Definition
A propeller whose blade angle cannot be changed by the pilot in flight. A fixed pitch propeller has blades set at one permanent angle during manufacture. A ground adjustable propeller has blades that can be loosened and reset to a different angle on the ground, but once secured the angle remains fixed for that flight. Neither type allows in-flight pitch changes, so engine and propeller performance are optimized for one flight regime — typically either climb or cruise — but not both.
Plain English
A propeller with blades set at one angle that the pilot cannot change while flying. On a fixed pitch prop the angle is locked in at the factory. On a ground adjustable prop, a mechanic can change the angle on the ground before flight, but the pilot still cannot adjust it once airborne.
Context Anchor
Seen in light-sport aircraft descriptions, operating limitations, and aircraft equipment lists.
Derivation
Pitch' here refers to the angle of the propeller blade, similar to the pitch of a screw — the steeper the angle, the more air it tries to move with each turn. 'Fixed' means it cannot be changed; 'ground adjustable' means it can only be changed while the aircraft is on the ground.
Why Pilots Care
These designs are simpler, lighter, and cheaper than constant-speed propellers, suiting light-sport aircraft while limiting in-flight performance optimization.
Analogy
Think of it like a single-speed bicycle. It works fine, but you cannot shift gears for hills or flat ground — you live with the one setting you have.
Intuition Check
Fixed pitch does not mean the propeller cannot spin; it means the blade angle cannot be changed in flight. Ground adjustable does not mean adjustable while taxiing or flying; it means adjusted on the ground before flight, normally with tools and according to the aircraft instructions.
Example Sentence 1
The light-sport trainer was equipped with a fixed pitch or ground adjustable propeller, so the pilot had no in-flight prop control to manage.
Example Sentence 2
Before the test flight, the mechanic set the ground adjustable propeller blades to the recommended angle for the density altitude.