Aerodynamics Flashcards
(130 cards)
1
Q
What are the four forces acting on an aeroplane in flight?
A
- Lift
- Weight
- Thrust
- Drag
2
Q
What is lift?
A
The force generated by the wings that opposes weight and keeps the aeroplane in the air.
3
Q
How does lift act in relation to the relative airflow?
A
Lift acts at right angles to the relative airflow.
4
Q
What is weight in the context of aerodynamics?
A
Weight is the force acting vertically downwards through the centre of gravity (CG).
5
Q
What is thrust?
A
The force produced by the propeller or jet engine to move the aeroplane forward.
6
Q
In which direction does thrust act?
A
Thrust acts in the direction of motion.
7
Q
What is drag?
A
The force acting to oppose the forward motion of the aeroplane.
8
Q
How does drag relate to relative airflow?
A
Drag acts in the same direction as the relative airflow, or opposite to the direction of motion.
9
Q
What is the state of equilibrium for an aircraft?
A
Lift equals and opposes weight; thrust equals and opposes drag.
10
Q
What does it mean when an aircraft is in a state of equilibrium?
A
The aircraft is not speeding up, slowing down, climbing, or descending.
11
Q
What is wing loading?
A
A measure of how much mass is being supported by a given area of wing.
12
Q
How is wing loading calculated?
A
Wing loading = mass of aeroplane / wing area.
13
Q
True or False: Lift acts in the same direction as weight.
A
False
14
Q
Fill in the blank: The total reaction produced by lifting surfaces acts through the _______.
A
[centre of pressure]
15
Q
What is an aerofoil?
A
Any surface that produces lift, such as a wing, tail, fin or rotor blade.
Aerofoils are crucial for generating lift in various aircraft components.
16
Q
Define span in aerodynamics.
A
The distance between wingtips.
Span is an important measurement affecting an aircraft’s lift and drag characteristics.
17
Q
What is a chord line?
A
The straight line joining the leading and trailing edges of an aerofoil.
The chord line is a reference for measuring angles of attack and camber.
18
Q
What does the mean camber line represent?
A
The curved line halfway between the upper and lower surfaces of an aerofoil.
It is used to analyze the aerodynamic properties of the aerofoil.
19
Q
What is camber?
A
The distance between the mean camber line and the chord line.
Camber affects the lift characteristics of an aerofoil.
20
Q
Define thickness in the context of an aerofoil.
A
The greatest distance between the upper and lower surfaces of an aerofoil.
Thickness impacts the structural integrity and aerodynamic performance.
21
Q
What is relative airflow?
A
The motion of air relative to a body, opposite to the flightpath for an aircraft.
Understanding relative airflow is essential for analyzing lift and drag forces.
22
Q
What is the angle of attack?
A
The angle between the chord line and relative airflow.
The angle of attack is critical for controlling lift generation.
23
Q
Define total reaction in aerodynamics.
A
The aerodynamic force produced by an aerofoil.
Total reaction encompasses both lift and drag forces.
24
Q
What is lift?
A
The component of total reaction perpendicular to relative airflow.
Lift is vital for maintaining altitude and overcoming gravity.
25
What is drag?
The component of total reaction parallel to relative airflow.
## Footnote
Drag opposes the forward motion of the aircraft.
26
Define boundary layer.
A very shallow layer of air affected by friction with an aerofoil surface.
## Footnote
The boundary layer is crucial for understanding flow separation and drag.
27
What is laminar flow?
A smooth orderly airflow over an aerofoil.
## Footnote
Laminar flow is associated with lower drag and higher lift efficiency.
28
What is turbulent flow?
A disrupted flow over an aerofoil.
## Footnote
Turbulent flow can increase drag and affect the lift characteristics negatively.
29
What is a transition point?
The point at which laminar flow becomes turbulent.
## Footnote
Identifying the transition point is important for optimizing aerofoil design.
30
Fill in the blank: The distance between the mean camber line and the chord line is called _______.
camber.
## Footnote
Camber plays a significant role in determining the lift characteristics of an aerofoil.
31
What principle explains the relationship between static pressure and dynamic pressure in fluid flow?
Bernoulli's principle
## Footnote
Bernoulli's principle states that in a flowing fluid, an increase in the fluid's speed occurs simultaneously with a decrease in pressure.
32
What effect describes how the pressure exerted on the walls of a tube changes with the speed of fluid flow?
Venturi effect
## Footnote
The Venturi effect is a phenomenon where fluid speed increases as it passes through a constricted section of pipe, leading to a drop in pressure.
33
What is the formula that expresses the relationship between static pressure and dynamic pressure?
Static pressure + dynamic pressure = constant total pressure
34
List three ways a pilot can increase lift.
* Angle of attack
* Airspeed
* Camber or curvature of the wing
35
What is the Coanda Effect?
A moving stream of fluid in contact with a curved surface will tend to follow the curvature of the surface rather than continue traveling in a straight line.
36
How is the shape of an airplane wing designed to create lift?
The top side of the wing is curved while the bottom side is relatively flat.
37
What happens to air pressure above and below the wing during flight?
The air pressure on the top of the wing is less than that on the bottom of the wing.
38
What results from the pressure difference between the top and bottom of the wing?
A net force acting upwards called lift.
39
True or False: Lift pushes the wings downwards and keeps the airplane in the air.
False
## Footnote
Lift pushes the wings upwards, helping to keep the airplane in the air.
40
Fill in the blank: The air moving on the top of the curved wing must travel _______ than the air moving under the wing.
faster
41
What is the effect of increasing the angle of attack on lift?
It increases lift.
42
What can a pilot increase to increase lift?
Lift can be increased by increasing:
* angle of attack
* airspeed
* camber or curvature of the wing
## Footnote
These factors enhance the aerodynamic performance of the wing.
43
What is the Coanda Effect?
A moving stream of fluid in contact with a curved surface will tend to follow the curvature of the surface rather than continue traveling in a straight line.
## Footnote
This effect is crucial in understanding how wings generate lift.
44
How are airplane wings shaped to create lift?
Wings are shaped so that the top side is curved while the bottom side is relatively flat.
## Footnote
This design helps to create a pressure difference above and below the wing.
45
What happens to air as it moves over the top of a curved wing?
The air above the wing must move up and down to follow the curve around the wing and stay attached to it.
## Footnote
This is due to the Coanda effect.
46
What principle explains the pressure difference between the top and bottom of a wing?
Bernoulli's principle explains that the air pressure on the top of the wing is less than that on the bottom.
## Footnote
This pressure difference is what generates lift.
47
What is lift in the context of airplane wings?
Lift is the net force acting upwards that pushes the wings upwards and keeps the airplane in the air.
## Footnote
It occurs due to the pressure difference created by airflow over and under the wing.
48
What role does the Coanda effect play in lift generation?
The Coanda effect plays a larger role in producing lift than Bernoulli's principle.
## Footnote
It affects how airflow interacts with the wing's curvature.
49
What is the angle of attack?
The angle of attack is the angle between the wing and the direction of the airflow.
## Footnote
It is crucial for determining lift and airflow behavior.
50
How does increasing the angle of attack affect lift?
Increasing the angle of attack increases the amount of air deflected downwards, thereby increasing lift.
## Footnote
However, too high an angle can lead to stall.
51
What happens if the angle of attack is too high?
If the angle of attack is too high, the airflow will no longer follow the curve of the wing, resulting in stall.
## Footnote
This creates a small vacuum behind the wing and decreases efficiency.
52
What is cavitation in the context of wing aerodynamics?
Cavitation occurs when air rushes in to fill the vacuum created behind the wing during a stall.
## Footnote
It can cause heavy vibrations and greatly decreases wing efficiency.
53
What is the general design of aircraft wings in relation to airflow?
Aircraft wings are generally angled to efficiently direct airflow downward, producing lift.
## Footnote
This design helps maintain optimal performance and prevent stall.
54
Fill in the blank: Lift is produced when high-pressure air on the bottom of the wing pushes _______ on the wing.
up
## Footnote
This upward force is what allows the aircraft to ascend.
55
True or False: The air moving under the wing must travel faster than the air moving over the top of the wing.
False
## Footnote
The air above the wing travels faster than the air below it, creating a pressure difference.
56
What is the angle of attack at which lift is a maximum?
Stalling angle
## Footnote
The stalling angle is typically about 16° for most light aircraft.
57
What happens to lift when the speed of airflow over an aerofoil is increased?
Lift increases
## Footnote
This occurs due to a greater pressure difference between the air above and below the wing.
58
To maintain level flight, what must happen to the angle of attack if airspeed is increased?
It must be reduced
## Footnote
This is necessary to keep lift constant.
59
What is the relationship between airspeed and angle of attack for level flight?
Higher speed requires a lower angle of attack and vice versa
## Footnote
For example, an aeroplane flying level at 80 knots has a higher nose attitude than when flying level at 120 knots.
60
What is the centre of pressure?
The point on the chord line through which the total reaction is considered to act
## Footnote
At normal cruise speeds, it is towards the centre of the wing.
61
What happens to the centre of pressure as the angle of attack is increased?
It moves forward
## Footnote
Above the stalling angle, the centre of pressure moves back along the chord.
62
At what angle of attack is there no lift due to equal pressure reductions on the upper and lower surfaces?
-4°
## Footnote
This is considered a small negative angle of attack.
63
Fill in the blank: The stalling angle for most light aircraft is approximately _______.
16°
64
True or False: Increasing airspeed while maintaining level flight requires an increase in angle of attack.
False
## Footnote
Increasing airspeed requires a reduction in angle of attack.
65
How does a balance tab work?
Moved automatically when the control surface is deflected
Deflects in a direction opposite to the control surface
66
Which direction does an anti balance tab deflect?
Same direction as the control surface
67
What tab does a stabilator usually have?
Anti balance tab
68
What is the benefit of a stabilator?
Requires less deflection to produce a given load than an elevator and therefore helps reduce parasite drag
69
What is the purpose of a mass balance?
To bring the centre of gravity of the control surface closer to the hinge line to reduce the danger of flutter
70
What are the two types of flaps?
Leading edge devices
Trailing edge flaps
71
What are the advantages of flaps?
Steeper descent without increasing speed due to increased drag
Slower approach speed because the extra lift lowers the stall speed
72
What is the purpose of slotted flaps?
Have a slot to allow some high pressure air from beneath the wing to flow through to the lower pressure area above - energising the boundary layer and delaying separation of the airflow and onset of stall
73
What effect does lowering a Fowler flap have?
Increases both the area and camber of the wing
74
Define maximum angle of climb
Maximum gain in altitude for a distance over the ground
75
Define max rate of climb
Allows maximum ROC to a specific altitude over a given time. Occurs at a speed closest to best L/D ratio
76
What is load factor?
A measure of how hard a wing is having to work
77
Does weight affect turning performance?
No
78
What is the effect of increasing the angle of bank at a constant TAS?
Radius of turn reduces
Rate of turn increases
79
Changing TAS at a constant angle of bank
Radius increases with square of speed
Rate of turn reduces
80
Is slipping too much or not enough rudder?
Not enough rudder in the direction of the turn
81
What two errors are accounted for when determining CAS?
Position error
Instrument error
82
How is TAS determined?
IAS and CAS with variations in air density taken into account which occur with air pressure and temperature
83
What is drag?
The component of total reaction parallel to the relative airflow and opposing motion
84
What are the two types of drag affecting an aircraft?
Parasite drag
Induced drag
85
What does parasite drag include?
Form drag
Skin friction
Interference drag
Cooling drag
86
What reduces form drag?
Streamlining
87
Skin friction drag is affected by what
Surface area
Roughness
Airspeed
88
What causes interference drag?
The mixing or interfacing of air at the joining of various surfaces such as the wing roots
89
What causes cooling drag?
Cooling devices such as cowl flaps
90
When is induced drag highest?
Low speeds
91
How does weight affect induced drag?
Greater weight requires greater lift which results in greater induced drag
92
How can induced drag be minimised?
Tapering the wing
Making the wing narrower
Washout
Wing tip modifications such as winglets
93
What is washout?
The angle of incidence and therefore the angle of attack of the wingtip is smaller than that at the root, meaning most of the lift is generated on the inboard part of the wing
94
What is stability?
The inherent ability of an aircraft to return to its original flight path after an interruption with minimal input from the pilot
95
What does dihedral do?
Enhances lateral stability
96
How does dihedral help stability?
As an aeroplane sideslips the lower wing will have a higher angle of attack than the upper wing, and the fuselage shields the higher wing, disrupting the relative airflow across it. These result in the lower wing producing more lift
97
What are the two best sources of achieving directional stability
Large fin and rudder
Forward CG
98
What are the propeller effects on stability on the ground?
Gyroscopic effect
Asymmetric blade effect
Propeller torque
Slipstream effect
99
When taxiing with a strong tailwind how should the column be?
Forward
100
How does ground effect restrict the airflow
Reduces upwash and down wash
Restricts the formation of wingtip vortices
101
The amount of thrust generated by a propeller depends on:
The mass of air being accelerated
The change in velocity imparted to the air by the propeller
102
At what speed do you attain the best angle of climb?
The speed for maximum surplus thrust (distance between TR and TA is maximum)
103
What speed gives you best range
The speed which requires minimum thrust in level flight at which drag is a minimum
104
How is power calculated?
Thrust x speed
105
What are we trying to achieve aiming for maximum range?
Maximum distance per litre of fuel
Or
Minimum fuel burn over a given distance
106
When aiming for maximum endurance what are we trying to achieve?
Maximum time aloft for a given amount of fuel
Or
A given time in flight for the minimum amount of fuel
107
How do we get best range - normally aspirated engine?
Best range is at full throttle height (for the power setting which gives minimum drag speed)
108
How do we get best endurance - normally aspirated engine
Flying as low as possible
109
How do we get best range - supercharged engine?
High altitude
110
Does weight have an effect on turn performance?
No
111
Is glide range affected by weight?
No but with lower speed the rate of descent will be less so it will take longer to reach the ground
112
Is endurance affected by wind?
No - it is a function of time airborne and not distance covered
113
How to achieve maximum range in a headwind?
Fly faster than the best range speed
114
How to achieve maximum range in a tailwind?
Fly slower than best range speed to maximise the effect of a tailwind
115
What does best angle of climb achieve?
The aeroplane gains maximum height in the smallest possible horizontal distance
116
What does the best rate of climb allow?
The aeroplane gains maximum height in the shortest time
117
What variables can affect the rate and angle of climb?
Weight
Power
Use of flaps
Wind
Density altitude
118
What is the effect of gliding at any other speed than best glide speed?
Steeper glide angle
Increased rate of descent
Shorter glide distance
119
How do you determine the stalling speed increase due to load factor
Stalling speed increases with the square root of the load factor
120
What two variables affect turn performance?
Angle of bank
TAS
121
Where does the centre of pressure move after a stall?
Rearward
122
What effect does increased weight have on stall speed?
Increased weight means a higher stall speed
123
What effect does power have on stall speed?
Applied power reduces the stall speed
124
Why is a stall with power and flaps more likely to be accompanied by a wing drop
Slipstream and flaps generate lift on the inboard sections of the wing so the outer sections may stall first - any uneven lift production will result in a wing drop due to the long moment arm from the outer wing to CG
125
What is the effect of aft moving CG on stall speed?
Stall speed reduces
126
What is the definition of spiral instability
Strong directional stability with weak lateral stability
127
What is the cause of adverse yaw?
Aileron drag
128
Load factor in 30 degree AoB
1.15
129
What is the load factor in a 45 degree AoB turn?
1.4
130
What is the load factor in a 60 degree AoB turn?
2
