WPR21LA064

During an instructional flight in the tailwheel-equipped airplane, the airplane veered left. Despite the instructor’s application of corrective control inputs, the airplane did not respond as expected, ultimately resulting in a ground loop and substantial damage to the left wing. Postaccident examination revealed that both of the airplane’s tailwheel steering springs and tension chains were missing. The springs were found on the runway following the accident, separated from each other by about 1,700 ft. Neither of the chains were located. The manufacturer’s instructions called for the spring to connect directly to the tailwheel yoke, and the chain to connect to the steering arm with a connector clip. Evidence suggests that the spring was instead incorrectly connected directly to the steering arm. This reverse installation, while not in compliance with the maintenance instructions, did not appear to functionally affect the operation of the steering system, and therefore without examination of the missing chains or further examination of the tailwheel assembly, the significance of this finding could not be determined.

On November 03, 2020, about 1235 Pacific daylight time, a Stinson 108-3, N6855M, sustained substantial damage when it was involved in an accident in El Monte, California. The flight instructor and the pilot receiving instruction were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the flight instructor, the purpose of the flight was to provide tailwheel instruction to the private pilot. The pilot receiving instruction performed three full-stop takeoffs and landings from runway 19. During the landing roll following the fourth landing, the airplane began to veer to the left. The instructor assumed the flight controls and applied rudder, but the airplane did not respond. The instructor then applied right brake and the airplane began to turn to the right, but his subsequent application of left rudder produced no response. The airplane continued to turn to the right, and the left wing impacted the ground. The airplane came to rest facing the opposite direction and sustained substantial damage to the left wing and aileron. The airplane was equipped with a Scott 3000 series tailwheel assembly. The design incorporated a swiveling steering arm, that was connected to and controlled by the tailwheel steering yoke through a spring and a tension chain on both the left and right sides. The manufacturer’s instructions called for the spring to be connected directly to the tailwheel yoke, and the chain to be connected to the steering arm with a connector clip. Postaccident examination of the airplane revealed that both of the steering springs and chains had separated from both the tailwheel steering yoke and steering arm assembly and that the tension chain connector clips were connected to the tailwheel steering yoke rather than the steering arm. Both steering springs were located on the runway after the accident. One spring was recovered near the runway 19 centerline about 230 ft beyond the runway threshold, and the second was recovered from the safety area on the left side of the runway about 1,900 ft beyond the threshold. The left and right tension chains were not located. According to the airplane’s maintenance logbooks, the most recent annual inspection was completed 7 flight hours prior to the accident.