Bell 47G 3B 1 N4002G accident near Camden, Alabama

Probable cause

A failure of the helicopter's hydraulic flight control systems for reasons that could not be determined due to the fire damage, and the pilot's inability to turn off the hydraulic system to relieve control pressure.

NTSB analysis

The airline transport pilot was repositioning the helicopter in preparation for spraying operations the next day. He reported that, about 1/2 mile from the intended off-airport landing area, while at an altitude of 300 ft above ground level, the helicopter's cyclic control became very stiff, consistent with a hydraulic system failure. He continued the approach to the landing zone, which was a cleared area of forest that contained brush, fallen trees, and dirt mounds. During the approach, he unsuccessfully attempted to follow the procedure to relieve hydraulic system control pressure, which included turning off the hydraulic system switch, but was unable to remove his hands from the controls and also maintain control of the helicopter. He ultimately elected to land without turning off the hydraulic system switch. During the landing, a portion of the helicopter's agricultural spray boom contacted the trees and brush, and the helicopter yawed to the left. The helicopter then began to oscillate as its skids contacted the uneven ground and obstructions before it ultimately rolled over, impacted the ground and caught fire. Fire damage to the engine and hydraulic system components precluded a postaccident examination, and its mode of failure could not be determined.

Text from the NTSB. Open the NTSB docket for ERA15LA296 for the full record.