Definition 1 of 2
Definition
A pump that has no moving parts and uses the venturi principle to move fluid. A high-velocity stream of fluid is directed through a narrowing passage, which lowers the pressure at that point and draws additional fluid in through a side inlet. The two streams combine and exit together.
Plain English
A pump with no moving parts. A fast-moving stream of fluid is forced through a narrow opening, and the resulting low pressure sucks more fluid in from the side. Both streams then flow out together.
Context Anchor
Commonly seen in aircraft fuel systems, where jet pumps may help move fuel from one part of a tank to another or help supply fuel to the engine system.
Derivation
The word 'jet' here means a fast, narrow stream of fluid forced through an opening — the same sense as a jet of water from a hose nozzle. The pump is named for the high-speed jet of fluid that does the work of pumping.
Why Pilots Care
Maintains fuel balance across tanks and prevents engine starvation from unported or trapped fuel.
Analogy
It is like water flowing quickly past the end of a small tube and pulling liquid up through that tube. The moving stream does the work without a separate moving pump part.
Intuition Check
Do not assume jet pump means a pump for a jet engine. Here, jet means a high-speed stream of fluid used to create suction and move more fluid.
Example Sentence 1
The aircraft uses a jet pump to transfer fuel from the outboard tank into the main tank.
Example Sentence 2
During the preflight inspection the mechanic confirmed the jet pump was scavenging fuel from the sump area.