NTSB Identification: CHI00FA266.
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Accident occurred Saturday, August 19, 2000 in Valparaiso, IN
Probable Cause Approval Date: 07/01/2002
Aircraft: Fairchild Hiller FH-1100, registration: N250AD
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.

During cruise flight the main rotor mast fractured and the main rotor separated from the helicopter. Witnesses to the accident reported seeing the helicopter falling to the ground in multiple sections. The aft 7.5 feet of tailboom, including the tail rotor gearbox, was located 220 feet from the main wreckage. The main rotor hub and blades were located 146 feet from the main wreckage. The main rotor blades remained attached to the rotor hub assembly. The main rotor mast was fractured approximately 6 inches below the rotor hub assembly. The fracture was transverse to the longitudinal direction of the mast. The interior diameter of the main rotor mast was corroded and had several areas of surface pitting. According to the NTSB Materials Laboratory Factual Report, the main rotor mast contained a "flat" crack that contained crack arrest features indicative of fatigue cracking. The report states, "The crack arrest features in the flat fracture region emanated from corrosion pits on the inside diameter surface of the mast. The entire inside diameter surface had been affected by this corrosion in the area of the flat fracture region."

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

The in-flight fracture of the main rotor mast and the separation of the main rotor. Factors to the accident were the corroded main rotor mast that resulted in fatigue.

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