Hartzell HC-E4 3 Series Owner's Manual page 78

If governor supplied oil is lost during operation, the propeller
will increase pitch and feather. Feathering occurs because
the summation of internal propeller forces causes the oil to
drain out of the propeller until the feather stop position is
reached.
Normal in-flight feathering is accomplished when the pilot
retards the propeller condition lever past the feather detent.
This permits control 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 condition lever into the normal flight
(governing) range and restarts the engine. As engine speed
increases, the governor supplies oil to the propeller and the
blade angle decreases.
In reverse mode of operation, the governor operates in an
underspeed condition to act strictly as a source of
pressurized oil, without attempting to control RPM. Control of
the propeller blade angle in reverse is accomplished with the
beta valve.
NOTE: The beta valve is normally located on the side of
reduction gearbox opposite the propeller.
The propeller is reversed by manually repositioning the
cockpit-control to cause the beta valve to supply oil from the
governor pump to the propeller. A beta rod inserted into the
front of the propeller communicates propeller blade angle
position to the beta valve.
When the propeller reaches the desired reverse position,
movement of the beta rod, initiated by the propeller
piston, will cause the beta valve to shut off flow of oil to
the propeller. Any additional unwanted movement of the
propeller toward reverse or any movement of the manually
positioned beta valve control toward high pitch position
will cause the beta valve to drain oil from the propeller to
increase pitch.
DESCRIPTION AND OPERATION
Propeller Owner's Manual
147
61-00-47
Page 2-22
Rev. 16 May/20