Definition
An aircraft system that allows the flight crew to dump fuel overboard in flight to quickly reduce aircraft weight. It typically consists of pumps, valves, dedicated plumbing, and dump nozzles or masts located on the wings, allowing fuel to be discharged at a controlled rate while preventing the tanks from being emptied below a safe minimum reserve.
Plain English
A built-in way for the crew to release fuel out of the aircraft while flying, so the aircraft becomes light enough to land safely.
Context Anchor
Seen in large-aircraft systems, emergency procedures, weight-limit discussions, and maintenance checks of fuel valves, lines, pumps, controls, and outlet nozzles.
Derivation
Jettison comes from the Old French getaison, meaning 'a throwing,' from Latin iactare, 'to throw.' Historically it referred to throwing cargo overboard from a ship in distress. The aviation use carries the same idea: deliberately throwing something overboard, in this case fuel, to lighten the aircraft.
Why Pilots Care
Reduces landing weight to stay within structural and runway limits, preventing damage or runway overrun after a takeoff emergency.
Analogy
Like tossing sandbags out of a balloon so it can descend safely.
Grounding Statement
Picture a heavy airplane shortly after takeoff needing to return: the system provides a controlled way to get rid of fuel before landing.
Intuition Check
A fuel jettison system is not a fuel leak and not normal fuel use by the engines. It is a controlled, intentional system for dumping fuel when procedures call for it.
Example Sentence 1
After an engine warning shortly after takeoff, the crew used the fuel jettison system to reduce weight before returning for landing.
Example Sentence 2
During the walk-around, the technician checked the fuel jettison system nozzles for proper operation.