Summary
The FAA is revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 747-400, 747-400D, and 747-400F series airplanes. The original NPRM would have required replacement of an electronic flight instrument system/engine indicating and crew alerting system (EFIS/EICAS) interface unit (EIU) located on the E2-6 shelf of the main equipment center with a new or modified EIU. The original NPRM resulted from two instances where all six integrated display units (IDUs) on the flight deck panels went blank in flight. This action revises the original NPRM by reducing the compliance time for replacing the EIU. We are proposing this supplemental NPRM to prevent loss of the IDUs due to failure of all three EIUs, which could result in the inability of the flightcrew to maintain safe flight and landing of the airplane.