Accident Overview
On August 14, 2025, at 1714 central daylight time, a Piper PA-18-150 airplane, registered as N476SM, was substantially damaged in an accident near Joliet, Illinois. The pilot sustained no injuries. The aircraft was operating as a Title 14 Code of Federal Regulations Part 91 banner tow flight.
Pilot Account
According to the pilot, he fueled the airplane and departed for a planned three-hour banner tow flight in and around the Joliet area. Approximately two hours into the flight, he heard a "loud bang" from the engine, which was accompanied by strong vibrations and a gradual loss of engine power. Shortly thereafter, the engine experienced a total loss of power, prompting the pilot to execute a forced landing to a field. During the landing roll, the airplane ground looped and impacted a fence, resulting in substantial damage to the left elevator.
Examination Findings
An FAA inspector who responded to the scene noted engine oil on the bottom of the fuselage, extending from the engine cowling to the empennage, as well as oil leaking from the engine exhaust pipe. A postaccident examination of the engine revealed that the No. 2 cylinder exhaust valve had failed. Most of the valve stem remained inside the valve guide, while the valve head was destroyed within the cylinder. No other mechanical malfunctions or anomalies that would have precluded normal operation were found.