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

This amendment supersedes an existing airworthiness directive (AD), applicable to Schweizer Aircraft Corporation and Hughes Helicopters, Inc. Model 269A, 269A-1, 269B, 269C, and TH-55A series helicopters, that currently requires an initial and repetitive visual inspection of the clutch control spring assembly for component wear and replacement of affected unairworthy parts. This amendment requires the same initial and repetitive visual inspection and replacements required by the existing Priority Letter AD, but references a revised service bulletin and provides replacement procedures for the aluminum spring retainer thermofit tube (plastic sleeve). This amendment is prompted by a recent accident involving a Model 269C helicopter that reportedly lost engine drive power at 100 feet above ground level (AGL) with a resulting unsuccessful autorotative landing, and the manufacturer's issuance of revised service information that provides more detailed instructions for replacement of two components of the belt drive clutch control assembly. The actions specified by this AD are intended to prevent failure of the aluminum spring retainer, loss of power to the rotor drive system, and a subsequent forced landing.