Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain McDonnell Douglas Model MD-90-30 series airplanes, that would have required replacement of certain ground block screws with new screws; and retermination of the circuit ground wires of the electrical power control unit (EPCU) to separate grounding points. That proposal was prompted by reports of complete loss of the primary electrical power on an airplane during flight. This new action revises the proposed rule by expanding the applicability of the proposed AD to include additional airplanes. The actions specified by this new proposed AD are intended to prevent a loose electrical ground block of the circuit ground wires of the EPCU, which could result in complete loss of the primary electrical power of an airplane during flight.