Definition
The angle between the chord line of a propeller blade and the plane of rotation of the propeller, measured at a specified point along the blade. Pitch angle determines how much air the blade displaces with each revolution and is adjusted by the propeller governor in a constant-speed system. In the beta range, the pitch angle can be reduced toward flat or driven negative to produce reverse thrust.
Plain English
Pitch angle is how steeply a propeller blade is twisted relative to its spinning circle. A steeper angle takes a bigger 'bite' of air; a flatter angle takes a smaller bite. On reversible propellers, the angle can be pushed past flat to push air forward and slow the airplane.
Context Anchor
Seen in turboprop discussions of beta range, reverse thrust, and propeller blade control during taxi, landing rollout, or rejected takeoff procedures.
Derivation
Pitch' comes from the same idea as the pitch of a screw — how far it advances in one turn. A propeller blade is essentially a rotating airfoil set at an angle; the steeper the angle, the further the airplane is pulled forward per revolution, just like a coarser-pitched screw drives further into wood per turn.
Why Pilots Care
Determines thrust direction and strength on the ground, directly affecting landing rollout distance and directional control.
Analogy
Think of a hand fan. Held edge-on to the air, it slices through and moves almost nothing. Tilted flat against the air, it pushes a lot. The propeller blade's pitch angle works the same way — it sets how much air the blade grabs each time it sweeps past.
Intuition Check
Do not read pitch angle here as the airplane’s nose-up or nose-down attitude. In this context, it means the angle of the propeller blade, not the angle of the airplane.
Example Sentence 1
When the pilot moved the power lever into the beta range, the propeller blade pitch angle decreased toward flat, reducing forward thrust.
Example Sentence 2
A slightly positive pitch angle was selected during taxi to keep engine RPM low while still providing forward thrust.