What is the allowable Np during stabilized ground operations?

During stabilized ground operations, the allowable Np (propeller speed) range is set to ensure the safe and efficient operation of the aircraft’s propeller system. The correct range of 62% to 80% is specified to maintain optimal performance while the aircraft is on the ground. This range is critical because it allows for adequate thrust without risking over-torque conditions that could potentially lead to mechanical failures or unsafe operating conditions.

Operating within this range provides a good balance between maintaining engine efficiency and ensuring that the propeller does not experience undue stress or vibration, which could lead to damage or operational issues during ground operations. Understanding these limits ensures pilots can manage engine performance correctly during taxi, takeoff preparations, and other ground activities, promoting safety and aircraft integrity.