constant speeding variable pitch propeller system propeller control unit (pcu) operation how the pcu...
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Constant Speeding Variable Pitch Propeller SystemConstant Speeding Variable Pitch Propeller System
Propeller Control Unit (PCU) Propeller Control Unit (PCU) OperationOperation
How the PCU changes propeller pitch and maintains How the PCU changes propeller pitch and maintains constant engine speedsconstant engine speeds
The Pilot moves the throttle lever which, as well as The Pilot moves the throttle lever which, as well as changing fuel flow and therefore engine power, selects changing fuel flow and therefore engine power, selects an RPM for the engine to run at.an RPM for the engine to run at.
The PCU maintains the selected speed by adjusting The PCU maintains the selected speed by adjusting propeller pitch.propeller pitch.
This eases pilot workload :-This eases pilot workload :-
Especially during combat as the engine is automatically Especially during combat as the engine is automatically prevented from over speeding and therefore potential prevented from over speeding and therefore potential destruction and the pilot can concentrate on defeating destruction and the pilot can concentrate on defeating the enemythe enemy
Basic Principal of OperationBasic Principal of Operation
And during civilian/transport duties giving the same And during civilian/transport duties giving the same engine safeguards as above allowing the pilot to engine safeguards as above allowing the pilot to concentrate on flying the aircraft, and therefore deliver concentrate on flying the aircraft, and therefore deliver the passengers and/or cargo safely to their destinationthe passengers and/or cargo safely to their destination
(You will see later that the throttle is connected to both the Fuel Control Unit and the PCU)(You will see later that the throttle is connected to both the Fuel Control Unit and the PCU)
Propeller HubEngine Mounted
Simplified System
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Start& Idle
Cruise
Take Off
Throttle Positions: -
Pilot Input Signal
Hydraulic Pressure
Supply
Hydraulic Return
Operation Piston
Spinner
Connecting Linkage
Hydraulic Connections
PCU
Sliding Collar
Engine RPM Signal (Mechanical Drive)
Spring
Hydraulic Valve
Counter Balance Weights
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
FMUFMU PCUPCU
Piston Engine driven propellerPiston Engine driven propeller
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
FMUFMU PCUPCU
Jet Engine driven propeller – Turbo-PropJet Engine driven propeller – Turbo-Prop
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Start& Idle
Cruise
Take Off
Throttle Positions
Pilot Input Signal
Engine StationaryEngine Stationary
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Start& Idle
Cruise
Take Off
Throttle Positions
Pilot Input Signal
Start Initiated – Engine Begins to RotateStart Initiated – Engine Begins to Rotate
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Start& Idle
Cruise
Take Off
Throttle Positions
Engine At IdleEngine At Idle
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Start& Idle
Cruise
Take Off
Throttle Positions
Take Off SelectedTake Off Selected
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Start& Idle
Cruise
Take Off
Throttle Positions
Engine Accelerates to Take Off SpeedEngine Accelerates to Take Off Speed
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Start& Idle
Cruise
Take Off
Throttle Positions
Engine Running at Take Off SpeedEngine Running at Take Off Speed
Flying straight and levelFlying straight and level
DiveDive
Flying straight and levelFlying straight and level
Look at how the PCU changes propeller pitch Look at how the PCU changes propeller pitch and maintains constant engine speeds during and maintains constant engine speeds during Dive commencementDive commencement
In all these manoeuvres, all the pilot is doing is flying (redirecting) the aircraft, the throttle is not touched.In all these manoeuvres, all the pilot is doing is flying (redirecting) the aircraft, the throttle is not touched.
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
And then at Level OutAnd then at Level Out
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Throttle Positions
Start& Idle
Cruise
Take Off
Aircraft Starts DiveAircraft Starts DiveThrottle (and Engine) at Cruise – Throttle (and Engine) at Cruise –
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Throttle Positions
Start& Idle
Cruise
Take Off
RPM IncreasesRPM IncreasesThrottle at Cruise – Throttle at Cruise –
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Throttle Positions
Start& Idle
Cruise
Take Off
RPM Increases - Prop Goes to Coarser PitchRPM Increases - Prop Goes to Coarser PitchThrottle at Cruise – Throttle at Cruise –
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Throttle Positions
Throttle at Cruise – Throttle at Cruise –
Start& Idle
Cruise
Take Off
Aircraft in Dive – RPM RestoredAircraft in Dive – RPM Restored
Flying straight and levelFlying straight and level
DiveDive
Flying straight and levelFlying straight and level
Looked at how the PCU changes propeller pitch Looked at how the PCU changes propeller pitch and maintains constant engine speeds during and maintains constant engine speeds during Dive commencementDive commencement
In all these manoeuvres, all the pilot is doing is flying (redirecting) the aircraft, the throttle is not touched.In all these manoeuvres, all the pilot is doing is flying (redirecting) the aircraft, the throttle is not touched.
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Now at Level OutNow at Level Out
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Throttle Positions
Throttle at Cruise – Throttle at Cruise –
Start& Idle
Cruise
Take Off
Aircraft Levels OutAircraft Levels Out
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Throttle Positions
Start& Idle
Cruise
Take Off
RPM ReducesRPM ReducesThrottle at Cruise – Throttle at Cruise –
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Throttle Positions
Start& Idle
Cruise
Take Off
Prop Pitch ReducesProp Pitch ReducesThrottle at Cruise – Throttle at Cruise –
Propeller HubEngine Mounted
PROPELLER SYSTEM – VARIABLE PITCH CONTROL
Throttle Positions
Start& Idle
Cruise
Take Off
RPM RestoredRPM RestoredThrottle (and Engine) at Cruise – Throttle (and Engine) at Cruise –