Hartzell HC-E4 3 Series Owner's Manual page 71

Propeller Owner's Manual
147
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.
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DESCRIPTION AND OPERATION
Rev. 17 Sep/20