Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain McDonnell Douglas airplane models, that would have required a one-time inspection for chafing or signs of arcing of the wire bundle for the auxiliary hydraulic pump, and other specified and corrective actions, as applicable. This new action revises the proposed rule by proposing that certain airplanes be required to install additional protective sleeving on the upper portion of the auxiliary hydraulic pump wire assembly. The proposed AD results from reports of shorted wires and evidence of arcing on the power cables of the auxiliary hydraulic pump, as well as fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent shorted wires or arcing at the auxiliary hydraulic pump, which could result in loss of auxiliary hydraulic power, or a fire in the wheel well of the airplane. The proposed actions are also intended to reduce the potential of an ignition sourceadjacent to the fuel tanks, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.