NTSB Identification: BFO86FA018.
The docket is stored on NTSB microfiche number 31682.
Accident occurred Sunday, March 09, 1986 in MT. CRAWFORD, VA
Aircraft: HUGHES 500D, registration: N8352F
Injuries: 1 Serious,3 Uninjured.

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.

AFTER REFUELING AT SHENANDOAH VALLEY AIRPORT LOCATED NEAR STAUNTON, VIRGINIA, THE HELICOPTER CLIMBED TO ABOUT 1800 FEET MSL ON A NORTH HEADING. APPROXIMATELY 15 MINUTES AFTER DEPARTURE A LOUD RUMBLE WAS HEARD COMING FROM THE REAR OF THE AIRCRAFT AND THE PILOT IMMEDIATELY LOWERED THE COLLECTIVE AND ROLLED OFF THE THROTTLE. THE STUDENT PILOT, SITTING IN THE RIGHT FRONT SEAT, STATED THAT AFTER THE PILOT INITIATED THE FLARE, THE HELICOPTER 'HUNG IN THE AIR FOR A MONENT AT APPROX. 30' AGL THEN DROPPED TO THE GROUND AND ROLLED OVER.' DISASSEMBLY OF THE TAIL ROTOR DRIVE GEAR ASSEMBLY REVEALED THAT THE OUTPUT DRIVE PINION HAD FAILED. LABORATORY EXAMINATION REVEALED THAT THE FRACTURE SURFACES REVEALED MARKINGS TYPICAL OF FATIGUE PROGRESSION. MCDONNELL DOUGLAS HELICOPTER COMPANY HAD ISSUED AN ENGINEERING ORDER #139419 WHICH CONCERNED REWORKING THE DRIVE PINION, HOWEVER, A SERVICE BULLETIN WAS NOT ISSUED REGARDING THE NEED TO REWORK THE PINION AT OVERHAUL.

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

ROTOR DRIVE SYSTEM,COMBINING GEARBOX..FATIGUE

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

ACFT/EQUIP,INADEQUATE STANDARD/REQUIREMENT..MANUFACTURER

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

LEVEL OFF..MISJUDGED..PILOT IN COMMAND

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

ROTOR DRIVE SYSTEM,COMBINING GEARBOX..FAILURE,TOTAL



Contributing Factors

TERRAIN CONDITION..RISING

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