On July 22, 2022, about 0920 central daylight time, a Robinson R44 helicopter, N442JE, was substantially damaged when it was involved in an accident near Waterloo, Illinois. The pilot was not injured. The helicopter was operated under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. The pilot reported that he was in a descent approaching a field to apply fungicide to a corn field. The collective flight control stiffened to a point that the pilot was unable to arrest the helicopter’s descent rate. The pilot attempted to use cyclic control to flare the helicopter and arrest the descent; however, the cyclic control was not responsive. The helicopter’s skids contacted the ground, which resulted in a rollover and cartwheel as the main rotors impacted the ground. The helicopter sustained substantial damage to the tail boom, fuselage, and main rotor system. The pilot stated that he suspected that the flight controls’ hydraulic assist system malfunctioned. During the on-site inspection, no obvious anomalies were found with the flight control system. Collective, cyclic, and anti-torque pedals were all connected and appeared to be normal. Flight control continuity was confirmed from the cockpit to the main rotor swashplate linkages and main rotor blades. Flight control continuity was confirmed from the cockpit anti-torque pedals to the tail rotor gearbox and tail rotor linkages. The hydraulic components were removed for detailed examinations. All 3 servos (2 forward and 1 aft) passed bench functionality tests. The hydraulic pump, reservoir, and fluids were normal. The forward right servo had a slightly bent piston shaft, but still was fully functional. The spool drives of the forward and aft servos exhibited signatures with normal operations. No anomalies were found that would preclude normal operation.