Plain English Meaning
Fuel coming out of the airplane somewhere it shouldn't — through a loose fitting, a damaged line, a worn seal, or a tank that isn't sealed properly.
Full Definition
The unintended escape of fuel from any part of the airplane's fuel system, including tanks, lines, fittings, drains, vents, fuel caps, or the engine fuel system. Leakage may appear as visible drips, wet stains, blue dye streaks on the airframe, or a persistent fuel odor.
Context Anchor
Seen during preflight inspection, especially when checking fuel tanks, caps, drains, the underside of the wing or fuselage, and the engine area.
Why Pilots Care
Fuel leakage creates an immediate fire hazard, risks fuel starvation in flight, and indicates a problem that must be .