On September 4, 1985, a Bell 47G-2 (registration N8429E) was involved in an aviation accident near Moore Haven, FL. Investigators recorded the probable cause as: Loss of engine power due to carburetor ice buildup, with atmospheric conditions conducive to carburetor venturi icing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced a loss of engine power due to carburetor ice buildup while at approximately 40 feet altitude during a descent for landing. The pilot performed an autorotation, but on touchdown the right skid contacted a boulder, causing the main rotor to strike the tailboom.
Accident Narrative
A helicopter pilot reported that while flying in the vicinity of his property, he reduced the helicopter's speed to descend and land. At an altitude of approximately 40 feet, the engine lost power due to the buildup of carburetor ice. The pilot executed an autorotative descent to the ground. During touchdown, the helicopter's right skid contacted a large boulder. The contact caused the main rotor to tilt backward, resulting in the rotor blades striking the tailboom.
Investigation Findings
Investigation revealed that at the time of the accident, the helicopter was operating under temperature and dewpoint conditions that, according to performance charts, are conducive to carburetor venturi icing. The investigation did not identify any other factors.
Probable cause
Loss of engine power due to carburetor ice buildup, with atmospheric conditions conducive to carburetor venturi icing.