What is the purpose for an expansion space in the fuel tank?

• A. Allows for an increase in temperature
• B. Prevents expansion of fuel
• C. Increases fuel capacity
• D. Reduces vaporization

Answer: (A)

The main idea is that liquids expand when heated. In an aircraft fuel tank, fuel can warm from sun and flight conditions, causing a small increase in volume. The expansion space gives room for that extra liquid, preventing overflow or overpressure and avoiding fuel venting or tank stress. This is why the purpose is described as allowing the fuel to expand with temperature. The others don’t fit: expanding isn’t prevented, the headspace doesn’t increase the tank’s usable fuel capacity, and while some vapor forms, the expansion space isn’t intended to reduce vaporization.