Finals-Module 6- Drag Measurement

Question 1

The four (4) forces of flight

Answer 1

Weight, Lift, Thrust, Drag

Question 2

An airplane like all bodies have
mass, with the aircraft positioned in the
ground, it has only the force of the acceleration due to gravity. This force, called ____________ acts vertically
downwards at all times.

Answer 2

weight

Question 3

Before an airplane can leave the
ground and fly the force “weight: must be
surpassed or balanced by a force which
acts upwards called __________

Answer 3

lift

Question 4

To generate lift, the airplane must
be propelled forward through air by a force
called _________. Provided by its ________

Answer 4

thrust
engine

Question 5

From the very moment the airplane
moves forward, the air pushing against the aircraft relatively resists the motion, and is
called ______

Answer 5

drag

Question 6

the force that resists the forward motion of an object
moving through a medium.

Answer 6

drag

Question 7

It acts parallel to and in the opposite direction of the aircraft.

Answer 7

drag

Question 8

As an aircraft moves/travel through air, every part of it that is exposed to the airflow produces a different type of resistance to the forward motion which constitute to the __________

Answer 8

Total Drag.

Question 9

Total Drag is sub-divided into two (2 )main types. These two main types are:

Answer 9

Parasite drag
Induced Drag

Question 10

type of drag is comprised of all the forces that work to
slow an aircraft’s movement

Answer 10

Parasite

Question 11

the drag that is not
associated with the production of lift

Answer 11

Parasite Drag

Question 12

As the term parasitic implies, it is the drag that is not
associated with the production of lift. This includes the

Answer 12

1.the displacement of the air by the
aircraft
2.turbulence generated in the airstream,
3. a hindrance of air moving over the
surface of the aircraft and

Question 13

It is an inevitable
consequence of lift and is produced by the passage
of an airfoil through the air.

Answer 13

Induced drag

Question 14

Induced drag proves that
there is no system that does work in a mechanical
sense can be ________ efficient

Answer 14

100%

Question 15

the induced drag is inherent in the production of lift, as whenever an airfoil is producing one, the pressure on the lower surface is ___________ than that on the upper surface.

Answer 15

greater

Question 16

This difference in level of pressure results in air tending to flow from the high pressure area below the tip upward to the low pressure area on the upper surface, creating ____________

Answer 16

wing tip vortices

Question 17

3 Types of Parasite Drag

Answer 17

Skin Friction Drag
Form Drag
Interference Drag

Question 18

It is the aerodynamic
resistance due to the contact of moving air with the surface of an object, and in this particular
case that object would be an aircraft

Answer 18

Skin Friction Drag

Question 19

As distance from the surface _________, less and less acceleration of the layers takes place

Answer 19

increases

Question 21

This layer of air extending from the surface (in direct contact) to the point where no viscous effect is noticeable is known as the ___________

Answer 21

Boundary layer

Question 21

At the top of the boundary layer, the molecules ___________velocity and move at the _____________ as the molecules outside the boundary layer

Answer 21

increase
same speed

Question 22

The actual speed at which the
molecules move depends upon the:

Answer 22

1. shape of the wing,
2. the viscosity (stickiness) of the air through which the wing or airfoil is moving,
3. its compressibility (how much it can be
   compacted)

Question 23

The boundary can exist in two forms

Answer 23

laminar and turbulent

Question 24

The ___________rate of change in velocity at the surface in the turbulent flow, then gives more skin friction than the laminar flow

Answer 24

increased

Question 25

____________movement of the transition point will give rise to an increase in skin friction, as this gives a _______ area of turbulent

Answer 25

Forward Greater

Question 26

The position of the transition point is dependent upon a number of factors. Some of the factors are:

Answer 26

Surface Condition and Adverse Pressure Gradient

Question 27

The thin laminar layer is extremely sensitive to surface irregularities. Any roughness on the skin of a leading portion of an aircraft will cause transition to __________ at that point and the thickening, turbulent boundary layer will spread out ____________causing a marked increase in skin friction drag

Answer 27

turbulence fanwise down-stream

Question 28

A laminar layer cannot exist when _______________

Answer 28

pressure is rising in the direction of the flow.

Question 29

On a curved surface, such as an airfoil, the transition point is usually at, or near ____________

Answer 29

to the point of maximum thickness.

Question 30

the adverse pressure gradient existing on a curved surface the transition point will be _______________ than if the surface was flat.

Answer 30

further forward

Question 31

generated by the aircraft due to its shape and the airflow around it.

Answer 31

Form Drag

Question 32

When the air has to separate to move around a moving aircraft and its components, it eventually rejoins after passing the body. How quickly and smoothly it rejoins is representative of the resistance it creates, which creates additional force to overcome.

Answer 32

Form Drag

Question 33

Easiest type of drag to reduce when designing an aircraft.

Answer 33

Form Drag

Question 34

Solution for Form Drag

Answer 34

Streamlining

Question 35

Each part of an aircraft (exposed) will be subject to form drag. To reduce form drag, it is necessary to _______________________

Answer 35

delay the separation as close to the trailing edge as possible.

Question 36

It increases the ratio between the length and depth of the body, reducing the curvature of the surfaces and thus the adverse pressure gradient

Answer 36

Streamlining

Question 37

it is the measurement of streamlining

Answer 37

fitness ratio

Question 38

What is fitness ratio

Answer 38

ratio of length to depth of an airfoil

Question 39

the combination of skin friction and form drag.

Answer 39

Profile drag

Question 40

It can be considered that these drags result from the “profile” of the aircraft presented to the relative airflow

Answer 40

Profile drag

Question 41

When considering a complete aircraft, parasite drag will always be __________ than the sum of its parts that is because of the additional drag resulting from the boundary layer created at the ____________

Answer 41

greater junctions of the aircraft

Question 42

The most interference drag is observed when two surfaces meet at ______________angles.

Answer 42

perpendicular

Question 43

_____________ are used to reduce interference drag

Answer 43

Fairings

Question 44

Parasite Drag Formula

Answer 44

Dp= (1/2)(density)(Velocity)^2(Area)(Parasite Drag Coeffiecient)

Question 45

Factors Affecting Parasite Drag

Answer 45

1. Indicated Air Speed 2. Configuration 3. Airframe Contamination

Question 46

Parasite drag varies with the ____________ of the Indicated Air Speed (IAS).

Answer 46

square

Question 47

If the Indicated Air Speed is doubled the parasite drag will be__________ greater, however if it is halved, the value of parasite drag will be __________ of its previous value.

Answer 47

four times one quarter

Question 48

Parasite drag varies _____________________ to the frontal area presented to the airflow, also known as the ____________

Answer 48

directly in proportion Parasite Area

Question 49

Contamination by ice, frost, snow, mud or slush will increase the __________, and in the case of severe airframe icing, the area

Answer 49

parasite drag coefficient

Question 50

Methods in reducing contamination is by ______________ on these prone areas.

Answer 50

employing de-icing and anti-icing devices

Question 51

_________ is an inherent component, a rather undesirable by-product of lift.

Answer 51

Induced drag

Question 52

They modify upwash and downwash in the vicinity of the wing which produces a rearward component to the lift vector known as the “induced drag"

Answer 52

Wing Tip Vortices

Question 53

Wing tip vortices modify _________ and _________in the vicinity of the wing which produces a __________component to the lift vector known as the ___________

Answer 53

upwash downwash rearward Induced drag

Question 54

When an airfoil is flown at a positive AOA, a pressure differential exists between __________________________________________________________________

Answer 54

the upper and lower surfaces of the airfoil.

Question 55

The pressure above the wing is less than ___________ and the pressure below the wing is equal to or greater than __________

Answer 55

atmospheric pressure

Question 56

The pressure above the wing is ___________ atmospheric pressure and the pressure below the wing is _____________atmospheric pressure

Answer 56

less than equal to or greater than

Question 57

Movement of air relative to pressure

Answer 57

air always moves from high pressure toward low pressure

Question 58

Since air always moves from high pressure toward low pressure, and the path of least resistance is toward the airfoil’s tips, there is a __________ of air from the __________ from____________

Answer 58

spanwise movement bottom of the airfoil outward the fuselage around the tips.

Question 59

This flow of air results in “spillage” over the tips, thereby setting up a whirlpool of air called a ____________.

Answer 59

vortex

Question 60

Wing tip vortices create certain __________ velocity components in the airflow in the vicinity of the wing, both in front of and behind it

Answer 60

vertical

Question 61

These vertical velocities created by wing tip vortices strengthen ________________________________ which reduces the_______________

Answer 61

upwash and downwash effective angle of attack

Question 62

Relationship of Vortices and Effecitve angle of attack

Answer 62

The stronger the vortices, the greater the reduction in the effective angle.

Question 63

Relationship of Effective angle of attack and overall lift if there no was spanwise pressure differential

Answer 63

Due to the localised reduction in effective angle of attack, the overall lift generated by a wing will be below the value that would be generated if there were no spanwise pressure differential

Question 64

To replace the lift lost by the increased upwash and downwash the wing must be flown at a ____________

Answer 64

higher angle of attack,

Question 65

To replace the lift lost by the increased upwash and downwash the wing must be flown at a higher angle of attack, than would otherwise be necessary. This increases drag. This extra drag is called ___________

Answer 65

induced drag

Question 66

Relationship of IAS, AOA ,vortices, and induce drag

Answer 66

The lower the Indicated Air Speed (IAS), the higher the Angle of Attack (α - the stronger the vortices- the greater the induced drag

Question 67

Factors that affect induced Drag

Answer 67

1. Size of the lift force 2. Speed of the aircraft 3. Aspect Ratio of the wing

Question 68

Relationship of lift and induced drag

Answer 68

the greater the lift, the greater will be the induced drag

Question 69

Relationship of induced drag and weight of an aircraft.

Answer 69

Induced drag will be greater at higher aircraft weights

Question 70

Relationship of lift to weight ratio

Answer 70

load factor

Question 71

Why does induced drag increase during a steady turn compared to straight and level flight?

Answer 71

Induced drag increases during a steady turn because the lift generated by the aircraft must be greater than its weight

Question 72

Relationship of load factor and induced drag

Answer 72

induced drag also increases as the load factor increases

Question 73

Relationship of induced drag coefficient and lift coeffiecient

Answer 73

the induced drag increases as the square of the lift coefficient.

Question 74

Relationship of induced drag and speed of an aircraft

Answer 74

Induced drag decreases with increasing speed.

Question 75

Why does induced drag decrease with increasing speed?

Answer 75

Induced drag decreases with increasing speed because the downwash from the tip vortices becomes less significant, reducing the rearward inclination of the lift and thereby lowering induced drag.

Question 76

Relationship of speed and dynamic pressure

Answer 76

As speed increases, dynamic pressure increases with the square of the speed.

Question 77

Relationship of Aspect Ratio and Induced Drag.

Answer 77

Induced drag therefore decreases as aspect ratio increases (for a given lift force)

Question 78

How does increasing the aspect ratio affect the wing angle of attack needed to produce a given lift coefficient?

Answer 78

Increasing the aspect ratio decreases the wing angle of attack needed to produce a given lift coefficient.

Question 79

How do higher aspect ratio wings affect the sensitivity to changes in angle of attack and the angle required to reach maximum lift?

Answer 79

Higher aspect ratio wings are more sensitive to changes in angle of attack, but they require a smaller angle of attack to reach maximum lift compared to lower aspect ratio wings.

Question 80

What happens to induced drag at high lift coefficients (low indicated airspeed)?

Answer 80

At high lift coefficients (low indicated airspeed), induced drag becomes very high and increases rapidly as the lift coefficient increases.

Question 81

Factors to consider if one decides to continue the increase of Aspect Ratio

Answer 81

1. Excessive wing bending 2. reduced roll of rate 3. reduced Ground Clearance in roll during take-off and landing

Question 82

How can excessive wing bending moments be reduced?

Answer 82

Excessive wing bending moments can be reduced by carrying fuel in the wings and mounting the engines in pods beneath the wing

Question 83

What causes a reduced rate of roll in an aircraft?

Answer 83

A reduced rate of roll is caused by the down-going wing experiencing an increased effective angle of attack

Question 84

Methods of Reducing Induced Drag

Answer 84

1. Wing end-plates 2. Tip tanks 3. winglets 4. Wing tip shape

Question 85

What effect do wing end-plates have on aircraft performance?

Answer 85

Wing end-plates restrict tip vortices, similar to increasing aspect ratio, without adding extra bending loads. However, they generate parasite drag, and at higher speeds, the overall drag reduction may not be significant.

Question 86

How do tip tanks affect induced drag and wing bending moments?

Answer 86

Tip tanks reduce induced drag by limiting tip vortices, similar to wing end-plates, and also help reduce wing bending moments.

Question 87

How do winglets reduce induced drag?

Answer 87

Winglets reduce induced drag by blocking the airflow from the bottom to the top surface of the wing, weakening the tip vortex. Additionally, the vortex generated by the winglets interacts with and further weakens the main wingtip vortex.

Question 88

designs of wing tip

Answer 88

turned down and turned up

Question 89

How does wing tip shape affect induced drag?

Answer 89

The shape of the wing tip affects the strength of the tip vortices

Question 90

The __________ of an aircraft in flight is the sum of its induced drag and parasite drag

Answer 90

total drag

Question 91

The _______________ is a number that aerodynamicists use to model all of the complex dependencies of shape, inclination, and flow conditions on aircraft drag.

Answer 91

drag coefficient

Question 92

The total drag coefficient Cd is equal to the _____________ plus the _________________

Answer 92

drag coefficient at zero lift induced drag coefficient

Question 93

Factors that affect the type of flow in the Boundary Layer:

Answer 93

1. Flow Quality 2. Shape 3. Texture 4. Pressure Gradient 5. Reynolds Number 6. Heating of the fluid