SANTA ANA, CA, USA
N5840T
Westland Helicopters WG30
DURING A CLIMB TO CRUISE, THE CREW EXPERIENCED CONTROL DIFFICULTIES WHEN THE FOR-&-AFT TRIM ACTUATOR BEGAN TO MOTOR FORWARD AND WOULD NOT STOP. AN EMERG DESCENT WAS MADE WITH BOTH PLTS EXERTING AFT CYCLIC PRESSURE TO PREVENT THE SPEED FROM INCREASING OVER 120 KTS. THE ACFT RETURNED SUCCESSFULLY TO THE DEPARTURE ARPT. ALL GAGES INDICATED NORMAL AND NO WARNING LIGHTS WERE OBSERVED. AN INVESTIGATION REVEALED A FATIGUE FAILURE OF THE FB 10 ELECTRICAL RELAY AND SUBSEQUENT FOULING OF THE CONTACT OPERATION BY A BROKEN FRAGMENT. THE RELAY SPRING FAILED FROM FATIGUE, INITIATED AS MICRO CRACKS WHICH RESULTED FROM COLD FORMING BENDING AND SUBSEQUENT STRAIGHTENING PROCESS DURING MANUFACTURE.
Source: NTSB Aviation Accident Database
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