1. Propellers The engines are equipped with four bladed, full
feathering, constant speed, reversing propellers. Governor
boosted oil moves the propeller blades to low pitch. Feathering springs and counterweights move the propeller blades to high pitch.
When not in operation, propellers should be restrained
as a safety measure for personnel and to prevent
windmilling at zero oil pressure.
Propeller operation in the range of RPM
should be avoided as it may cause ILS glideslope interference.

2. Primary Governor
The propeller is controlled by two governors: the primary governor
and the overspeed governor. The primary governor is located on top
of, and is driven by, the reduction gearbox and controls the propeller
through its normal range.
RPM normal
operating range.
Major components of the primary governor include an integral
gear type oil pump, flyweights, a speeder spring, and a pilot valve.

3. Overspeed Governor
In the event of a primary governor failure, when propeller speed
exceeds selected RPM the overspeed governor (hydraulic topping
governor) will take control and prevent the propeller from
exceeding 2080 RPM.
2080 RPM
1870
RPM
Test
Mode
A solenoid, actuated by the
PROP GOV TEST switch located on the overhead control panel, is provided for resetting the overspeed governor to approximately 1830 to 1910 RPM for
test purposes. NC To
Case
Drain
Autofeather
Dump
Solenoid

4. Low pitch propeller position is determined by the low pitch stop which is a mechanically actuated,
hydraulic stop.
BETA
VALVE

5. Primary Low Pitch Stop Schematic
Oil
Prop
Lever
Hydraulic Overspeed
Governor RPM
Governor
Pump
Primary
Prop Governor
RPM
Beta valve provides
a hydraulic lock limiting
blade angle
Power Lever/
Reverse Lever
1870
RPM
Test
Mode
While on the PLPS the
primary governor senses
an underspeed. Attempts to
supply governor boosted
oil to the propeller. NC To
Case
Drain
BETA
VALVE To
Case
Drain
Autofeather
Dump
Solenoid
LEGEND
Governor Pump Pressure
Servo Pressure
Drain
Low Pitch
(High Oil Pressure)
Primary Low Pitch Stop Schematic

6. Propellers
Propeller speed is selected by the propeller control levers. Movement of a propeller control lever sets the tension of a
speeder spring in its associated primary governor.

7. Propeller Underspeed Schematic
Oil
Prop
Lever
Hydraulic Overspeed
Governor RPM
When the prop RPM
is less than selected
the primary governor
senses an underspeed.
This allows governor
boosted oil into the
propeller decreasing the
pitch and increasing
RPM.
Governor
Pump
Primary
Prop Governor
RPM
Power Lever/
Reverse Lever
1870
RPM
Test
Mode NC To
Case
Drain
BETA
VALVE To
Case
Drain
Autofeather
Dump
Solenoid
LEGEND
Governor Pump Pressure
Servo Pressure
Drain
Low Pitch
(High Oil Pressure)
Propeller Underspeed Schematic

8. Propeller Onspeed Schematic
Oil
Prop
Lever
Hydraulic Overspeed
Governor RPM
An on speed condition
will result in the oil
flow being stopped to the
propeller.
Governor
Pump
Primary
Prop Governor
RPM
Power Lever/
Reverse Lever
1870
RPM
Test
Mode NC To
Case
Drain
BETA
VALVE To
Case
Drain
Autofeather
Dump
Solenoid
LEGEND
Governor Pump Pressure
Servo Pressure
Drain
Low Pitch
(High Oil Pressure)
Propeller Onspeed Schematic

9. Propeller Overspeed Schematic
Oil
Prop
Lever
Hydraulic Overspeed
Governor RPM
When the prop RPM
is more than selected
the primary governor
senses an overspeed.
This allows governor
boosted oil to drain from
the propeller increasing
the pitch and decreasing
RPM.
Governor
Pump
Primary
Prop Governor
RPM
Power Lever/
Reverse Lever
1870
RPM
Test
Mode NC To
Case
Drain
BETA
VALVE To
Case
Drain
Autofeather
Dump
Solenoid
LEGEND
Governor Pump Pressure
Servo Pressure
Drain
Low Pitch
(High Oil Pressure)
Propeller Overspeed Schematic

10. Reversing
Lifting the power levers and moving them aft past the IDLE detents
allows the propellers to be used for reverse thrust braking action.
Note: Propeller reverse operation is limited to one minute.
Caution: Do not select reverse while in flight
Caution:To ensure constant reversing characteristics,
the propeller control must be in full increase position.

11. Power Lever/
Reverse Lever
Beta and reverse blade angles are controlled by the power levers in the beta and reverse
range.
Pivot
Power Lever/
Reverse Lever
Pivot

12. Movement of the power lever into the reverse range causes
a cable linkage to reposition
the low pitch stop and moves
the BETA valve to a position
which allows governor
boosted oil into the propeller.
This drives the propeller to a
lower or reverse pitch.
Power Lever/
Reverse Lever
Pivot
Power Lever/
Reverse Lever
Pivot
In the reverse position, the power lever
is linked to the power turbine (fuel topping)
governor to limit propeller RPM and
prevent overspeed.

13. Beta and Reverse Control Schematic
Oil
Prop
Lever
Hydraulic Overspeed
Governor RPM
Governor
Pump
Primary
Prop Governor
RPM
Power Lever/
Reverse Lever
1870
RPM
Test
Mode NC To
Case
Drain
BETA
VALVE
Pivot To
Case
Drain
Autofeather
Dump
Solenoid
LEGEND
Governor Pump Pressure
Servo Pressure
Drain
Low Pitch
(High Oil Pressure)
Beta and Reverse Control Schematic

14. Propeller Coming Out of Reverse to the Low Pitch Stop Schematic
Oil
Prop
Lever
Hydraulic Overspeed
Governor RPM
Governor
Pump
Primary
Prop Governor
RPM
Power Lever/
Reverse Lever
1870
RPM
Test
Mode
Pivot NC To
Case
Drain
BETA
VALVE To
Case
Drain
Autofeather
Dump
Solenoid
LEGEND
Governor Pump Pressure
Servo Pressure
Drain
Low Pitch
(High Oil Pressure)
Propeller Coming Out of Reverse to the Low Pitch Stop Schematic

15. Power Turbine Governor
A third governor in incorporated to prevent overspeed if the overspeed governor fails or the propeller should stick or move slowly during a transient condition. The power turbine (fuel topping) governor, when sensing 2120 RPM (106%), will restrict fuel flow through the fuel control unit and reduce the N1 power to prevent the propeller from exceeding 2200 RPM.
The power turbine governor in an integral part of the primary governor and shares the pilot valve and fly weights. Failure of the primary governor may result in failure of the power turbine (fuel topping) governor.

16. When the RPM exceeds 2120 (106%) the power turbine governor
Primary Governor
When the RPM
exceeds 2120
(106%) the power
turbine governor
releases air.
Minimum
Pressurizing
Valve
Fuel Control
P3 Air
Minimum
Flow Stop
Air
Fuel

17. The reduction in air in the fuel control control reduces
Primary Governor
The reduction in air in the
fuel control control reduces
fuel flow to the gas generator,
thereby reducing the
power driving the propeller.
Minimum
Pressurizing
Valve
P3 Air
Minimum
Flow Stop
Air
Fuel

18. Autofeather System
An automatic propeller feathering system is installed for use during takeoff and landing. Major components of the system include right and left engine autofeather dump valves, arming relays, torque pressure sensors, power lever position switches, and green annunciator lights.

19. To test the autofeather
system
Torque Switches
9-14%
Power
lever
switches
16-21%
200
400
Arming Relay
Left
Dump
Valve
Arm
OFF
Autofeather lights
Test
Right
Dump
Valve
Closed
at high N1
400
200
16-21%
9-14%

20. Retard the left power lever
Place autofeather
test switch in test
position, Set torque to
approximately 22%
Torque Switches
9-14%
Power
lever
switches
16-21%
200
400
Arming Relay
Left
Dump
Valve
Arm
Retard the left power lever
below 16-21%
OFF
Autofeather lights
Test
Right
Dump
Valve
Closed
at high N1
400
200
16-21%
9-14%

21. 200 400 Left Arm Test Torque dropping below 16-21% disarms
Torque Switches
9-14%
Power
lever
switches
16-21%
200
400
Arming Relay
Left
Dump
Valve
Arm
OFF
Autofeather lights
Test
Torque dropping below
16-21% disarms
the opposite side
Right
Dump
Valve
Closed
at high N1
400
200
16-21%
9-14%

22. 9-14% causes the propeller
Torque Switches
9-14%
Power
lever
switches
16-21%
200
400
Arming Relay
Left
Dump
Valve
Arm
OFF
Autofeather lights
Torque dropping below
9-14% causes the propeller
to feather
Test
Right
Dump
Valve
Closed
at high N1
400
200
16-21%
9-14%