What must the hydraulic fluid level indicator read to indicate a full reservoir?

A full hydraulic fluid reservoir in the T-6A should read "FULL AC or FULL AD." This indicates that the hydraulic system is properly filled to the required level, ensuring optimal performance of flight control surfaces and other hydraulic components. Having a clear and accurate reading of the hydraulic fluid level is crucial for operational safety and reliability, as insufficient fluid can lead to system failure.

The other options do not reliably indicate a full reservoir. Fluctuating readings may occur due to various factors but do not convey a precise status of the fluid level. "NEAR EMPTY" clearly indicates that the hydraulic fluid reservoir is low, which could pose a risk during flight operations. Lastly, "CONFLICTING INDICATORS" suggests uncertainty in the system status, which is not only inadequate for confirming a full reservoir but also raises safety concerns regarding the operation of the aircraft's hydraulic system.