NTSB Identification: CEN11LA050
14 CFR Part 91: General Aviation
Accident occurred Monday, November 01, 2010 in Praire Du Sac, WI
Probable Cause Approval Date: 08/07/2012
Aircraft: MCFARLAND BILL CHALLENGER II, registration: N448WM
Injuries: 1 Fatal.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The airplane impacted the ground following an in-flight separation of the left wing during cruise flight. The pilot, who was the sole occupant, was fatally injured. Witnesses reported seeing the airplane traveling north, about 300-500 feet above ground level, when one wing suddenly separated from the airplane. One of the witnesses stated that the other wing separated shortly after the first one. Postaccident examination confirmed that both wings were completely separated from the airplane with the exception of the right wing aft spar and aileron. Examination of the fractures in the wing attachment fittings revealed signatures consistent with overload failure with the exception of one fitting that had no perceptible damage due to deformation or fracture. The attachment bolt for the fitting that showed no perceptible overload damage was not recovered during the investigation; however, the relative lack of damage to the strut fitting indicates that the attachment bolt either failed, or its corresponding nut had loosened and separated during the flight. A portion of wing fabric retained for testing showed that the fabric met the minimum performance requirements as set forth in regulations. No preaccident defects were found with regard to the components examined.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The separation of the fuselage-mounted wing strut attachment fitting for an undetermined reason, which resulted in the separation of the left wing of the airplane. Full narrative available
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