Airworthiness Directives; Airbus Model A300 B4-600, B4-600R, and F4-600R (Collectively Called A300-600) Series Airplanes, and Airbus Model A310 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Airbus Model A300 B4-600, B4-600R, and F4- 600R (collectively called A300-600) series airplanes, and Airbus Model A310 series airplanes, that currently requires replacement of Honeywell inertial reference units (IRU) with new or modified Honeywell IRUs. For certain airplanes, that existing AD also requires replacement of Litton IRUs, mode selector units (MSU), and an inertial sensor display unit (ISDU) with new Honeywell IRUs, MSUs, and a new ISDU. This amendment removes the requirement to replace the Litton IRUs, MSUs, and ISDU with Honeywell IRUs, MSUs, and ISDU. This amendment also allows the use of certain Honeywell IRUs as spare parts until the final compliance date of this AD. The actions specified in this AD are intended to prevent loss of positioning data and a display of incorrect attitude data, which could compromise the ability of the flightcrew to maintain the safe flight and landing of the airplane. This action is intended to address the identified unsafe condition.