Definition
Pitch is the angle at which a propeller blade meets the oncoming air, measured between the blade's chord line and the plane of rotation. Geometric pitch is the theoretical distance a propeller would advance in one revolution if it were moving through a solid medium; effective pitch is the actual distance it advances through the air, which is always less due to slippage.
Plain English
Pitch describes how steeply the propeller blades are tilted as they spin. A flatter blade takes a smaller bite of air; a steeper blade takes a bigger bite. It's also used to describe how far forward the propeller would travel in one full turn if there were no slippage.
Context Anchor
Seen when learning basic propeller principles, comparing fixed-pitch and adjustable-pitch propellers, and reading aircraft performance information.
Derivation
From the everyday sense of 'pitch' meaning the angle or slope of something (as in the pitch of a roof). The propeller blade is set at a slope to the air it's cutting through, so the same word transferred naturally.
Why Pilots Care
Proper pitch keeps the engine within its efficient RPM range, directly affecting takeoff performance, climb rate, cruise speed, and fuel economy.
Analogy
Think of turning a screw into wood. A coarse screw thread moves farther with each turn than a fine thread. Propeller pitch is similar, except the propeller is turning through air, so the actual movement is less than the perfect, no-slip distance.
Intuition Check
Pitch does not mean the airplane’s nose-up or nose-down attitude here. In propeller use, pitch means how far the propeller is designed to move forward with each full turn.
Example Sentence 1
On takeoff, the pilot selected a low blade pitch to allow the engine to reach full RPM and produce maximum thrust.
Example Sentence 2
During cruise the pilot increased pitch to lower RPM and improve fuel efficiency.