Definition
The two main components of a hydraulic brake master cylinder assembly. The cylinder houses the piston that generates hydraulic pressure when the brake pedal is applied, and the reservoir is the small fluid container mounted to or connected with the cylinder that supplies hydraulic fluid to the system and accommodates fluid volume changes as the brakes are used and as brake linings wear.
Plain English
In a small aircraft brake system, the cylinder is the part that pushes brake fluid through the lines when you press the pedal, and the reservoir is the little tank that holds extra fluid to feed the cylinder. They work together as one unit.
Context Anchor
Seen in aircraft brake-system and hydraulic master-cylinder descriptions, especially when discussing fluid flow, ports, leaks, or brake release.
Derivation
“Cylinder” comes from an older word meaning a roller or round tube, which fits the round chamber where the piston moves. “Reservoir” comes from a word meaning something kept back or stored, which fits the fluid-holding part of the unit.
Why Pilots Care
Understanding these components helps pilots recognize normal system behavior, detect leaks or low fluid levels, and follow emergency procedures when hydraulic pressure is lost.
Intuition Check
Do not read “cylinder” here as an engine cylinder. In this context, it means the pressure chamber in a hydraulic master cylinder; the reservoir is the nearby fluid storage area.
Example Sentence 1
During the preflight, the pilot checked the cylinder and the reservoir for any signs of hydraulic fluid leakage.
Example Sentence 2
After landing gear extension, fluid returns from the cylinder to the reservoir.