NTSB Identification: DEN08LA008.
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Accident occurred Wednesday, October 10, 2007 in Afton, WY
Probable Cause Approval Date: 03/31/2008
Aircraft: Flight Design GMBH CTSW, registration: N245CT
Injuries: 2 Minor.
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 pilot said he flew over the airport and noted the wind sock, segmented circle, and wind-T were indicating a calm wind from the north. He made his approach to runway 34 using 30 degrees of flaps and maintained 45 knots using elevator control, but did not trim for this speed. He sensed he was slightly low so he increased power until he saw both VASI (visual approach slope indicator) bars turn white. He then reduced power to idle. The airplane bounced but "not hard enough to have a wheel fall off." The pilot said he was going straight down the runway into "a few knots of wind." When the airplane touched down again, "the stub of the right main gear dug into the runway" and caused the airplane to veer to the right and off the runway. The right wing struck the ground and the airplane nosed over. The flight instructor's version of events was somewhat different. He said the pilot's performance in the traffic pattern was "somewhat ragged and less precise and exhibited tension." He overshot his downwind-to-base turn by 20 degrees. The instructor took control of the airplane to reestablish a stable approach, and then returned control to the pilot. Threshold crossing airspeed was 55 knots. The pilot allowed the right wing to settle giving a right turn. The instructor tried to recover but it was too late. The airplane "landed hard with the right wing low resulting [in] major ballooning. When the bottom fell out, the plane landed extremely hard on the right main gear [and] proceeded off the runway" at a 20 to 30 degree angle and nosed over in the grass. The airport manager, who witnessed the accident, said the airplane was not aligned with the runway centerline when it landed hard. The impact tore off the right main landing gear. The airplane veered off the runway and nosed over. The right wheel was found on the left side of the runway, and the airplane came to a halt about 300 feet off the right side of the runway. Laboratory examination revealed "the fracture was overstress, consistent with bending from a hard landing impact. There was a compression buckle at the top and a tensile fracture at the bottom. There was also considerable plastic deformation, but no indication of pre-existing cracks or defects." Steel type, wall thickness, yield strength, tensile strength, and hardness measurements met or exceeded. "The fracture . . . [was the] result of impact on landing." According to the airplane manufacturer, the gear assembly was designed in accordance with ASTM 2245, and successfully passed a drop test of 550 mm (21.7 inches) at a weight of 600 kg (1,323 pounds).
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to correct the alignment of the airplane and his improper recovery from a bounced landing, resulting in exceeding the design stress limits that caused the right main landing gear to fail. A contributing factor in this accident was the instructor's inadequate supervision of the pilot. Full narrative available
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