propeller control unit (pcu) operation 10... · constant speeding variable pitch propeller system...

Constant Speeding Variable Pitch Propeller System

Propeller Control Unit (PCU) Operation

How the PCU changes propeller pitch and maintains constant engine speeds

The Pilot moves the throttle lever which, as well as changing fuel flow and therefore engine power, selects an RPM for the engine to run at.

The PCU maintains the selected speed by adjusting propeller pitch.

This eases pilot workload :-Especially during combat as the engine is automatically prevented from over speeding and therefore potential destruction and the pilot can concentrate on defeating the enemy

Basic Principal of Operation

And during civilian/transport duties giving the same engine safeguards as above allowing the pilot to concentrate on flying the aircraft, and therefore deliver the 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)

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

FMU PCU

Piston Engine driven propeller

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

FMU PCU

Jet Engine driven propeller – Turbo-Prop

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Start& Idle

Cruise

Take Off

Throttle Positions

Pilot Input Signal

Engine Stationary

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Start& Idle

Cruise

Take Off

Throttle Positions

Pilot Input Signal

Start Initiated – Engine Begins to Rotate

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Start& Idle

Cruise

Take Off

Throttle Positions

Engine At Idle

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Start& Idle

Cruise

Take Off

Throttle Positions

Take Off Selected

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Start& Idle

Cruise

Take Off

Throttle Positions

Engine 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 Speed

Flying straight and level

Flying straight and level

Look at how the PCU changes propeller pitch and maintains constant engine speeds during Dive commencement

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 Out

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Throttle Positions

Start& Idle

Cruise

Take Off

Aircraft Starts DiveThrottle (and Engine) at Cruise –

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Throttle Positions

Start& Idle

Cruise

Take Off

RPM IncreasesThrottle at Cruise –

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Throttle Positions

Start& Idle

Cruise

Take Off

RPM Increases - Prop Goes to Coarser PitchThrottle at Cruise –

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Throttle Positions

Throttle at Cruise –

Start& Idle

Cruise

Take Off

Aircraft in Dive – RPM Restored

Flying straight and level

Flying straight and level

Looked at how the PCU changes propeller pitch and maintains constant engine speeds during Dive commencement

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 Out

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Throttle Positions

Throttle at Cruise –

Start& Idle

Cruise

Take Off

Aircraft Levels Out

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Throttle Positions

Start& Idle

Cruise

Take Off

RPM ReducesThrottle at Cruise –

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Throttle Positions

Start& Idle

Cruise

Take Off

Prop Pitch ReducesThrottle at Cruise –

Propeller HubEngine Mounted

PROPELLER SYSTEM – VARIABLE PITCH CONTROL

Throttle Positions

Start& Idle

Cruise

Take Off

RPM RestoredThrottle (and Engine) at Cruise –