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PPL > Aerodynamics > Flashcards

Aerodynamics Flashcards

1
Q

What are the four main forces acting on an aircraft in flight?

A

Lift, weight, thrust, and drag.

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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.

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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.

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4
Q

What is ‘angle of attack’?

A

The angle between the wing’s chord line and the relative airflow.

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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.

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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.

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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.

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8
Q

What is ‘induced drag’?

A

Induced drag is associated with the generation of lift and increases as the angle of attack increases.

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9
Q

What is the purpose of winglets on an aircraft?

A

Winglets reduce induced drag by limiting wingtip vortices, improving fuel efficiency.

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10
Q

Describe ‘thrust’ in aerodynamics.

A

Thrust is the forward force produced by the aircraft’s engine, propelling it through the air.

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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.

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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.

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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.

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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.

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15
Q

What is the function of ailerons?

A

Ailerons control roll, allowing the aircraft to bank left or right.

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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.

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17
Q

Define ‘static stability.’

A

Static stability is the aircraft’s initial tendency to return to its original attitude after a disturbance.

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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.

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19
Q

What is the purpose of the horizontal stabilizer?

A

The horizontal stabilizer provides pitch stability, helping maintain the aircraft’s level attitude.

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20
Q

Explain ‘stall speed.’

A

Stall speed is the minimum speed at which an aircraft can maintain level flight before stalling occurs.

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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).

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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.

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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.

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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.

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25
Q

What is the purpose of the ‘empennage’?

A

The empennage, or tail section, provides stability and control, housing the horizontal and vertical stabilizers.

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26
Q

What are the ‘ailerons,’ and where are they located?

A

Ailerons are located on the outer trailing edge of each wing and control the aircraft’s roll around the longitudinal axis.

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27
Q

Describe the purpose of the ‘rudder’ on an aircraft.

A

The rudder, located on the vertical stabilizer, controls the yaw, helping the aircraft to turn left or right.

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28
Q

What is the role of the ‘horizontal stabilizer’?

A

The horizontal stabilizer prevents unwanted pitching and provides longitudinal stability.

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29
Q

What does the ‘landing gear’ do?

A

The landing gear supports the aircraft during takeoff, landing, and while taxiing on the ground.

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30
Q

What is the ‘powerplant’ in an aircraft?

A

The powerplant typically refers to the engine(s) and propeller(s), providing the thrust necessary for flight.

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31
Q

What is the function of the ‘propeller’?

A

The propeller converts engine power into thrust, pulling or pushing the aircraft forward.

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32
Q

Define ‘cockpit’ in an aircraft.

A

The cockpit is the area where the pilots control the aircraft, with flight instruments and controls.

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33
Q

What is an ‘aircraft skin,’ and what is its purpose?

A

The skin is the outer covering of the aircraft, which provides an aerodynamic shape and structural integrity.

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34
Q

What is the purpose of ‘spoilers’ on an aircraft?

A

Spoilers are used to disrupt airflow over the wing, reducing lift and helping with descent and braking.

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35
Q

What is the ‘cowling’ on an aircraft?

A

Cowling is the removable cover around the engine compartment, which improves aerodynamics and aids in engine cooling.

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36
Q

Describe the purpose of the ‘fuel tank’ in an aircraft.

A

The fuel tank stores the fuel needed for the engine, usually located in the wings for weight distribution.

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37
Q

What is an ‘instrument panel’?

A

The instrument panel is located in the cockpit and contains essential instruments for navigation, engine performance, and flight status.

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38
Q

What is the function of the ‘trim tab’?

A

A trim tab is a small adjustable surface on a control surface that helps relieve control pressures and maintain steady flight.

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39
Q

What is a ‘spar’ in the wing structure?

A

A spar is a primary structural component in the wing that runs spanwise, providing strength and rigidity.

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40
Q

What are ‘ribs’ in the structure of an aircraft wing?

A

Ribs are structural elements that shape the wing and provide support to maintain the airfoil contour.

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41
Q

What are the three axes of rotation for an aircraft?

A

The longitudinal, lateral, and vertical axes.

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42
Q

What is the ‘longitudinal axis’ and what motion does it control?

A

The longitudinal axis runs from the nose to the tail of the aircraft and controls roll.

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43
Q

What is the ‘lateral axis’ and what motion does it control?

A

The lateral axis runs wingtip to wingtip and controls pitch.

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44
Q

What is the ‘vertical axis’ and what motion does it control?

A

The vertical axis runs vertically through the aircraft’s center of gravity and controls yaw.

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45
Q

Which control surface affects roll, and around which axis does it occur?

A

Ailerons control roll, which occurs around the longitudinal axis.

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46
Q

Which control surface affects pitch, and around which axis does it occur?

A

The elevator controls pitch, which occurs around the lateral axis.

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47
Q

Which control surface affects yaw, and around which axis does it occur?

A

The rudder controls yaw, which occurs around the vertical axis.

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48
Q

What is ‘roll stability,’ and why is it important?

A

Roll stability helps keep the aircraft level during flight, preventing unintentional banking or rolling.

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49
Q

How does the dihedral angle affect stability in the roll motion?

A

The dihedral angle increases roll stability by creating a restoring force when the aircraft rolls away from level flight.

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50
Q

What is ‘yaw,’ and how does it help in turning the aircraft?

A

Yaw is the rotation around the vertical axis, which helps align the nose in the direction of the turn.

51
Q

What happens if an aircraft’s center of gravity (CG) is too far forward?

A

The aircraft may have difficulty maintaining nose-up attitudes, making it hard to pitch.

52
Q

What is ‘adverse yaw,’ and how is it counteracted?

A

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
Q

Define ‘coordinated turn.’

A

A coordinated turn uses a combination of aileron and rudder inputs to prevent skidding or slipping in a turn.

54
Q

What is a ‘slip’ in aircraft motion?

A

A slip occurs when the aircraft’s nose is pointed outside of the turn, causing one side to slide downward.

55
Q

What is a ‘skid’ in aircraft motion?

A

A skid occurs when the aircraft’s nose is pointed too far into the turn, causing the aircraft to move outward.

56
Q

How does an aircraft achieve ‘straight and level flight’?

A

By balancing the four forces of flight (lift, weight, thrust, drag) and keeping all three axes of rotation stable.

57
Q

What is the ‘center of gravity’ (CG), and why is it crucial for aircraft stability?

A

The CG is the point where weight is balanced, affecting stability and control around all three axes.

58
Q

How does a forward CG position affect pitch stability?

A

A forward CG increases pitch stability but can make it harder to lift the nose on takeoff and landing.

59
Q

What does ‘dynamic stability’ refer to in an aircraft?

A

Dynamic stability refers to an aircraft’s ability to return to its original attitude after a disturbance over time.

60
Q

What is a ‘rudder pedal,’ and how is it used in flight?

A

Rudder pedals control the rudder and are used to adjust yaw, helping with turns and coordinating movement along the vertical axis.

61
Q

What is the primary effect of the ailerons?

A

The primary effect of the ailerons is to roll the aircraft around the longitudinal axis.

62
Q

What is the secondary effect of aileron input?

A

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
Q

What is the primary effect of the elevator?

A

The primary effect of the elevator is to pitch the nose of the aircraft up or down around the lateral axis.

64
Q

What is the secondary effect of elevator input?

A

The secondary effect of elevator input is a change in airspeed: pitching up decreases speed, and pitching down increases speed.

65
Q

What is the primary effect of rudder input?

A

The primary effect of the rudder is to yaw the nose of the aircraft left or right around the vertical axis.

66
Q

What is the secondary effect of rudder input?

A

The secondary effect of rudder input is roll in the same direction as the yaw due to the aircraft’s design and aerodynamics.

67
Q

What happens to lift on each wing when ailerons are used?

A

Using the ailerons increases lift on one wing and decreases it on the other, causing the aircraft to roll.

68
Q

Why does adverse yaw occur when ailerons are used?

A

Adverse yaw occurs because the downward-deflected aileron increases drag, pulling the nose away from the turn.

69
Q

How do you counteract adverse yaw?

A

Adverse yaw is countered by applying rudder in the direction of the roll (coordinated turn).

70
Q

What is the ‘further effect’ of prolonged rudder use without coordinated aileron input?

A

Prolonged rudder use can lead to a spiral dive, as yaw induces roll, and the aircraft begins to bank and lose altitude.

71
Q

What is the effect of increasing power on pitch?

A

Increasing power generally causes the nose to pitch up due to additional thrust and airflow over the tailplane.

72
Q

What is the effect of decreasing power on pitch?

A

Decreasing power causes the nose to pitch down as less airflow over the tailplane reduces lift.

73
Q

What is the effect of applying left rudder on an aircraft’s motion?

A

Applying left rudder yaws the aircraft’s nose to the left, with a secondary effect of a slight left roll.

74
Q

What is the primary effect of lowering flaps?

A

The primary effect of lowering flaps is to increase lift and drag, allowing for a steeper descent angle without increasing airspeed.

75
Q

What is a secondary effect of lowering flaps during descent?

A

A secondary effect of lowering flaps is an increase in nose-up pitching moment due to changes in lift distribution.

76
Q

How does the secondary effect of elevator affect an aircraft’s energy state?

A

Pitching up with the elevator reduces kinetic energy (airspeed), while pitching down increases it.

77
Q

What further effect can occur if ailerons are used without coordinated rudder input in a turn?

A

If ailerons are used without rudder, the aircraft may experience a skidding or slipping turn.

78
Q

Describe the effect of aileron use on lift and drag balance.

A

Using ailerons unbalances lift and drag between wings, causing a roll with differential drag that can lead to adverse yaw.

79
Q

How does the secondary effect of control inputs affect coordinated flight?

A

Proper coordination of controls is required to balance primary and secondary effects, ensuring smooth, coordinated turns and maneuvers.

80
Q

Why is understanding primary, secondary, and further effects of controls important for pilots?

A

Understanding these effects is crucial for smooth, coordinated flight, and avoiding unintended rolls, yaws, or altitude changes.

81
Q

What is ‘propeller slipstream’?

A

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
Q

How does propeller slipstream affect the rudder and vertical stabilizer?

A

Slipstream increases airflow over the rudder and vertical stabilizer, enhancing their effectiveness, especially at low speeds.

83
Q

What effect does propeller slipstream have on yaw?

A

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
Q

How can a pilot counteract the yaw caused by propeller slipstream?

A

A pilot can counteract yaw from slipstream by applying slight right rudder input, especially during takeoff and climb.

85
Q

Why is slipstream more noticeable at high power settings and low airspeeds?

A

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
Q

What is a ‘spiral dive’?

A

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
Q

What are common causes of a spiral dive?

A

Spiral dives can be caused by uncoordinated turns, excessive rudder input, failure to level wings, or disorientation in poor visibility.

88
Q

How should a pilot recover from a spiral dive?

A

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
Q

What happens when you pull back on the controls?

A

Deflects the elevator up, putting a downward force on the tail and raising the nose.

90
Q

What happens when you move the controls left?

A

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
Q

What does pressing the left rudder pedal do?

A

The rudder goes left, yawing the aircraft to the left.

92
Q

What are the steps for spiral dive recovery?

A
  1. Reduce power 2. Gently level wings 3. Ease nose up to level flight 4. Add power back.
93
Q

At higher speeds, which controls are more effective and why?

A

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
Q

What are the two types of energy?

A
  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
Q

What is altitude?

A

Height above mean sea level.

96
Q

What is elevation?

A

Vertical distance/height of a fixed point above mean sea level.

97
Q

What is relative airflow?

A

Comes from the direction an aircraft is travelling, always the opposite direction of motion.

98
Q

What is a chord line?

A

A straight line joining the leading edge to the trailing edge.

99
Q

What does AoA stand for?

A

Angle of attack; the angle formed by the relative airflow and the chord line.

100
Q

What is lift?

A

Acts at a right angle to the direction of relative airflow.

101
Q

What is the center of pressure?

A

Average location of pressure variation on an object’s surface; the CP moves depending on the AoA.

102
Q

What is the critical angle of attack?

A

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
Q

What is the center of gravity?

A

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
Q

When are wingtip vortices at their most powerful?

A

At low air speeds, during takeoff and landing.

105
Q

What is induced drag?

A

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
Q

What is parasite drag?

A

Caused by the airframe dragging through the air; increases with airspeed. Retracting flaps and undercarriage can help reduce it.

107
Q

What is total drag?

A

Combination of induced drag and parasite drag; high at low speeds, reduces at medium speeds, and increases at high speeds.

108
Q

What is aspect ratio?

A

Ratio of the span (wings) to the chord line; a higher aspect ratio results in lower induced drag.

109
Q

What is IAS?

A

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
Q

What is TAS?

A

True airspeed; the actual speed at which the aircraft is travelling through the air.

111
Q

What is GS?

A

Ground speed; the speed at which the aircraft travels over the ground, same as TAS in no wind, then adjusted for wind.

112
Q

What effect does weight have on gliding distance?

A

Weight has no effect on the distance an aeroplane can glide.

It is the AoA that determines the lift/drag ratio.

113
Q

What is the formula for performance in aviation?

A

Power + Attitude = Performance

114
Q

What determines the angle of climb?

A

The angle of climb is determined by the height gained in a given distance.

115
Q

How does Vy relate to best rate of climb?

A

Vy speed will always be a little higher than best angle.

116
Q

What is Vy?

A

Best rate of climb will reach target altitude in a faster time but covers a greater ground distance more fpm than best angle.

It has a shallower rate of climb than best angle.

117
Q

What is Vx?

A

Best angle of climb will reach higher altitude in less ground distance, good for clearing obstacles after takeoff.

It takes longer to get to a certain altitude compared with best rate Vy.

118
Q

What is the load factor during a 60 degree turn?

A

The load factor is 2.

119
Q

How do you calculate the stall speed during a 60 degree turn?

A

Square root of 2 = 1.4, which is added onto stall speed.

120
Q

What indicates slipping in a turn?

A

Slipping is identified by the ball deflected towards the center of the turn.

Apply more rudder in the direction of the turn.

121
Q

What indicates skidding in a turn?

A

Skidding is indicated by the balance ball deflected away from the center of the turn.

122
Q

What factors affect stall speeds?

A

Power reduces stall speed, flaps reduce stall speed, weight increases stall speeds, and frost or damage increases stall speed.

Stalling angle will decrease with frost or damage.

123
Q

What is a spin in aviation?

A

A spin may develop when one wing becomes more stalled than the other, causing a continuous roll and yaw towards the dropping wing.

124
Q

What is the recovery procedure for a spin?

A

Release back pressure, apply opposite rudder until the wing is unstalled, and resume straight and level or climbing configuration.

PPL (11 decks)

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