Definition
A propeller equipped with a governor that automatically adjusts blade pitch to maintain a pilot-selected engine rpm across varying flight conditions and power settings. As airspeed, altitude, or throttle position change, the blades rotate to a flatter or coarser angle so that engine speed stays at the chosen value.
Plain English
A propeller whose blades twist on their own to keep the engine spinning at the rpm the pilot selected, no matter what the airplane is doing.
Context Anchor
Encountered when operating airplanes with a separate propeller control, especially during takeoff, climb, cruise, descent, and power changes.
Derivation
Constant' comes from Latin 'constare', meaning 'to stand firm' or 'stay the same'. The name describes the propeller's job: keeping engine speed standing firm at the selected rpm while the blades quietly do the adjusting in the background.
Why Pilots Care
It lets the engine run at its most efficient RPM for power, fuel economy, and reduced wear across climb, cruise, and descent.
Analogy
Think of it like cruise control for the propeller: you pick the rpm you want, and the system makes small adjustments on its own to hold it there as conditions change.
Intuition Check
“Constant-speed” does not mean the airplane flies at a constant speed. It means the propeller system tries to hold a selected propeller RPM by changing blade angle.
Example Sentence 1
After takeoff, the pilot reduced the throttle and propeller controls to climb power, and the constant-speed propeller automatically adjusted blade pitch to hold the selected rpm.
Example Sentence 2
When descending, the propeller automatically increases blade angle to prevent overspeeding while holding the selected RPM.