Incident Overview
A pilot reported that while towing a banner, the engine's revolutions per minute (RPM) began to decrease. The pilot initiated emergency procedures but was unable to restore power. The aircraft was maneuvered for a forced landing on a beach. During the landing, the pilot turned to avoid people and driftwood, and the aircraft crashed on the beach.
Investigation Findings
An investigation was conducted following the incident. Examination of the engine revealed that the No. 3 cylinder had no compression when checked. Significant lead deposits were found on the stem of the No. 3 exhaust valve and on its valve seat. The face of the valve was making contact with only about 60 percent of the seat.
Conclusion
The investigation documented the mechanical condition of the engine but did not explicitly state a probable cause for the power loss.