DAGGETT, CA, USA
N58WH
SIKORSKY SK-58
WHILE RETURNING FROM AN EXTERNAL LOAD OPERATION, THE HELICOPTER'S ENGINE STARTED VIBRATING AND THEN STARTED BACK FIRING. THE PILOT REPORTED HEARING A LOUD 'BANG' AND THEN NOTED A DECREASE IN ENGINE POWER. HE PERFORMED NECESSARY EMERGENCY PROCEDURES AND ENTERED AN AUTOROTATION. HE SAID THAT HE TOUCHED DOWN WITH SOME FORWARD SPEED. THE HELICOPTER HIT A DIRT BERM. THE ROTOR BLADES CONTACTED THE GROUND AND THE AIRCRAFT ROLLED OVER. AN ENGINE TEARDOWN WAS PERFORMED UNDER THE SUPERVISION OF AN FAA AIRWORTHINESS INSPECTOR. A BROKEN ROD WAS FOUND DURING THE TEARDOWN. THE TEARDOWN WAS TERMINATED AT THAT POINT AND THE REASON FOR THE BROKEN ROD WAS NOT DETERMINED.
THE FAILURE OF AN ENGINE CONNECTING ROD CAUSING A REDUCTION OF ENGINE POWER TO THE POINT WHERE LEVEL FLIGHT COULD NOT BE MAINTAINED. A FACTOR IN THE ACCIDENT WAS THE DARK NIGHT CONDITIONS WHICH RESTRICTED THE PILOT'S ABILITY TO SELECT THE BEST LANDING SITE.
Source: NTSB Aviation Accident Database
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