UNIONVILLE, PA, USA
N79K
SIKORSKY S-76A
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.
Source: NTSB Aviation Accident Database
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