Definition
A backup display mode in a glass cockpit (electronic flight display) system that consolidates the primary flight instruments and engine information onto a single working screen when the other screen fails. The remaining display reverts to showing all critical flight data so the pilot retains the essential information needed to fly the aircraft.
Plain English
If one of the cockpit screens stops working, the other screen automatically rearranges itself to show all the most important flight information on that one screen so the pilot can keep flying safely.
Context Anchor
Seen in glass-cockpit aircraft when discussing what happens after a cockpit display fails, especially during instrument flying or display-failure training.
Derivation
From 'revert,' Latin 'revertere' meaning 'to turn back.' A reversionary display 'turns back' to a fallback layout when normal operation fails. Knowing this helps the pilot remember it is a backup mode, not the standard mode.
Why Pilots Care
Maintains access to attitude, airspeed, altitude, and navigation data after a display failure, preventing loss of situational awareness in instrument conditions.
Intuition Check
Reversionary does not mean the display is old, less accurate, or optional. It means the system has shifted to a backup display layout after the normal layout is no longer available.
Example Sentence 1
When the MFD failed in cruise, the system switched to reversionary display and the pilot saw the engine instruments combined with the flight data on the remaining screen.
Example Sentence 2
During the preflight check the pilot verified that reversionary mode would engage correctly if either screen malfunctioned.