Definition
A mechanical limit built into a constant-speed propeller that prevents the blades from rotating beyond their maximum (coarsest) blade angle. It defines one end of the propeller's governing range, beyond which the governor can no longer increase blade pitch to maintain the selected RPM.
Plain English
A built-in stop inside the propeller that keeps the blades from twisting any further toward their flattest-bite-of-air-per-revolution position. Once the blades reach this stop, the propeller can't take a bigger bite even if the engine is producing more power than the governor can absorb.
Context Anchor
Seen in constant-speed propeller and propeller governor discussions, especially when explaining the limits of the propeller’s governing range.
Derivation
"Pitch" here refers to propeller blade angle -- how steeply the blade is twisted into the oncoming air. "High pitch" means a coarse, steep angle that takes a big bite of air per revolution (used at cruise). The "stop" is literally a mechanical stop inside the hub. Naming it the high pitch stop tells you exactly which end of the blade-angle range it limits.
Why Pilots Care
Keeps the propeller within its effective operating range so the governor can still control RPM.
Intuition Check
“High pitch” does not mean the airplane is nose-high. Here it means the propeller blades are at a higher angle, which tends to slow engine rpm.
Example Sentence 1
At cruise power with the RPM lever pulled well back, the blades moved toward, but did not reach, the high pitch stop.
Example Sentence 2
During preflight the pilot confirms the propeller reaches the high pitch stop without exceeding it.