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Lewis Revision > 8.2 > Flashcards

8.2 Flashcards

1
Q

What does the continuity equation state about the speed of airflow and the area of The cross section of the tube if the density remains constant

A

They’re inversely proportional

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2
Q

What’s the term jet outlet mean?
Diffuser outlet?

A

Jet- diameter decrease so speed increases
Diffuser- diameter increase so speed decreases

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3
Q

What’s the formula for dynamic pressure

A

1/2 density x velocity squared

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4
Q

How’s dynamic pressure indicated to the pilot

A

As indicated air speed

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5
Q

What happens to the speed of airflow and the air pressure at the stagnation point

A

Speed of airflow is ZERO and static pressure increases and dynamic pressure is none existent

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6
Q

What’s laminar flow

A

When particles all flow parrallel to one another in layers with streamlines not crossing each other

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7
Q

What are characteristics of laminar air flow

A

Smooth
Uninterrupted
Less energy than turbulent flow
Difficult to achieve

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8
Q

What’s more desireable, laminar or turbulent flow and why

A

Laminar is because it will give high lift and low skin friction

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9
Q

Is laminar air flow easier to achieve with a positive or negative pressure gradient

A

Positive

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10
Q

What’s more maturallt occuring, laminar or turbulent flow

A

Turbulent

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11
Q

What type of drag is caused as a result of turbulent airflow

A

Friction drag

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12
Q

What’s free stream velocity

A

It’s fluid that’s far enough away from the moving body that it is not affected by the body’s movement through the fluid

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13
Q

What’s thicker, the laminar boundary layer or the turbulent boundary layer and what’s the negative and positive of this

A

turbulent thicker which causes more drag but less flow separation

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14
Q

Why happens to the transition point of the laminar flow to turbulent flow when the angle of attack increases and what happens to the adverse pressure gradient

A

Moves closer to the leading edge
Becomes stronger

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15
Q

What are advantages of laminar flow

A

Less surface friction meaning less fuel usage which gives greater range, faster top speeds and ability to glide in event of engine failure

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16
Q

What’s disadvantages of laminar flow

A

Due to low kinetic energy flow separation is more common
Easier to stall at low angle of attack due to this

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17
Q

When’s it harder to achieve laminar flow

A

At high angle of attack and high speeds

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18
Q

Is it safer to stall at wing root or tip

A

Root

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19
Q

What are consequences of dowmwash

A

Reduces effective aoa meaning a reduction in lift (can be compensated by tilting wing at a greater aoa to compensate)
Increased induced drag due to increase in alpha tips

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20
Q

What’s the induced alpha

A

The angle between the effective airflow and relative airflow

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21
Q

What happens to induced drag the stronger vortices get

A

Induced drag is greater

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22
Q

What’s the chord line

A

The lien that goes from the leading to trailing edge of the wing

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23
Q

What’s the mean camber line

A

The line drawn in between upper and lower surface of wing from trailing to leading edge

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24
Q

What’s the maximum camber

A

The greatest distance of the mean camber line from thee chord line which is expressed as a percentage of its chord

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25
Q

What’s positive camber and negative camber

A

Positive camber is when the mean camber line is above the chord line
Negative camber is when the camber line is below the chord line

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26
Q

What’s the maximum camber of a typical low speed profile and where is located on the wing

A

5 percent
45 percent aft of the leading edge

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27
Q

What’s the fineness ratio

A

The maximum thickness or depth of a section expressed as a percentage of chord from leading edge to trailing edge

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28
Q

What’s the aspect ratio

A

The ratio between the length and average width of the surface of the winds

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29
Q

How do you calculate aspect ratio if the chord is equal to throughout the length of the wing

How do you calculate aspect ratio if chord isn’t constant

A

Length of wing/width of wing

Wing span squared / wing area

30
Q

What’s induced drag affected by

A

Speed
Wing tip design
Aspect ratio

31
Q

What’s wash in ans wash out

A

Wash in- an angle of incidence that’s greater towards wing tips
Wash out- refers to angle of incidence that’s greater at the wing roots

32
Q

What’s a geometrically twisted wing

A

The camber is constant across the span of the wing but the angle of incidence is greater at the root

33
Q

What’s aerodynamically twisted wings

A

The camber of the wing is greater at the root than the tip and angle of incidence is constant

34
Q

What’s MAC

A

Mean aerodynamic chord
The average chord length of a tapered of swept wing

35
Q

What’s the angle of attack

A

Angle between the chord line and relative airflow

36
Q

What’s the angle of incidence

A

The angle between the longitudinal axis and chord line

37
Q

What’s the centre of pressure

A

The point on the chord line where the total sum of a pressure field acts on a body

38
Q

At what point of the wing does the resultant vector of lift and drag act

A

At centre of pressure

39
Q

What are the 4 different wing shapes

A

Elliptical
Rectangular
Tapered
Swept

40
Q

What wing type stalls across the whole wing at the same time

A

Elliptical

41
Q

What wing designs stall at the tip first

A

Swept
Tapered

42
Q

What wings stall at the root first

A

Rectangular

43
Q

What’s the difference between positively and negatively swept wings

A

Positively is backwards
Negative is forwards

44
Q

What’s a sweep angle

A

The angle between the line of 25 percent chords and a line perpendicular to the root chord

45
Q

What’ happens to the stability of the aircraft the more a wing is swept back

A

Becomes more stable on roll axis

46
Q

What’s a disadvantage of swept wings

A

Causes a loss of lift at wing tips due to spanwise flow

47
Q

What’s a dihedral wing

A

Where the tip is above the root

48
Q

What’s an anhedrwl wing

A

Where the root is higher than the tip

49
Q

What’s an advantage of dihedral angles

A

Increases roll stability (lateral stability)

50
Q

What’s induced drag

A

The drag on the wing caused by lift

51
Q

What’s parasite drag

A

Drag chased by the distribution of pressure, skim friction or interference

52
Q

What’s compressible drag

A

Drag caused by the shock waves on an aircraft approaching speed of sound

53
Q

What are the three types of parasite drag

A

Form
Friction
Interference

54
Q

What causes form drag

A

Pressure distribution through the body

55
Q

What speed regions does compressible drag occur in

A

Transonic and supersonic

56
Q

What happens to the boundary layer as if passes trough the shockwave

A

Thickens

57
Q

What’s total drag the sum of

A

Induced
Parasite

58
Q

What type of drag only occurs at transonic speed regions

A

Wave/compressible

59
Q

What’s the maximum camber of a low speed profile and where’s it located

A

5% max

45% aft of the leading edge

60
Q

What’s the sweep angle

A

The angle between the line of 25% of chords and a line perpendicular to roots chord

61
Q

How do you calculate coefficient of drag

A

Measured drag/ theoretical drag

62
Q

How do you calculate coefficient of lift

A

Measure lift/theoretical lift

63
Q

How is rime ice formed

A

When a small supercooled water droplets freeze on contact with a surface that is below freezing temps

64
Q

What’s the dangerous type of ice

A

Clear ice because it’s heaviest

65
Q

What’s up wash

A

When a air flows towards a wing it will be turned to the low pressure region of upper surface of aerofoil

66
Q

What’s down wash

A

When air goes over aerofoil and returns to natural state

67
Q

What’s the aerodynamic centre

A

The particular point where the coefficient moment is constant

68
Q

Where’s the aerodynamic centre on most aerofoil

A

25% of the chord from the leading edge

69
Q

What acts in the opposite direction of relative wind

A

Sideslip

70
Q

What type of stability is keel

A

Lateral

Lewis Revision (4 decks)

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