Definition
A pressure vessel in a hydraulic system that stores fluid under pressure, typically using a compressed gas (usually nitrogen) on one side of a piston, diaphragm, or bladder, and hydraulic fluid on the other. It supplements pump output during high demand, absorbs pressure surges, and provides a reserve of pressurized fluid for emergency use or when the pump is not running.
Plain English
A storage tank that holds hydraulic fluid under pressure, ready to deliver an extra burst of power when the system needs it or to keep things working briefly if the pump fails.
Context Anchor
Seen in aircraft hydraulic system descriptions, landing gear and brake system discussions, and some emergency system procedures.
Derivation
From the Latin accumulare, meaning to heap up or pile together. The accumulator 'piles up' pressure energy by storing pressurized fluid until it is needed.
Why Pilots Care
Provides emergency hydraulic power to flight controls if the pump fails or the engine is shut down.
Analogy
Think of it like a charged-up water balloon plumbed into the system. While the pump is running, it fills and pressurizes the balloon. If the pump stops, the balloon's stored squeeze still pushes fluid out for a short time.
Intuition Check
Do not read accumulator as just “something that collects fluid.” In aviation systems, it means a device that stores pressure for system operation.
Example Sentence 1
After engine shutdown, the brake accumulator still held enough pressure for several applications of the parking brake.
Example Sentence 2
The pilot verified accumulator pressure on the gauge before starting the engine.