ERA20LA326

The airplane departed and was in a continuous climb at 70 mph, at 2,500 rpm. The pilot observed a cylinder depart the engine and experienced a partial loss of engine power. A video of the event recorded the sound of the engine becoming quieter and the tachometer showed a continuous 1,000 rpm reading following the separation. The video captured the airplane maneuvering over open fields suitable for a forced landing as it descended back towards the departure airstrip. The recording ended before the airplane was destroyed by contact with trees and terrain 500 feet prior to the landing strip. Examination of the nine-cylinder radial engine revealed a separated cylinder, with all of its associated mounting studs fractured. Three of the mounting studs displayed features consistent with fatigue, likely due to inadequate torque applied at overhaul, which was completed less than 100 aircraft hours prior to the accident.

On September 21, 2020, about 1949 eastern daylight time, a Stearman E75, N1524M, was destroyed when it was involved in an accident near Honea Path, South Carolina. The private pilot and his airline transport pilot-rated student were seriously injured. The flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The pilot and his passenger were interviewed by Federal Aviation Administration (FAA) aviation safety inspectors. According to the pilot, he performed the takeoff from Ashley Field (SC01) and a few minutes into the flight he saw a “puff of smoke” and watched as a “jug” passed by the cockpit. He said the engine experienced a “50%” loss of engine power, which surprised him, and then he initiated a turn back to the departure airstrip. The passenger estimated the airplane was 1,000 ft- 1,100 ft altitude when he heard “a pop, then saw something went up in the air.” He added that he made a video recording of the flight and provided it to the FAA. Examination of the video revealed a shallow, continuous climb at 70 mph and 2,500 rpm. The sound of the engine was smooth and continuous when the recorder was held inside the open cockpit. As the passenger recorded the view outside the airplane, the wind noise overcame the soundtrack. The sound of the engine became quieter, the tachometer showed a continuous 1,000 rpm reading, and one of the occupants could be heard to say “…I heard that” as the airplane maneuvered over open fields as it descended. The recording ended before the airplane was destroyed by contact with trees and terrain 500 feet prior to the departure airstrip. Examination of photographs revealed a separated cylinder that was recovered and returned to the wreckage by an unknown person. The connecting rod was bent and remained attached to the crankshaft, but the piston was not recovered. All cylinder attachment/mounting studs were fractured. Photographs of the fracture surfaces examined at the NTSB Materials Laboratory revealed fractures consistent with fatigue on multiple studs. According to FAA aviation safety inspectors, the airplane’s tachometer displayed 919 aircraft hours. Excerpts of maintenance records revealed the airplane’s most recent annual inspection was completed on March 16, 2020, at 822.2 AC Hobbs time. On February 1, 2019, at 758.0 recording tach time, the nine-cylinder radial engine was overhauled. Prior to that, the engine was overhauled on March 12, 2016, at 669.9 recording tach time. Each overhaul, which occurred 88 hours apart, was performed by the same airframe and powerplant mechanic, who was deceased at the time of the accident.