What should responders know about fuel tanks and fuel systems?

• A. Fuel tanks may be vented; external tanks can be jettisoned; fuel lines may range 1/8-4 in and operate about 4-40 psi.
• B. Fuel tanks are always sealed and never vented; external tanks cannot be jettisoned; fuel lines are always 8-12 inches; pressure 100-200 psi.
• C. Fuel tanks vented; external tanks can be jettisoned only under certain conditions; fuel lines are 1-8 inches; pressure 1-5 psi.
• D. Fuel tanks are permanently sealed; external tanks are permanent; fuel lines vary from 1/16 to 2 inches; pressure 10-100 psi.

Answer: (C)

Understanding how aircraft fuel systems manage venting, jettison capability, and line pressure helps you anticipate what firefighters may encounter near fuel tanks. Fuel tanks are vented to relieve vapor pressure as fuel moves and temperatures change, preventing pressure buildup and venting flammable vapors. External tanks exist on some aircraft, and they can be jettisoned, but only under specific conditions such as emergency situations or weight and balance considerations dictated by the aircraft design. This isn’t automatic or universal for every flight, and crews rely on defined procedures to release external tanks when needed.

Fuel lines in aircraft are designed to be small in diameter and operate at relatively low pressure, because the system typically uses pumps and gravity to feed fuel to the engines or tanks rather than delivering it under high pressure. That combination of venting, limited and conditional jettison capability, and low-pressure, small-diameter fuel lines aligns with how airframes manage fuel safely. The other statements contradict common fuel-system design—tanks that are not vented, external tanks that cannot be jettisoned, or lines that are large and high-pressure—so they don’t fit real-world operation.