Definition
The angle between the chord line of a propeller blade section and the propeller's plane of rotation, measured at a specified radial station along the blade. It describes how steeply the blade is set relative to the disc the propeller sweeps through as it turns.
Plain English
It is how much a propeller blade is twisted compared to the flat circle it spins in. A small angle means the blade is nearly flat to that circle; a larger angle means the blade is tilted more steeply into the oncoming air.
Context Anchor
Seen in propeller specifications, propeller inspection, and maintenance procedures that describe blade setting or propeller adjustment.
Derivation
Pitch comes from an old sense meaning 'to set or fix at a slope.' The same idea appears in a roof's pitch — how steeply it is set. For a propeller, the pitch angle is how steeply each blade is set against the plane it rotates in.
Why Pilots Care
Pitch angle determines how much air each blade moves per revolution, which affects thrust, engine load, and efficiency at different airspeeds. A blade set at a low pitch angle gives better performance at low speeds (takeoff, climb); a higher pitch angle is more efficient at cruise.
Intuition Check
Pitch angle here does not mean the airplane’s nose-up or nose-down attitude. It means the set angle of a propeller blade at a specific point on the blade.
Example Sentence 1
The technician measured the blade's pitch angle at the 75 percent radius station and found it within the manufacturer's tolerance.
Example Sentence 2
A higher pitch angle lets the propeller move the airplane farther forward per revolution but requires more engine power.