NTSB Identification: CEN12FA001
14 CFR Part 91: General Aviation
Accident occurred Saturday, October 01, 2011 in Philip, SD
Probable Cause Approval Date: 04/10/2014
Aircraft: ROBINSON HELICOPTER CO R66, registration: N266CY
Injuries: 1 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The helicopter was on a cross-country flight when it experienced a separation of the main rotor mast 8 inches below the teeter bolt, and the main rotor blade assembly separated from the flying helicopter. Subsequently, the helicopter impacted terrain and a postimpact fire ensued. Examination of the mast revealed fracture features consistent with overload failure and mechanical damage indicative of mast bumping. An examination of the airframe, engine, and remaining systems revealed no preimpact anomalies. The reason for the mast bumping event could not be determined due to the amount of thermal damage to the wreckage.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The in-flight separation of the main rotor mast following a mast bumping event. The reason for the mast bumping event could not be determined due to postaccident damage.
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