Accident Details
On April 20, 2016, at approximately 0715 Pacific daylight time, a Bell 47G-5 helicopter, registration N6288N, was substantially damaged in an accident near San Ardo, California. The pilot sustained minor injuries. The helicopter was being operated under Title 14 Code of Federal Regulations Part 137 as an agricultural flight.
Pilot's Account
According to the pilot, he had completed spraying five fields without any anomalies. While descending the helicopter for a spray pass over the sixth field, a loud noise was heard, immediately followed by a vibration. The helicopter was level but began to roll to one side. The pilot moved the cyclic laterally to correct, but found the cyclic to be stiffer than normal. Although the helicopter responded to the control inputs, there was a lag in response, resulting in an overcorrection. The pilot went through two cycles of oscillations before the helicopter became level again. He then attempted a run-on landing; however, the helicopter rolled to the left, and the pilot was unable to correct with right cyclic before the main rotor blades impacted the ground. The helicopter came to rest on its left side.
Wreckage Examination
A Federal Aviation Administration (FAA) inspector examined the wreckage and identified that the pin of the outboard end torque tube, which controlled lateral movement of the swashplate, had fractured. The control tube and the upper threaded end were attached to the clevis, which in turn attached to the swashplate and controlled the forward and aft cyclic. The lower end of the control tube remained attached, while the upper end had separated.