During takeoff, what is the allowable fluctuation percentage for Np when PMU is off?

When the PMU (Power Management Unit) is off during takeoff, the allowable fluctuation percentage for Np (propeller speed) is vital for ensuring safe engine operation. The correct answer of 2% reflects the tolerance level that pilots must maintain for acceptable performance of the aircraft's systems.

This fluctuation percentage is crucial because it indicates the range of acceptable variation in the propeller speed during critical phases of flight, such as takeoff. Keeping Np within the specified limits allows for optimal performance and prevents potential issues that could arise from excessive fluctuation, such as engine instability or power loss.

This 2% threshold is established to provide a balance between operational safety and performance, ensuring pilots can manage engine parameters effectively while maintaining control of the aircraft. It is essential for flight training to understand these limits, as they play a significant role in safe aircraft operation and adherence to flight regulations.