10. Propeller Systems - Sections 1-4 Flashcards by C MC

Design and construction

A propeller system comprises of 2 or more blades connected to what

CENTRAL HUB

Pg 221

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Design and construction

The central hub is enclosed inside of a fairing called what

SPINNER

Pg 221

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Design and construction

What are the 2 key purposes of a spinner

Other than encasing the central hub

REDUCE DRAG
ORDERLY AIRFLOW

Encourages orderly airflow around the hub

Pg 221

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Design and construction

What is the hub attached to in the engine

DRIVE SHAFT

Either directly or via a gearbox

Pg 221

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Design and construction

The hub is connected to the drive shaft by either of what 2 methods

DIRECTLY
GEARBOX

Pg 221

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Design and construction

On a simple piston engine, the propeller is connected directly to what

ENGINE DRIVE SHAFT

Pg 222

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Design and construction

what is the result of the propeller being directly connected to the engine drive shaft

ROTATES AT SAME SPEED

2000 - 3000 rpm

As a result of the propeller beign directly connected to the engine drive shaft, the propeller rotates at the same speed as the engine, usually between 2000 - 3000 rpm

Pg 222

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Design and construction

On more powerful engines, what component is introduced to translate large amounts of power through high RPM to large amounts of torque for a slow turning propeller

REDUCTION GEARBOX

Pg 222

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Design and construction

What is the purpose of a reduction gearbox

On more powerful engines;
Translates LARGE amounts of power to LARGE amounts fo torque for a SLOW turning propeller

Pg 222

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Design and construction

What is the name given to the component that swivels the baldes on their bearings in complex design aircraft

PITCH CONTROL UNIT
(PCU)

Pg 222

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Design and construction

What is the purpose of a pitch control unit

SWIVIL BLADES on their BEARINGS

Pg 222

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Design and construction

What 2 materials are typical blades on modern aircraft made from

ALUMINIUM ALLOY
COMPOSITES

Pg 223

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Variable pitch systems

What is the name of the aerodynamic force in-line with the drive shaft

THRUST

Pg 224

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Variable pitch systems

What must engine power (torque) overcome on a propeller system in order to produce thrust

TORQUE DRAG

Pg 224

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Variable pitch systems

On a fixed pitch propeller system, how is thrust increased

INCREASE RPM

Pg 225

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Variable pitch systems

What happens to the engine on any piston aero engine if acting outside of the narrow range of efficiency

LESS EFFICIENT

Pg 225

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Variable pitch systems

Which type of propeller system is most of the time operating outside of its optimum RPM

FIXED PITCH PROPELLER

Pg 225

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Variable pitch systems

Obtaining the optimum efficiency range means what 2 things relating to the blade have been achieved

MAX THRUST for LEAST DRAG

Pg 225

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Variable pitch systems

What is the purpose of a variable pitch propeller system

ACHIEVE OPTIMUM AoA

Adjust blade pitch to achieve optimum Angle of Attack

Pg 225

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Variable pitch systems

On a variable pitch propeller system how is thrust increased

INCREASING BLADE AoA

Pg 225

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Variable pitch systems

Torque drag is a result of an increase in what

INCREASE BLADE AoA

Pg 225

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Variable pitch systems

As a result of torque drag through an increase in thrust, to maintain propeller RPM at a constant speed, what must happen

INCREASE POWER

Increase in thrust needs an increase in power

Increase in power needed to overcome the torque drag and maintain the RPM at a constant speed

Pg 225

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Variable pitch systems

What is the primary component of a PCU that operates the pins or links to move the blades

PISTON

Pg 226

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Variable pitch systems

When the piston inside of a PCU moves, what devices connected to the piston and the blade subsequently change the blade angle

LINKS or PINS

Pg 226

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# Variable pitch systems Movement of the piston in a PCU converts what movement from the piston into what movement in the blade

LINEAR MOVEMENT into ROTATIONAL MOVEMENT ## Footnote Pg 226

# Variable pitch systems What are the 3 common methods of driving a Pitch Control Unit (PCU)

1. ELECTRIC MOTOR 2. OIL PRESSURE 3. OIL and SPRING PRESSURE ## Footnote Pg 226

# Variable pitch systems What are the 2 basic types of a pitch control unit

1. SINGLE acting 2. DOUBLE acting ## Footnote Pg 226

# Variable pitch systems *"Pressurised oil is fed to one side of a piston to drive a pitch angle towards coarse"* This describes what sort of PCU system

SINGLE ACTING ## Footnote Pg 227

# Variable pitch systems How does a *single acting* PCU unit work

PRESSURISED OIL is fed to ONE SIDE of the piston to drive the pitch angle TOWARDS COARSE when OIL PRESSURE REDUCED, blade MOVE BACK TO FINE ## Footnote Pg 227

# Variable pitch systems What does CTM stand for

CENTRIFUGAL TWISTING MOMENT ## Footnote Pg 227

# Variable pitch systems What 2 things happen for the propellers to move back to fine in a *single acting* Pitch Control Unit (PCU)

1. OIL PRESSURE REDUCED 2. CENTRIFUGAL TWISTING MOMENT ## Footnote As oil pressure is reduced, the CTM moves the propeller back to fine Pg 227

# Variable pitch systems In a *single acting* PCU, as RPM is reduced, what would CTM have a tendancy to do

REDUCE ## Footnote Pg 227

# Variable pitch systems What component is fitted to help a *single acting* PCU overcome the reduction in CTM with a reduction in RPM

SPRING ## Footnote Pg 227

# Variable pitch systems In a *single acting* PCU, if the engine develops a fault and power output drops, what is an associated risk to the PCU

DROP IN OIL PRESSURE ## Footnote Pg 227

What is the advantage of a *fined off* propeller blade after the loss of oil pressure on a light aircraft

REDUCED TORQUE DRAG ## Footnote Pg 228

# Variable pitch systems What is the name given to the resultant action the propeller does to fining off a blades following loss of power

WINDMILLING ## Footnote Pg 228

# Variable pitch systems What may *windmilling* assist with following a loss of power

RESTARTING ## Footnote Pg 228

# Variable pitch systems What is the preferred position for blades to assume on a *twin engine* light aircraft following an engine failure

COARSE ## Footnote You do not want blades to move to fine as this has signfiicant effect on asymmetric drag Pg 229

# Variable pitch systems On a *twin engine* light aircraft, what force would significantly increase as a result of a fine pitch propeller following an engine failure

ASYMMETRIC DRAG ## Footnote Pg 229

# Variable pitch systems On a light *twin engine* aircraft, what is added to the blade root and at what angle, to assist with coarsening the blade

1. COUNTERWEIGHT 2. 90° ## Footnote Pg 229

# Variable pitch systems What 2 components are used to help overcome the CTM of the blades on a *twin engine* light aircraft following an engine failure

1. COUNTERWEIGHTS 2. SPRING ## Footnote Pg 229

# Variable pitch systems How does a *double-acting* PCU unit work

HIGH PRESSURE oil supplied to BOTH SIDES of a piston ## Footnote High pressure oil is supplied to the appropraite side of the piston to adjust the propeller pitch from fine to coarse Pg 230

# Variable pitch systems What sort of propeller system would use a *double-acting* PCU and why

1. LARGE propeller systems 2. SPRING and COUNTERWEIGHTS not enough ## Footnote Spring and counterweights not enough alone to overcome the centrifugal forces created by large propeller systems. A double acting PCU which uses high pressure oil is fitted Pg 231

# Centrifugal latch What is the importance of minimising drag on start up

REDUCE LOAD ON ENGINE ## Footnote Pg 232

# Centrifugal latch What component is incorporated into a PCU to help minimise propeller drag on startup

CENTRIFUGAL LATCH ## Footnote Pg 232

# Centrifugal latch Where is the PCU mounted

ON PROPELLER HUB ## Footnote Pg 232

# Centrifugal latch What forces the *centrifugal latch* out of the recess

SPRING PRESSURE ## Footnote Pg 232

# Centrifugal latch What happens to the *centrifugal latch* when the RPM is above 700-1000 RPM

FORCED INTO RECESS ## Footnote The centrifual force forces the pins into their recess, overcoming the spring pressure Pg 232

# Centrifugal latch When the RPM drops below 1000 RPM, what happens to the *centrifugal latch* and what must the piston do before it can function

1. SPRING PRESSURE overcomes CENTRIFUGAL FORCE 2. Piston must MOVE FORWARD ## Footnote Once below 1000 RPM, the spring pressure overcomes the centrifugal force and tries to push the latch out of the recess. The piston must travel far enough forward (fine pitch) for the latches to pop out behind the piston, preventing it moving backwards in the cylinder. Pg 232

# Centrifugal latch What should a pilot do after starting the engine of a variable pitch propeller aircraft that utilises a *centrifugal latch* and why

1. ADVANCE PROPELLER SLIGHTLY FORWARD 2. REMOVE CONTACT betwee PISTON and LATCH ## Footnote Advance the propeller lever slightly forward as the RPM is below 1000 and the piston is subsequently contacting with the pins of the centrifugal latch. Moving the propeller pitch slightly forward will break the contact. Pg 232

# Constant Speed Unit (CSU) What is the purpose of the *constant speed unit (CSU)*

MAINTAIN PROPELLER at STABLE RPM | Constantly MATCH propeller torque drag to the engine torque ## Footnote Maintain the propeller at a stable RPM corresponding to the design RPM for the engine "*match torque drag to engine torque*" Pg 234

# Constant Speed Unit (CSU) If *engine torque* exceeds *torque drag* the propeller will ACCELERATE or DECELARATE

ACECELERATE ## Footnote Pg 234

# Constant Speed Unit (CSU) If the *torque drag* exceeds *engine torque* the propller will ACCELERATE or DECELERATE

DECELERATE ## Footnote Pg 234

# Constant Speed Unit (CSU) *torque drag* will INCREASE or DECREASE with any change in forward speed

INCREASE ## Footnote RPM would vary continuously with TAS if there were not a control mechanism in place Pg 234

# Constant Speed Unit (CSU) If *engine torque* exceeds *torque drag* , the CSU will FINE or COARSEN the blade

COARSEN ## Footnote Pg 235

# Constant Speed Unit (CSU) If *torque drag* exceeds *engine torque*, the CSU will FINE or COARSEN the blade

FINE ## Footnote Pg 235

# Constant Speed Unit (CSU) 1. If RPM falls, the CSU moves blades to a ____ 2. If RPM rises, the CSU moves blades to a ____ | FINE PITCH or COARSE PITCH

1. FINE PITCH 2. COARSE PITCH ## Footnote Pg 235

What is a PEC

PROPELLER ELECTRONIC CONTROL (PEC) ## Footnote Pg 235

# Constant Speed Unit (CSU) What is the function of a *propeller electronic control (PEC)* unit

CONTROL PCU ## Footnote A PEC on each engine senses inputs from aircraft, engine, and propeller system to calculate the correct propeller pitch for each combination of conditions per engine Pg 235

What does CSU stand for

CONTSTANT SPEED UNIT (CSU) ## Footnote Pg 236

# Constant Speed Unit (CSU) What are the 2 types of CSU

1. SINGLE ACTING 2. DOUBLT ACTING ## Footnote Pg 236

# Constant Speed Unit (CSU) Both a *single acting* and a *double acting* CSU comprise of what 4 components

1. GEAR PUMP 2. ROTATING GOVENER 3. PILOT VALVE 4. REGULATING SPRING ## Footnote 1. GEAR PUMP - Boost engin oil pressure 2. ROTATING GOVENER - Driven by engine 3. PILOT VALVE - Attached to govener 4. REGULATING SPRING - Opposes movement of governor flyweight Pg 236

# Constant Speed Unit (CSU) In a CSU unit, what is the purpose of the *gear pump*

BOOST ENGINE OIL PRESSURE | Boost pressure to the higher pressure required by PCU ## Footnote Pg 236

# Constant Speed Unit (CSU) In a CSU unit, what is the *rotating governor* drive by

ENGINE | Drive directly by the engine ## Footnote Pg 236

# Constant Speed Unit (CSU) In a CSU unit, what is the *pilot valve* attached to

GOVERNOR ## Footnote Pg 236

# Constant Speed Unit (CSU) In a CSU unit, what is the purpose of a *regulating spring*

OPPOSE MOVEMENT of GOVERNOR FLYWEIGHT ## Footnote Pg 236

# Constant Speed Unit (CSU) In a CSU, which component provides the mechanism for directing oil pressure to one or both sides of the PSU piston

PILOT VALVE ## Footnote Pg 237

# Constant Speed Unit (CSU) Name each of the component parts in the CSU [LINK HERE](https://drive.google.com/file/d/1PIO2XL8kvghzUfds8F0I_kNruwoKuZzt/view?usp=sharing)

1. Speeder spring 2. Governor 3. Relief Valve 4. Drive shaft from engine 5. CSU oil pump 6. Flyweights 7. Governor control [LINK HERE](https://drive.google.com/file/d/18_4DYuC5oCmva1wMFJxegcVEwELequoB/view?usp=sharing) ## Footnote Pg 236

# Constant Speed Unit (CSU) A *single acting* CSU has how many outlet ports A *double acting* CSU has how many outlet ports

1. 1 2. 2 ## Footnote Pg 236

# Constant Speed Unit (CSU) What is the key difference in regards to the pilot valve between a *double acting* and a *single acting* constant speed units

_SINGLE ACTING_ Only *ONE* output Directs pressurised oil to PCU _DOUBLE ACTING_ Directs pressurised oil to *EITHER* coarsen or fine the PCU piston ## Footnote Pg 238

# Constant Speed Unit (CSU) What is the *pilot valve* controlled by

GOVERNOR ## Footnote Pg 239

# Constant Speed Unit (CSU) What component does the *governor* control

PILOT VALVE ## Footnote Pg 239

# Constant Speed Unit (CSU) A governors flyweights move *INWARDS* or *OUTWARDS* as RPM increases

OUTWARDS | Lifts valve against spring pressure ## Footnote Pg 239

# Constant Speed Unit (CSU) Within a CSU, when the governer flyweights *lift* the spring, the pilot valve directs pressurised oil to which side of the PCU | PCU - Pitch Control Unit

COARSE ## Footnote Pg 239

# Constant Speed Unit (CSU) When the governer flyweights lift the spring as a result of increased RPM, the return line *OPENS* or *CLOSES* to the fine side of the PCU | PCU - Pitch Control Unit

OPENS ## Footnote Pg 239

# Constant Speed Unit (CSU) When blades *coarsen*, what happens to propeller torque drag. What does this do to engine RPM. What name is given to this situation

1. INCREASE 2. DECREASE 3. OVERSPEED ## Footnote Pg 239

# Constant Speed Unit (CSU) When RPM reduces to a point where *propeller torque* matches *engine torque* are matched, what happens to the governor flyweights

MOVE INWARDS ## Footnote Pg 241

# Constant Speed Unit (CSU) As the governor flyweights move inwards, what happens to the *pilot valve*

LOWERS | Lowering pilot valve shuts off supply of high pressure oil into chamber ## Footnote Pg 241

# Constant Speed Unit (CSU) What is the name given when a hydraulic lock is created in the CSU piston, locking the propeller at the selected pitch angle for a given RPM

ON-SPEED ## Footnote Pg 241

# Constant Speed Unit (CSU) At *on-speed* condition, what 2 forces from which 2 components are counterbalanced

1. LIFTING from GOVERNER COUNTERWEIGHTS 2. PRESSURE of REGULATING SPRING ## Footnote At on-speed condition, the lfiting action of the governer counterweights is exactly counterbalanced by the pressure of the regulating spring Pg 241

# Constant Speed Unit (CSU) Governor flyweights experience *MORE* or *LESS* centrifiugal force as RPM decreases

LESS ## Footnote Pg 242

# Constant Speed Unit (CSU) As RPM decreases and flyweights experience less centrifugal force, which direction will they move. What happens to the pilot valve

1. INWARDS 2. LOWERS ## Footnote Pg 242

# Constant Speed Unit (CSU) When *spring pressure* becmes the dominante force in the CSU due to decreased RPM and inward moving flyweights, what this this condition called

UNDER-SPEED ## Footnote Pg 242

# Constant Speed Unit (CSU) In an *under-speed* condition, what side of the pitch control unit (PCU) does the valve direct high pressure oil

FINE PITCH SIDE ## Footnote Pg 242

# Constant Speed Unit (CSU) In an *under-speed* condition, with high pressure oil being directed to the fine pitch side of the pitch control unit (PCU), what does this do to the blades and what effect does it have

1. Blades move FINER 2. PROPELLER TORQUE DRAG REDUCES ## Footnote Blades moving finer means that the torque drag reduces Reduced propeller torque drag is now below the engine torque. This allows the propeller to accelerate back to equilibrium Pg 242

# Constant Speed Unit (CSU) What 2 factors is *on-speed* condition determined by

1. MASS of GOVERNOR WEIGHTS 2. FORCE applied to OPPOSING SPRING ## Footnote Pg 244

# Constant Speed Unit (CSU) What component is added for the pilot to select different RPM *on-speed* conditions

RPM LEVER ## Footnote Pg 244

# Constant Speed Unit (CSU) What effect does the RPM lever have on the governor spring when moved forward

ALTERS COMPRESSION FORCE ## Footnote Moving the lever forward presses on the spring, altering the compression force. Increased force makes it harder for flyweights to lift the pilot valve Pg 245

# Constant Speed Unit (CSU) With the RPM lever forward and the spring force further compressed, what effect does this have on the *flyweights* to the pilot valve*. What does it allow the propeller to do with regards to speed

1. FLYWEIGHTS unable to LIFT PILOT VALVE 2. Blades STABILISE at FINER PITCH (on-speed) ## Footnote Pg 245