Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Gulfstream Model G-IV series airplanes. For certain airplanes this proposal would require installation of an additional indicator located on the pilot's instrument panel in primary view of the flight crew. The indicator would inform the flight crew 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 proposal would require the EICAS (Engine Instruments/ Caution Advisory System) to be used for this indication. This action is necessary to ensure that the flight crew is aware that an electrical system failure has occurred and that the airplane main batteries are powering the essential DC bus. If the flight crew 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.