On July 10, 2020, about 1455 central daylight time, an Air Tractor AT-502B airplane, N61315, was substantially damaged when it was involved in an accident near Dalhart, Texas. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 flight. The operator reported that the pilot was returning to the airport after completing an aerial application when the engine lost power. The pilot executed a forced landing to a pasture. Both wings sustained substantial damage during the landing. An engine examination revealed that the fuel control unit (FCU) input drive shaft would not rotate. Further examination established that the FCU input drive spool bearing had failed; however, the cause of the bearing failure could not be determined. The FCU was overhauled in July 2016. The overhaul facility reported that the spool bearing was replaced at that time. The airplane maintenance records do not include a notation as to when the FCU was installed on the engine. As a result, the exact time in service was not determined. However, the engine accumulated about 594 hours since December 2016. The FCU manufacturer recommended an inspection every 3,000 hours and an overhaul every 6,000 hours time-in-service. Both the spool and drive bearings are required to be replaced at those intervals.