Plain English Meaning

It is the working zone in which the propeller's automatic speed controller can still do its job. As long as the blades can swing freely between their two limits, the system holds the RPM the pilot has set. If the blades hit either limit, the controller can no longer keep the RPM steady.

Full Definition

The range of propeller blade angles, between the low-pitch (high-RPM) stop and the high-pitch (low-RPM) stop, within which a constant-speed propeller governor can automatically adjust blade pitch to maintain the RPM selected by the pilot.

Context Anchor

Used when learning constant-speed propeller operation, especially how the holds RPM during , , and changes.