Which statement is true about fuel lines on aircraft?

• A. Fuel lines may range 1/8-4 inches in diameter and operate about 4-40 psi.
• B. Fuel lines are always a fixed 2 inches in diameter.
• C. Fuel lines may range from 1/2 to 6 inches and operate at 50-60 psi.
• D. Fuel lines are not used in aircraft fuel systems.

Answer: (A)

Fuel lines vary in both size and pressure because different parts of an aircraft’s fuel system have different flow needs and operating environments. Because of that, you’ll see lines as small as about 1/8 inch for some feed or vent paths and as large as around 4 inches for main supply lines. The pressures in these lines are typically modest and spread across a range roughly from 4 to 40 psi, depending on the system and aircraft type. This combination of wide diameter variation and relatively low to moderate pressures reflects how fuel is moved safely from tanks to engines, through pumps and regulators, without forcing every line to a single size or pressure. The other statements imply a fixed size, an unrealistically large range and higher pressures, or that fuel lines aren’t used at all, none of which align with how aircraft fuel systems are actually designed.