What Are Primary Flight Displays in Aircraft?

Located within the cockpit, flight displays are an essential part of the flight deck where all instrumental readings may be monitored. Commonly consisting of flight instruments that rely on air pressure, barometric readings, and gyroscopes, flight displays and their instruments help provide the pilot with altitude, airspeed, vertical speed, runway diagrams, and various other functions. Although specific placement of the combined instruments is dependent on a manufacturer's overall design, the consolidation of these devices allows for the construction of the primary flight displays (PFDs) that are commonly seen in modern aircraft.

Replacing older displays using mechanical gauges and dials, most aircraft now utilize electronic flight systems and devices. Evolving from the use of cathode ray tubes (CRT) to liquid crystal displays (LCD), these components have succeeded most flight instruments available to a pilot. Typical EFIS systems encompass the PFD, electronic attitude direction indicator (EADI), and the navigation display. Below, we will highlight the key components necessary in every PFD and how each component within such equipment functions in tandem to provide a central LCD display of information for pilots.

Attitude Indicator

Projecting a reading upon the pilot's main display, the central attitude indicator depicts an aircraft's orientation relative to the earth's horizon. At face value, this instrument portrays a small-scale plane surrounded by parameters indicating the aircraft position in comparison to the horizon. Divided horizontally through the middle of the display to provide a visible separation between land and sky, this component is used to depict the vehicle's angle of bank.

Vertical Speed Indicator

An aircraft's vertical speed can be depicted on a display as a thin vertical ribbon at the outermost sides of an electronic attitude direction indicator (EADI). Although older model aircraft make use of circular scale and needle instruments to determine vertical speed, both modern and pre-existing types calculate such information based off of static pressure received from the pitot-static system.

Airspeed Indicator

Comparing static pressure to the compression being supplied by an aircraft's forward motion, known as total pressure, an airspeed indicator can calculate an aircraft's changes in speed. This is achieved through the pitot tube and the internal components of the indicator, that of which is a device usually filled with mercury or parts capable of conducting measurements.

Heading Indicator

Found on the flight display, this device is used alongside a compass to determine which direction an aircraft is heading. Previously known as directional gyros, heading indicators ascertain direction with the use of a rotating gyro affixed along a vertical plane.

Turn Coordinator

The turn coordinator and the turn and slip indicator are two separate instruments that are contained within a single device. Functioning as gyroscopic instruments, these components operate off of the property of precession in order to calculate an aircraft's rate of change in the direction an aircraft is heading as well as its slip or skid.


For the purpose of measuring how high an aircraft is from the ground, altimeters take advantage of static ports. These ports, embedded within the vehicle's body, allow ambient pressure to be directed towards the altimeter. Subsequently sent to an aneroid, this small component within the altimeter expands or contracts when exposed to changes in altitude pressure.


A common component aiding in calculating key readings for the PFD are gyroscopes. Used for instruments such as attitude indicators, compasses, and turn indicators, gyroscopes are components constructed out of gimbals and rings fixed to a gyro. Rotating at high speeds of RPM with the assistance of a vacuum or pressure system, these mechanical devices are allowed to rotate with relative freedom with rigidity and precession. Typically, these parts are used to calculate, generate, and define direction.

For a trusted supplier of primary flight display parts and components, look no further than Fulfillment by ASAP. Whether for modern PFDs or parts or those within a mechanical gauge board, we provide qualifying certifications or manufacturing trace documentation for every purchase as applicable. If you would like to request a quote for your comparisons, you can submit an RFQ form as provided on our website. Upon receipt, a dedicated account manager will quickly review and respond with a personalized solution to your needs in just 15 minutes or less, 24/7x365.


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