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Aviation Accident

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NTSB Identification: CHI83FA428
The docket is stored on NTSB microfiche number 27876.
Accident occurred Wednesday, September 14, 1983 in CHICAGO, IL
Aircraft: SIKORSKY S-76A, registration: N521AC
Injuries: 3 Minor, 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.

WHILE CRUISING AT 2000 FT MSL & 150 KTS, THE CREW HEARD A LOUD NOISE, AND SIMULTANEOUSLY, THE HELICOPTER YAWED APRX 30 TO 40 DEG TO THE RIGHT & PITCHED NOSE DOWN. THE AIRCREW BEGAN AN AUTOROTATION & ACTIVATED THE EMERGENCY FLOATS. THE HELICOPTER CONTINUED IN A RIGHT DESCENDING TURN DURING THE AUTOROTATION. TOUCHDOWN IN THE WATER (LAKE MICHIGAN) OCCURRED WITH A FORWARD SPEED OF ABOUT 40 TO 50 KTS. AFTER CONTACTING THE WATER, THE HELICOPTER TURNED AN ADDITIONAL 180 DEG, THEN LISTED ABOUT 10 DEG TO THE LEFT. THE OCCUPANTS DONNED THEIR LIFE VESTS & EXITED THE HELICOPTER. ABOUT 11 TO 13 MINUTES AFTER LANDING, THE ACFT ROLLED OVER IN THE WATER & EVENTUALLY SUNK. THE OCCUPANTS WERE RESCUED BEFORE THE HELICOPTER SANK. AN INVESTIGATION REVEALED THAT THE LEFT SIDE TAIL ROTOR CABLE. PN 76400-03191-043, HAD FAILED WHERE IT HAD BEEN RUBBING. THE RUBBING WAS ATTRIBUTED TO INCORRECT ROUTING OF THE CABLE.


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

  • ROTORCRAFT FLIGHT CONTROL,TAIL ROTOR CABLE..CHAFED
  • MAINTENANCE,INSTALLATION..IMPROPER..OTHER MAINTENANCE PERSONNEL
  • ROTORCRAFT FLIGHT CONTROL,TAIL ROTOR CABLE..FAILURE,TOTAL

Contributing Factors:
Full narrative is not available