Definition
The actual distance a propeller advances through the air during one full revolution in flight. Effective pitch is always less than geometric pitch because the air yields and the propeller slips slightly as it rotates.
Plain English
How far the airplane actually moves forward each time the propeller turns one full circle. It is always a bit less than the distance the propeller would travel if the air were solid.
Context Anchor
Seen in propeller performance discussions, especially when comparing the propeller’s designed pitch with the airplane’s actual forward movement.
Derivation
Pitch comes from the idea of the angle or advance of a turning blade, like the threads on a screw. 'Effective' here means 'the actual result in practice,' as opposed to the theoretical figure. So effective pitch is the real-world advance, not the design advance.
Why Pilots Care
Effective pitch directly affects climb rate, cruise speed, and fuel efficiency; understanding the difference from geometric pitch helps pilots interpret performance data accurately.
Analogy
Think of a screw being driven into soft wood. A perfect screw in solid material would advance exactly one thread per turn. In softer material, it advances a little less per turn. Effective pitch is that smaller, real-world advance.
Intuition Check
Do not read “effective” as meaning “best” or “most powerful” here. It means the actual distance produced in operation. Do not read “pitch” as nose attitude here; it means forward distance per propeller turn.
Example Sentence 1
The difference between geometric pitch and effective pitch is what pilots call propeller slip.
Example Sentence 2
In level cruise the effective pitch was close to the geometric pitch because slip was minimal at the design airspeed.