Definition
The mechanical assembly of a constant-speed propeller governor that senses engine RPM and controls oil pressure to the propeller hub, thereby adjusting blade angle to maintain the RPM selected by the pilot. It contains flyweights, a speeder spring, and a pilot valve that together regulate the flow of engine oil to or from the propeller piston.
Plain English
The part of the propeller governor that senses how fast the engine is turning and uses oil pressure to change the propeller blade angle so the engine stays at the RPM the pilot selected.
Context Anchor
Seen in discussions of constant-speed propellers and blade angle control, especially when explaining how the propeller governor maintains selected RPM.
Derivation
‘Governor’ comes from the Latin gubernare, meaning ‘to steer or control.’ A governor head, then, is the controlling unit — the assembly that regulates (governs) propeller behavior in response to engine speed.
Why Pilots Care
Correct operation prevents engine overspeed or underspeed, protects the powerplant, and maintains efficient thrust throughout the flight envelope.
Intuition Check
Do not think of a governor head as a political leader or as the front of the propeller. Here it means an internal mechanical part of the propeller governor that senses RPM and helps control blade angle.
Example Sentence 1
When the pilot moved the propeller control forward, the governor head directed more oil to the propeller hub, decreasing blade angle and allowing RPM to rise.
Example Sentence 2
During an overspeed event the governor head sensed the RPM rise and directed oil to fine the blades before engine limits were exceeded.