What is the transient N2 percentage limit?

• A. 101-103%
• B. 105%
• C. 108% for 10 seconds
• D. 103.2% for 5 minutes

Answer: (C)

The transient N2 percentage limit of 108% for 10 seconds is established to ensure operational safety and engine performance during dynamic conditions such as abrupt changes in power demand or conditions that push the engine beyond its normal operational limits. This limit allows for temporary exceedance of the maximum continuous operating speed of the N2 rotor, providing some leeway for pilot maneuvers and tactical situations.

This limit is specifically designed to accommodate short-duration performance needs while preventing potential damage to the engine. It is essential for pilots to understand these transient limits to effectively manage engine performance under various flight profiles, especially in critical scenarios where engine responsiveness is vital.

The choice of 108% for 10 seconds represents a strategic balance between performance requirements and the inherent safety margins built into the engine design, ensuring that the transient operation does not lead to failure or excessive wear when the limits are respected.