Summary
This document proposes to revise an existing airworthiness directive (AD), applicable to certain McDonnell Douglas Model MD-11 series airplanes, that currently requires a one-time inspection to identify the part numbers of two dimmer controls for the overhead instrument panel light and circuit breaker lightplate located in the flight compartment. For airplanes on which a dimmer control having an incorrect part number is installed, that AD also requires replacing the dimmer control with a new part; modifying and reinstalling the existing dimmer control; or reinstalling a dimmer control following modification of the part by the part manufacturer. That AD was prompted by reports of smoke emitting from the overhead panels in the cockpit area. The actions specified by that AD are intended to prevent an electrical failure in the overhead dimmer control due to overheating of a printed circuit board capacitor in the dimmer control, which could result in rupture of the capacitor and smoke in the flight compartment. This action would revise the term "serial numbers" in the applicability statement to "fuselage numbers."