Definition
The pressurized engine oil supplied to and regulated by the propeller governor, used to move the propeller blades to a higher (coarser) pitch in a constant-speed propeller system. The governor boosts engine oil to a higher pressure and meters its flow into the propeller hub, where it acts against spring force, counterweights, or compressed gas to change blade angle and maintain the selected RPM.
Plain English
It is engine oil that the governor pressurizes and sends into the propeller to twist the blades to a different angle, keeping the propeller spinning at the RPM the pilot selected.
Context Anchor
Seen in constant-speed propeller discussions, especially when learning how blade angle is changed and how selected rpm is held.
Derivation
Governor comes from the Latin gubernare, meaning to steer or control. The governor steers the propeller's blade angle by controlling how much pressurized oil reaches it.
Why Pilots Care
Correct governor oil pressure prevents engine overspeed or underspeed, protects the engine, and keeps the propeller operating efficiently across different flight conditions.
Intuition Check
Governor oil pressure is not simply the same thing as the oil pressure shown on the engine oil pressure gauge. Here it means oil pressure controlled by the propeller governor and directed to the propeller to change blade angle.
Example Sentence 1
During the runup, the pilot cycled the propeller control to circulate warm governor oil pressure through the hub before takeoff.
Example Sentence 2
During a go-around the pilot advances the throttle and the governor immediately adjusts oil pressure to fine the blades and prevent an overspeed.