Definition
A mechanical limit built into a constant-speed propeller hub that prevents the blades from rotating beyond a set blade angle. The two main pitch stops are the low-pitch stop (high rpm limit) and the high-pitch stop (low rpm limit), which together define the governing range within which the propeller governor can adjust blade angle.
Plain English
A physical stop inside the propeller that keeps the blades from twisting past a minimum or maximum angle. It sets the boundaries the governor is allowed to work within.
Context Anchor
Seen in constant-speed propeller discussions, especially when the propeller control system can no longer change blade angle enough to hold the selected rpm.
Derivation
From 'pitch' (the blade angle of a propeller) and 'stop' (a mechanical block that prevents further movement). Together: a block that prevents further pitch change.
Why Pilots Care
Pitch stops keep the propeller within safe operating angles, protecting the engine from overspeed and ensuring adequate thrust is available.
Analogy
A pitch stop is like a doorstop. The door can move freely until it reaches the stop, but it cannot go beyond that point.
Intuition Check
Pitch stop does not mean stopping the airplane from pitching nose-up or nose-down. Here, pitch means propeller blade angle, and stop means the blade-angle travel limit.
Example Sentence 1
On the takeoff roll, the propeller blades were against the low-pitch stop, so the engine reached full rated rpm as airspeed built.
Example Sentence 2
The high pitch stop prevents the blades from coarsening too far and allows the engine to stay within its rpm limits.