What is the function of "reversionary mode" on primary displays?

The function of "reversionary mode" on primary displays is specifically designed to switch to backup instruments should the primary display systems encounter a failure. This mode ensures that pilots maintain access to critical flight information even if the main systems are compromised. In situations where a malfunction occurs, the reversionary mode activates backup displays, enabling continued monitoring of essential data such as altitude, airspeed, and heading. This capability is crucial for maintaining safety and situational awareness during flight, particularly in high-pressure scenarios where reliance on primary displays might become risky.

Enhancing navigation capabilities, improving brightness, or providing a detailed flight plan do not directly relate to the primary purpose of the reversionary mode, which is fundamentally centered around instrument redundancy and reliability.