NTSB Identification: DEN82FTC03
Nonscheduled 14 CFR Part 133: Rotorcraft Ext. Load
Accident occurred Tuesday, April 20, 1982 in BIG PINEY, WY
Probable Cause Approval Date: 04/20/1983
Aircraft: AEROSPATIALE SA315B, registration: N9007N
Injuries: 1 Serious.

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 ACFT WAS ENGAGED IN SEISMIC ACTIVITY SUPPLYING EXPLOSIVES BY LONG LINE. THE ENG FAILED AT ABOUT 400-500 FT AGL. THE LOAD WAS RELEASED & AN OPEN FIELD WAS SELECTED. AT ABOUT 150 FT AGL THE PLT WAS UNABLE TO MAINTAIN ROTOR RPM & THE ACFT IMPACTED THE GROUND IN AN UPRIGHT POSITION. THE ENG TEARDOWN INDICATED A FATIGUE FAILURE OF THE #4 BLADE ON THE AXIAL COMPRESSOR ASSEMBLY. FATIGUE CRACK DEVELOPOMENTOCCURRED ACROSS APPROXIMATELY 2/3 OF THE PLATFORM AREA BEFORE FINAL SEPARATION OCCURRED. THE BLADE SEPARATION CAUSED SEVERE INTERNAL DAMAGE WITHIN THE COMPRESSOR ASSEMBLY INCLUDING EXTREME AXIAL WHEEL DAMAGE, DESTRUCTIONOF THE AXIAL COMPRESSOR DIFFUSER & BEARING FAILURE.

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

COMPRESSOR ASSEMBLY,BLADE..FATIGUE

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

COMPRESSOR ASSEMBLY,BLADE..FAILURE,TOTAL


Contributing Factors

AUTOROTATION..PERFORMED..PILOT IN COMMAND


Contributing Factors

ADEQUATE ROTOR RPM..NOT POSSIBLE..PILOT IN COMMAND

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