NTSB Identification: LAX83FA395.
The docket is stored on NTSB microfiche number 22993.
Accident occurred Saturday, August 20, 1983 in SHAVER LAKE, CA
Aircraft: BOEING VERTOL BV-107-II, registration: N190CH
Injuries: 2 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

THE ONLY WITNESS, THE HOOKER, WHO GETS LOGS READY FOR TRANSPORT BY THE HELICOPTER, STATED THAT HE HEARD NOISES AND THE ROTOR BLADES BEGAN COMING APART AS THE ACFT STARTED DOWNHILL WITH A LOG. EXAMINATION OF THE WRECKAGE REVEALED THAT #3 SYCHRONIZING SHAFT (BOEING P/N 10703141-13) HAD FAILED A FATIGUE CRACK ORIGINATING AT A RIVET HOLE. THE TOTAL TIME ON THE SHAFT WAS 17492 HOURS WITH 435 HOURS SINCE OVERHAUL. THE QUALITY OF THE SURFACE FINISH ON THE RIVET HOLES WAS CONSIDERED UNSATISFACTORY IN A POST ACCIDENT LABORATORY EVALUATION. AS A INTERIM MEASURE BOEING VERTOL ARBITRAILY IMPOSED A LIFE OF 8750 HOURS ON ALL SYNCHRONIZING SHAFTS OF THIS TYPE. THIS WAS BASED ON THE LIFE OF THIS FAILED PART. A PROGRAM IS ALSO BEING DEVELOPED TO DO A FLT STRAIN SURVEY ON A BV-107 FOR LOGGING OPERATIONS. THE HOOKER STATED THAT THE LOG BEING LIFTED BY THE ACCIDENT ACFT WEIGHED BETWEEN 8000 AND 9000 POUNDS.

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

ROTOR DRIVE SYSTEM..FATIGUE

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

ROTOR DRIVE SYSTEM..FAILURE,TOTAL


Contributing Factors

TERRAIN CONDITION..DOWNHILL


Contributing Factors

TERRAIN CONDITION..ROUGH/UNEVEN


Contributing Factors

TERRAIN CONDITION..MOUNTAINOUS/HILLY


Contributing Factors

OBJECT..TREE(S)

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