Why does the fuel system operate on negative pressure?

Why does the fuel system operate on negative pressure?

• A. To reduce fuel consumption
• B. To lessen the potential of fire in case of fuel system damage
• C. To increase system pressure
• D. To improve engine idle stability

Answer: (B)

Negative pressure keeps the fuel system under suction rather than push, so a leak tends to draw air in instead of spraying fuel out. This greatly reduces the amount of flammable liquid that could be expelled and ignite if a line is damaged, which is a critical safety feature in flight. The engine-driven pumps create and maintain this slight suction, pulling fuel from the tanks to the engine and helping ensure a steady supply even as the helicopter maneuvers. So, the design choice is about safety—minimizing fire risk in case of damage—rather than changing fuel use, increasing system pressure, or improving idle stability.

Negative pressure keeps the fuel system under suction rather than push, so a leak tends to draw air in instead of spraying fuel out. This greatly reduces the amount of flammable liquid that could be expelled and ignite if a line is damaged, which is a critical safety feature in flight. The engine-driven pumps create and maintain this slight suction, pulling fuel from the tanks to the engine and helping ensure a steady supply even as the helicopter maneuvers. So, the design choice is about safety—minimizing fire risk in case of damage—rather than changing fuel use, increasing system pressure, or improving idle stability.