What is a common message received from RAIM indicating an issue?

The common message received from RAIM (Receiver Autonomous Integrity Monitoring) indicating an issue is that there are not enough satellites. RAIM is a technology used in GPS receivers to ensure the accuracy and integrity of the position being reported. For RAIM to function effectively, the system needs a minimum of five satellites to perform integrity checks. If fewer satellites are available, RAIM cannot verify the accuracy of the GPS signals, leading to a warning that indicates a potential issue with navigation reliability.

This message is essential as it informs the pilot that the GPS system may not provide accurate positioning data due to inadequate satellite coverage, which is critical for safe navigation, especially during instrument flight. Hence, it serves as a caution to the pilot that they may need to rely on alternative navigation methods until adequate satellite coverage is restored.