The event that closes the start valve occurs as N2 reaches ______.

The event that closes the start valve occurs as N2 reaches ______.

• A. 75%
• B. 65%
• C. 50%
• D. 80%

Answer: (B)

During an A320 engine start, the start valve opens to feed the pneumatic starter with high‑pressure air. As the core speed (N2) climbs to a point where ignition can be established and the engine can run on its own, the valve automatically closes. That transition occurs at about 65% N2, ensuring the engine is ignited and self-sustaining before the starter air is cut off. Opening the valve too long or closing it too early would either waste bleed air or risk an unstable start, respectively, so 65% N2 is the appropriate threshold.

During an A320 engine start, the start valve opens to feed the pneumatic starter with high‑pressure air. As the core speed (N2) climbs to a point where ignition can be established and the engine can run on its own, the valve automatically closes. That transition occurs at about 65% N2, ensuring the engine is ignited and self-sustaining before the starter air is cut off. Opening the valve too long or closing it too early would either waste bleed air or risk an unstable start, respectively, so 65% N2 is the appropriate threshold.