NTSB Identification: NYC96LA135.
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Accident occurred Monday, July 01, 1996 in SOUTH CARVER, MA
Probable Cause Approval Date: 02/01/1997
Aircraft: Bell 206B III, registration: N444JB
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot was doing aerial spraying of a cranberry bog, and had completed four passes before he executed a right turn to the north to begin the next run. After completing the turn, the helicopter began to spin to the right. After about three to four turns it stopped in a level hover, but then started spinning again to the right. After another three to four spins, it again stopped, and began a final spin to the right when it collided with the bog. Bell Helicopter Textron (BHT) published an Operations Safety Notice, in 1983, which dealt with unanticipated right yaw of the Bell 206 series. It stated that unanticipated right yaw could occur when maneuvering between hover and 30 MPH, and that a tail wind could reduce relative wind speed if a down wind translation occurred. It also stated that a loss of translational lift could result in a high power demand and an additional anti-torque requirements, which included high power demand situations such as low speed downwind turns. A local automated weather report indicated that the winds from were from 210 degrees at 6 knots. The pilot stated that the uncontrolled event initiated when he had completed a right hand application turn, and did not report a lateral cyclic displacement during the last application run.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to maintain control of the helicopter during an aerial application maneuver. This put the helicopter in a low slow down wind, high power demand turn, where it encountered a loss of tail rotor effectiveness, and the subsequent collision with the marsh. Full narrative available
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