Where does gravity flow function in the Citation Longitude's fuel system?

• A. In the Air
• B. On the Ground
• C. Both In Air And On Ground
• D. Gravity flow does not function on the ground

Answer: (D)

Gravity flow relies on a fuel head from higher tanks feeding into the engine lines without pump assistance. In the Citation Longitude, that path is designed to be active only when the aircraft is in flight. On the ground, the fuel system valves and routing prevent gravity from delivering fuel to the engines, so fuel delivery on the ground depends on pumps instead. In short, gravity flow is not functional on the ground.