Definition
A backup display configuration in a glass cockpit where, if either the Primary Flight Display (PFD) or the Multi-Function Display (MFD) fails, the surviving screen automatically (or manually, depending on the system) consolidates the essential flight, navigation, and engine information onto a single screen so the pilot can continue to fly and navigate safely.
Plain English
If one of the cockpit screens goes blank or fails, the other screen takes over and shows the most important flight and engine information together, so you still have what you need to fly the airplane.
Context Anchor
Seen in glass-cockpit aircraft during instrument flying, especially when the main flight screen or map-and-systems screen fails or goes blank.
Derivation
‘Reversionary’ comes from the Latin revertere, meaning ‘to turn back.’ The system reverts — turns back — to a simpler, combined display when the normal split-screen setup is no longer available.
Why Pilots Care
Reversionary mode prevents total loss of flight information, allowing the pilot to maintain control and complete the flight using the remaining display.
Grounding Statement
The key idea is that a failed screen does not always mean the information is gone; it may be moved to another screen in a backup layout.
Intuition Check
Do not assume reversionary mode fixes the failed display. It does not repair the screen; it changes what the remaining screen shows.
Example Sentence 1
When the MFD went dark in cruise, the PFD automatically entered reversionary mode and displayed engine indications alongside the flight instruments.
Example Sentence 2
The pilot immediately recognized the reversionary mode symbology and continued the approach using the backup display configuration.