Definition
The theoretical distance, in inches, that a propeller would advance forward in one full revolution if it were moving through a solid medium with no slippage. It is calculated from the blade angle and the radius at which the angle is measured, ignoring the fact that air actually slips around the blades.
Plain English
How far the propeller would screw itself forward in one turn if the air acted like a solid material. It is a calculated, ideal figure, not what really happens in flight.
Context Anchor
Seen in propeller descriptions, maintenance discussions, and explanations of how blade angle affects aircraft performance.
Derivation
Geometric comes from the Latin and Greek roots meaning 'measurement of the earth' — here it simply means 'calculated from shape and angles.' Pitch comes from the idea of how steeply something is set, like the pitch of a screw thread. So geometric pitch is the pitch you get from pure geometry, before real-world losses are considered.
Why Pilots Care
Geometric pitch is always larger than the actual distance the aircraft moves per revolution. The difference between geometric pitch and real travel is called propeller slip, which is a useful concept when discussing propeller efficiency.
Analogy
Think of a wood screw turning into solid wood: one full turn drives it forward by exactly the thread spacing. Geometric pitch treats air the same way — as if the propeller were biting into a solid block.
Intuition Check
Do not read pitch here as sound, attitude, or a sales talk. In propeller geometric pitch, pitch means the forward distance intended for one full turn of the propeller.
Example Sentence 1
The propeller's geometric pitch was 60 inches, but actual advance per revolution was about 50 inches due to slip.
Example Sentence 2
A higher propeller geometric pitch produces more thrust at cruise but requires more power during takeoff.