NTSB Factual Report

On August 29, 2018, about 1130 central daylight time, a Grumman G-164A airplane, N956X, experienced a total loss of engine power while maneuvering over an open field near Opelousas, Louisiana. The pilot subsequently made an off-airport forced landing in the field. The private pilot was not injured. The airplane sustained substantial damage to the top wings and vertical stabilizer. The airplane was registered to Acadian Dusters LLC, Church Point, Louisiana, and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions were reported at the accident site about the time of the accident, and no flight plan had been filed. The local flight originated from Church Point about 1100.

According to the pilot's accident report, he was practicing crop dusting maneuvers when the engine lost all power. Being at low altitude, the pilot made a forced landing in an open muddy rice field, and the airplane nosed over. Post-accident examination of the engine revealed that two bolts that secure the left magneto had come loose and were missing. This disrupted the spark timing, resulting in a complete power loss. The magneto was identified as an American Bosh SB9RU-3 magneto, serial number BB3829, that was installed on January 13, 1998.

A Federal Aviation Administration inspector examined the airplane. In his e-mail, he reported finding two of the three bolts for the left magneto had come out. The safety wire was also broken. He stated the left magneto was barely holding on. The Sims coupling was heavily damaged as well. He could easily move the magneto around.