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 deactivation of the forward and center cargo control units (CCU). That AD was prompted by a report of failure of a CCU, which produced overheating of the electrical pins inside the CCU; the subsequent release of hot gases and flames ignited an adjacent insulation blanket. This action would require, among other actions, a general visual inspection to verify that all six external connectors of suspect CCU's have a certain part number stamped on the connector bodies on all CCU assemblies, and follow-on actions, which would constitute terminating action for the deactiviation requirements. The actions specified by the proposed AD are intended to prevent overheating of the electrical pins inside the CCU's and subsequent release of hot gases and flames, which could result in smoke and fire in the cargo compartment.