Which of the following is NOT an indication of ADHARS failure?

In the context of aircraft systems, specifically relating to the Advanced Digital Head-Up Display (ADHARS), it's crucial to understand the functions of different flight parameters and what indicates a failure in these systems. An indication of ADHARS failure typically involves the failure of critical flight data references like attitude, heading, and altitude.

Attitude, heading, and altitude are fundamental components derived from the ADHARS, and their failure would directly impact the pilot's ability to control the aircraft. However, speed information does not traditionally rely on ADHARS as it is sourced differently, typically from pitot-static systems. The speed readout may be more associated with airspeed indicators that rely on other systems and instrumentation, making it less likely to be classified as an indicator of ADHARS failure.

Because speed is generated through separate systems and does not directly correlate with the ADHARS, it stands out as the correct answer, indicating that it is not a failure symptom of the ADHARS. This understanding highlights the interconnectedness of aircraft systems while also clarifying which parameters are monitored for a specific failure scenario.