Propellers

The engines are equipped with four bladed, fullfeathering, 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 1750 - 1850 RPMshould be avoided as it may cause ILS glideslope interference.

Primary Governor

The propeller is controlled by two governors: the primary governorand the overspeed governor. The primary governor is located on topof, and is driven by, the reduction gearbox and controls the propellerthrough its normal range.

1600-2000 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.

Overspeed Governor

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2080 RPM 1870RPMTestMode

Autofeather DumpSolenoid

A solenoid, actuated by thePROP 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.

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.

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

BETAVALVE

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BETAVALVE

Autofeather DumpSolenoid

Primary Low Pitch Stop Schematic

Hydraulic OverspeedGovernor 2080 RPM

PrimaryProp Governor1600 - 2000 RPM

PropLever

Oil

1870RPMTestMode

Low Pitch(High Oil Pressure)

LEGEND Governor Pump Pressure Servo Pressure Drain

Power Lever/Reverse Lever

GovernorPump

While on the PLPS theprimary governor senses

an underspeed. Attempts to supply governor boosted

oil to the propeller.

Beta valve providesa hydraulic lock limiting

blade angle

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.

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BETAVALVE

Autofeather DumpSolenoid

Propeller Underspeed Schematic

Hydraulic OverspeedGovernor 2080 RPM

Oil

1870RPMTestMode

Low Pitch(High Oil Pressure)

LEGEND Governor Pump Pressure Servo Pressure Drain

Power Lever/Reverse Lever

PrimaryProp Governor1600 - 2000 RPM

PropLever

GovernorPump

When the prop RPM is less than selected

the primary governor senses an underspeed.This allows governorboosted oil into the

propeller decreasing thepitch and increasing

RPM.

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BETAVALVE

Autofeather DumpSolenoid

Propeller Onspeed Schematic

Hydraulic OverspeedGovernor 2080 RPM

Oil

1870RPMTestMode

Low Pitch(High Oil Pressure)

LEGEND Governor Pump Pressure Servo Pressure Drain

Power Lever/Reverse Lever

PrimaryProp Governor1600 - 2000 RPM

PropLever

GovernorPump

An on speed condition will result in the oil

flow being stopped to the propeller.

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BETAVALVE

Autofeather DumpSolenoid

Propeller Overspeed Schematic

Hydraulic OverspeedGovernor 2080 RPM

Oil

1870RPMTestMode

Low Pitch(High Oil Pressure)

LEGEND Governor Pump Pressure Servo Pressure Drain

Power Lever/Reverse Lever

PropLever

GovernorPump

PrimaryProp Governor1600 - 2000 RPM

When the prop RPM is more than selected the primary governor senses an overspeed.This allows governor

boosted oil to drain fromthe propeller increasing the pitch and decreasing

RPM.

Reversing

Lifting the power levers and moving them aft past the IDLE detentsallows 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.

Power Lever/Reverse Lever

Pivot

Power Lever/Reverse Lever

Pivot

Beta and reverse blade angles are controlled by the power levers in the beta and reverserange.

Power Lever/Reverse Lever

Pivot

Power Lever/Reverse Lever

Pivot

Movement of the power leverinto the reverse range causes a cable linkage to reposition the low pitch stop and movesthe BETA valve to a positionwhich allows governor boosted oil into the propeller.This drives the propeller to a lower or reverse pitch.

In the reverse position, the power leveris linked to the power turbine (fuel topping)governor to limit propeller RPM and prevent overspeed.

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BETAVALVE

Autofeather DumpSolenoid

Beta and Reverse Control Schematic

Hydraulic OverspeedGovernor 2080 RPM

Oil

1870RPMTestMode

Low Pitch(High Oil Pressure)

LEGEND Governor Pump Pressure Servo Pressure Drain

Power Lever/Reverse Lever

Pivot

PrimaryProp Governor1600 - 2000 RPM

PropLever

GovernorPump

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BETAVALVE

Autofeather DumpSolenoid

Propeller Coming Out of Reverse to the Low Pitch Stop Schematic

Hydraulic OverspeedGovernor 2080 RPM

Oil

1870RPMTestMode

Low Pitch(High Oil Pressure)

LEGEND Governor Pump Pressure Servo Pressure Drain

Power Lever/Reverse Lever

PrimaryProp Governor1600 - 2000 RPM

PropLever

GovernorPump

Pivot

Power Turbine GovernorA 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.

Minimum Flow Stop

MinimumPressurizingValveP3 Air

When the RPM exceeds 2120

(106%) the powerturbine governor

releases air.

Air Fuel

Primary Governor

Fuel Control

Minimum Flow Stop

MinimumPressurizingValve

Air

P3 Air

The reduction in air in the fuel control control reduces

fuel flow to the gas generator, thereby reducing the

power driving the propeller.

Fuel

Primary Governor

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.

Arm

Test

Torque Switches

Autofeather lights

200

200

400

40016-21%

9-14%

9-14%

Powerleverswitches

Closedat highN1

Left

Right

OFF

DumpValve

DumpValve

16-21%

Arming RelayTo test the autofeather

system

Arm

Test

Torque Switches

Autofeather lights

200

200

400

40016-21%

9-14%

9-14%

Powerleverswitches

Closedat highN1

Left

Right

OFF

DumpValve

DumpValve

16-21%

Arming Relay

Retard the left power leverbelow 16-21%

Place autofeathertest switch in test

position, Set torque to approximately 22%

Arm

Test

Torque Switches

Autofeather lights

200

200

400

40016-21%

9-14%

9-14%

Powerleverswitches

Closedat highN1

Left

Right

OFF

DumpValve

DumpValve

16-21%

Arming Relay

Torque dropping below16-21% disarmsthe opposite side

Arm

Test

Torque Switches

Autofeather lights

200

200

400

40016-21%

9-14%

9-14%

Powerleverswitches

Closedat highN1

Left

Right

OFF

DumpValve

DumpValve

16-21%

Arming Relay

Torque dropping below9-14% causes the propeller

to feather