For gravity-fed fuel systems, up to what altitude is it guaranteed to operate?

For gravity-fed fuel systems, up to what altitude is it guaranteed to operate?

• A. Up to 6,000 feet
• B. Up to 10,000 feet
• C. Up to 15,000 feet
• D. Up to 25,000 feet

Answer: (A)

Gravity-fed fuel systems rely on the weight of the fuel to push it to the engine, with no pump boosting the pressure. The pressure at the engine is set by the hydrostatic head of the fuel column plus the atmospheric pressure at the fuel surface. As you climb, the outside air pressure drops, so the pressure available at the engine end falls as well. There’s a practical limit where the head pressure is no longer enough to meet the engine’s fuel flow needs, especially at high power. For typical light aircraft with gravity-fed systems, that guaranteed operating altitude is about 6,000 feet. At higher altitudes, fuel pressure can become insufficient, leading to possible fuel starvation.

Gravity-fed fuel systems rely on the weight of the fuel to push it to the engine, with no pump boosting the pressure. The pressure at the engine is set by the hydrostatic head of the fuel column plus the atmospheric pressure at the fuel surface. As you climb, the outside air pressure drops, so the pressure available at the engine end falls as well. There’s a practical limit where the head pressure is no longer enough to meet the engine’s fuel flow needs, especially at high power. For typical light aircraft with gravity-fed systems, that guaranteed operating altitude is about 6,000 feet. At higher altitudes, fuel pressure can become insufficient, leading to possible fuel starvation.