FORT SMITH, AR, USA
N223AS
EMBRAER BRASILIA EMB-120
THE FLIGHT CREW STATED THAT THEY WERE INITIATING A DESCENT INTO FINAL APPROACH FOR A LANDING WHEN THE RIGHT ENGINE GEARBOX CHIP DETECTOR LGITH ILLUMINATED FOLLOWED BY A LOUD BANG AND SEVERE VIBRATION.WHEN THE PROPELLER WAS FEATHERED AND THE ENGINE SHUT DOWN WITH THE CONDITION LEVER THE ROTATION AND VIBRATION STOPPED, THE CREW FURTHER STATED. THE AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. A POST-INCIDENT TEARDOWN INSPECTION OF THE POWERPLANT AT THE FACTORY REVEALED A SUDDEN AND CATASTROPHIC FAILURE OF THE PROPELLER REDUCTION GEARBOX ASSEMBLY DUE TO A HIGH CYCLE, METAL FATIGUE FRACTURE ON ONE, OF TWO, HELICAL GEARS. TEARDOWN AND INSEPCTION OF THE PROPELLER ASSEMBLY REVEALED SEVERE DAMAGE TO THE COMPOSITE PLASTIC BLADE RETAINER RINGS AND METAL ACTUATOR YOKES DUE TO SUDDEN DECELERATION AND STOPPAGE.
Source: NTSB Aviation Accident Database
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