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ATPL - [Mod 2] AGK - Engines > 10. Propeller Systems - Sections 1-4 > Flashcards

10. Propeller Systems - Sections 1-4 Flashcards

1
Q

Design and construction

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

A

CENTRAL HUB

Pg 221

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2
Q

Design and construction

The central hub is enclosed inside of a fairing called what

A

SPINNER

Pg 221

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3
Q

Design and construction

What are the 2 key purposes of a spinner

Other than encasing the central hub

A
  1. REDUCE DRAG
  2. ORDERLY AIRFLOW

Encourages orderly airflow around the hub

Pg 221

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4
Q

Design and construction

What is the hub attached to in the engine

A

DRIVE SHAFT

Either directly or via a gearbox

Pg 221

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5
Q

Design and construction

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

A
  1. DIRECTLY
  2. GEARBOX

Pg 221

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6
Q

Design and construction

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

A

ENGINE DRIVE SHAFT

Pg 222

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7
Q

Design and construction

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

A

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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8
Q

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

A

REDUCTION GEARBOX

Pg 222

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9
Q

Design and construction

What is the purpose of a reduction gearbox

A

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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10
Q

Design and construction

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

A

PITCH CONTROL UNIT
(PCU)

Pg 222

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11
Q

Design and construction

What is the purpose of a pitch control unit

A

SWIVIL BLADES on their BEARINGS

Pg 222

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12
Q

Design and construction

What 2 materials are typical blades on modern aircraft made from

A
  1. ALUMINIUM ALLOY
  2. COMPOSITES

Pg 223

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13
Q

Variable pitch systems

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

A

THRUST

Pg 224

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14
Q

Variable pitch systems

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

A

TORQUE DRAG

Pg 224

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15
Q

Variable pitch systems

On a fixed pitch propeller system, how is thrust increased

A

INCREASE RPM

Pg 225

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16
Q

Variable pitch systems

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

A

LESS EFFICIENT

Pg 225

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17
Q

Variable pitch systems

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

A

FIXED PITCH PROPELLER

Pg 225

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18
Q

Variable pitch systems

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

A

MAX THRUST for LEAST DRAG

Pg 225

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19
Q

Variable pitch systems

What is the purpose of a variable pitch propeller system

A

ACHIEVE OPTIMUM AoA

Adjust blade pitch to achieve optimum Angle of Attack

Pg 225

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20
Q

Variable pitch systems

On a variable pitch propeller system how is thrust increased

A

INCREASING BLADE AoA

Pg 225

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21
Q

Variable pitch systems

Torque drag is a result of an increase in what

A

INCREASE BLADE AoA

Pg 225

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22
Q

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

A

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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23
Q

Variable pitch systems

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

A

PISTON

Pg 226

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24
Q

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

A

LINKS or PINS

Pg 226

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25
Q

Variable pitch systems

Movement of the piston in a PCU converts what movement from the piston into what movement in the blade

A

LINEAR MOVEMENT
into
ROTATIONAL MOVEMENT

Pg 226

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26
Q

Variable pitch systems

What are the 3 common methods of driving a Pitch Control Unit (PCU)

A
  1. ELECTRIC MOTOR
  2. OIL PRESSURE
  3. OIL and SPRING PRESSURE

Pg 226

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27
Q

Variable pitch systems

What are the 2 basic types of a pitch control unit

A
  1. SINGLE acting
  2. DOUBLE acting

Pg 226

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28
Q

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

A

SINGLE ACTING

Pg 227

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29
Q

Variable pitch systems

How does a single acting PCU unit work

A

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

Pg 227

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30
Q

Variable pitch systems

What does CTM stand for

A

CENTRIFUGAL TWISTING MOMENT

Pg 227

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31
Q

Variable pitch systems

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

A
  1. OIL PRESSURE REDUCED
  2. CENTRIFUGAL TWISTING MOMENT

As oil pressure is reduced, the CTM moves the propeller back to fine

Pg 227

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32
Q

Variable pitch systems

In a single acting PCU, as RPM is reduced, what would CTM have a tendancy to do

A

REDUCE

Pg 227

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33
Q

Variable pitch systems

What component is fitted to help a single acting PCU overcome the reduction in CTM with a reduction in RPM

A

SPRING

Pg 227

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34
Q

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

A

DROP IN OIL PRESSURE

Pg 227

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35
Q

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

A

REDUCED TORQUE DRAG

Pg 228

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36
Q

Variable pitch systems

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

A

WINDMILLING

Pg 228

37
Q

Variable pitch systems

What may windmilling assist with following a loss of power

A

RESTARTING

Pg 228

38
Q

Variable pitch systems

What is the preferred position for blades to assume on a twin engine light aircraft following an engine failure

A

COARSE

You do not want blades to move to fine as this has signfiicant effect on asymmetric drag

Pg 229

39
Q

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

A

ASYMMETRIC DRAG

Pg 229

40
Q

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

A
  1. COUNTERWEIGHT
  2. 90°

Pg 229

41
Q

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

A
  1. COUNTERWEIGHTS
  2. SPRING

Pg 229

42
Q

Variable pitch systems

How does a double-acting PCU unit work

A

HIGH PRESSURE oil supplied to BOTH SIDES of a piston

High pressure oil is supplied to the appropraite side of the piston to adjust the propeller pitch from fine to coarse

Pg 230

43
Q

Variable pitch systems

What sort of propeller system would use a double-acting PCU and why

A
  1. LARGE propeller systems
  2. SPRING and COUNTERWEIGHTS not enough

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

44
Q

Centrifugal latch

What is the importance of minimising drag on start up

A

REDUCE LOAD ON ENGINE

Pg 232

45
Q

Centrifugal latch

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

A

CENTRIFUGAL LATCH

Pg 232

46
Q

Centrifugal latch

Where is the PCU mounted

A

ON PROPELLER HUB

Pg 232

47
Q

Centrifugal latch

What forces the centrifugal latch out of the recess

A

SPRING PRESSURE

Pg 232

48
Q

Centrifugal latch

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

A

FORCED INTO RECESS

The centrifual force forces the pins into their recess, overcoming the spring pressure

Pg 232

49
Q

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

A
  1. SPRING PRESSURE overcomes CENTRIFUGAL FORCE
  2. Piston must MOVE FORWARD

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

50
Q

Centrifugal latch

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

A
  1. ADVANCE PROPELLER SLIGHTLY FORWARD
  2. REMOVE CONTACT betwee PISTON and LATCH

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

51
Q

Constant Speed Unit (CSU)

What is the purpose of the constant speed unit (CSU)

A

MAINTAIN PROPELLER at STABLE RPM

Constantly MATCH propeller torque drag to the engine torque

Maintain the propeller at a stable RPM corresponding to the design RPM for the engine

“match torque drag to engine torque”

Pg 234

52
Q

Constant Speed Unit (CSU)

If engine torque exceeds torque drag the propeller will ACCELERATE or DECELARATE

A

ACECELERATE

Pg 234

53
Q

Constant Speed Unit (CSU)

If the torque drag exceeds engine torque the propller will ACCELERATE or DECELERATE

A

DECELERATE

Pg 234

54
Q

Constant Speed Unit (CSU)

torque drag will INCREASE or DECREASE with any change in forward speed

A

INCREASE

RPM would vary continuously with TAS if there were not a control mechanism in place

Pg 234

55
Q

Constant Speed Unit (CSU)

If engine torque exceeds torque drag , the CSU will FINE or COARSEN the blade

A

COARSEN

Pg 235

56
Q

Constant Speed Unit (CSU)

If torque drag exceeds engine torque, the CSU will FINE or COARSEN the blade

A

FINE

Pg 235

57
Q

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

A
  1. FINE PITCH
  2. COARSE PITCH

Pg 235

58
Q

What is a PEC

A

PROPELLER ELECTRONIC CONTROL
(PEC)

Pg 235

59
Q

Constant Speed Unit (CSU)

What is the function of a propeller electronic control (PEC) unit

A

CONTROL PCU

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

60
Q

What does CSU stand for

A

CONTSTANT SPEED UNIT
(CSU)

Pg 236

61
Q

Constant Speed Unit (CSU)

What are the 2 types of CSU

A
  1. SINGLE ACTING
  2. DOUBLT ACTING

Pg 236

62
Q

Constant Speed Unit (CSU)

Both a single acting and a double acting CSU comprise of what 4 components

A
  1. GEAR PUMP
  2. ROTATING GOVENER
  3. PILOT VALVE
  4. REGULATING SPRING

  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

63
Q

Constant Speed Unit (CSU)

In a CSU unit, what is the purpose of the gear pump

A

BOOST ENGINE OIL PRESSURE

Boost pressure to the higher pressure required by PCU

Pg 236

64
Q

Constant Speed Unit (CSU)

In a CSU unit, what is the rotating governor drive by

A

ENGINE

Drive directly by the engine

Pg 236

65
Q

Constant Speed Unit (CSU)

In a CSU unit, what is the pilot valve attached to

A

GOVERNOR

Pg 236

66
Q

Constant Speed Unit (CSU)

In a CSU unit, what is the purpose of a regulating spring

A

OPPOSE MOVEMENT of GOVERNOR FLYWEIGHT

Pg 236

67
Q

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

A

PILOT VALVE

Pg 237

68
Q

Constant Speed Unit (CSU)

Name each of the component parts in the CSU
LINK HERE

A
  1. Speeder spring
  2. Governor
  3. Relief Valve
  4. Drive shaft from engine
  5. CSU oil pump
  6. Flyweights
  7. Governor control

LINK HERE

Pg 236

69
Q

Constant Speed Unit (CSU)

A single acting CSU has how many outlet ports
A double acting CSU has how many outlet ports

A
  1. 1
  2. 2

Pg 236

70
Q

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

A

SINGLE ACTING
Only ONE output
Directs pressurised oil to PCU

DOUBLE ACTING
Directs pressurised oil to EITHER coarsen or fine the PCU piston

Pg 238

71
Q

Constant Speed Unit (CSU)

What is the pilot valve controlled by

A

GOVERNOR

Pg 239

72
Q

Constant Speed Unit (CSU)

What component does the governor control

A

PILOT VALVE

Pg 239

73
Q

Constant Speed Unit (CSU)

A governors flyweights move INWARDS or OUTWARDS as RPM increases

A

OUTWARDS

Lifts valve against spring pressure

Pg 239

74
Q

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

A

COARSE

Pg 239

75
Q

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

A

OPENS

Pg 239

76
Q

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

A
  1. INCREASE
  2. DECREASE
  3. OVERSPEED

Pg 239

77
Q

Constant Speed Unit (CSU)

When RPM reduces to a point where propeller torque matches engine torque are matched, what happens to the governor flyweights

A

MOVE INWARDS

Pg 241

78
Q

Constant Speed Unit (CSU)

As the governor flyweights move inwards, what happens to the pilot valve

A

LOWERS

Lowering pilot valve shuts off supply of high pressure oil into chamber

Pg 241

79
Q

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

A

ON-SPEED

Pg 241

80
Q

Constant Speed Unit (CSU)

At on-speed condition, what 2 forces from which 2 components are counterbalanced

A
  1. LIFTING from GOVERNER COUNTERWEIGHTS
  2. PRESSURE of REGULATING SPRING

At on-speed condition, the lfiting action of the governer counterweights is exactly counterbalanced by the pressure of the regulating spring

Pg 241

81
Q

Constant Speed Unit (CSU)

Governor flyweights experience MORE or LESS centrifiugal force as RPM decreases

A

LESS

Pg 242

82
Q

Constant Speed Unit (CSU)

As RPM decreases and flyweights experience less centrifugal force, which direction will they move.
What happens to the pilot valve

A
  1. INWARDS
  2. LOWERS

Pg 242

83
Q

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

A

UNDER-SPEED

Pg 242

84
Q

Constant Speed Unit (CSU)

In an under-speed condition, what side of the pitch control unit (PCU) does the valve direct high pressure oil

A

FINE PITCH SIDE

Pg 242

85
Q

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

A
  1. Blades move FINER
  2. PROPELLER TORQUE DRAG REDUCES

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

86
Q

Constant Speed Unit (CSU)

What 2 factors is on-speed condition determined by

A
  1. MASS of GOVERNOR WEIGHTS
  2. FORCE applied to OPPOSING SPRING

Pg 244

87
Q

Constant Speed Unit (CSU)

What component is added for the pilot to select different RPM on-speed conditions

A

RPM LEVER

Pg 244

88
Q

Constant Speed Unit (CSU)

What effect does the RPM lever have on the governor spring when moved forward

A

ALTERS COMPRESSION FORCE

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

89
Q

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

A
  1. FLYWEIGHTS unable to LIFT PILOT VALVE
  2. Blades STABILISE at FINER PITCH (on-speed)

Pg 245

ATPL - [Mod 2] AGK - Engines (23 decks)

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