WPR23LA021

On October 20, 2022, about 1010 Pacific daylight time, a Cessna 140 airplane, N55DC, was substantially damaged when it was involved in an accident near Georgetown, California. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The student pilot reported he was returning from a 1-hour local practice flight when the accident occurred. He noted that the weather was clear, and wind was calm at the time. The pilot entered the downwind leg of the airport traffic pattern at 1,000 ft above ground level on a 45° entry for runway 16. He set the throttle, trim, and flaps for landing and maintained 65-70 mph while he flew a stable approach to the runway. As the pilot crossed the runway numbers, he reduced the engine speed to IDLE with the airspeed at 65 mph and landed on the runway centerline. When the main landing gear first touched down the airplane bounced, and the pilot floated the airplane down the runway to decelerate. During the landing roll following the second touchdown, the right wing banked upward at a 30°- 40° angle. The pilot reported that neither touchdown was hard. He applied full right aileron but was unable to level the wings. The airplane began to veer left on the runway and the pilot applied full power to abort the landing. The airplane veered off the left side of the runway, the left wing contacted vegetation, and the airplane spun 180° before it came to rest. The right main gear leg and wheel separated and came to rest in vegetation before a slope about 70 ft from the airplane. In his statement the pilot reported no issues with the flight controls, but in reference to any mechanical failures he noted that he was uncertain: “the right main gear leg and wheel separated and were approx 70 feet from the plane still on the edge of the runway. That could have caused the right wing to abruptly raise or it was from a freak gust of wind at the wrong time. I don't know if the gear separation was from an attachment failure or the accident itself.” According to the airplane parts manual, the main landing gear legs bolt to the fuselage airframe structure with a bolt, washer, and a nut. (See figure 1). Figure 1: Excerpt of main landing gear drawing from parts manual The landing gear bolt remained inside the bolt hole along with its associated hardware, including the nut and washer at the fuselage primary structure. The bolt head separated and was not located. In addition, a portion of the landing gear support assembly was fractured and partially separated. Figure 2: Landing gear leg assembly hardware on accident airplane A National Transportation Safety Board materials laboratory examination revealed that the fracture features of the bolt were consistent with ductile overstress from a shear overload. No evidence of preexisting damage was observed. The forward end of the landing gear support assembly outboard attachment was fractured at 2 locations on the lower support. The upperside of the lower support was deformed downward near the forward attachment location and the outboard flange was fractured, which appeared to coincide with the downward bend at the upper surface. The downward deformation at the forward end of the lower support is consistent with wheel loading in the aft direction, and the deformation suggests the applied load was sufficient to produce stresses that exceeded the yield strength of the material.