What is the acceptable range for N_1 during takeoff?

The acceptable range for N_1 during takeoff is indeed 67% to 70%. This range is critical as it indicates the required engine performance for takeoff, ensuring that the aircraft has sufficient thrust for a safe and effective departure. Proper adherence to this range is essential for maintaining engine efficiency and ensuring the aircraft can clear any obstacles during takeoff climb.

While 65% to 67% might seem like an acceptable range on the lower end, it does not meet the minimum requirements to guarantee safety and performance standards during takeoff. Operating outside the specified limits can lead to inadequate thrust, performance issues, or engine strain, which may compromise flight safety. Therefore, understanding and following the appropriate N_1 percentages for takeoff is crucial for pilots to ensure operational integrity and safety.