUL, WHICH HAD BEEN CONDUCTED 27 HOURS PRIOR TO THE ACCIDENT, HAD NOT BEEN PERFORMED IN ACCORDANCE WITH THE MANUFACTURER'S PROCEDURES AND SPECIFICATIONS.

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

loss of power as a result of an intake valve failure due to improper maintenance performed during the major engine overhaul, and pilot misjudgment of the flare during autorotation.

Full narrative available

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