During all starts, do not exceed what N1 value for how long after start, or until indications are normal?

• A. 75%N1; 2 minutes
• B. 80%N1; 1 minute
• C. 70%N1; 3 minutes
• D. 85%N1; 4 minutes

Answer: (A)

During a start, you need a controlled, gentle spool-up to light off the engine without stressing the core or the starter. Limiting N1 to 75% and holding it for about 2 minutes gives enough time for ignition and initial stabilization while keeping the rotor speed low enough to prevent compressor surge, overheating, or excessive turbine loading. You continue the start and allow N1 to rise toward normal operating levels once indications are normal—meaning oil pressure has come up, ITT is within limits, and RPM is stabilizing.

Raising the limit or extending the duration beyond this window increases risk: higher N1 too early can stress the engine and starter, and longer durations can waste starter life or fuel without added benefit. So the 75% N1 for about 2 minutes is the safest, most effective guideline while you verify proper indications.