Hartzell HC-82XF-1 Owner's Manual page 64

Propeller Owner's Manual
175
Oil is metered by the governor to oppose these constant
forces and maintain a constant engine RPM.
The forces of the installed spring and counterweight attempt
to rotate the blades to a higher blade angle.
A governor is an engine speed-sensing device that maintains
a constant engine/propeller RPM by changing blade angle
and varying load on the engine.
The governor uses an internal pump that is driven by an
accessory drive from the engine. This pump uses engine
lubricating oil and increases the engine oil pressure for
supply to the propeller. Engine speed sensing hardware
within the governor controls the supply of oil to, or drain of
oil from the propeller, resulting in a change of blade pitch to
maintain constant engine speed.
Oil pressure from the engine-driven governor is supplied to
the propeller mounted hydraulic cylinder through the engine
shaft and propeller hub. Increasing the oil volume within the
hydraulic cylinder decreases blade angle to increase engine
RPM. Decreasing the oil volume will increase the blade angle
to decrease engine RPM. By changing the blade angle, the
governor maintains constant engine RPM (within limits),
independent of the throttle setting.
If the oil supply is lost during flight, the propeller will feather.
Feathering occurs because the spring and blade clamp
mounted counterweight forces are no longer opposed by
hydraulic oil pressure and are free to increase blade pitch to
the feathering (high pitch) stop.
Normal in-flight feathering of these propellers is
accomplished when the pilot retards the propeller pitch
control past the feather detent. This permits oil to drain
from the propeller and return to the engine sump. Engine
shutdown is normally accomplished during the feathering
process.
Normal in-flight unfeathering is accomplished when the
pilot positions the propeller pitch control into normal flight
(governing) range and restarts the engine. As engine speed
increases, oil is supplied by the governor to the propeller, and
the blade angle decreases.
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DESCRIPTION AND OPERATION
Dec/05