Airworthiness Directives; Airbus Model A320 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Airbus Model A320-111, -211, and -231 series airplanes, that currently requires replacing the existing standby generator control unit (GCU) with a new improved standby GCU. That action was prompted by reports of improper functioning of the standby GCU. This amendment requires replacement of the GCU on addition affected airplanes. For some airplanes, it also will require that a wiring modification be accomplished prior to replacement of the GCU. The actions specified by this AD are intended to prevent such improper functioning of the GCU, which could result in the loss of the standby emergency generation system.