Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain McDonnell Douglas Model MD-11 series airplanes, that currently requires a revision of the Airplane Flight Manual to alert the flightcrew that both flight management computers (FMC) must be installed and operational. This action would require an inspection to verify if a certain modification is on the front and rear identification plates of the FMC's; and applicable follow-on and corrective actions. This proposal is prompted by the FAA's determination that further rulemaking action is necessary to ensure that all affected airplanes are inspected for suspected defective multiplexers. The actions specified by the proposed AD are intended to prevent loss of airspeed and altitude indications on both primary flight displays in the cockpit, and/or loss or degradation of the autopilot functionality, and consequent failure of the data busses.