What is the maximum Np when the PMU is off?

The maximum Np, or propeller speed, when the PMU (Power Management Unit) is off is 100% +/- 2%. This specification is important due to the operating limits of the T-6A aircraft. When the PMU is off, it allows for some manual control over engine parameters, including the propeller speed. However, exceeding this maximum limit can lead to various performance or safety issues, as the propeller design and engine capabilities have strict operational thresholds.

The tolerance of +/- 2% provides an acceptable range around the nominal value, which helps pilots understand the limits they have to operate within. If the propeller speed falls below or exceeds this range, it can affect the efficiency of the aircraft's performance and risk engine damage.

Understanding this limit underscores the importance of adhering to operational parameters in aircraft systems to ensure safe and efficient flight operations.