NTSB Identification: NYC84FA319.
The docket is stored on NTSB microfiche number 26945.
Nonscheduled 14 CFR
Accident occurred Saturday, September 22, 1984 in UNIONVILLE, PA
Aircraft: SIKORSKY S-76A, registration: N79K
Injuries: 1 Serious,5 Minor,8 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.

ON APPROACH, ACFT YAWED RIGHT. PLT REDUCED POWER AND EXECUTED EMERG LNDG. BEFORE SHUTDOWN, IT WAS NOTED THE T/R WAS STATIONARY WHILE THE MAIN ROTOR CONTINUED TO TURN. INVESTIGATION REVEALED T/R DRIVE SHAFT HAD SEPARTED DUE TO THERMAL/MECHANICAL DAMAGE INCURRED BY CONTACT WITH ENGINE FIREWALL. FURTHER INVESTIGATION REVEALED THAT A FIREWALL MODIFICATION HAD BEEN DESIGNED WHICH INCLUDED A DOUBLER STRIP AT THE FWD AND AFT FIREWALL SECTION CONNECTION. PRESENCE OF DOUBLER WOULD DECREASE CLRNC BETWEEN FIREWALL AND T/R SHAFT. IT WAS FURTHER DETERMINED THAT, DURING INSTALLATION, THE FWD FIREWALL SECTION, TO WHICH THE DOUBLER IS ATTACHED, WAS MISPOSITIONED WITH RESULT THAT CLRNC WAS REDUCED TO NIL. COMPONENTS CAME INTO CONTACT DURING OPERATIONS.

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

MAINTENANCE,DESIGN CHANGE..INADEQUATE..MANUFACTURER

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

MAINTENANCE,INSTALLATION..IMPROPER..COMPANY MAINTENANCE PERSONNEL

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

ROTOR DRIVE SYSTEM,TAIL ROTOR DRIVE SHAFT..FAILURE,TOTAL



Contributing Factors

ENGINE INSTALLATION,FIRE SHIELD..CHAFED


Contributing Factors

ROTOR DRIVE SYSTEM,TAIL ROTOR DRIVE SHAFT..CHAFED

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