During engine warm-up, do not exceed what percentage of N1 for two minutes?

• A. 50%
• B. 75%
• C. 85%
• D. 95%

Answer: (B)

During engine warm-up procedures, it is critical to avoid exceeding 75% N1 for the first two minutes after engine start. This limitation is in place to ensure the integrity and longevity of engine components while allowing necessary warm-up, which helps to stabilize engine temperatures and pressures. Operating above this threshold prematurely could place excessive stress on engine components that are not yet at optimal operating temperature, potentially leading to mechanical failures or reduced performance.

In the context of the operation of the CRJ 900, adhering to this limitation aids in maintaining engine health, ensuring that all systems function correctly, and prolongs the operational life of the engine. It also helps pilots develop safe operating habits that align with manufacturer guidance and operational protocols. Therefore, the correct percentage of N1 during engine warm-up is 75%.