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 –

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