NTSB Identification: LAX86LA283.
The docket is stored on NTSB microfiche number 32932.
Accident occurred Sunday, July 06, 1986 in VALENCIA, CA
Aircraft: TEXAS HELICOPTER OH-13H/M, registration: N51856
Injuries: 1 Serious.

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 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.

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

ROTOR DRIVE SYSTEM,MAIN GEARBOX/TRANSMISSION..FAILURE,TOTAL

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

ROTOR DRIVE SYSTEM,MAIN GEARBOX/TRANSMISSION..OVERLOAD

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