On July 9, 2018, about 1100 Pacific daylight time, a Grumman G-164B airplane, N6696K, was substantially damaged when it was involved in an accident near Colusa, California. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot reported that he was approaching a field to begin the application when the engine made a popping noise and started to vibrate. The airplane slowed and the pilot initiated a turn toward a nearby runway. Since the airplane was still losing speed, the pilot added power, but the vibration increased until the engine lost total power. The airplane impacted terrain and came to rest upside down, resulting in substantial damage to the wings and empennage. The operator reported that the engine was sent to a repair and overhaul facility following the accident. No anomalies were found with the engine that would have precluded normal operation.