San Ardo, CA, USA
N6288N
BELL 47G 5
While performing an agricultural flight, the pilot of the helicopter heard a loud noise followed by a vibration in the flight controls, and the helicopter began to roll. He noted that the cyclic was stiffer than normal, and his control inputs produced a delayed response from the helicopter. The pilot was able to return the helicopter to level flight and attempted a run-on landing; however, the helicopter began a roll to the left, which he was not able to correct before the main rotor blades impacted the ground and the helicopter rolled onto its side, resulting in substantial damage. Postaccident examination revealed that the pin for the outboard end torque tube, which controlled lateral movement of the swashplate, was fractured.
On April 20, 2016, about 0715 Pacific daylight time, a Bell 47G-5, N6288N, was substantially damaged when it was involved in an accident near San Ardo, California. The pilot received minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations (CFR) Part 137 agricultural flight. The pilot stated that he had sprayed five fields that day with no anomalies. After performing a reconnaissance of the sixth field, the pilot was descending the helicopter for a spray pass when the helicopter made a loud noise immediately followed by a vibration. The pilot stated that the helicopter was level but started to roll to one side. He moved the cyclic laterally to correct, but the cyclic was stiffer than normal. The pilot stated that, although the helicopter responded to his inputs, there was a lag in its response that resulted in an overcorrection. He went through two cycles of oscillations before the helicopter was level. He subsequently attempted a run-on landing; however, the helicopter rolled to the left and he was not able to correct with right cyclic before the main rotor blades impacted the ground. The helicopter came to rest on its left side. A Federal Aviation Administration (FAA) inspector examined the wreckage and identified that the pin of the outboard end torque tube that controlled lateral movement of the swashplate had fractured. The control tube and the upper threaded end were attached to the clevis, which attached to the swashplate and controlled the forward and aft cyclic. The lower end of the control tube remained attached and the upper end had separated.
The failure of the pin in the outboard end of the lateral flight control torque tube.
Source: NTSB Aviation Accident Database
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