Summary
This document proposes to supersede an existing airworthiness directive (AD), applicable to Schweizer Aircraft Corporation and Hughes Helicopters, Inc. Model 269A, 269A-1, 269A-2, and 269B helicopters, that currently requires initial and repetitive inspections of the main rotor thrust bearing (bearing) for bearing rotational roughness, corrosion, inadequate lubrication, physical damage, or excessive zinc chromate paste or moisture. This action would require the same initial and repetitive inspections required by the existing AD, but would extend the retirement life for certain bearings, and would remove the Model 269A-2 helicopter from, and add the Model TH-55A helicopters to the applicability of this AD. This proposal is prompted by an FAA analysis of service information issued by the manufacturer that extends the retirement life for certain bearings. The actions specified by the proposed AD are intended to prevent failure of the bearing, loss of the main rotor, and subsequent loss of control of the helicopter.