A Comprehensive Guide to Electronic Flight Instrument Systems (EFIS)

Gone are the days of purely analog "steam gauge" cockpits in many modern aircraft. Today, pilots are often greeted by a sleek array of digital displays that consolidate critical flight information into an integrated and customizable format. This is the Electronic Flight Instrument System (EFIS), a fundamental technology that has revolutionized how pilots fly.

EFIS Simulation On Board our CRJ RJT

At its core, an EFIS is a suite of electronic displays that replaces traditional electromechanical instruments. Instead of individual gauges for airspeed, altitude, and attitude, an EFIS presents this information on one or more Liquid Crystal Display (LCD) screens. This move to a "glass cockpit" drastically improves a pilot's ability to monitor the aircraft's status and surrounding environment.

The Key Components of an EFIS

While specific setups can vary, most EFIS configurations are built around two primary displays: the PFD and the MFD.

Primary Flight Display (PFD)

This is the most crucial component, often called the "six-pack" of the digital age. The PFD presents the essential information needed for controlling the aircraft in flight. It integrates key flight parameters into one cohesive view, which typically includes:

• Attitude Indicator (Artificial Horizon): Displays the aircraft's pitch and roll.

• Airspeed Indicator: Presents the current speed through the air on a digital "tape" or "ribbon." These tapes often include trend vectors—short lines that predict where the airspeed will be in the next few seconds—to help pilots anticipate changes.

• Altimeter: Shows the aircraft's altitude above a set reference.

• Vertical Speed Indicator (VSI): Indicates the rate of climb or descent.

• Heading Indicator: Displays the aircraft's magnetic heading.

Advanced PFDs can also overlay Flight Director cues, which are command bars that provide guidance for following a pre-programmed flight path, helping pilots make precise control inputs.

Multi-Function Display (MFD)

The MFD is a versatile screen that can display a variety of information depending on the pilot's needs. Its primary function is to enhance situational awareness by integrating data from various systems. Common MFD displays include:

• Navigation Display: A moving map that shows the aircraft's position relative to waypoints, flight plans, and navigation aids.

• Weather Overlays: Displays real-time weather information from onboard radar or a datalink service (like FIS-B), showing storm cells and precipitation.

• Traffic Information: Integrates data from a Traffic Collision Avoidance System (TCAS) or ADS-B to display nearby aircraft, including their altitude and trajectory.

• Engine & System Monitoring (EICAS/ECAM): In larger aircraft, this system consolidates all engine and aircraft system parameters (oil pressure, hydraulic fluid) and provides alerts or checklists in a clear, digital format.

The Power Behind the Pixels: EFIS Architecture

The EFIS displays are merely the visual outputs of a highly integrated network of digital sensors and computers. Two key systems that feed the EFIS are:

• Attitude and Heading Reference System (AHRS): This is the brain behind the PFD's attitude and heading information. It uses solid-state sensors (magnetometers, accelerometers, and gyros) to determine the aircraft's orientation. This modern system is more reliable and requires less maintenance than traditional spinning gyroscopes.

• Air Data Computer (ADC): The ADC is a computer that receives inputs from the aircraft’s pitot-static system. It calculates and outputs crucial flight parameters like airspeed, altitude, and vertical speed to the EFIS displays.

All of these components communicate over a high-speed digital network called a data bus (e.g., ARINC 429), allowing for the seamless and rapid sharing of information.

Redundancy and Safety: A Top Priority

The reliance on electronics in EFIS cockpits is backed by a high degree of redundancy to ensure safety. Most systems feature:

• Dual Displays: Multiple displays for the PFD and MFD, allowing for a pilot to switch a display from one function to another in case of a screen failure.

• Independent Systems: The AHRS, ADC, and GPS receivers are often dual or triple redundant, ensuring a continuous supply of valid flight data.

• Standby Instruments: Despite the digital nature of the cockpit, most aircraft still have a small set of analog or self-powered digital standby instruments for the most critical parameters (attitude, airspeed, altitude) as a final failsafe against a total electrical failure.

The Modern Frontier of Flight

The EFIS represents more than a collection of digital gauges; it is a fundamental building block for many advanced avionics systems, from Flight Management Systems to autopilots. It has evolved from a simple replacement for gauges into a sophisticated, interconnected system that makes flying more intuitive, safer, and more efficient for the pilot. Understanding the EFIS is key to appreciating the sophistication and capabilities of today's modern aircraft cockpits.