What is the transient N1 percentage limit?

• A. 103.2% for 5 minutes
• B. 108% for 10 seconds
• C. 103.8% for 30 seconds
• D. 101-103%

Answer: (C)

The transient N1 percentage limit of 103.8% for 30 seconds is specified in operational guidelines to accommodate situations where brief, increased engine speed is required, for instance during takeoff or certain emergency scenarios. This limit acknowledges the need for the engine to perform beyond its normal operational range for short durations, thus allowing for enhanced performance when necessary.

The specification of 30 seconds for this transient condition ensures that the engine can handle the increased stress without compromising safety or reliability, as longer durations could lead to potential engine damage or failure. Ensuring adherence to the maximum limit is vital as exceeding it can lead to adverse effects on engine health.

In contrast, other options either exceed the recommended transient limits or involve different durations that do not align with the established guidelines for transient operation in the TH-73A. This reinforces the importance of understanding and applying the correct transient N1 limits to maintain the integrity and performance of the aircraft engine.