What action is performed to test the MFD?

To test the Multifunction Display (MFD), Control 4 is the action performed. This control is specifically designed to execute diagnostics and test various functions of the MFD to ensure its operational integrity. The testing process may involve checking the display for color, contrast, brightness, and response to various inputs, ensuring that all features function correctly and that the display is fully operational for flight duties.

Other controls may perform different functions that are not related to MFD testing, such as managing other cockpit displays, settings, or systems that do not pertain directly to the MFD's performance. Therefore, using Control 4 is essential for effectively verifying the functionality of the MFD, which is critical for situational awareness and navigation during flight operations.