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 1750 - 1850 RPM should be avoided as it may cause ILS glideslope interference.

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. 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 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

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

Primary Low Pitch Stop Schematic Oil Prop Lever Hydraulic Overspeed Governor 2080 RPM Governor Pump Primary Prop Governor 1600 - 2000 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

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.

Propeller Underspeed Schematic Oil Prop Lever Hydraulic Overspeed Governor 2080 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 1600 - 2000 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

Propeller Onspeed Schematic Oil Prop Lever Hydraulic Overspeed Governor 2080 RPM An on speed condition will result in the oil flow being stopped to the propeller. Governor Pump Primary Prop Governor 1600 - 2000 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

Propeller Overspeed Schematic Oil Prop Lever Hydraulic Overspeed Governor 2080 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 1600 - 2000 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

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.

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

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.

Beta and Reverse Control Schematic Oil Prop Lever Hydraulic Overspeed Governor 2080 RPM Governor Pump Primary Prop Governor 1600 - 2000 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

Propeller Coming Out of Reverse to the Low Pitch Stop Schematic Oil Prop Lever Hydraulic Overspeed Governor 2080 RPM Governor Pump Primary Prop Governor 1600 - 2000 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

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.

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

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

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.

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%

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%

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%

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%