VALENCIA, CA, USA
N51856
TEXAS HELICOPTER OH-13H/M
THE PILOT REPORTED THAT HE HEARD A LOUD BANG AND GRINDING NOISE FROM THE ENGINE/MAIN TRANSMISSION AREA WHILE ON A SWATH RUN. HE STATED THAT THE MAIN ROTOR RPM DECAYED IMMEDIATELY AFTER HE HEARD THE NOISE. AS THE HELICOPTER DESCENDED TO ABOUT 50 FEET ABOVE THE GROUND THE PILOT SAID HE FLARED FOR THE TOUCHDOWN. THE HELICOPTER LANDED HARD SEVERING THE SKIDS, TAIL AND SPRAY BOOMS. THE PILOT SAID THE ENGINE CONTINUED TO RUN AFTER THE ACCIDENT, HOWEVER, THE ROTOR WAS NOT TURNING. POST ACCIDENT INSPECTION OF THE TRANSMISSION REVEALED A MASSIVE OVERLOAD FAILURE OF THE LOWER PINION GEAR ASSEMBLY. BOGUS PINION GEARS WERE FOUND INSTALLED IN THE TRANSMISSION.
Source: NTSB Aviation Accident Database
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