About Two Hours Into The Flight, (Pilot) Heard A “Loud Bang” From The Engine

Location: Joliet, IL Accident Number: CEN25LA322
Date & Time: August 14, 2025, 17:14 Local Registration: N476SM
Aircraft: Piper PA-18-150 Injuries: 1 None
Flight Conducted Under: Part 91: General aviation - Banner tow

On August 14, 2025, at 1714 central daylight time, a Piper PA-18-150 airplane, N476SM, was substantially damaged when it was involved in an accident near Joliet, Illinois. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 banner tow flight.

The pilot reported that he fueled the airplane and departed for a planned 3-hour banner tow flight in and around the Joliet area. About two hours into the flight, he heard a “loud bang” from the engine, which resulted in strong vibrations and a gradual loss of engine power. Shortly after, the engine experienced a total loss of power, and the pilot executed a forced landing to a field. During the landing roll, the airplane ground looped and impacted a fence, which resulted in substantial damage to the left elevator.

The responding FAA inspector reported that there was engine oil on the bottom of the fuselage from the engine cowling to the empennage. There was also oil leaking from the engine exhaust pipe.

Postaccident examination of the engine revealed that the No. 2 cylinder exhaust valve failed. Most of the valve stem remained inside the valve guide while the valve head was destroyed inside the cylinder. There were no other engine mechanical malfunctions or anomalies that would have precluded normal operation. 

FMI: www.ntsb.gov