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

This amendment revises an existing airworthiness directive (AD), for the specified Schweizer Aircraft Corporation (Schweizer) model helicopters, that currently requires inspecting the lugs on certain aft cluster fittings and each aluminum end fitting on certain tailboom struts. Modifying or replacing each strut assembly within a specified time period and serializing certain strut assemblies are also required. Additionally, a one-time inspection and repair, if necessary, of certain additional cluster fittings, and replacement and modification of certain cluster fittings within 150 hours time-in- service (TIS) or 6 months, whichever occurs first, is required. This amendment requires the same actions as the existing AD, but revises the Applicability section of the AD. This amendment is prompted by the discovery of an error in the Applicability section of the existing AD. The actions specified by this AD are intended to prevent failure of a tailboom support strut or a cluster fitting, which could cause rotation of a tailboom into the main rotor blades, and subsequent loss of control of the helicopter.