A flow increase valve operates to increase the volume of bleed air flowing through the venturi of the ACM when the engine thrust lever is set:

• A. Above 60% N1
• B. Below 60% N1
• C. At 60% N1
• D. Idle

Answer: (B)

The flow increase valve is part of the environmental control system that ensures enough bleed air passes through the ACM’s venturi to drive the air cycle machine and supply conditioned air. When the engine thrust lever is set below 60% N1, the bleed air available from the engines drops, so the valve opens to increase the volume of bleed air flowing through the ACM venturi. This keeps the ACM operating effectively, maintaining cabin pressure and temperature even at reduced thrust. At idle or when thrust is above that threshold, the bleed flow is typically sufficient or managed by other control paths, so the flow increase valve isn’t needed. That’s why the correct setting is below 60% N1.