Definition
A hydraulic chamber inside the hub of a constant-speed propeller that uses pressurized engine oil acting on a piston to move the propeller blades to a higher or lower blade angle. The propeller governor regulates the oil pressure supplied to this cylinder, which in turn changes the pitch of the blades to maintain the selected engine rpm.
Plain English
It is the small oil-driven piston unit built into the propeller hub that physically twists the blades to a flatter or steeper angle when the governor sends it pressurized oil.
Context Anchor
Seen in constant-speed propeller operation when explaining how oil pressure changes the angle of the propeller blades.
Derivation
‘Cylinder’ comes from the Greek kylindros, meaning ‘roller’ or ‘tube,’ and refers to any tube-shaped chamber that houses a moving piston. In this case, it is the cylinder inside the propeller hub where oil pressure pushes a piston to change blade angle.
Why Pilots Care
The cylinder enables automatic blade-angle adjustment that prevents engine overspeed, improves climb and cruise efficiency, and protects the engine from damage.
Analogy
Think of a small oil-powered plunger. When oil pressure pushes on it, the plunger moves another part of the mechanism.
Intuition Check
Do not confuse the propeller cylinder with an engine cylinder where fuel and air burn. Here, cylinder means a hydraulic chamber in the propeller that uses oil pressure to move parts.
Example Sentence 1
When the pilot moved the propeller control forward, the governor increased oil pressure to the propeller cylinder, decreasing blade angle and allowing engine rpm to rise.
Example Sentence 2
A loss of oil pressure to the propeller cylinder will cause the blades to move toward high pitch and reduce RPM.