On November 29, 1986, a Hiller UH-12B (registration N48209) operated by Mark W. Smith was involved in an aviation accident near Capac, MI. Investigators recorded the probable cause as: Progressive fatigue through a threaded portion of the main rotor blade drag strut. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A main rotor blade drag strut failed due to progressive fatigue shortly after takeoff, resulting in partial control and a hard landing. Substantial damage occurred.
Accident Overview
Approximately ten minutes after takeoff, just prior to a letdown from 350 feet above ground level, the drag strut of a main rotor blade failed. The failure was attributed to progressive fatigue through a threaded portion of the strut.
Failure Sequence
Following the strut failure, the pilot experienced only partial control of the helicopter. At one point, control was lost entirely, but the pilot managed to regain it in time to perform a hard, sliding landing in a field. The entire sequence of events unfolded within 10 to 15 seconds. The landing resulted in substantial damage to the aircraft.
Pilot Information
The pilot held a private certificate for fixed-wing aircraft and a student certificate for rotorcraft.
Probable cause
Progressive fatigue through a threaded portion of the main rotor blade drag strut.