Airworthiness Directives; McDonnell Douglas Model MD-90-30 Series Airplanes

This document supersedes an existing airworthiness directive (AD) that applies to certain McDonnell Douglas Model MD-90-30 series airplanes. That AD currently requires 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. The actions specified in that 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. This amendment is prompted by the Federal Aviation Administration's determination that the existing AD must be revised to ensure that the requirements apply to the appropriate airplane groups.