Albuquerque, NM, USA
N102RK
Flight Design USA CT-SW
The company's chief pilot and student instructor had performed four successful touch-and-go landings. On the mishap landing, the student instructor started his flare at normal approach speed about 2 to 3 feet above the runway. As the airplane settled, the chief pilot raised the nose of the airplane slightly to prevent a bounced landing. The airplane subsequently ballooned. They elected to perform a go-around. The chief pilot advanced the power and "pitched the airplane to the landing attitude." The airplane settled to the runway in a slight left crab, touching down on the left main landing gear, which subsequently broke aft. The airplane came down on the runway and slid for 300 feet, departing the left side and flipping over onto its back. The airplane had been recently purchased by the company. Total airframe time was approximately 25 hours. An examination of the airplane showed the left main lower landing gear tube had fractured due to overstress at the landing gear wheel and brake attachment fitting. The overstress appeared consistent with a hard landing impact as a small compression buckle was observed at the top of the part and some tensile indications were seen at the bottom. There were also contact impressions on the inside of the tube most-likely made by the end of the main landing gear spring bar. The wheel and brake attachment fitting was identified as a steel with designation St37, according to the German DIN classification for steels. The St37 steel is specified to have a yield strength of at least 34 ksi (235 MPa) and tensile strength between 51 ksi and 70 ksi (350 MPa to 480 MPa). According to the ASM Metals Handbook, St37 is similar to SAE 1013 steel, which is a low-carbon steel. Hardness measurements on the fitting averaged 63.5 Rockwell B, with a standard deviation of 2 Rockwell B. For steel, a hardness of 65 Rockwell B corresponds to a tensile strength of 56 ksi, so the fitting appears to be within specification. This steel is at the lower end of the range of strength possible for steel. The ASM Metals Handbook indicates that fatigue resistance would also improve with increasing tensile strength. Information from the manufacturer indicates that the gear assembly was designed in accordance with ASTM F 2245, and successfully passed a drop test of 550 mm (21.7 inches) at a weight of 600 kg (1323 pounds). **This narrative was modified on August 13, 2007.**
On March 10, 2007, at 1558 mountain standard time, a Flight Design USA, CT-SW light sport aircraft, N102RK, was substantially damaged, when during an aborted landing at Double Eagle II Airport, Albuquerque, New Mexico, the airplane's right main landing gear separated. The local instructional flight was being conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The two flight instructors on board sustained minor injuries. Visual meteorological conditions prevailed at the time of the accident. The flight originated approximately 1500. The airplane operator's chief pilot, who was one of the instructors on board the airplane, reported that he and the other company instructor (student instructor) were in the traffic pattern performing touch-and-go landings on runway 22 (7,400 feet by 100 feet, dry asphalt). They had performed 4 successful touch-and-go landings with no problems. On the mishap landing, the chief pilot said they started the flare at normal approach speed about 2 to 3 feet above the runway. As the airplane settled, the chief pilot raised the nose of the airplane slightly to prevent a bounced landing. The airplane subsequently ballooned. They elected to perform a go-around. The chief pilot advanced the power and "pitched the airplane to the landing attitude." The airplane settled to the runway in a slight left crab, touching down on the left main landing gear, which subsequently broke aft. The airplane came down on the runway and slid for 300 feet, departing the left side and flipping over on to it's back. An examination of the airplane showed crush damage to the composite wings, fuselage, vertical stabilizer, and rudder. The airplane's nose gear and right main landing gear were broken aft. An initial examination of the left main landing gear showed a fracture of the lower landing gear tube at the landing gear wheel and brake attachment fitting. The airplane had been recently purchased by the company. Total airframe time was approximately 25 hours. The fractured wheel and brake attachment fitting were sent to the National Transportation Safety Board Materials Laboratory for examination. The examination showed that the fitting was constructed of welded steel tubing. All of the welds were intact. The fracture through the angled tube of the fitting appeared to coincide with the position of the lower end of the main landing gear spring bar. The fracture was consistent with being caused by overstress. There were no indications of pre-existing cracks or defects. A small compression buckle was observed at the top of the part and some tensile indications were seen at the bottom. There were contact impressions on the inside of the tube most-likely made by the end of the main landing gear spring bar. The tube wall away from the fracture measured 0.080 inch - 0.085 inch thick, which matches the 2 mm (0.079 inch) thickness indicated on drawings provided by the manufacturer. Adjacent to the fracture, there is an area where the tube wall appears thinner. The top part of the fitting was not submitted, so the wall thickness of the top part of the tube away from the fracture was not measured. The wheel and brake attachment fitting was identified as a steel with designation St37, according to the German DIN classification for steels. The St37 steel is specified to have a yield strength of at least 34 ksi (235 MPa) and tensile strength between 51 ksi and 70 ksi (350 MPa to 480 MPa). According to the ASM Metals Handbook, St37 is similar to SAE 1013 steel, which is a low-carbon steel. The drawings indicate that the main landing gear spring bar is made of an aluminum alloy. Hardness measurements on the fitting averaged 63.5 Rockwell B, with a standard deviation of 2 Rockwell B. For steel, a hardness of 65 Rockwell B corresponds to a tensile strength of 56 ksi. This steel is at the lower end of the range of strength possible for steel. The ASM Metals Handbook indicates that fatigue resistance would also improve with increasing tensile strength. Information from the manufacturer indicates that the gear assembly was designed in accordance with ASTM F 2245, and successfully passed a drop test of 550 mm (21.7 inches) at a weight of 600 kg (1323 pounds). **This narrative was modified on August 13, 2007**
The total failure of the left main landing gear strut due to overload during the landing resulting in the loss of control and subsequent nose over. A factor contributing to the accident was the chief pilot 's inability to maintain directional control of the airplane after the landing gear failed. **This report was modified on August 13, 2007.**
Source: NTSB Aviation Accident Database
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