What is the maximum altitude at which the gravity-fed fuel system should still function?

What is the maximum altitude at which the gravity-fed fuel system should still function?

• A. 25,000 feet
• B. 20,000 feet
• C. 15,000 feet
• D. 30,000 feet

Answer: (A)

Gravity-fed fuel systems rely on the weight of the fuel to push it to the engine when pumps aren’t supplying it. As you climb, ambient pressure drops and fuel can vaporize in the lines, reducing the pressure available to push fuel to the engine. That limits how high the system can reliably operate on gravity alone. For this aircraft, that reliable gravity feed is up to about 25,000 feet. Below that, gravity head is sufficient to feed the engine; above that, you’d risk fuel starvation and would depend on powered pumps to maintain flow.

Gravity-fed fuel systems rely on the weight of the fuel to push it to the engine when pumps aren’t supplying it. As you climb, ambient pressure drops and fuel can vaporize in the lines, reducing the pressure available to push fuel to the engine. That limits how high the system can reliably operate on gravity alone. For this aircraft, that reliable gravity feed is up to about 25,000 feet. Below that, gravity head is sufficient to feed the engine; above that, you’d risk fuel starvation and would depend on powered pumps to maintain flow.