EASTON, PA, USA
N4953X
ENSTROM F-28C
IN CRUISE FLT THE HELICOPTER UNEXPECTEDLY ROLLED 90 DEGREES LEFT. THE PILOT AUTOROTATED TO A LANDING, ROLLING OVER UPON TOUCHDOWN. THE LEFT SIDE CABIN MOUNT BRACKET WHICH HOLDS THE INTERMEDIATE BELLCRANK FOR LATERAL CONTROL HAD FRACTURED. THE FRACTURE SURFACE BORE EVIDENCE OF OVERLOAD AND FATIGUE. THE BELLCRANK WAS TIGHT IN THE CABIN MOUNT BRACKET. IN ADDITION, THE RIGHT SIDE CABIN MOUNT BRACKET WHICH HOLD THE INTERMEDIATE BELLCRANK FOR FORE AND AFT CONTROL HAD A CRACK. THE FRACTURE SURFACE WAS TYPICAL OF OVERLOAD. THE HELICOPTER HAD PREVIOUSLY BEEN INVOLVED IN A HARD LANDING WITH A BLADE STRIKE ON THE TAIL BOOM. NO RECORDS WERE AVAILABLE TO INDICATE THE REPAIRS CONDUCTED. ACCORDING TO ENSTROM HELICOPTERS, THESE FRACTURES ARE TYPICALLY SEEN FOLLOWING A BLADE STRIKE. ACCORDING TO AN ENSTROM HELICOPTERS SERVICE LETTER, '...CYCLIC AND COLLECTIVE TORQUE TUBES, BELLCRANKS, AND FITTING...' ARE REQUIRED INSPECTIONS ITEMS FOLLOWING A BLADE STRIKE.
AN INFLIGHT FAILURE OF THE LEFT SIDE CABIN MOUNT BRACKET WHICH RESULTED IN A LOSS OF LATERAL CYCLIC CONTROL. FACTORS RELATED TO THE ACCIDENT WERE: AN INCOMPLETE INSPECTION OF THE HELICOPTER FOLLOWING A HARD LANDING WITH A BLADE STRIKE.
Source: NTSB Aviation Accident Database
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