Accident Sequence
The pilot reported that while maintaining a heading of 050 degrees with the wind from 270 degrees at 5 knots, the helicopter began to shudder and veer to the right. The pilot attempted remedial action, but the helicopter continued descending in a right spiral until it contacted the ground.
Examination Findings
Post-accident examination of the helicopter did not reveal any mechanical failure or malfunction.
Background Information
Bell Helicopter Textron, Inc. had previously published Information Letter 206-84-41 dated July 6, 1984, which describes an unanticipated right yaw as "the occurrence of an uncommanded right yaw rate which does not subside of its own accord and which, if not corrected can result in loss of aircraft control." At the time of the accident, the pilot was in the post-solo phase of helicopter training and one passenger was on board.