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XPrinciples of Flight > Lesson 3 > Flashcards

Lesson 3 Flashcards

1
Q

The stall occurs at CL ?

A

CL MAX

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2
Q

If you are flying at the stall speed then what percentage of the coefficient are you flying at?

A

100%

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3
Q

Stalling occurs when which angle it too big?

A

αe
AoA effective

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4
Q

In relation to vortices, which part of the wing would stall first?

A

The part of the wing where vortices are weakest will stall first.

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5
Q

With a constant chord length, would the vortices be stronger at the root or tip?

A

Tip

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6
Q

On an aerofoil - what can be increased to increase lift?

A

Speed
Surface area
AoA, camber, thickness

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7
Q

Which part of the lift formula is essentially a measure of how hard the wing is working.

A

Coefficent of lift
CL

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8
Q

What are the properties of a rectangular wing?

A

-Constant chord along the span
-Weakest vortex at wing root
-Overall strong vorticies

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9
Q

Where are the weakest vortices on a tapered wing?

A

Mid-span

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10
Q

Which part of a tapered wing would stall first?

A

Mid point

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11
Q

Vortices sink from the trailing edge of the wing increasing what?

A

Downwash

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12
Q

RAF stands for

A

Relative airflow

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13
Q

In 2D airflow. How would you describe the relationship between upwash and downwash?

A

equal

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14
Q

In 3D airflow, what causes Effective airflow?

A

Upwash is greater than downwash because of span wise flow.

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15
Q

AoA: in 2D flow the lift acts perpendicular to the ________ air flow

A

Relative air flow

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16
Q

AoA: in 3D flow the lift acts perpendicular to the _________ air flow

A

Effective air flow

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17
Q

AoA: in 3D flow the lift points further back because of Effective airflow. It now features a component of???

A

INDUCED Drag

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18
Q

αe
Alpha effective
Is the angle between what and what?

A

Chord line
and
Effective airflow

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19
Q

αi
Alpha induced
Is the angle between what and what?

A

Effective airflow
And
Relative airflow

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20
Q

αi determines the amount of _______ ____

A

Induced drag

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21
Q

αe determines the amount of ____

A

Lift

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22
Q

What determines an efficient wing

A

One that produces the required lift while minimising the induced drag

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23
Q

What part of the lift equation is essentially a measure of how hard the wing is working?

A

Coefficient of lift
CL

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24
Q

Lift can come from multiple sources. Name some

A

Speed, surface area, AoA, camber, thickness

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25
Q

When the wing has to work harder, eg. at slow speed there will be more of what?

A

Induced drag

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26
Q

Induced drag will be minimised with a high aspect ratio wing, why?

A

Only weaker vortices will develop.

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27
Q

What characteristics could be important about a wing alongside efficiency?

A

Safety
High speed flight
Cost
Practicality

28
Q

With a constant chord wing there will be a gradient of vortex strength along the span. They will be stronger at the root/tip?

29
Q

Which bit of a ‘normal’ wing will stall first?

A

Trailing root

30
Q

Rectangular wing properties are:
Chord?
Vortex strength?
Stall location?
Stall characteristics?

A

Constant Chord
Weakest Vortex at root, building to tip
Stalls aft root and spreads from there.
Provides the elevator with buffet
Suited to training aircraft

31
Q

Tapered wing properties are:
Chord?
Vortex strength?
Stall location?
Stall characteristics?

A

Chord reduces along length
Vorted strongest in the middle aft part of the wing
Stalls from the middle with little warning. Higher change of wing drop stall
Relatively efficient
Suited to more expensive GA and twins

32
Q

Elliptical wing properties are:
Chord?
Vortex strength?
Stall location?
Stall characteristics?

A

Vortex are equal along the span
The whole span stalls at the same time. (Aft to forward)
Very efficient
Very unusual to see.

33
Q

Swept wing properties are:
Chord?
Vortex strength?
Stall location?
Stall characteristics?

A

Vortex are strongest at the root
Stalls at the tip, wing drop likely
Centre of pressure can move meaning that it stalls nose high
Vorcticies are strong and the wing is inefficient.
Good at fast - terrible at the rest.

34
Q

What can be done to prevent or protect from a stall at the tip.

A

Reduce AoA at the tip / increase at the root
Twist / washout
Stall strip, forcing the root to stall first

35
Q

What type of drag is created by vortices forming at the junctions of different aircraft surfaces. How to reduce?

A

Interference drag
Can use fillets to smooth the corners.

36
Q

What can you split total drag into?

A

Induced drag
Parasite drag

37
Q

What can you divide parasite drag into? (3)

A

1/ Form drag
2/ Skin friction drag
3/ Interference drag

38
Q

How would one reduce drag?
(split into 4 types of drag)

A

Form - streamlining
Skin friction - smooth polished surfaces
Interference - fillets
Induced - Wing tip modifications

39
Q

Coefficient of drag CD is broken down into?

A

Coefficient of parasite drag CDP
Coefficient of induced drag CDI

40
Q

How does a wing tip modification help

A

Reduces vortex strength by blocking the rotation around the wingtip.

41
Q

Name 2 types of wing tip modification:

A

Winglet (split or blended)
Tip tanks

42
Q

What is a wing fence and what is it for?

A

Sits on the upper surface, blocking spanwiseflow to reduce training edge vortices

43
Q

Strakes are what and do what?

A

Fin on the engine creating a high energy vortex that flows over the top of the wing.

44
Q

Vortilons are what and do what?

A

Fence on the leading edge to generate a high energy vortex over the top of the wing.

45
Q

Which wing modification improves the low speed characteristics by generating a high energy vortex that runs over the top.

A

Vortilon
Strakes
Notched leading edge

46
Q

Vortilons, Strakes and Notched leading edge do what to the the spa wise flow?

A

Creates a barrier and reduced trailing edge vortex strength.

47
Q

What does a vortex generator do and where is it used?

A

Pulls high energy free stream air down to the boundary layer to re-energise it. It delays low and high speed stalls.

48
Q

Parasite drag mainly effected by what?

A

Speed and frontal area

49
Q

Flaps and Drag:
How do flaps effect the two main types of drag.

A

Parasite drag: Drag is always lowest in clean config.

Induced drag: Flaps have no effect.

50
Q

VMD - stands for and represents

A

Velocity minimum drag

51
Q

Above what speed could speed be describes as stable?

A

Velocity of minimum drag.
VMD

52
Q

“The backside of the drag curve” and “reigion of reversed command” can be describes as?

A

Slower than the velocity of minimum drag
VMD

53
Q

Drag vs. mass. What happens to the curve on the speed/drag graph when mass increases?

A

Velocity of minimum drag VMD increases
The curve moves up and right

54
Q

As gear is extended and flaps are lowered the curve moves up and left. What happens to VMD?

A

Gets slower

55
Q

Density vs. drag
If you are measuring IAS where does the drag / IAS curve move?

56
Q

If you were comparing drag and TAS. How would you describe the direction the curve moves as altitude increases.

A

Curve remains the shape. Low altitude is to the left, high altitude is to the right

57
Q

Given an aerofoil in a given configuration with no ice or damage, what charities would a stall have related to AoA.

A

The stall will be predictable and at the same AoA

58
Q

What does VS mean?

A

stall speed

59
Q

What does VS1G mean?

A

Stall speed at 1g

60
Q

What does VS1 mean?

A

Stall speed in a given configuration.

61
Q

What does VSO mean?

A

Stall speed in a landing configuration

62
Q

What does VSR mean

A

The reference stall speed. Defined by the manufacturer when the stall is not pronounced and a number needs to be provided.

63
Q

What does the adverse pressure gradient do?

A

Initiates a stall by absorbing the energy of the country layer.

64
Q

How could you reduce the chance of tip stall?

A

1/ Reduce AoA at tip (or force an earlier stall at the root by increasing AoA at the root)
2/ Geometric washout (twist)
3/ Aerodynamic washout (changing camber along the span)
4/Stall strip (can force an early root stall)

65
Q

An increased load factor can be caused by what (3) and which ‘drag’ will it increase?

A

Increased AoA
Increased weight
Pulling up

66
Q

Induced drag ∝ 1⁄???

A

Induced drag ∝ 1⁄V2

67
Q

CDI ∝ ___
(Coefficient induced drag)

A

CDI ∝ CL2

XPrinciples of Flight (5 decks)

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