During the start, the start valve closes _______.

During the start, the start valve closes _______.

• A. Manually by pilot
• B. At engine stop
• C. When N2 reaches 20%
• D. Automatically when N2 reaches 65%

Answer: (D)

During start, bleed air is supplied to the pneumatic starter through the start valve. This valve is designed to close automatically once the engine RPM reaches a sufficient speed, specifically around 65% N2. The automatic shutoff stops the starter air at the right moment, allowing the engine to continue spooling up and transition to normal operation without the risk of overstressing the starter or wasting bleed air. The pilot does not manually close it, and it is not tied to engine stop or to a lower N2 value like 20%.

During start, bleed air is supplied to the pneumatic starter through the start valve. This valve is designed to close automatically once the engine RPM reaches a sufficient speed, specifically around 65% N2. The automatic shutoff stops the starter air at the right moment, allowing the engine to continue spooling up and transition to normal operation without the risk of overstressing the starter or wasting bleed air. The pilot does not manually close it, and it is not tied to engine stop or to a lower N2 value like 20%.