Definition 1 of 2
Definition
A propeller whose blade angle is built in at manufacture and cannot be changed by the pilot or by any in-flight mechanism. The blade pitch is a permanent compromise chosen by the manufacturer to give acceptable performance across climb and cruise, but it cannot be optimized for any single phase of flight.
Plain English
A propeller with blades set at one fixed angle. The pilot has no way to adjust them — what you take off with is what you cruise and land with.
Context Anchor
Common on many training airplanes and smaller general aviation aircraft, and often discussed when comparing simple propeller systems with constant-speed propellers.
Derivation
‘Pitch’ here refers to the blade angle — the angle the blade meets the oncoming air. ‘Fixed’ means it is locked in place at manufacture. So a fixed-pitch propeller is one whose blade angle is permanently set and cannot be varied.
Why Pilots Care
These propellers are simple, light, and inexpensive but limit performance flexibility across different flight speeds.
Analogy
Think of a single-speed bicycle. It works fine, but you cannot shift gears for a steep hill or a flat straightaway — you accept one setting for everything.
Intuition Check
Fixed-pitch does not mean the propeller always spins at a fixed speed. It means the blade angle is fixed; the propeller speed can still change.
Example Sentence 1
The Cessna 152 has a fixed-pitch propeller, so the student manages engine power with the throttle alone.
Example Sentence 2
During a climb the pilot monitors RPM closely because a fixed-pitch propeller cannot change its angle to maintain efficiency.