Airworthiness Directives; Gulfstream Model G-IV Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Gulfstream Model G-IV series airplanes. For certain airplanes, this AD requires installation of an additional indicator located on the pilot's instrument panel in primary view of the flightcrew. The indicator will inform the flightcrew that the airplane main batteries are powering the direct current (DC) essential bus, which supplies power to vital communication and navigation equipment. For certain other airplanes, this AD will require the EICAS (Engine Instruments/Caution Advisory System) to be used for this indication. This action is necessary to ensure that the flightcrew is aware that an electrical system failure has occurred and that the airplane main batteries are powering the essential DC bus. If the flightcrew is unaware of this situation, action to stop depletion of the airplane batteries will not be taken, and critical communications and navigation equipment could fail. This action is intended to address the identified unsafe condition.