Propellers The engines are equipped with four bladed, full feathering, constant speed, reversing...
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Transcript of Propellers The engines are equipped with four bladed, full feathering, constant speed, reversing...
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
ToCaseDrain
NC
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
ToCaseDrain
ToCaseDrain
NC
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.
ToCaseDrain
ToCaseDrain
NC
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.
ToCaseDrain
ToCaseDrain
NC
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.
ToCaseDrain
ToCaseDrain
NC
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.
ToCaseDrain
ToCaseDrain
NC
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
ToCaseDrain
ToCaseDrain
NC
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