What are the two types of aircraft fuel systems?

• A. Gravity fed systems
• B. Pressurized systems
• C. Gravity fed systems or pressurized systems
• D. Manual fuel systems

Answer: (C)

Fuel delivery to the engine is organized into two main arrangements: gravity-fed and pressurized (pump-driven). In gravity-fed systems, fuel flows from the tanks to the engine simply by the weight of the fuel—the tanks must be positioned so gravity can supply the engine, and no pump is required for normal operation (though an auxiliary pump may be used for priming or transferring fuel). In a pressurized system, an engine-driven pump (with a possible backup electric pump) creates pressure to push fuel to the engine, providing a steady supply regardless of fuel head or aircraft attitude. These two cover the typical methods used, with manual priming being a secondary feature rather than a primary category.