The pilot reported that, during the climb-to-cruise portion of the cross-country interisland flight over open ocean water, the Beech C23’s engine began to run roughly.
He applied carburetor heat, which resolved the engine roughness. He decided to continue his flight.
As the flight approached his destination, the engine began running roughly again, accompanied by a significant loss of engine rpm. He applied carburetor heat and adjusted the mixture, but the engine power was not restored.
He then ditched the airplane into the water just offshore of Waianae, Hawaii.
The airplane wreckage was recovered from the water three days after the accident, and it had sustained significant damage from tidal forces.
Post-accident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
Weather conditions in the area at the time of the accident were conducive to the formation of carburetor icing at glide and cruise power and serious carburetor icing at glide power.
If the pilot had either kept the carburetor heat on or applied it earlier, the loss of engine power and subsequent ditching could have been avoided.
Probable cause: The total loss of engine power during cruise flight due to carburetor icing. Contributing to the accident was the pilot’s delay in applying carburetor heat during flight while operating in an area conducive to carburetor icing.
NTSB Identification: WPR16LA119
This May 2016 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.