NTSB Identification: NYC92GA147.
The docket is stored on NTSB microfiche number 46648.
Accident occurred Friday, August 07, 1992 in GRAEFENBURG, KY
Probable Cause Approval Date: 09/20/1993
Aircraft: SIKORSKY S-76A, registration: N50KY
Injuries: 5 Serious,1 Minor.

: 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 public aircraft accident report.

BEFORE FLT, THE COPLT BGN A PREFLT INSPN, & SUBSEQUENTLY, THE HELICOPTER WAS MVD FM THE HANGAR TO THE TERMINAL, WHERE A WITNESS OBSERVED THE ENG COWLING OPEN. THE PLT ALSO MADE A WALKAROUND VISUAL INSPN OF THE HELICOPTER BFR FLT. NEITHER OF THE FLTCREW NOTED ANY DISCREPANCY. ABT 1 MIN & 40 SEC AFTER TAKEOFF, THE FLT CREW HEARD A NOISE, FLWD BY LOSS OF DRCTNL CTL; 3 OF THE PSGRS NOTED THE ODOR OF SOMETHING OVERHEATING. AN AUTOROTATION & LANDING WERE MADE ON HILLY TRRN, WHERE THE HELICOPTER CAME TO REST IN A RAVINE AGAINST A TREE. DRG AN EXAM, THE 2 LEFT SIDE ENG COWLING LATCHES WERE FND OPEN; ALSO, THE LEFT SIDE OF THE AFT ENG COWLING WAS OPEN. THERE WAS EVIDENCE THAT DURING FLT, THE LEFT SIDE OF THE COWLING CONTACTED THE MAIN ROTOR BLADES; THE COWLING THEN MADE CONTACT WITH SECTION II OF THE TAIL ROTOR DRIVESHAFT. FRICTION BTN THE COWLING & THE DRIVESHAFT RESULTED IN LOCALIZED HIGH TEMPERATURE & THE TAIL ROTOR SHAFT FAILED AT THAT LOCATION. ONE OF THE 4 TAIL ROTOR BLADES SEPARATED DURING THE OCCURRENCE.

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

AN INADEQUATE PREFLIGHT INSPECTION BY THE FLIGHT CREW BY FAILING TO ASSURE THAT ALL FOUR OF THE ENGINE COWLING LATCHES WERE PROPERLY SECURED, WHICH RESULTED IN SUBSEQUENT FAILURE OF SECTION II OF THE TAIL ROTOR DRIVESHAFT AFTER THE COWLING CONTACTED THE MAIN ROTOR BLADES AND TAIL ROTOR DRIVESHAFT.

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