On June 28, 2015, at 1230 central daylight time, a Piper PA-25-235 single-engine airplane, N94MC, sustained substantial damage during a forced landing following a loss of engine power near Galveston, Texas. The commercial pilot sustained serious injuries. The airplane was registered to Sky-Signs, LLC, Lewes, Delaware, and operated by Nighthawk Aerial Advertising, Pearland, Texas, under the provisions of 14 Code of Federal Regulations Part 91 as a banner tow flight. Visual meteorological conditions prevailed for the flight, and no flight plan was filed. The local flight departed the Pearland Regional Airport (LVJ), Pearland, Texas, at 1030. According to the pilot, while towing a banner about 1,100 feet mean sea level, the engine lost power. The pilot's attempts to restart the engine were unsuccessful. The pilot reported there were no anomalies or indications prior to the loss of engine power. The pilot executed a forced landing to a pasture area. During the forced landing, the right wing struck a temporary fence, and the airplane came to rest upright. The airplane sustained substantial damage to the right wing and fuselage. The airplane was recovered for further examination. The Lycoming O-540-G1A5 engine was disassembled under the supervision of a Federal Aviation Administration inspector at the operator's facility. Disassembly of the engine revealed a crankshaft idler gear shaft failed and separated from the accessory gear case. The failed idler gear shaft and attach hardware were not located and a metallurgical examination could not be completed. According to the engine logbooks, on February 16, 2006, the engine underwent a major overhaul at a total engine time of 2,760 hours. On September 4, 2009, the engine was disassembled due to a propeller strike. The engine total time at disassembly was not recorded in the engine logbook. The engine's most recent 100-hour inspection was completed on March 23, 2015, at a total engine time of 5,232 hours and 1,078 hours since major overhaul.