Definition
An electronic cockpit screen that consolidates the core flight instruments — attitude, airspeed, altitude, vertical speed, heading, and slip/skid indication — into a single integrated display, replacing the traditional six-pack of mechanical gauges in glass-cockpit airplanes.
Plain English
A single screen in front of the pilot that shows all the basic flying information — how the airplane is pointing, how fast it is going, how high it is, and which way it is heading — instead of having a separate round gauge for each one.
Context Anchor
Seen in glass-panel cockpits, especially during normal instrument scanning, takeoff, climb, cruise, approach, and landing.
Derivation
Primary because it shows the most important flight information the pilot needs to fly the airplane, and Display because it presents that information on a screen rather than through individual mechanical instruments.
Why Pilots Care
It reduces instrument scan time and workload, allowing faster recognition of flight path deviations.
Intuition Check
Primary does not mean it is the only display or the only instrument to trust. It means it is the main display for basic flight control information.
Example Sentence 1
After engine start, the pilot scanned the PFD to confirm the attitude indicator, airspeed tape, and altitude readout were all showing valid data.
Example Sentence 2
During the instrument approach the PFD showed a decreasing altitude trend.