NTSB Identification: WPR09LA028
14 CFR Part 91: General Aviation
Accident occurred Thursday, October 30, 2008 in Powder River, WY
Probable Cause Approval Date: 09/30/2009
Aircraft: HILLER UH-12E, registration: N61436
Injuries: 1 Minor,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.

While maneuvering about 50 feet above ground level during an aerial observation flight, one blade associated with the control rotor assembly separated from the helicopter, and a violent vibration started. Unable to maintain control, the pilot made a forced landing on the underlying sloping terrain, and the helicopter rolled over. During the subsequent inspection of the rotor system, one of the two control rotor blade assemblies was found separated from the rotor head. A rotor blade control tube had cracked and broken off outboard of the two attachment bolts. The component had been operated 21 hours since receiving its last inspection. The reason for the cracking and separation of the control tube could not be determined.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A flight control system malfunction while the helicopter was maneuvering at low altitude due to the failure/separation of the rotor blade control tube.

Full narrative available

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