What are two types of fuel nozzles?

• A. Primary and Secondary
• B. Fixed and Movable
• C. Variable and Fixed
• D. Simplex and Duplex

Answer: (D)

Fuel nozzles in aviation fuel systems are commonly categorized by how many spray paths they use. A simplex nozzle has a single spray orifice that atomizes fuel into one jet. A duplex nozzle provides two spray paths (two orifices) within the same nozzle, producing two coordinated sprays. This dual-path design improves fuel atomization and distribution in the incoming air, especially at higher engine power, leading to more uniform combustion. Because the question asks for two types of fuel nozzles, simplex and duplex is the standard pairing, making it the best answer. Other terms like primary/secondary or fixed/movable describe different concepts and aren’t the conventional way to classify nozzle designs.