Which message indicates that the RAT did not deploy during an electrical emergency?

The message indicating that the RAT (Ram Air Turbine) did not deploy during an electrical emergency is specifically designed to alert the flight crew to the situation concerning the emergency power system. When the RAT is required to deploy but fails to do so, a direct indication is given to emphasize that the auxiliary power source is not available, which is critical for maintaining essential systems during an emergency.

The message "BATT DISCHARGING" implies a state of battery usage and can indicate that the battery power is being depleted, but it does not specifically denote whether the RAT has deployed or failed to deploy. Conversely, the appropriate indication that reflects RAT deployment failures would be more straightforward and explicit, reinforcing the importance of the RAT in providing backup power when the main power is lost.

In contrast, other options provide information about various conditions regarding electrical power status but do not directly indicate RAT deployment status. Therefore, identifying the clear communication regarding RAT status helps maintain situational awareness for the flight crew in emergency scenarios.