On September 3, 2023, about 1420 Pacific daylight time, a Piper PA-18-135, N7199K, was substantially damaged when it was involved in an accident near Compton, California. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 banner tow flight. The pilot reported that shortly after takeoff, during a banner tow operation, the back of the pilot’s seat broke and he slid aft into a horizontal position. The abrupt rearward movement resulted in the pilot pulling back on the control yoke, which caused the airplane to pitch up to a nose-high attitude. Due to the high pitch attitude, the pilot slid further back in the seat. Unable to push the flight control stick forward, he let go of the flight controls and used the crossbeam to pull himself forward. About 200 ft agl, at the onset of an aerodynamic stall, he was able to push the flight control stick forward and recover the airplane. As he recovered from the imminent stall, the airplane’s engine began to “cough” and sustained a partial loss of power. Unable to maintain altitude, he elected to make a forced landing to a nearby baseball field. As the airplane descended toward a baseball field, it impacted a fence along a concrete wash and came to rest upright. The pilot believes that when he fell back or when he was pulling himself forward, his foot or knee may have moved the fuel selector lever out of the “both/on” position. Postaccident examination of the airplane revealed that both wings were substantially damaged. The pilot’s seat back frame was fracture separated on the left and right side near the back rest and seat junction. Examination of the engine revealed no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. The pilot’s seat was sent to National Transportation Safety Board Materials Laboratory, Washington, DC, for examination. The examination of the fracture surface revealed characteristics consistent with an overstress fracture. A review of the airplane’s maintenance records could not determine the age of the pilot’s seat, or if recent maintenance had been performed on it.