Definition
A hand-operated, double-acting reciprocating pump used in aircraft fuel and hydraulic systems. The operator moves a handle back and forth, and fluid is pumped on both the forward and return strokes. Wobble pumps are typically used to prime fuel lines before engine start, transfer fuel between tanks, or build up hydraulic pressure for systems such as landing gear or flaps when the engine-driven pump is not running.
Plain English
A small hand pump in the cockpit that the pilot works back and forth like a lever to move fuel or hydraulic fluid through the system when the engine isn't doing it.
Context Anchor
Seen in aircraft fuel system discussions, engine starting procedures, and emergency checklists for some older or simpler aircraft.
Derivation
Called a 'wobble pump' because the handle wobbles or rocks side to side as the pilot works it. The name describes the motion, not the mechanism.
Why Pilots Care
Provides backup fuel delivery when electric pumps are unavailable or during engine start on aircraft without boost pumps.
Intuition Check
Do not read “wobble” as meaning the pump is broken or shaking loose. A wobble pump is named for the back-and-forth handle motion used to operate it.
Example Sentence 1
Before starting the engine, the pilot used the wobble pump to bring fuel pressure into the green arc.
Example Sentence 2
With the electric fuel pump inoperative, the pilot switched to the wobble pump to maintain pressure during the approach.