Two screens that replaced a wall of gauges

On the 747-400, entire panels of mechanical gauges were replaced by EICAS - a pair of CRT displays showing engine parameters and every system alert the crew needs, ordered by urgency.

Key facts
Full name	Engine Indication and Crew Alerting System
Displays	Main and auxiliary EICAS among the six display units (PFDs, NDs, EICAS ×2)
Alert levels	Advisory, caution and warning, shown as text and graphics
Maintenance	Central Maintenance Computer (CMC) records LRU-level faults

EICAS cut the classic 747's dense instrument landscape down to six display units - the captain's and first officer's PFDs and NDs plus two EICAS screens. Because all six share display electronics, a single electronics unit failure blanks the whole deck, an important design constraint for the type.

The 747-400 was the first Boeing airliner with a centralised maintenance system: its Central Maintenance Computer gathers fault records from every system and shows mechanics exactly which line-replaceable unit failed - the ancestor of today's onboard diagnostics.

Three levels of urgency

EICAS's defining idea is that it does not merely show data - it decides what matters and in what order. Alerts are separated into three levels so a crew can triage at a glance:

• Advisory - a condition to be aware of, no immediate action.
• Caution - a condition requiring attention and awareness of a possible consequence.
• Warning - a condition requiring immediate action.

Alongside the numeric engine indications, this tiered alerting is what let the 747-400 delete a large fraction of the classic 747's dedicated gauges and warning lights without losing the information the crew actually needs.

The shared-electronics constraint

EICAS and the primary flight and navigation displays all sit on the same six display units, which share common display electronics. That concentration is efficient, but it introduces a design consideration: a failure of the shared electronics can affect multiple displays at once. This is precisely the kind of interaction the NTSB safety correspondence in the sources examined, since display-unit failure handling is about how the crew retains essential information when a shared resource is lost.

The maintenance legacy

The 747-400 also pioneered centralised fault reporting on a Boeing airliner. Its Central Maintenance Computer collects fault records from across the aircraft and presents them to maintenance personnel, identifying the failed line-replaceable unit and the circumstances. This is the direct ancestor of the onboard diagnostics and health-monitoring systems that are now standard across the industry - the shift from "the crew saw a light" to "the aircraft recorded a fault signature."

Related

• Flight deck
• Flight guidance and autopilot
• Navigation and avionics
• Alerting and collision avoidance