Summary
This document proposes the supersedure of an existing airworthiness directive (AD) applicable to Schweizer Aircraft Corporation (Schweizer) Model 269A, 269A-1, 269B, 269C, 269C-1, and 269D helicopters. That AD currently 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 new action would reduce the applicability by specifying certain serial number tail rotor pitch control (pitch control) assemblies and shipping dates but would add the Schweizer Model TH- 55A helicopter to the applicability. This proposal is prompted by the discovery of an undersized replacement shaft during routine maintenance. The actions specified by this proposed AD are intended to prevent failure of the shaft, loss of the tail rotor, and subsequent loss of control of the helicopter.