What indication should a pilot look for that suggests a failure of the AHRS?

The indication that suggests a failure of the Attitude and Heading Reference System (AHRS) is reflected by an "Attitude fail" message on the Electronic Attitude Display Indicator (EADI). This message indicates that the AHRS has encountered a significant issue that compromises its ability to provide accurate flight attitude data.

The AHRS is essential for providing pilots with vital information about the aircraft's orientation relative to the earth’s horizon. When the system fails, it can no longer accurately determine or display this information, which is critical for safe flight operations. Thus, when pilots see an "Attitude fail" alert, it is a direct and clear indication of AHRS malfunction, prompting further investigation or appropriate action.

Other options may point to various flight system problems but do not specifically correlate directly to an AHRS failure. For example, a heading displayed in red could indicate a malfunction but is not definitive of AHRS failure alone; warning tones might signify a wide range of system alerts unrelated to AHRS, and a GPS malfunction may indicate issues with navigation or positioning systems rather than attitude or heading reference systems.