Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

M17 > 17.1 > Flashcards

17.1 Flashcards

1
Q

What is a propeller

A
  • consists of rotating hub with 2 or more radiating blades
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a hub

A
  • central portion of propeller which carries the blades
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a blade

A
  • aero foil section attached to hub
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a blade butt

A
  • base of propeller blade where root ends
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a blade root/shank

A
  • thickened portion blade nearest to hub
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a blade station

A

Distance measured from centre rotation (cm/inches)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Explain master reference station

A
  • distance measured from centre of rotation when all measurements are taken from
  • 75% from centre of rotation on fixed pitch propeller
  • 50-75% on variable pitch propeller
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is blade face

A
  • flat thrust producing side of a propeller blade
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a blade back

A
  • curved side of propeller blade facing the direction of flight
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a blade chord line

A
  • line through blade profile at points between face and back surfaces
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a plane of rotation

A
  • plane in which propeller rotates
  • 90* to engine centreline
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a blade angle

A
  • angle between blade chord line and plane of rotation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Explain pitch

A
  • distance advanced in one complete revolution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does the ‘pitch change mechanism’ do

A
  • device to alter blade angle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is fine pitch

A
  • vertical blade angles
  • referred as ‘low pitch’
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is coarse pitch

A
  • horizontal blade angles
  • referred as ‘high pitch’
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is reverse pitch

A
  • turning propeller blade to negative angle to produce braking or reversing thrust
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is dome assembly

A
  • encases pitch change mechanism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is a spinner

A
  • aerodynamic fairing that covers centre of propeller
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a tractor propeller

A
  • propeller mounted in front of LE of wing or on nose of aircraft
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Explain pusher propeller

A
  • propeller mounted behind trailing edge of wing or at rear of fuselage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Anything moving to 90* does what to the pitch

A

Increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Which newtons law does the propeller work

A

3rd law

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Propellers accelerate airflow over their what surface

A

Cambered surfaces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What face produces thrust in a propeller blade

A

Blade face

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the backward moving air called

A

Slipstream

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Ratio between power developed by propeller and power obtained is referred to as what

A

Propellers efficiency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the ‘momentum theory’ based on

A

Consideration of momentum and kinetic energy imparted to this mass of air

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Diameter before the disc is greater or smaller

A

Greater

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Explain diameter after the disc

A
  • diameter is smaller
  • air is compressed and has more kinetic energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What does the element theory involve

A

Involves breaking a blade down into several independent sections along the length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the element theory

A
  • aerodynamic forces acting on the propeller blades
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the blade angle (Theta)

A

Angle between chord of blade and plane of rotation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

When discussing the blade angle, reference is often made to what

A

Pitch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

When a blade is pitched to a fully vertical angle what is it called

A

‘Feathered’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Which pitch allows for large distance with every revolution

A

Coarse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Having a coarse setting limits what

A

Speed at which engine operates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Which pitch gives you short distance with every revolution

A
  • fine pitch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is blade angle (alpha) range

A

Designed to vary pitch in flight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is angle of attack

A

Angle between profile chord line and relative airflow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

As propeller rotates and advances through air, the path the blades follow is described as what

A

Helix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is the angle of advance (helix angle)(phi)

A
  • angle between rotational plane of propeller and relative airflow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

The angle of advance increases with what

A

Increasing airspeed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Reverse pitch does what to the blade angle

A

Blade pitch is decreased to a -ve value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What is blade angle (beta) range

A
  • available on ground
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What is flight fine also known as

A

‘Flat pitch’ and produces no thrust

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Explain brake moment at reverse pitch

A
  • air should not drive engine. Therefore more engine power required to maintain propeller speed
48
Q

What are the 3 things that produce lift

A
  • aerofoil shape
  • RPM
  • AOA
49
Q

The further the blade section is from rotational axis results in greater velocity

A

True

50
Q

To ensure constant angle of pitch, propeller blade must be twisted from root to tip which is known as

A

Propellers geometric twist

51
Q

Blade angle becomes smaller the further it is from centre axis to keep constant AOA is known as

A

Pitch distribution

52
Q

Explain root losses

A

Can withstand stresses but loses aerodynamic efficiency

53
Q

Explain tip losses

A
  • tip vortices and induced drag cause tip losses at high rotational speeds
  • further losses caused by compressibility effects
54
Q

Explain blade washout

A

Maintain constant AOA at different rotational speeds along the blade

55
Q

How is blade washout constructed

A
  • leading edge of propeller blade is twisted downwards from root to tip
56
Q

What is the ratio for efficiency

A

Useful power output/actual power input

57
Q

Propeller efficiency varies between

A

50%-90%

58
Q

What is propeller slip

A
  • difference between geometric pitch of propeller and it’s effective pitch
59
Q

What is geometric pitch

A
  • theoretical distance a propeller should advance in 1 revolution
60
Q

What is effective pitch

A

Distance it actually advances

61
Q

The larger the prop diameter means what with efficiency

A

More efficient

62
Q

Usual symbol for propeller efficiency is

A

Greek symbol (eta)

63
Q

Which load is the greatest felt on the propeller

A

-centrifugal force
- load created can be >7500 times the weight of the propeller blade

64
Q

What is thrust bending force

A

Attempts to bend propeller blade tips forward

65
Q

Normal propeller efficient ranges from

A

80%-90%

66
Q

Explain the torque bending force

A
  • bend the blade against the direction of propeller rotation
67
Q

Explain aerodynamic twisting moment (ATM)

A
  • CP being fWD of blades centre of rotation
  • tries to turn blade to higher (coarser) blade angle
68
Q

Explain centrifugal twisting moment (CTM)

A
  • mass of the blade is thrown out from blades centre of rotation trying to turn the blade to a lower (finer) blade angle
69
Q

Where are the greatest static loads felt

A

At blade root and hub

70
Q

The natural frequency of a propeller blade ranges from

A

20Hz (metal) - 60Hz (wood)

71
Q

Highest vibrational loads are felt in the area of about ——% of blade length

A

80

72
Q

80% of blade length region is susceptible to failure. This is also known as ?

A

Outer nodal point

73
Q

Any vibrations is decreased by

A

Using correct aerofoil shape and tip design

74
Q

As solidity increases, a propeller can transfer more power to the air

A

True

75
Q

What is more efficient. Increasing blade chord or increasing number of blades

A

Increasing number of blades

76
Q

Explain twin propellers

A
  • propellers on same engine rotating in opposite directions
77
Q

What are twin propellers also known as

A

Contra- rotating propellers

78
Q

The high speed rotation of an aircraft propeller gives what type of rotation to the slipstream

A

Spiralling

79
Q

Gyroscopes are based upon 2 fundamental properties of gyroscopic action

A
  • rigidity in space and precision
80
Q

Propeller tip to ground for tail wheel

A

9 inches

81
Q

Propeller tip to ground for nose wheel

A

7 inches

82
Q

Propeller to tip to fuselage

A

1 inch

83
Q

Propeller to nose wheel

A

1/2 inch

84
Q

Vertical stab is mounted obliquely at what angle

A

1* or 2*

85
Q

To correct gyroscopic action what is required by pilot

A
  • to use elevator and rudder to prevent undesired pitching and yawing
86
Q

Define relative airflow

A
  • defined as speed and direction of air movement past an aerofoil
87
Q

In normal flight which 2 angles are giving positive thrust and positive torque

A
  • blade angle
  • AOA
88
Q

If critical engine fails what occurs to flight performance

A

Usually too low

89
Q

What is the solution of a failing critical engine

A

Propellers turn opposite direction

90
Q

In a climb does the downward blade create more thrust (T or F)

A

True

91
Q

Explain windmilling

A
  • airflow driving the propeller which will drive engine and produce negative torque
92
Q

What is propeller brake moment

A
  • effort required to spin propeller
93
Q

Fixed pitch propeller are designed to ensure

A
  • good climb performance
  • high cruising speeds
  • towing
94
Q

How does the brake moment work when windmilling

A

Works in the direction of rotation and begins to drive propeller

95
Q

Explain blade shake

A

Blade is not rotating, there is a certain amount of movement in the mountings

96
Q

What is natural vibration

A
  • body oscillates under action of own gravitational or elastic forces
97
Q

If a vibration occurs at one particular RPM or a range, the vibration is not normally a propeller problem but a problem of poor engine propeller match

A

True

98
Q

Explain resonant frequency

A

Natural vibration frequency that occurs if the object is stuck

99
Q

Explain forced vibration

A
  • vibrating body that contacts another body
100
Q

The propeller spinners can be a contributing factor of what condition

A

Out of balance

101
Q

Propeller noise is made up of

A

Tonal and a broadband component

102
Q

Explain Broadband noise

A
  • occur as a result of turbulence in the boundary layer of the blade
103
Q

Which component is perceived as disturbance to the human ear

A

Tonal compartment

104
Q

What is rotating noise

A

Product of pressure field created by the rotating propeller

105
Q

What is vortex noise

A

Caused by vortices leaving the blade tip and blade trailing edge

106
Q

Where is the maximum value of vortex noise found

A

In the plane of rotation of the propeller

107
Q

What is displacement noise

A

Displacement of air by the propeller blades as they have finite thickness

108
Q

What is the blade vibration noise

A
  • noise that occurs with periodic stalls
109
Q

If diameter of propeller is double at constant peripheral speed, propeller noise is decreased by

A

decreased by 6db

110
Q

If diameter of propeller and rotational speed is increased what happens to the noise level

A

Increased

111
Q

Constant RPM with more blades does what to the noise

A

Reduced

112
Q

Which propeller shape produces least noise

A

Scimitar-shaped propeller

113
Q

Which materials have favourable vibrational behaviour

A

Wood or composite

114
Q

How is the critical range indicated on the engine tachometer

A

Red

115
Q

How do you fix gyroscopic effect

A

Rudder
Elevator

M17 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions