# Electronic flight instrument system > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Electronic_flight_instrument_system > Markdown URL: https://mediated.wiki/source/Electronic_flight_instrument_system.md > Source: https://en.wikipedia.org/wiki/Electronic_flight_instrument_system > Source revision: 1325849776 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) Display system in an aircraft's cockpit which displays flight information electronically For the French international school with the acronym EFIS, see [École Franco-Indienne Shishya](/source/%C3%89cole_Franco-Indienne_Shishya). This article needs more citations. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Electronic flight instrument system" – news · newspapers · books · scholar · JSTOR (June 2009) (Learn how and when to remove this message) This article needs editing to comply with Wikipedia's Manual of Style. Please help improve the content. (December 2025) (Learn how and when to remove this message) EFIS on an [Airbus A380](/source/Airbus_A380) EFIS on an [Eclipse 500](/source/Eclipse_500) [Garmin G1000](/source/Garmin_G1000) on a [Diamond DA42](/source/Diamond_DA42) Primary flight display of a [Boeing 747-400](/source/Boeing_747-400) In [aviation](/source/Aviation), an **electronic flight instrument system** (**EFIS**) is a [flight instrument](/source/Flight_instrument) display system in an aircraft [cockpit](/source/Cockpit) that displays flight data electronically rather than electromechanically. An EFIS normally consists of a [primary flight display](/source/Primary_flight_display) (PFD), [multi-function display](/source/Multi-function_display) (MFD), and an [engine indicating and crew alerting system](/source/Engine_indicating_and_crew_alerting_system) (EICAS) display. Early EFIS models used [cathode-ray tube](/source/Cathode-ray_tube) (CRT) displays, but [liquid crystal displays](/source/Liquid_crystal_display) (LCD) are now more common. The complex electromechanical [attitude director indicator](/source/Attitude_indicator) (ADI) and [horizontal situation indicator](/source/Horizontal_situation_indicator) (HSI) were the first candidates for replacement by EFIS. Now, however, few flight deck instruments cannot be replaced by an electronic display. ## Display units ### Primary flight display (PFD) On the flight deck, the display units are the most obvious parts of an EFIS system, and are the features that lead to the term *[glass cockpit](/source/Glass_cockpit)*. The display unit that replaces the artificial horizon is called the [primary flight display](/source/Primary_flight_display) (PFD). If a separate display replaces the HSI, it is called the navigation display. The PFD displays all information critical to flight, including [calibrated airspeed](/source/Calibrated_airspeed), altitude, heading, attitude, vertical speed and yaw. The PFD is designed to improve a pilot's situational awareness by integrating this information into a single display instead of six different analog instruments, reducing the amount of time necessary to monitor the instruments. PFDs also increase situational awareness by alerting the aircrew to unusual or potentially hazardous conditions — for example, low airspeed, high rate of descent — by changing the color or shape of the display or by providing audio alerts. The names Electronic Attitude Director Indicator and Electronic Horizontal Situation Indicator are used by some manufacturers.[1] However, a simulated ADI is only the centerpiece of the PFD. Additional information is both superimposed on and arranged around this graphic. Multi-function displays can render a separate navigation display unnecessary. Another option is to use one large screen to show both the PFD and navigation display. The PFD and navigation display (and multi-function display, where fitted) are often physically identical. The information displayed is determined by the system interfaces where the display units are fitted. Thus, spares holding is simplified: the one display unit can be fitted in any position. LCD units generate less heat than CRTs; an advantage in a congested instrument panel. They are also lighter, and occupy a lower volume. ### Multi-function display (MFD) The navigation display (ND) of a [Boeing 747-400](/source/Boeing_747-400) aircraft The MFD (multi-function display) displays navigational and weather information from multiple systems. MFDs are most frequently designed as "chart-centric", where the aircrew can overlay different information over a map or chart. Examples of MFD overlay information include the aircraft's current route plan, weather information from either on-board radar or lightning detection sensors or ground-based sensors, e.g., NEXRAD, restricted airspace and aircraft traffic. The MFD can also be used to view other non-overlay type of data (e.g., current route plan) and calculated overlay-type data, e.g., the glide radius of the aircraft, given current location over terrain, winds, and aircraft speed and altitude. MFDs can also display information about aircraft systems, such as fuel and electrical systems (see EICAS, below). As with the PFD, the MFD can change the color or shape of the data to alert the aircrew to hazardous situations. ### Engine indications and crew alerting system (EICAS) / electronic centralized aircraft monitoring (ECAM) [EICAS](/source/EICAS) (Engine Indications and Crew Alerting System) displays information about the aircraft's systems, including its fuel, electrical and propulsion systems (engines). EICAS displays are often designed to mimic traditional round gauges while also supplying digital readouts of the parameters. EICAS improves situational awareness by allowing the aircrew to view complex information in a graphical format and also by alerting the crew to unusual or hazardous situations. For example, if an engine begins to lose oil pressure, the EICAS might sound an alert, switch the display to the page with the oil system information and outline the low oil pressure data with a red box. Unlike traditional round gauges, many levels of warnings and alarms can be set. Proper care must be taken when designing EICAS to ensure that the aircrew are always provided with the most important information and not overloaded with warnings or alarms. [ECAM](/source/Electronic_Centralised_Aircraft_Monitor) is a similar system used by Airbus, which in addition to providing EICAS functions also recommend remedial action. A 737NG EICAS after landing, showing outside air temperature, N1 RPM, exhaust gas temperature, N2 RPM, fuel flow, fuel used, fuel in the tanks, oil pressure, oil temperature, oil quantity, engine vibration, hydraulic pressure and hydraulic quantity ## Control panels EFIS provides pilots with controls that select display range and mode (for example, map or compass rose) and enter data (such as selected heading). Where other equipment uses pilot inputs, [data buses](/source/ARINC_429) broadcast the pilot's selections so that the pilot need only enter the selection once. For example, the pilot selects the desired level-off altitude on a control unit. The EFIS repeats this selected altitude on the PFD, and by comparing it with the actual altitude (from the air data computer) generates an altitude error display. This same altitude selection is used by the automatic flight control system to level off, and by the altitude alerting system to provide appropriate warnings. ## Data processors The EFIS visual display is produced by the symbol generator. This receives data inputs from the pilot, signals from sensors, and EFIS format selections made by the pilot. The symbol generator can go by other names, such as display processing computer, display electronics unit, etc. The symbol generator does more than generate symbols. It has (at the least) monitoring facilities, a graphics generator and a display driver.[2] Inputs from sensors and controls arrive via data buses, and are checked for validity. The required computations are performed, and the graphics generator and display driver produce the inputs to the display units. ### Capabilities Like personal computers, flight instrument systems need power-on-self-test facilities and continuous self-monitoring. Flight instrument systems, however, need additional monitoring capabilities: - Input validation — verify that each sensor is providing valid data - Data comparison — cross check inputs from duplicated sensors - Display monitoring — detect failures within the instrument system ### Former practice Traditional (electromechanical) displays are equipped with [synchro](/source/Synchro) mechanisms that transmit the pitch, roll, and heading shown on the captain and [first officer's](/source/First_Officer_(civil_aviation)) instruments to an instrument comparator. The comparator warns of excessive differences between the captain and first officer displays. Even a fault as far *downstream*[3] as a jam in, say, the roll mechanism of an ADI triggers a comparator warning. The instrument comparator thus provides both comparator monitoring and display monitoring. ### Comparator monitoring With EFIS, the comparator function is simple: Is roll data (bank angle) from sensor 1 the same as roll data from sensor 2? If not, display a warning caption (such as **CHECK ROLL**) on both PFDs. Comparison monitors give warnings for airspeed, pitch, roll, and altitude indications. More advanced EFIS systems have more comparator monitors. ### Display monitoring In this technique, each symbol generator contains two display monitoring channels. One channel, the internal, samples the output from its own symbol generator to the display unit and computes, for example, what roll attitude should produce that indication. This computed roll attitude is then compared with the roll attitude input to the symbol generator from the [INS](/source/Inertial_guidance_system) or [AHRS](/source/Attitude_and_Heading_Reference_Systems). Any difference has probably been introduced by faulty processing, and triggers a warning on the relevant display. The external monitoring channel carries out the same check on the symbol generator on the other side of the flight deck: the Captain's symbol generator checks the First Officer's, the First Officer's checks the Captain's. Whichever symbol generator detects a fault, puts up a warning on its own display. The external monitoring channel also checks sensor inputs (to the symbol generator) for reasonableness. A spurious input, such as a radio height greater than the radio altimeter's maximum, results in a warning. ## Human factors ### Clutter At various stages of a flight, a pilot needs different combinations of data. Ideally, the avionics only show the data in use—but an electromechanical instrument must be in view all the time. To improve display clarity, ADIs and HSIs use intricate mechanisms to remove superfluous indications temporarily—e.g., removing the glide slope scale when the pilot doesn't need it. Under normal conditions, an EFIS might not display some indications, e.g., engine vibration. Only when some parameter exceeds its limits does the system display the reading. In similar fashion, EFIS is programmed to show the glideslope scale and pointer only during an [ILS](/source/Instrument_Landing_System) approach. In the case of an input failure, an electromechanical instrument adds yet another indicator—typically, a bar drops across the erroneous data. EFIS, on the other hand, removes invalid data from the display and substitutes an appropriate warning. A de-clutter mode activates automatically when circumstances require the pilot's attention for a specific item. For example, if the aircraft pitches up or down beyond a specified limit—usually 30 to 60 degrees—the attitude indicator de-clutters other items from sight until the pilot brings the pitch to an acceptable level. This helps the pilot focus on the most important tasks. ### Color Traditional instruments have long used color, but lack the ability to change a color to indicate some change in condition. The electronic display technology of EFIS has no such restriction and uses color widely. For example, as an aircraft approaches the glide slope, a blue caption can indicate glide slope is armed, and capture might change the color to green. Typical EFIS systems color code the navigation needles to reflect the type of navigation. Green needles indicate ground-based navigation, such as VORs, Localizers and ILS systems. Magenta needles indicate GPS navigation. ## Advantages EFIS provides versatility by avoiding some physical limitations of traditional instruments. A pilot can switch the same display that shows a course deviation indicator to show the planned track provided by an area navigation or flight management system. Pilots can choose to superimpose the weather radar picture on the displayed route. The flexibility afforded by software modifications minimises the costs of responding to new aircraft regulations and equipment. Software updates can update an EFIS system to extend its capabilities. Updates introduced in the 1990s included the [ground proximity warning system](/source/Ground_proximity_warning_system) and [traffic collision avoidance system](/source/Traffic_collision_avoidance_system). A degree of redundancy is available even with the simple two-screen EFIS installation. Should the PFD fail, transfer switching repositions its vital information to the screen normally occupied by the navigation display. ## Advances in EFIS In the late 1980s, EFIS became standard equipment on most [Boeing](/source/Boeing) and [Airbus](/source/Airbus) [airliners](/source/Airliner), and many business aircraft adopted EFIS in the 1990s. Recent advances in computing power and reductions in the cost of liquid-crystal displays and navigational sensors (such as GPS and [attitude and heading reference system](/source/Attitude_and_heading_reference_system)) have brought EFIS to [general aviation](/source/General_aviation) aircraft. Notable examples are the [Garmin](/source/Garmin) G1000 and [Chelton Flight Systems](/source/Chelton_Flight_Systems) EFIS-SV. Several EFIS manufacturers have focused on the [experimental aircraft](/source/Experimental_aircraft) market, producing EFIS and EICAS systems for as little as [US$](/source/United_States_dollar)1,000-2000. The low cost is possible because of steep drops in the price of sensors and displays, and equipment for experimental aircraft doesn't require expensive [Federal Aviation Administration](/source/Federal_Aviation_Administration) certification. This latter point restricts their use to experimental aircraft and certain other aircraft categories, depending on local regulations. Uncertified EFIS systems are also found in [Light-sport aircraft](/source/Light-sport_aircraft), including factory built, microlight, and ultralight aircraft. These systems can be fitted to certified aircraft in some cases as secondary or backup systems depending on local aviation rules. ## See also - [Index of aviation articles](/source/Index_of_aviation_articles) - [Acronyms and abbreviations in avionics](/source/Acronyms_and_abbreviations_in_avionics) ## Notes 1. **[^](#cite_ref-source1_1-0)** Primary flight display and navigation display are the names used in the Federal Aviation Administration Advisory Circulars and also in ARINC Specification 725 1. **[^](#cite_ref-driver_2-0)** This driver is hardware, not software! 1. **[^](#cite_ref-term1_3-0)** Downstream and upstream refer to the direction of data flow: from sensor, to processor, to display ## Further reading - [Advisory Circular AC25-11A](http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/7D6139991C94E7D9862573080063F84D?OpenDocument&Highlight=ac%2025-11) [Archived](https://web.archive.org/web/20220813070605/https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/7D6139991C94E7D9862573080063F84D?OpenDocument&Highlight=ac%2025-11) 2022-08-13 at the [Wayback Machine](/source/Wayback_Machine) Electronic Flight Deck Displays, at the U.S. Federal Aviation Administration - [Electronic Aircraft Instruments](https://thommen.aero/product-categories/air-data-computer-and-displays/) Air Data Computer and Displays v t e Flight instruments Pitot-static Altimeter Airspeed indicator Machmeter Variometer Gyroscopic Attitude indicator Heading indicator Horizontal situation indicator Turn and slip indicator Turn coordinator Turn indicator Navigational Aircraft periscope Course deviation indicator Horizontal situation indicator Inertial navigation system Magnetic compass Satellite navigation SIGI Related topics Air data inertial reference unit ECAM EFIS Glass cockpit Head-up display Integrated standby instrument system Primary flight display V speeds Yaw string v t e Jet engines and aircraft gas turbines Gas turbines and jet propulsion Types Air turborocket Pulsejet/Valveless pulsejet/Gluhareff Pressure Jet Pulse detonation engine Propfan Turbofan Turbojet Turboprop Turboshaft Ramjet Scramjet Shcramjet Rocket Rotating detonation engine Mechanical components Accessory drive Air intake Afterburner (reheat) Axial compressor Centrifugal compressor Combustor Constant speed drive Impeller Nose bullet Propelling nozzle Turbine blade Principles Aircraft engine starting Bleed air Brayton cycle Bypass ratio Compressor stall Engine pressure ratio (EPR) Flameout Jet engine performance Overall pressure ratio Propulsive efficiency Specific impulse Thrust Thrust lapse Thrust specific fuel consumption Thrust to weight ratio Variable cycle engine Windmill restart Propellers Components Propeller governor Propeller speed reduction unit Principles Autofeather Blade pitch Constant-speed Contra-rotating Counter-rotating Proprotor Scimitar Variable-pitch Engine instruments Annunciator panel Electronic centralised aircraft monitor (ECAM) Electronic flight instrument system (EFIS) Engine-indicating and crew-alerting system (EICAS) Flight data recorder Glass cockpit Engine controls Autothrottle Full Authority Digital Engine/Electronics (FADEC) Thrust lever Thrust reversal Fuel and induction systems Flame holder Jet fuel Other systems Air-start system Auxiliary power unit (APU) Bleed air system Hydraulic system Ice protection system v t e Aircraft components and systems Airframe structure Aft pressure bulkhead Cabane strut Canopy Crack arrestor Cruciform tail Dope Empennage Fabric covering Fairing Flying wires Former Fuselage Hardpoint Interplane strut Jury strut Leading edge Lift strut Longeron Nacelle Rib Spar Stabilizer Stressed skin Strut T-tail Tailplane Trailing edge Triple tail Twin tail V-tail Vertical stabilizer Wing root Wing tip Wingbox Flight controls Aileron Airbrake Artificial feel Autopilot Canard Centre stick Deceleron Dive brake Dual control Electro-hydraulic actuator Elevator Elevon Flaperon Flight control modes Fly-by-wire Gust lock HOTAS Rudder Rudder pedals Servo tab Side-stick Spoiler Spoileron Stabilator Stick pusher Stick shaker Trim tab Wing warping Yaw damper Yoke Aerodynamic and high-lift devices Active Aeroelastic Wing Adaptive compliant wing Anti-shock body Blown flap Channel wing Dog-tooth Drag-reducing aerospike Flap Gouge flap Gurney flap Krueger flap Leading-edge cuff Leading-edge droop flap LEX Slats Slot Stall strips Strake Variable-sweep wing Vortex generator Vortilon Wing fence Winglet Avionic and flight instrument systems ACAS Air data boom Air data computer Aircraft periscope Airspeed indicator Altimeter Annunciator panel Astrodome Attitude indicator Compass Course deviation indicator EFIS EICAS Flight management system Glass cockpit GPS Head-up display Heading indicator Horizontal situation indicator INS ISIS Multi-function display Pitot–static system Radar altimeter TCAS Transponder Turn and slip indicator Variometer Yaw string Propulsion controls, devices and fuel systems Autothrottle Drop tank FADEC Fuel tank Gascolator Inlet cone Intake ramp NACA cowling NACA duct Self-sealing fuel tank Splitter plate Throttle Thrust lever Thrust reversal Townend ring War emergency power Wet wing Landing and arresting gear Aircraft tire Arrestor hook Autobrake Conventional landing gear Drogue parachute Landing gear Landing gear extender Oleo strut Tricycle landing gear Tundra tire Escape systems Ejection seat Escape crew capsule Other systems Aircraft lavatory Auxiliary power unit Bleed air system Deicing boot Emergency oxygen system Environmental control system Flight recorder Hydraulic system Ice protection system In-flight entertainment system Landing lights Navigation light Passenger service unit Ram air turbine --- Adapted from the Wikipedia article [Electronic flight instrument system](https://en.wikipedia.org/wiki/Electronic_flight_instrument_system) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Electronic_flight_instrument_system?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.