Propeller Owner's Manual
115N
DESCRIPTION AND OPERATION
61-00-15
Page 2-27
Rev. 24 Dec/20
4. Unfeathering Accumulators
(Rev. 2)
A. System Overview
(1) An unfeathering accumulator is a device that stores
a volume of oil at a pressure and supplies it to the
propeller when commanded to. This supplied pressure
will lower blade angle which will cause the propeller to
windmill and make the engine easier to start.
(2) Hartzell Propeller Inc. manufactures an accumulator
that is a cylinder with a moveable internal piston. One
end of the cylinder and piston is filled with engine oi
l,
and the other end of the cylinder and piston is filled with
air or nitrogen to a designated pressure through an air
valve. The accumulator is a self-contained unit and is
usually installed at some remote location in the engine
compartment. An oil supply hose is connected between
the accumulator and the governor.
(3)
Hartzell Propeller Inc. manufactures governors that have
unfeathering and feathering capability, although some
governors are able to feather a propeller they are not
automatically capable of unfeathering the propeller.
B. Mechanical Models
(1)
The governor has a fitting or threaded hole to attach with
an oil supply hose that is connected to the accumulator
on the other end. During operation of the engine and
propeller, the governor supplies oil to the accumulator
and maintains oil in the accumulator during engine
operation.
(2) The pilot commands feather of the propeller by moving
the RPM control of the governor toward lower RPM
to reach the feather command location. The governor
disconnects the oil supply to the accumulator and seals
a volume of oil under pressure in the accumulator. The
governor then connects the oil supply line from the
propeller piston and permits the propeller blades to
move to a feather stop in the propeller.
