Definition
A condition in which a fuel tank outlet (port) becomes momentarily uncovered by fuel during certain flight attitudes or maneuvers, allowing air to enter the fuel line and interrupt fuel flow to the engine. Unporting is most likely to occur when fuel quantity is low and the airplane is in a nose-high attitude, in a slip, or in a skid that pushes fuel away from the outlet.
Plain English
When the fuel in a tank sloshes away from the small opening that feeds the engine, air gets drawn in instead of fuel. The engine can hesitate or quit because it is briefly being fed air rather than fuel.
Context Anchor
Encountered in takeoff and climb discussions, especially when aircraft attitude, acceleration, or low fuel can make fuel move inside the tank.
Derivation
Built from 'un-' (reversal) and 'port' (an opening or outlet). The fuel tank outlet is called a port; when fuel no longer covers it, the port is 'un-covered' — hence 'unporting.'
Why Pilots Care
Marks the transition from high-drag displacement mode to lower-drag planing mode, directly affecting acceleration and the length of the takeoff run.
Analogy
It is like tipping a drink container so the straw is no longer in the liquid. The container still has liquid in it, but the straw can pull air instead of liquid.
Intuition Check
Unporting does not mean removing a port from the airplane. It means the fuel has moved away from the tank opening that feeds the engine.
Example Sentence 1
With only a few gallons remaining in each tank, the instructor warned that a prolonged slip on final could cause unporting and a brief loss of engine power.
Example Sentence 2
Smooth power application helps produce clean unporting without the nose pitching up and down.