WPR20LA226

The pilot of the tailwheel equipped biplane reported that, during a landing roll on runway 26R, the left wing “dipped” and that he applied right aileron to counteract. The pilot stated that the airplane began to turn to the right and that, despite the application of full left rudder, left brake, and a brief application of power, he was unable to correct the movement. The lower left wing subsequently struck the ground. The airplane then veered sharply to the right, exited the runway, and the left main landing gear collapsed as the airplane came to rest upright. Postaccident examination of the airplane revealed that the fuselage was structurally damaged. The left rudder/tailwheel cable idler arm was found fractured. Examination of the two pieces of fractured left rudder/tailwheel cable idler arm revealed that the fracture progressed though the section due to a monotonic bending load. It’s likely that the fracture occurred during the pilot’s attempt to counteract the airplane’s movement to the right when directional control was lost. The airport’s automated weather observation station reported that, about 4 minutes after the accident, the wind was calm. However, the pilot reported that while on short final to the runway, the air traffic control tower controller reported wind was from 270° at 4 knots.

On July 5, 2020, about 1124 Pacific daylight time, a Boeing B75, N61445, was substantially damaged when it was involved in an accident near Chino, California. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations part 91 personal flight. The pilot reported that, during a landing roll on runway 26R, the left wing “dipped,” and he applied right aileron to counteract. The pilot stated that the airplane began to turn to the right, and despite the application of full left rudder, left brake, and a brief application of power, he was unable to correct the movement, and the lower left wing struck the ground. The airplane then veered sharply to the right and exited the runway. Subsequently, the left main landing gear collapsed, and the airplane came to rest upright. Postaccident examination of the airplane revealed that the fuselage was substantially damaged. The left rudder/tailwheel cable idler arm was found fractured. The idler arm was subsequently sent to the National Transportation Safety Board Materials Laboratory for further examination. Examination of the two pieces of fractured left rudder/tailwheel cable idler arm revealed that the fracture progressed through the central pivot portion of the arm. The surface features, surface roughness, and presence of parting lines are consistent with sand-casting fabrication of the arm. The fracture surfaces were relatively flat, and the peripheral edges did not exhibit deformation associated with in-plane contraction, consistent with fracture through a material of relatively low fracture toughness. Along the exterior of the T portion, minor in-plane plastic deformation was observed and based on fractographic features, the fracture initiated at the ligament and progressed though the section due to a monotonic bending load, as depicted in figure 1. Figure 1: The left rudder/tailwheel cable idler arm fracture surfaces.