Bleed valve position for take-off from a short runway at MTOW to maximize mass air flow?

• A. ON
• B. OFF
• C. Partially Open
• D. Closed

Answer: (B)

Maximizing the air mass flowing through the engine requires not taking bleed air from the compressor. Bleed air is tapped off to supply other systems (packs, anti-ice, etc.), so when the bleed valve is open or partially open, some compressor air is diverted away from the engine core, reducing thrust. To get the most core mass flow and therefore the most thrust for takeoff, you set the bleed system to OFF so no bleed air is drawn. Only if anti-ice or environmental systems truly need bleed air would you enable it; for the goal of maximizing mass flow on a short MTOW takeoff, OFF is the best choice.