Which statement is true about typical fuel system configurations described?

• A. The two main system types are gravity fed and pressurized
• B. All tanks are fully sealed with no vent
• C. No fuel pumps are required in any system
• D. Cross feed is never used in two-engine aircraft

Answer: (A)

Fuel systems in aircraft generally fall into two main approaches: gravity-fed and pressurized (pumped). In gravity-fed layouts, fuel flows to the engine mainly by gravity, with tanks positioned above the engine inlet so a natural head of fuel provides the flow. These systems still require venting to prevent pressure buildup and allow air to replace the fuel as it moves; a boost or transfer pump may be used to ensure reliable feed when needed. In pumped systems, pumps create the pressure to move fuel to the engine, which helps maintain consistent flow during high power, maneuvers, or at various attitudes. Some airplanes use both: gravity head supplemented by a pump for reliability.

This makes the statement that the two main system types are gravity-fed and pressurized correct. The other ideas aren’t true in typical configurations: tanks are not left completely sealed without venting; pumps are usually present in some form to ensure fuel delivery; and cross-feed between tanks is commonly used in multi-engine aircraft to balance fuel and ensure continued engine supply.