What is the propeller overspeed limit?

The correct choice is 110% Np for the propeller overspeed limit. This limit is established to protect the propeller and the engine from operating at excessively high speeds that could cause mechanical failure or damage. When the propeller exceeds this limit, it can lead to serious safety risks, including catastrophic failure of the propeller blades, which may endanger the aircraft's flight characteristics and overall stability.

In flight operations, it's critical to maintain the propeller speed within specified limits to ensure safe and efficient performance. Exceeding 110% Np indicates a malfunction or abnormal condition that needs immediate attention, thus highlighting the importance of adhering strictly to these operational limits to ensure safety in the aircraft.