Summary
Highlights
The Electronic Flight Instrument System (EFIS) is an integrated digital system displaying flight and navigation information. Its introduction drastically changed cockpit designs and operating philosophies, moving from analog to digital instrumentation, as seen in the evolution from the Boeing 727 to the 787 Dreamliner.
The transition to EFIS was gradual. Initially, the attitude indicator and horizontal situation indicator were replaced by digital displays (EADI and EHSI). Complete EFIS systems, known as "glass cockpits," are entirely composed of digital displays, such as the Garmin G1000 and ProLine 21 systems.
A complete EFIS system comprises displays, a control panel, and one or more symbol generators. Displays present processed information, the control panel allows system interaction, and symbol generators process data from aircraft systems to create the visual output.
Early EFIS systems utilized Electronic Attitude Director Indicators (EADI) and Electronic Horizontal Situation Indicators (EHSI). Modern complete EFIS systems employ a Primary Flight Display (PFD), which condenses six basic flight instruments into one screen, and a Multi-Function Display (MFD) or Navigation Display (ND), which provides advanced navigation, weather, and terrain information. Some MFDs on smaller aircraft also show engine and system data.
Early EFIS displays used Cathode Ray Tubes (CRTs), but most modern systems use more efficient Liquid Crystal Displays (LCDs). Digital instruments offer easier readability, less ambiguity, greater accuracy, and intuitive designs compared to their analog predecessors.
The control panel allows pilots to manage displayed information and brightness. The symbol generator (SG) acts as the interface, processing data from aircraft systems and control panel settings to generate the images for the displays. Symbol generators can also be known as display management computers or display processing computers.
Simple aircraft typically have one symbol generator, while larger, more complex aircraft may have up to three for redundancy. In case of a symbol generator failure, a backup unit can provide information to the affected displays. Pilots may also be able to manually select the symbol generator for a specific display. If a display itself fails, its information can often be transferred to another screen.
Symbol generators also monitor the system through data validation, data comparison between units, and display monitoring. In the event of a total system failure, most aircraft are equipped with completely independent backup instrument systems, which can be either analog or digital.