SARASOTA, FL, USA
N46937
HILLER UH-12C
THE COMMERCIAL PILOT WAS IN CRUISE FLIGHT AT ABOUT 400 FEET AGL WHEN HE OBSERVED A SUDDEN DROP IN ENGINE RPM FOLLOWED BY AN INCREASE IN RPM. THE PILOT INITIATED A FORCED LANDING BY ENTERING AN AUTOROTATION. DURING THE DECELERATION THE HELICOPTER COLLIDED WITH POWER LINES AND CRASHED. REVIEW OF THE HELICOPTER LOGBOOKS REVEALED THE CARBURETOR FLOAT ASSEMBLY HAD NOT BEEN CHANGED, AND NUMEROUS SERVICE BULLETIN PROCEDURES PERTAINING TO THE MA 4-5 CARBURETOR HAD NOT BEEN PERFORMED. DISASSEMBLY INSPECTION OF THE CARBURETOR REVEALED THE CARBURETOR WAS CONTAMINATED. SAND WAS PRESENT IN THE CARBURETOR BOWL, THE FUEL INLET ASSEMBLY WAS DIRTY AND THE PUMP PLUNGER ASSEMBLY WAS RUSTY.
THE PILOT-IN-COMMAND'S IMPROPER APPLICATION OF THE FLIGHT CONTROLS DURING AN AUTOROTATIVE LANDING, RESULTING IN AN IN-FLIGHT COLLISION WITH WIRES AND TERRAIN. CONTRIBUTING TO THE ACCIDENT WAS THE IMPROPER INSPECTION OF THE ENGINE FUEL SYSTEM (CARBURETOR) BY MAINTENANCE PERSONNEL, RESULTING IN A CONTAMINATED CARBURETOR AND A PARTIAL LOSS OF ENGINE POWER WHILE IN CRUISE FLIGHT.
Source: NTSB Aviation Accident Database
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