LIHUE, HI, USA
N53EP
Fairchild Hiller FH-1100
THE PILOT SAID THAT THE AIRCRAFT WAS IN NORMAL CRUISE FLIGHT WHEN HE NOTICED THAT THE ENGINE WAS NO LONGER DRIVING THE ROTOR SYSTEM. THE PILOT ENTERED AN AUTOROTATION AND HAD TO STRETCH THE GLIDE SLIGHTLY TO A SUITABLE LANDING AREA ON AN OFF SHORE REEF. THE HELICOPTER MADE A HARD LANDING ON THE REEF IN ABOUT ONE FOOT OF WATER. ON SITE EXAMINATION OF THE HELICOPTER BY FAA AIRWORTHINESS INSPECTORS REVEALED THAT THE BENDIX COUPLING ON THE ENGINE TO TRANSMISSION SHAFT HAD RUPTURED ON THE ENGINE END OF THE SHAFT. METALLURGICAL EXAMINATION OF THE FAILED COUPLING REVEALED A FATIGUE FRACTURE IN A CIRCUMFERENTIAL ORIENTATION ON THE COUPLING DISK. THE DRIVE SHAFT COUPLINGS ARE THE SUBJECT OF A RECURRING AD WHICH MANDATES ALIGNMENT MEASUREMENTS OF THE DRIVE SHAFT EVERY 100 HOURS. THE LAST ALIGNMENT CHECK WAS DONE ABOUT 60 HOURS PRIOR TO THE ACCIDENT.
FATIGUE FAILURE OF THE ENGINE TO TRANSMISSION DRIVE SHAFT ENGINE COUPLING DUE TO AN ANGULAR MISALIGNMENT OF THE DRIVE SHAFT.
Source: NTSB Aviation Accident Database
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