Airworthiness Directives; Airbus Model A300 B2 and A300 B4 Series Airplanes; Model A300 B4-600, B4-600R and F4-600R Series Airplanes, and Model A300 C4-605R Variant F Airplanes (Collectively Called A300-600 Series Airplanes); and Model A310-200 and -300 Series Airplanes

The FAA is adopting a new airworthiness directive (AD) for all the Airbus models identified above. This AD requires modifying the electrical power supply logic for the integral lighting of the standby horizon indicator in the cockpit, accomplishing repetitive operational tests of the integral lighting logic system, and performing corrective action if necessary. This AD is prompted by a report of temporary loss of six cathode ray tube (CRT) flight displays and the integral lighting of the standby horizon indicator backlight in the cockpit during takeoff, due to failure of the normal electrical power circuit. That power circuit supplies power to both the CRTs and the standby horizon indicator backlight. We are issuing this AD to prevent loss of the integral lighting due to failure of the normal electrical power circuit, which could result in inability of the pilot to read the backup attitude information during takeoff, and possible deviation from the intended flight path.