What is Electronic flight instrument system?

In aviation, an electronic flight instrument system is a flight instrument display system in an aircraft cockpit that displays flight data electronically rather than electromechanically. An EFIS normally consists of a primary flight display , multi-function display , and an engine indicating and crew alerting system display. Early EFIS models used cathode ray tube displays, but liquid crystal displays are now more common. The complex electromechanical attitude director indicator and horizontal situation indicator were the first candidates for replacement by EFIS. Now, however, few flight deck instruments cannot be replaced by an electronic display.