Accident Overview
On June 5, 2023, at approximately 1517 Pacific daylight time, a Cessna 172R, registration N819KS, was substantially damaged during a landing roll at Santa Monica, California. The pilot was not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a maintenance test flight, following repairs from a previous collision with a fuel truck.
Sequence of Events
The pilot performed a preflight inspection of the nose landing gear assembly and found no anomalies. After a high-speed taxi, he determined the airplane was safe for pattern operations. Departing runway 21, the pilot remained in the traffic pattern and executed a normal touchdown on the same runway. During the landing roll, as the nose landing gear contacted the runway, a shimmy developed. The pilot applied back pressure to the control yoke to relieve weight from the nosewheel, but the shimmy intensified as the airplane slowed. Subsequently, a sound resembling metal striking the lower engine cowling was heard. The airplane veered left despite right rudder input. Attempted braking exacerbated the turn, and the pilot relied on aerodynamic braking. The airplane veered aggressively left, and upon reapplying brakes, the right wing dipped and contacted the ground. The airplane nosed over and came to rest inverted, resulting in substantial damage to the rudder.
Post-Accident Examination
A bolt from the nose wheel torque link assembly was recovered from the runway during a foreign object debris sweep. The torque link had separated from the nose wheel steering arm assembly at the upper bolt. According to the airplane maintenance manual, the torque links provide a mechanical link between the top and bottom parts of the shock strut and help maintain nosewheel alignment. The illustrated parts catalogue indicates the upper torque link connects to the nose gear steering arm assembly, and the lower torque link connects to the nose wheel fork.
Bolt Examination
A National Transportation Safety Board Materials Laboratory examination determined that both upper and lower torque link bolt measurements and thread profiles matched the proper bolt for installation. The bolthead had separated from the shank, but the castellated nut and cotter pin remained secure. The fracture surface exhibited directional dimples consistent with shear overstress.
Prior Damage
In May 2023, the airplane collided with a fuel truck while being towed. Video documentation showed a bent tow point and a curved bolt with a castellated nut protruding from the upper torque link to nose gear steering arm assembly connection. An invoice indicated that damage was inspected and ten shock mounts on the cowling were replaced to prepare the airplane for a ferry flight, with strut and other damage scheduled for repair at another facility. The operator stated that an instructor was asked to perform the maintenance flight (the accident flight) after servicing to verify airworthiness before the ferry flight.