Airworthiness Directives; Schweizer Aircraft Corporation Model 269A, 269A-1, 269B, 269C, 269C-1, 269D, and TH-55A Helicopters

This amendment supersedes an existing airworthiness directive (AD) that applies to Schweizer Aircraft Corporation (Schweizer) Model 269A, 269A-1, 269B, 269C, 269C-1, 269D helicopters. That AD requires inspecting the tail rotor swashplate shaft (shaft) nut for looseness and, if loose, inspecting the shaft for proper size; subsequently inspecting the shafts not previously inspected; and replacing any undersized shaft prior to further flight. This amendment reduces the applicability by specifying certain serial number tail rotor pitch control (pitch control) assemblies and shipping dates but adds the Schweizer Model TH-55A helicopter to the applicability. This amendment is prompted by the discovery of an undersized replacement shaft during routine maintenance. The actions specified by this AD are intended to prevent failure of the shaft, loss of the tail rotor, and subsequent loss of control of the helicopter.