What happened
The aircraft was operating under visual flight rules when it entered an area with forecast icing conditions. During the flight, structural ice began to accumulate on the induction air filter. This accumulation significantly restricted the flow of air entering the engine.
Despite the visible icing, the pilot did not apply carburetor heat. The application of this system would have bypassed the obstructed filter and restored adequate airflow to the engine. Without this corrective action, the engine lost power. Unable to maintain altitude or reach a suitable airport, the pilot was forced to execute an emergency water landing in Coos Bay.
The investigation
The investigation focused on the mechanical state of the aircraft following the recovery from the water. Examination revealed that structural ice had formed on the induction air filter. This ice buildup partially blocked the flow of induction air, which is critical for engine operation. The lack of carburetor heat application was identified as a key factor in the inability to clear the obstruction.
Findings
The primary cause of the incident was the failure to use available anti-icing systems. The pilot encountered forecast icing conditions but did not take the necessary steps to prevent or mitigate ice accumulation on critical engine components. Specifically, the failure to apply carburetor heat allowed ice to block the induction air filter. This blockage led directly to a loss of engine power. The pilot's decision to ditch the aircraft was a result of this mechanical failure and the inability to recover power before reaching the water.
Safety message
Pilots must be vigilant when flying into forecast icing conditions. If structural ice is observed on induction components, immediate application of carburetor heat or other anti-icing systems is essential. Failure to do so can result in rapid loss of engine power and force an emergency landing.