Definition
A manually operated pump used in aircraft hydraulic and fuel systems to move fluid under pressure when the engine-driven or electric pump is unavailable, inoperative, or not yet running. In hydraulic systems it provides backup pressure to extend gear or flaps; in fuel systems it primes the carburetor or fuel injection lines before engine start.
Plain English
A pump you work by hand, usually with a lever, to push fluid through a system when the normal powered pump isn't doing the job.
Context Anchor
Seen in aircraft systems descriptions, emergency landing gear extension procedures, and maintenance instructions for fuel or hydraulic systems.
Why Pilots Care
Provides the only means to operate critical hydraulic functions such as gear extension or braking after loss of engine power or primary pump failure.
Intuition Check
Do not assume a hand pump is just any loose pump carried in the airplane. In aircraft text, it usually means a built-in system component operated by hand for a specific purpose.
Example Sentence 1
After the hydraulic pump failed, the pilot used the hand pump to lower the landing gear before landing.
Example Sentence 2
The student practiced using the hand pump to apply brakes during a simulated electrical failure on the ground.