During start, the thrust lever should be moved from shutoff at what percent N2?

• A. 10% N2
• B. 20% N2
• C. 30% N2
• D. 40% N2

Answer: (B)

During start, fuel is not introduced until the core is turning fast enough to support reliable ignition. The threshold at which light-off can be achieved safely is around 20% N2, so moving the thrust lever from shutoff to the start/idle position at about this speed ensures there is enough airflow for the fuel-air mixture to ignite and sustain the flame. If you go to 10% N2, there’s typically not enough air for ignition, so light-off won’t occur. Waiting until 30% or 40% N2 delays ignition and can waste time or complicate the start. So, 20% N2 is the appropriate point to transition from shutoff.