Aerodynamics Flashcards
(124 cards)
1
Q
What are the four main forces acting on an aircraft in flight?
A
Lift, weight, thrust, and drag.
2
Q
Define ‘lift’ in the context of aerodynamics.
A
Lift is the upward force that opposes weight, created by the pressure difference between the upper and lower surfaces of the wing.
3
Q
What principle explains how lift is generated on an aircraft wing?
A
Bernoulli’s Principle, which states that an increase in the speed of airflow results in a decrease in pressure.
4
Q
What is ‘angle of attack’?
A
The angle between the wing’s chord line and the relative airflow.
5
Q
What happens if the angle of attack is increased beyond a certain point?
A
The wing will stall as airflow separates from the surface, reducing lift.
6
Q
What is ‘drag,’ and what are the two main types?
A
Drag is the resistance force that opposes the motion of the aircraft. The two main types are parasitic drag and induced drag.
7
Q
Define ‘parasitic drag.’
A
Parasitic drag is caused by friction and increases with the square of the airspeed, including forms like skin friction, form drag, and interference drag.
8
Q
What is ‘induced drag’?
A
Induced drag is associated with the generation of lift and increases as the angle of attack increases.
9
Q
What is the purpose of winglets on an aircraft?
A
Winglets reduce induced drag by limiting wingtip vortices, improving fuel efficiency.
10
Q
Describe ‘thrust’ in aerodynamics.
A
Thrust is the forward force produced by the aircraft’s engine, propelling it through the air.
11
Q
What is a ‘boundary layer’?
A
A boundary layer is a thin layer of air next to the aircraft’s surface where air velocity changes from zero (at the surface) to the free-stream velocity.
12
Q
Define ‘laminar flow’ and ‘turbulent flow.’
A
Laminar flow is smooth and orderly, while turbulent flow is chaotic. Laminar flow produces less drag but is less stable.
13
Q
What is ‘load factor’?
A
Load factor is the ratio of the total lift generated by the wings to the actual weight of the aircraft. It increases in turns and maneuvers.
14
Q
Why does an aircraft require more lift during a turn?
A
Because the aircraft experiences an increased load factor, which requires greater lift to maintain altitude.
15
Q
What is the function of ailerons?
A
Ailerons control roll, allowing the aircraft to bank left or right.
16
Q
What is the ‘center of gravity’ (CG) in an aircraft?
A
The point where the aircraft’s weight is considered to be concentrated, affecting stability and controllability.
17
Q
Define ‘static stability.’
A
Static stability is the aircraft’s initial tendency to return to its original attitude after a disturbance.
18
Q
What is ‘dihedral angle,’ and how does it contribute to stability?
A
Dihedral angle is the upward angle of the wings relative to horizontal. It provides lateral stability by helping the aircraft return to level flight after rolling.
19
Q
What is the purpose of the horizontal stabilizer?
A
The horizontal stabilizer provides pitch stability, helping maintain the aircraft’s level attitude.
20
Q
Explain ‘stall speed.’
A
Stall speed is the minimum speed at which an aircraft can maintain level flight before stalling occurs.
21
Q
What are the main structural components of an aircraft?
A
The main components are the fuselage, wings, empennage (tail), landing gear, and powerplant (engine).
22
Q
What is the ‘fuselage’ of an aircraft?
A
The fuselage is the main body of the aircraft, housing the cockpit, passengers, cargo, and equipment.
23
Q
What is the primary function of an aircraft’s wings?
A
Wings generate lift, allowing the aircraft to become airborne and stay in flight.
24
Q
What are ‘flaps’ and where are they located?
A
Flaps are control surfaces on the trailing edge of the wings. They extend downward to increase lift during takeoff and landing.
25
What is the purpose of the 'empennage'?
The empennage, or tail section, provides stability and control, housing the horizontal and vertical stabilizers.
26
What are the 'ailerons,' and where are they located?
Ailerons are located on the outer trailing edge of each wing and control the aircraft's roll around the longitudinal axis.
27
Describe the purpose of the 'rudder' on an aircraft.
The rudder, located on the vertical stabilizer, controls the yaw, helping the aircraft to turn left or right.
28
What is the role of the 'horizontal stabilizer'?
The horizontal stabilizer prevents unwanted pitching and provides longitudinal stability.
29
What does the 'landing gear' do?
The landing gear supports the aircraft during takeoff, landing, and while taxiing on the ground.
30
What is the 'powerplant' in an aircraft?
The powerplant typically refers to the engine(s) and propeller(s), providing the thrust necessary for flight.
31
What is the function of the 'propeller'?
The propeller converts engine power into thrust, pulling or pushing the aircraft forward.
32
Define 'cockpit' in an aircraft.
The cockpit is the area where the pilots control the aircraft, with flight instruments and controls.
33
What is an 'aircraft skin,' and what is its purpose?
The skin is the outer covering of the aircraft, which provides an aerodynamic shape and structural integrity.
34
What is the purpose of 'spoilers' on an aircraft?
Spoilers are used to disrupt airflow over the wing, reducing lift and helping with descent and braking.
35
What is the 'cowling' on an aircraft?
Cowling is the removable cover around the engine compartment, which improves aerodynamics and aids in engine cooling.
36
Describe the purpose of the 'fuel tank' in an aircraft.
The fuel tank stores the fuel needed for the engine, usually located in the wings for weight distribution.
37
What is an 'instrument panel'?
The instrument panel is located in the cockpit and contains essential instruments for navigation, engine performance, and flight status.
38
What is the function of the 'trim tab'?
A trim tab is a small adjustable surface on a control surface that helps relieve control pressures and maintain steady flight.
39
What is a 'spar' in the wing structure?
A spar is a primary structural component in the wing that runs spanwise, providing strength and rigidity.
40
What are 'ribs' in the structure of an aircraft wing?
Ribs are structural elements that shape the wing and provide support to maintain the airfoil contour.
41
What are the three axes of rotation for an aircraft?
The longitudinal, lateral, and vertical axes.
42
What is the 'longitudinal axis' and what motion does it control?
The longitudinal axis runs from the nose to the tail of the aircraft and controls roll.
43
What is the 'lateral axis' and what motion does it control?
The lateral axis runs wingtip to wingtip and controls pitch.
44
What is the 'vertical axis' and what motion does it control?
The vertical axis runs vertically through the aircraft’s center of gravity and controls yaw.
45
Which control surface affects roll, and around which axis does it occur?
Ailerons control roll, which occurs around the longitudinal axis.
46
Which control surface affects pitch, and around which axis does it occur?
The elevator controls pitch, which occurs around the lateral axis.
47
Which control surface affects yaw, and around which axis does it occur?
The rudder controls yaw, which occurs around the vertical axis.
48
What is 'roll stability,' and why is it important?
Roll stability helps keep the aircraft level during flight, preventing unintentional banking or rolling.
49
How does the dihedral angle affect stability in the roll motion?
The dihedral angle increases roll stability by creating a restoring force when the aircraft rolls away from level flight.
50
What is 'yaw,' and how does it help in turning the aircraft?
Yaw is the rotation around the vertical axis, which helps align the nose in the direction of the turn.
51
What happens if an aircraft's center of gravity (CG) is too far forward?
The aircraft may have difficulty maintaining nose-up attitudes, making it hard to pitch.
52
What is 'adverse yaw,' and how is it counteracted?
Adverse yaw is the tendency for the nose to yaw in the opposite direction of a turn. It's counteracted by using the rudder.
53
Define 'coordinated turn.'
A coordinated turn uses a combination of aileron and rudder inputs to prevent skidding or slipping in a turn.
54
What is a 'slip' in aircraft motion?
A slip occurs when the aircraft’s nose is pointed outside of the turn, causing one side to slide downward.
55
What is a 'skid' in aircraft motion?
A skid occurs when the aircraft’s nose is pointed too far into the turn, causing the aircraft to move outward.
56
How does an aircraft achieve 'straight and level flight'?
By balancing the four forces of flight (lift, weight, thrust, drag) and keeping all three axes of rotation stable.
57
What is the 'center of gravity' (CG), and why is it crucial for aircraft stability?
The CG is the point where weight is balanced, affecting stability and control around all three axes.
58
How does a forward CG position affect pitch stability?
A forward CG increases pitch stability but can make it harder to lift the nose on takeoff and landing.
59
What does 'dynamic stability' refer to in an aircraft?
Dynamic stability refers to an aircraft’s ability to return to its original attitude after a disturbance over time.
60
What is a 'rudder pedal,' and how is it used in flight?
Rudder pedals control the rudder and are used to adjust yaw, helping with turns and coordinating movement along the vertical axis.
61
What is the primary effect of the ailerons?
The primary effect of the ailerons is to roll the aircraft around the longitudinal axis.
62
What is the secondary effect of aileron input?
The secondary effect of aileron input is yaw, as the aircraft tends to yaw in the direction of the roll due to differential drag.
63
What is the primary effect of the elevator?
The primary effect of the elevator is to pitch the nose of the aircraft up or down around the lateral axis.
64
What is the secondary effect of elevator input?
The secondary effect of elevator input is a change in airspeed: pitching up decreases speed, and pitching down increases speed.
65
What is the primary effect of rudder input?
The primary effect of the rudder is to yaw the nose of the aircraft left or right around the vertical axis.
66
What is the secondary effect of rudder input?
The secondary effect of rudder input is roll in the same direction as the yaw due to the aircraft's design and aerodynamics.
67
What happens to lift on each wing when ailerons are used?
Using the ailerons increases lift on one wing and decreases it on the other, causing the aircraft to roll.
68
Why does adverse yaw occur when ailerons are used?
Adverse yaw occurs because the downward-deflected aileron increases drag, pulling the nose away from the turn.
69
How do you counteract adverse yaw?
Adverse yaw is countered by applying rudder in the direction of the roll (coordinated turn).
70
What is the 'further effect' of prolonged rudder use without coordinated aileron input?
Prolonged rudder use can lead to a spiral dive, as yaw induces roll, and the aircraft begins to bank and lose altitude.
71
What is the effect of increasing power on pitch?
Increasing power generally causes the nose to pitch up due to additional thrust and airflow over the tailplane.
72
What is the effect of decreasing power on pitch?
Decreasing power causes the nose to pitch down as less airflow over the tailplane reduces lift.
73
What is the effect of applying left rudder on an aircraft’s motion?
Applying left rudder yaws the aircraft’s nose to the left, with a secondary effect of a slight left roll.
74
What is the primary effect of lowering flaps?
The primary effect of lowering flaps is to increase lift and drag, allowing for a steeper descent angle without increasing airspeed.
75
What is a secondary effect of lowering flaps during descent?
A secondary effect of lowering flaps is an increase in nose-up pitching moment due to changes in lift distribution.
76
How does the secondary effect of elevator affect an aircraft’s energy state?
Pitching up with the elevator reduces kinetic energy (airspeed), while pitching down increases it.
77
What further effect can occur if ailerons are used without coordinated rudder input in a turn?
If ailerons are used without rudder, the aircraft may experience a skidding or slipping turn.
78
Describe the effect of aileron use on lift and drag balance.
Using ailerons unbalances lift and drag between wings, causing a roll with differential drag that can lead to adverse yaw.
79
How does the secondary effect of control inputs affect coordinated flight?
Proper coordination of controls is required to balance primary and secondary effects, ensuring smooth, coordinated turns and maneuvers.
80
Why is understanding primary, secondary, and further effects of controls important for pilots?
Understanding these effects is crucial for smooth, coordinated flight, and avoiding unintended rolls, yaws, or altitude changes.
81
What is 'propeller slipstream'?
Propeller slipstream is the spiraling flow of air generated by the propeller, which moves around the fuselage and affects the airflow over the aircraft’s surfaces, especially the tail.
82
How does propeller slipstream affect the rudder and vertical stabilizer?
Slipstream increases airflow over the rudder and vertical stabilizer, enhancing their effectiveness, especially at low speeds.
83
What effect does propeller slipstream have on yaw?
Slipstream causes a left-turning tendency (especially in single-engine aircraft) due to the spiraling air pushing on the left side of the vertical stabilizer.
84
How can a pilot counteract the yaw caused by propeller slipstream?
A pilot can counteract yaw from slipstream by applying slight right rudder input, especially during takeoff and climb.
85
Why is slipstream more noticeable at high power settings and low airspeeds?
At high power and low airspeeds, slipstream effects are stronger because more airflow is directed over the tail, and the aircraft is less stabilized by forward speed.
86
What is a 'spiral dive'?
A spiral dive is a steep, descending turn where the aircraft loses altitude rapidly due to an excessive bank angle, increasing airspeed, and tightening turn radius.
87
What are common causes of a spiral dive?
Spiral dives can be caused by uncoordinated turns, excessive rudder input, failure to level wings, or disorientation in poor visibility.
88
How should a pilot recover from a spiral dive?
To recover, a pilot should reduce power, level the wings using ailerons, and then gently pull up to recover from the descent while avoiding excessive G-forces.
89
What happens when you pull back on the controls?
Deflects the elevator up, putting a downward force on the tail and raising the nose.
90
What happens when you move the controls left?
Left aileron goes up, right aileron goes down, creating a downward force on the left wing and an upward force (more lift) on the right.
91
What does pressing the left rudder pedal do?
The rudder goes left, yawing the aircraft to the left.
92
What are the steps for spiral dive recovery?
1. Reduce power 2. Gently level wings 3. Ease nose up to level flight 4. Add power back.
93
At higher speeds, which controls are more effective and why?
Controls found on the aft of the airplane (elevator & rudder) are more effective due to the slipstream effect creating more airflow over these surfaces.
94
What are the two types of energy?
1. Potential - energy due to height, often called gravitational potential (e.g., bike rolling down a hill gaining speed). 2. Kinetic - energy due to speed (e.g., speed becomes kinetic energy getting the bike back up the hill where gravity takes over again).
95
What is altitude?
Height above mean sea level.
96
What is elevation?
Vertical distance/height of a fixed point above mean sea level.
97
What is relative airflow?
Comes from the direction an aircraft is travelling, always the opposite direction of motion.
98
What is a chord line?
A straight line joining the leading edge to the trailing edge.
99
What does AoA stand for?
Angle of attack; the angle formed by the relative airflow and the chord line.
100
What is lift?
Acts at a right angle to the direction of relative airflow.
101
What is the center of pressure?
Average location of pressure variation on an object's surface; the CP moves depending on the AoA.
102
What is the critical angle of attack?
Produces the maximum possible lift at any given airspeed. Angles exceeding this will create a breakdown in smooth airflow over the aerofoils and create more drag than lift, stalling the aircraft.
103
What is the center of gravity?
The point at which you could suspend the aeroplane, and it would perfectly balance; its position depends on the distribution of weight within the aircraft.
104
When are wingtip vortices at their most powerful?
At low air speeds, during takeoff and landing.
105
What is induced drag?
A byproduct of lift and inversely proportionate to airspeed. High induced drag occurs at low airspeed, while low induced drag occurs at high airspeed.
106
What is parasite drag?
Caused by the airframe dragging through the air; increases with airspeed. Retracting flaps and undercarriage can help reduce it.
107
What is total drag?
Combination of induced drag and parasite drag; high at low speeds, reduces at medium speeds, and increases at high speeds.
108
What is aspect ratio?
Ratio of the span (wings) to the chord line; a higher aspect ratio results in lower induced drag.
109
What is IAS?
Indicated airspeed; the airspeed indicator uses the pitot static tube to collect total pressure of the oncoming airflow and transmits this to an expandable pressure capsule.
110
What is TAS?
True airspeed; the actual speed at which the aircraft is travelling through the air.
111
What is GS?
Ground speed; the speed at which the aircraft travels over the ground, same as TAS in no wind, then adjusted for wind.
112
What effect does weight have on gliding distance?
Weight has no effect on the distance an aeroplane can glide.
## Footnote
It is the AoA that determines the lift/drag ratio.
113
What is the formula for performance in aviation?
Power + Attitude = Performance
114
What determines the angle of climb?
The angle of climb is determined by the height gained in a given distance.
115
How does Vy relate to best rate of climb?
Vy speed will always be a little higher than best angle.
116
What is Vy?
Best rate of climb will reach target altitude in a faster time but covers a greater ground distance more fpm than best angle.
## Footnote
It has a shallower rate of climb than best angle.
117
What is Vx?
Best angle of climb will reach higher altitude in less ground distance, good for clearing obstacles after takeoff.
## Footnote
It takes longer to get to a certain altitude compared with best rate Vy.
118
What is the load factor during a 60 degree turn?
The load factor is 2.
119
How do you calculate the stall speed during a 60 degree turn?
Square root of 2 = 1.4, which is added onto stall speed.
120
What indicates slipping in a turn?
Slipping is identified by the ball deflected towards the center of the turn.
## Footnote
Apply more rudder in the direction of the turn.
121
What indicates skidding in a turn?
Skidding is indicated by the balance ball deflected away from the center of the turn.
122
What factors affect stall speeds?
Power reduces stall speed, flaps reduce stall speed, weight increases stall speeds, and frost or damage increases stall speed.
## Footnote
Stalling angle will decrease with frost or damage.
123
What is a spin in aviation?
A spin may develop when one wing becomes more stalled than the other, causing a continuous roll and yaw towards the dropping wing.
124
What is the recovery procedure for a spin?
Release back pressure, apply opposite rudder until the wing is unstalled, and resume straight and level or climbing configuration.
