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M17 Propeller > Propeller Pitch Control > Flashcards

Propeller Pitch Control Flashcards

1
Q

How many propellers type

A

2 , push and pull tractor

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2
Q

What 3 methods can you use to change controllable and constant speed propellers

A

Hydraulic , mechanical or electrical

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3
Q

In a multiple engine aircraft why is there a facility to shut down engine propeller

A

Be feathered to minimise drag

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4
Q

Why does a large aircraft need reverse thrust

A

Facility for reverse thrust go shorten landing distance and help with taxing

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5
Q

Propeller sub divisions

A

Fixed
Adjustable
Controllable
Constant speeding

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6
Q

What does distance breaking do

A

Move propeller to very low pitch on landing

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7
Q

Why do we distance break

A

For negative AoA and breaking force

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8
Q

What does reverse pitch (power on) do

A

Offers resistance to rotation

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9
Q

How does reverse pitch offer resistance

A

Moves propeller blades to make angle negative

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10
Q

Where does the propellor move in engine failure

A

Feather in one step

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11
Q

What are the pitch change mechanism categorised as

A

Moving piston & moving cylinder

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12
Q

How does moving piston work

A

Attached to propeller blade lugs and it moves with cylinder

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13
Q

What does a a balance weight do in a moving cylinder do

A

turns propeller in opposite direction

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14
Q

In a single acting propeller what way does the oil pressure move

A

One direction

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15
Q

In a single acting propeller what is movement in the opposite direction a result of

A

Spring force & moments of blades

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16
Q

What direction does oil pressure move in single acting propeller for single acting aircraft

A

Direction of high pitch

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17
Q

Where does spring move in single acting propellers for single engine aircraft

A

Spring moves towards low pitch

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18
Q

Single acting propellers for multi - engine aircraft what happens in engine failure

A

Decrease in oil pressure and the blades move to high pitch

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19
Q

What is high pitch

A

Coarse

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20
Q

What is low pitch

A

Fine

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21
Q

Which way is pitch change mechanism controlled

A

Both ways by oil pressure

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22
Q

If the control valve is behind gearbox where is the oil transfer tubes a

A

2 tubes , one at the front and one back

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23
Q

double acting propeller is connected by which what tubes

A

Coaxial tubes , one coarse and one fine

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24
Q

What are the 3 names of propeller governor

A

Propeller governor
Constant speed unit
Propeller control unit

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25
Q

What does a spur gear pump do

A

Positive operating pressure

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26
Q

How is a propeller governor mounted

A

Mounted on and driven by the reduction gearbox

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27
Q

What do centrifugal fly weights do

A

Oppose spring pressure and moves valve to coarser blade angle

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28
Q

What is the purpose of saftey spring

A

Permanently set blades to fine pitch position in event of lever failure

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29
Q

What are the flyweight position during on speed

A

Vertical

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30
Q

What does vertical fly weights do

A

Maintain the pilot value in position that allows no oil to flow into or out of governer assembly by use of HYDRAULIC LOCK

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31
Q

During on speed what does the spur gear pump increase to

A

250psi

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32
Q

Underspeed condition

A

More tension forces pilot valve down

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33
Q

Overspeed condition

A

Lower rpm causes centrifugal force on flyweight to lift pilot valve up

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34
Q

How is a change in power achieved

A

Changes in torque

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35
Q

What has greater range of pitch turboprop or piston engine

A

Turboprop

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36
Q

Max speed in turboprop variable pitch propeller

A

450 mph

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37
Q

GTE efficient at high rpm

A

8/10k RPM

38
Q

Propeller efficiency at low rpm

A

1-1.2k RPM

39
Q

How does propeller speed get matched to engine

A

Reduction gearbox

40
Q

Reduction gearbox ratios

A

6:1 & 20:1

41
Q

What engine is a compounded engine

A

Twin spool

42
Q

Disadvantage of compounded engine

A

Only suitable for large engines

43
Q

Disadvantage of direct coupled engine

A

Complex connection between throttle and propeller control

44
Q

Why is a compounded engine free from surge

A

It has a constant rpm

45
Q

Disadvantage to free power turbines

A

More intensive on pilot as he needs to constantly maintain parameters

46
Q

Advantage of free power turbine

A

Independent control of engine and propeller and they operate at optimum speed

47
Q

For overspeed where does the pilot pull the lever

A

Rearwards

48
Q

Reasons for overspeed

A

Aircraft into dive

Speeder spring force reduced on fly-weights

Pilot increase fuel flow by moving throttle forward

49
Q

Why would we unfeather an engine during flight

A

For engine restart

50
Q

How do we unfeather a propeller

A

Move it to a fine pitch

51
Q

What’s provides a reserved of pressure to turn blades when unfeathering

A

Unfeathering accumulator

52
Q

When are centrifugal latches used

A

At engine shut down to stop piston moving and lock it into a fine pitch

53
Q

What’s shaft horse power

A

Power available from engine at propeller driveshaft

54
Q

What is equivalent shaft horsepower

A

Residual power from engine exhaust plus SHP

55
Q

At static what is 1hp equivalent to in thrust

A

2.5lbs

56
Q

What do turboprop gas generators run at

A

100% rpm or near

57
Q

How is FFPS operated

A

Oil pressure which is controlled electronically in cockpit

58
Q

FFPS two positions

A

Engaged and withdrawn

59
Q

What does the electro hydraulic stop coarsen

A

Pitch of blade preventing propeller from drifting below flight fine pitch should FFPS fail

60
Q

When does the microswitch energise and engage electro-hydraulic stop

A

Blade angle reduces more then 2 degrees below FFPS

61
Q

On direct control of blade angle what does the engine follow

A

Propller

62
Q

Direct control of fuel flow

A

Propeller follows engine speed

63
Q

What’s the purpose of the CSU

A

Keep propeller rpm constant on free power turbines

64
Q

What are the 3 reasons for limit fine pitch

A

Engine failure
Propeller control
Control unit failure

65
Q

What does FFPS do

A

Ensures adequate thrust given when needed in flight operations

66
Q

What does constant speeding mean

A

Governer is regulating the speed of propeller within certain rpm range

67
Q

Where is resetting of beta valve done

A

Mechanical feedback via beta ring

68
Q

Is propeller governor effective in beta range

A

No

69
Q

How is beta range controlled

A

Power lever

70
Q

What does overspeed governer provide

A

Pcu with high pressure engine oil to change pitch of propeller

Governor prevents over speeding

71
Q

What type of propeller uses twin lever control

A

Single acting propeller

72
Q

What does the conditioning lever do in twin lever control

A

Selects propeller rpm

73
Q

What does the power lever control in twin lever control

A

Controls engine power

74
Q

What does a ground fine pitch stop do

A

Keeps blades at zero position for starting and initial acceleration

75
Q

When is feathering used automatically

A

During take off & cruise

76
Q

Lever movement C-D

A

When fuel flow increases , rpm increases to maintain optimum blade angle

77
Q

Lever movement D-E when is more rpm needed

A

During take off

78
Q

What’s the beta range power lever positions

A

Idle and maximum reverse

79
Q

Advantages of beta range

A

Reduce landing roll & brake wear

80
Q

How does beta range help while aircraft on ground

A

Improve manoeuvrability on ground and reversing during taxiing

81
Q

Disadvantages of beta range

A

Complicated control system and increased blade damage

82
Q

When is engine cooling reduced

A

When in reverse pitch

83
Q

Where is hydromechanical PCU mounted

A

Reduction gearbox

84
Q

How does pcu control pitch of propeller

A

Directing oil either side of pitch change piston through a dual concentric beta tube

85
Q

How much % more power to engine does uptrim give

A

10%

86
Q

What condition is auto feather used

A

Take off only

87
Q

What % of torque triggers uptrim

A

Below 25%

88
Q

What speed triggers uptrim

A

Below 80%

89
Q

When is uptrim triggered

A

When max take off not set & one engine automatically feathers which uptrims other engine

90
Q

What do you push to turn off autofeather

A

Push autofeather switch light off

91
Q

Where do you push power lever to turn off autofeather

A

One or both power levers to idle

92
Q

When is auto feather disarmed

A

Both engine torques drop below 50%

M17 Propeller (7 decks)

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