Definitions Flashcards
(106 cards)
1
Q
Datum
A
A reference point or base line from which measurements are taken.
2
Q
Lapse Rate
A
The rate at which air temperature decreases with an increase in altitude. The standard lapse rate is approximately 2°C / 1000’
3
Q
Standard Pressure Datum
A
In aviation, standard pressure refers to 29.92 inches of mercury (Hg), which is used to set altimeters for uniform pressure measurements.
4
Q
ISA Lapse Rate
A
The International Standard Atmosphere (ISA) lapse rate is 2°C / 1000’, 1Hg / 1000’ providing a standard for temperature decrease with altitude increase.
5
Q
Standard Temperature Datum
A
The standard temperature datum refers to the International Standard Atmosphere (ISA) temperature at mean sea level, which is defined as 15°C.
6
Q
Bernoulli’s Principle
A
Bernoulli’s Principle states that as the velocity of a fluid (air) increases, its pressure decreases.
*Remember Venturi Tube
7
Q
Airfoil
A
A structure designed to produce lift when air flows over it, such as an airplane wing or propeller blade.
Airfoil is 2D, Wing is 3D
8
Q
Camber
A
The curvature of the airfoil’s upper and lower surfaces, which influences the amount of lift generated. A greater camber generally increases lift.
9
Q
Mean Camber Line
A
Mean camber line is the line equidistant from the upper and lower surfaces of the airfoil.
Airfoils with more pronounced camber tend to produce more lift at lower angles of attack, whereas symmetrical airfoils (no camber) generate equal lift on both surfaces.
10
Q
Newton’s First Law
A
When a body is in motion it tends to remain in motion.
11
Q
Newton’s Second Law
A
A force must be applied to alter the state of uniform motion of a body.
12
Q
Newton’s Third Law
A
Every action has an equal and opposite reaction.
13
Q
Equilibrium
A
In flight, equilibrium occurs when all forces acting on the airplane (lift, weight, thrust, and drag) are balanced.
14
Q
Angle of Attack
A
The angle between the chord line of the wing and the direction of the relative airflow.
This angle is critical for maintaining lift, but if too steep, it may cause a stall.
15
Q
Boundary Layer
A
The thin layer of air that flows over the surface of an aircraft wing.
Proper management of the boundary layer is important to reduce drag and improve efficiency.
16
Q
Types of Drag
A
- Parasite Drag: Is the term given to the drag of all those parts of the aeroplane which do not contribute to lift.
Includes form drag, skin friction, and interference drag all of which resist forward motion.
2.Induced Drag: Is caused by those parts of an aeroplane which are active in production of lift.
Increases with a higher angle of attack.
17
Q
Drag
A
Drag is the resistance an aeroplane experiences in moving forward through air.
18
Q
Euler’s Equation
A
Describes the motion of a non-viscous fluid.
These equations help describe how the airflow behaves around an aircraft, influencing its stability, control, and lift generation.
19
Q
Coanda Effect
A
The Coanda effect refers to the tendency of a fluid jet (air in this case) to stay attached to a convex surface, such as an airplane wing, which helps generate lift.
20
Q
Washout
A
Washout refers to the twist in an aircraft wing where the angle of incidence decreases from root to tip.
This helps delay stall at the wingtips, improving control at lower speeds.
21
Q
Center of Pressure
A
The center of pressure is the point on an aircraft’s wing where the total sum of aerodynamic forces (lift and drag) acts.
It shifts as the angle of attack changes.
22
Q
Longitudinal Axis
A
The longitudinal axis is an imaginary line running from the nose to the tail of an aircraft.
Movement about this axis is called roll, controlled by the ailerons.
23
Q
Lateral Axis
A
The lateral axis is an imaginary line that runs horizontally across the aircraft from wingtip to wingtip.
Movement about this axis is called pitch, which controls the aircraft’s nose-up or nose-down attitude. The elevator controls pitch by adjusting the aircraft’s angle relative to the horizon, affecting ascent or descent.
24
Q
Vertical Axis
A
The vertical axis is an imaginary line that runs vertically through the center of the aircraft, from top to bottom.
Movement about this axis is called yaw, which controls the direction the nose of the aircraft points, left or right. The rudder controls yaw by adjusting airflow over the tail, helping to maintain directional control during flight.
25
Angle of Incidence
The angle of incidence is the angle formed between the aircraft wing’s chord line and the aircraft’s longitudinal axis.
It is fixed and designed to optimize lift and performance.
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Laminar Airflow
Laminar airflow is the smooth, orderly flow of air over an aircraft’s surface.
Maintaining laminar flow reduces drag, which improves fuel efficiency and performance.
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Turbulent Airflow
Turbulent airflow occurs when the smooth, laminar flow breaks down, causing chaotic movement.
It increases drag and can reduce efficiency.
28
Wingtip Vortices
Wingtip vortices are spirals of air created by the high-pressure air beneath the wing meeting the low-pressure air above the wing.
These vortices contribute to induced drag.
29
Transition Point
The transition point is the location on the wing where the airflow changes from laminar to turbulent.
Its position depends on the airfoil shape, speed, and conditions.
30
Skin Friction Drag
Skin friction is a type of parasite drag caused by the friction of air particles moving along the surface of the aircraft.
Reducing surface roughness helps decrease skin friction.
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Induced Drag
Induced drag is created by parts of the aeroplane involved in generating lift.
It increases with angle of attack and decreases with speed.
32
Parasite Drag
Parasite drag is the resistance experienced by the aircraft as it moves through the air.
It consists of form drag, skin friction drag and interference drag and increases with speed.
33
Form / Pressure Drag
Form drag, a type of parasite drag, is caused by the shape of the aircraft.
As air flows around the body, pressure differences create resistance. Streamlining the aircraft helps reduce this drag.
34
Interference Drag
Interference drag occurs when airflow around different aircraft components (such as the wing and fuselage) interact, creating additional resistance.
Reducing sharp intersections can minimize this drag.
35
Downwash
Downwash refers to the downward deflection of air behind an aircraft’s wing as a result of lift generation.
It contributes to induced drag but also stabilizes the airflow over the wing.
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Relative Airflow
Relative airflow is the direction of the airflow in relation to the wing. It is opposite to the direction of flight and affects lift and drag generation on the aircraft.
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Boundary Layer Separation
Boundary layer separation occurs when the airflow can no longer adhere to the surface of the wing due to adverse pressure gradients, leading to increased drag and potentially a stall.
38
Clean Configuration
In a clean configuration, an aircraft is in its most aerodynamically efficient state, with no flaps, slats, or landing gear extended, minimizing drag and maximizing speed.
39
Separation Point
The point at which the airflow pulls away from the wing.
40
Winglets
A winglet is a small, vertical or angled extension at the tip of an aircraft wing designed to reduce drag caused by wingtip vortices.
41
Feathering
Feathering means turning the blades to the extreme coarse pitch position, where they are streamlined and cease to turn.
This is typically done in the event of an engine failure to minimize drag and prevent the wind from turning the propeller (windmilling) and reducing drag on the blades. By feathering the propeller, the aircraft can maintain better performance and control during an engine-out situation. It also stops excessive vibration.
42
Fairing
A fairing is a smooth, streamlined covering placed over various parts of an aircraft to reduce drag and improve aerodynamic efficiency.
Fairings are commonly used on landing gear, wing-fuselage junctions, and other structural joints to minimize turbulence and resistance by smoothing out airflow over these areas. They contribute to better fuel efficiency and overall aircraft performance.
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Aileron Drag
During banking, the drag on the downgoing aileron is known as aileron drag.
44
Couples
In aviation, a couple refers to two equal and opposite forces that act on different points of an aircraft, creating a rotational motion without translation.
For example, the torque created by the engine and propeller can form a couple that causes the aircraft to roll or yaw. Couples are significant in understanding how certain forces, like thrust and drag or lift and weight, interact to affect an aircraft’s stability and control.
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Planform
The planform of an aircraft refers to the shape and layout of the wing when viewed from above or below.
46
Wash-in
Wash-in refers to a deliberate twist in the wing design where the angle of incidence at the wingtip is increased compared to the root.
This adjustment is used to improve an aircraft’s stall characteristics by ensuring that the root of the wing stalls before the tips, maintaining control authority, particularly in the ailerons, during low-speed flight or high angles of attack.
47
Wing fences
Wing fences are vertical surfaces attached to an aircraft’s wings, running from the upper to the lower surface.
Their purpose is to control airflow and prevent the spanwise flow of air along the wing, which can reduce lift and cause premature stalling at the wingtips. Wing fences help improve low-speed handling, especially during turns or at high angles of attack, by keeping airflow over the wing’s surface more uniform.
48
Flaps
Flaps are movable surfaces on the trailing edge of an aircraft’s wings that can be extended to increase lift and drag.
By changing the wing’s camber and increasing the surface area, flaps allow an aircraft to fly at slower speeds without stalling, which is particularly useful during takeoff and landing.
49
Vortex Generators
Vortex generators are small, aerodynamic surfaces installed on aircraft wings or other surfaces to create controlled vortices.
These vortices help delay boundary layer separation by energizing the airflow over the wing, reducing drag, and improving control, particularly at lower speeds or high angles of attack. Vortex generators enhance performance by improving airflow around the wing, which can also reduce the risk of stalls.
50
Stall
A stall occurs when the airflow over the wing is disrupted and the wing is no longer able to generate sufficient lift.
The stall occurs when the angle of attack is increased to the point where the steady streamlined flow of air is unable to follow the upper camber of the airfoil. This typically happens when the aircraft exceeds its critical angle of attack—the angle between the chord line of the wing and the relative airflow.
Stalls can occur at any airspeed or attitude if the critical angle is exceeded. Recovery from a stall involves reducing the angle of attack by lowering the nose and increasing airspeed to restore normal airflow over the wings.
51
Wing root
The wing root is the section of the aircraft wing that is closest to the fuselage.
This part of the wing is typically thicker and stronger than the wingtip, as it supports much of the structural load. The wing root is also where lift forces are concentrated and where critical components such as fuel tanks, landing gear, or control surfaces may be located. The design of the wing root affects the overall aerodynamic performance and efficiency of the aircraft.
52
Wing tip
The wingtip is the outermost part of the aircraft’s wing, farthest from the fuselage.
The design of the wingtip plays a crucial role in reducing drag caused by wingtip vortices, which are spirals of air created by the pressure differences between the upper and lower wing surfaces. Wingtip devices such as winglets or raked wingtips are often added to improve aerodynamic efficiency, reduce fuel consumption, and increase the aircraft’s range by minimizing vortex formation.
53
Aspect Ratio
The aspect ratio of a wing is the ratio of its wingspan to its average chord (the width of the wing).
A high aspect ratio (long, narrow wings) reduces induced drag, which is the drag caused by the production of lift. This is because higher aspect ratio wings produce less wingtip vortices and spread lift more evenly across the wing, making them more efficient. Gliders, for example, have high aspect ratios to minimize induced drag.
Conversely, low aspect ratio wings (short, wide wings) tend to generate more induced drag, as the lift is less evenly distributed and wingtip vortices are stronger.
54
Ground Effect
Ground effect is a phenomenon that occurs when an aircraft is flying close to the ground, typically at an altitude of about one wingspan or less.
In this situation, the interaction between the aircraft’s wings and the ground reduces wingtip vortices and induced drag, resulting in increased lift and reduced drag. Ground effect makes it easier for the aircraft to remain airborne at lower speeds during takeoff and landing. However, it can also cause difficulty in landing if the aircraft “floats” due to the extra lift near the ground.
55
Wake Turbulence
Wake turbulence refers to the disturbed air that forms behind an aircraft as it moves through the atmosphere, particularly due to the wingtip vortices created by lift.
This turbulence can pose a hazard to following aircraft, especially smaller ones, as it can cause sudden and uncontrollable rolling or yawing movements. Wake turbulence is more pronounced with larger, heavier aircraft, and pilots are trained to avoid these areas by using proper separation distances, especially during takeoff and landing.
56
Torque Effect
Torque effect refers to the tendency of an aircraft to rotate in the opposite direction of the propeller’s rotation due to Newton’s Third Law of Motion (“for every action, there is an equal and opposite reaction”).
In aircraft with a single-engine and a clockwise-rotating propeller, this effect causes the aircraft to roll to the left. Pilots must often compensate for torque effect with rudder or aileron inputs, particularly during takeoff and at high power settings.
57
Slipstream
Slipstream refers to the spiralling airflow generated by a rotating propeller as it moves backward around the fuselage of the aircraft.
This spiralling flow strikes the vertical stabilizer or rudder, creating a yawing moment, usually to the left in aircraft with a clockwise rotating propeller. Pilots must apply right rudder to counteract this yaw during takeoff and climb, especially at high power settings. The slipstream effect is most noticeable at low airspeeds and high engine power.
58
Gyroscopic Precession
Gyroscopic precession is the phenomenon where a force applied to a spinning object (such as a propeller or rotor) is felt 90 degrees ahead of the direction of rotation.
In aviation, this can cause unintended pitching or yawing motions when a force is applied to the propeller disk. For example, when the nose of an aircraft with a clockwise-rotating propeller is pitched up, the force is felt as a yaw to the right. Pilots must be aware of this effect, particularly during takeoff or sudden changes in pitch.
59
Critical Angle of Attack
The critical angle of attack is the maximum angle between the wing’s chord line and the relative airflow at which an aircraft can generate lift. Beyond this angle, the airflow over the wing becomes disrupted, leading to a stall.
The critical angle of attack is a fixed value for a given wing design and does not change with speed or altitude. Maintaining the correct angle of attack is crucial for avoiding stalls and ensuring safe flight performance.
60
Pitch
Pitch refers to the up or down movement of an aircraft’s nose about its lateral axis (wingtip to wingtip). It is controlled by the elevator and affects the aircraft’s ascent or descent.
61
Roll
Roll is the tilting motion of the aircraft’s wings from side to side around the longitudinal axis (nose to tail). It is controlled by the ailerons and determines the aircraft’s bank angle during turns.
62
Yaw
Yaw is the left or right movement of the aircraft’s nose around its vertical axis (top to bottom). It is controlled by the rudder and affects the aircraft’s direction or heading.
63
Adverse yaw
In a roll, the tendency of an aeroplane to yaw from the intended direction of the turn is the result of aileron drag and is called adverse yaw.
The co-ordinated use of rudder and ailerons correct for adverse yaw.
64
Types of Yaw
1. Static Yaw : is a condition in which the aeroplane is flying with some angle of sideslip, in which the longitudinal axis is not aligned with the aeroplane's flight path.
2. Dynamic Yaw : is the movement or rotation about the normal/vertical axis of the aeroplane.
65
Static Yaw
Is a condition in which the aeroplane is flying with some angle of sideslip, in which the longitudinal axis is not aligned with the aeroplane's flight path.
66
Thrust
The force exerted by the engine and its propeller(s) which pushes air backward causing a reaction, or, thrust in forward direction.
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Dynamic Yaw
Is the movement or rotation about the normal/vertical axis of the aeroplane.
67
Weight
It is the force which acts vertically downward toward the center of the earth and is a result of gravity.
68
Lift
The force upward which sustains the aeroplane in flight.
69
Mass balance
Mass balance refers to adding weight to a control surface (such as an aileron, elevator, or rudder) to prevent aerodynamic flutter or oscillation.
This is done by placing a mass(usually made of lead) forward of the hinge line of the control surface, helping maintain stability and control at higher speeds. Mass balance is primarily a stability feature, not directly involved in changing the aerodynamic properties of the aircraft.
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Stability
Stability is the tendency of an aeroplane in flight to remain in straight, level, upright flight and to return to this attitude, if displaced, without corrective action by the pilot.
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Static Stability
It is the initial tendency of an aeroplane, when disturbed, to return to the original position.
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Dynamic Stability
It is the overall tendency of an aeroplane to return to its original position, following a series of damped out oscillations.
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Longitudinal Stability
Is stability around the lateral axis of the aeroplane and its called pitch stability.
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Factors affecting Longitudinal Stability
1. Size and position of the horizontal stabilizer.
2. Position of the center of gravity.
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Lateral Stability
Is stability around the longitudinal axis and is called Roll stability.
It is achieved through:
1. Dihedral
2. Sweepback
3. Keel effect
4. Proper distribution of weight.
76
Dihedral Angle
It is the angle that each wing makes with the horizontal.
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Pitch (Propeller)
The distance in feet a propeller travels forward in one revolution is called pitch.
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Tractors
Propellers which are attached forward of the engine and which pull from the front of the aeroplane.
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Pushers
Propellers which are attached aft of the engine and push forward from behind.
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Propeller Torque
It is the resistance to the blades as they rotate and results in a tendency in the aeroplane to roll in a direction opposite to the rotation of the propeller.
Propeller torque is drag. When the propeller is revolving at a constant RPM, propeller torque and engine torque will be exactly equal and opposite.
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Engine Crankshaft Torque
It is the turning moment produced at the crankshaft.
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Theoretical Pitch or Geometric Pitch of Propeller
If the propeller was working in a perfect fluid, the distance it would travel forward in one revolution would be a theoretical distance dependent on the blade angle and diameter of the propeller and is called Theoretical or Geometric pitch.
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Practical Pitch or Effective Pitch of Propeller
In air, the propeller encounters lost motion and the distance it travels forward is somewhat less than the theoretical pitch. This lesser distance is called Practical or Effect pitch.
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Propeller Slip
The difference between Theoretical and Practical Pitch.
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Types of Propellers
1. Fixed Pitch Propellers - Blade angles cannot be adjusted by pilot, they are chosen by manufacturer to give best performance.
2. Variable Pitch Propellers - Propellers whose blade angles and consequent pitch may be altered to meet varying conditions of flight.
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Adjustable Pitch Propellers
Those whose blade angles may be adjusted on the ground.
However, the pitch cannot be altered during flight for changing flight condition.
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Controllable Pitch Propellers
Those whose blades can be adjusted during flight by the pilot to various angles during flight.
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Constant Speed Propellers
Those whose blades automatically adjust themselves to maintain a constant RPM as set by the pilot.
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Torque
The propeller usually rotates clockwise, as seen from the pilots seat. The reaction to the spinning propeller causes the aeroplane to rotate counterclockwise to the left. This left turning tendency is called torque.
Aileron trim tabs are used to compensate for torque. Use of right rudder during take-off roll corrects this condition.
90
Asymmetric Thrust or P Factor
It is a phenomenon in propeller-driven aircraft where the descending propeller blade on the pilots right side (in clockwise-rotating propellers) generates more thrust and a higher angle of attack than the ascending blade on the left.
This happens when the aircraft is at a high angle of attack, such as during takeoff or climb. The result is a yawing tendency to the left due to more lift being generated on the right side of the propeller, requiring the pilot to apply right rudder to maintain directional control.
P-Factor is most noticeable at low airspeeds and high power settings, especially during climbs.
91
Best Rate of Climb (Vy)
This is the rate of climb which will gain the most altitude in the least time.
For every aeroplane there is an at airspeed at a given power setting which will give the best rate of climb. The best rate of climb is normally used on take-off (after any obstacles are cleared) and is maintained until the aeroplane leaves the traffic circuit. The rate of climb is not affected by wind.
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Best Angle of Climb (Vx)
This is the angle which will gain the most altitude in a given distance.
The airspeed for steepest angle of climb is somewhat lower than the speed at which the best rate of climb is obtained. The best angle of climb should be maintained only until the obstacles are cleared then the nose of the aeroplane should be lowered to pick up the best rate of climb airspeed. The angle of climb is is appreciably affected by the wind.
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Normal climb
It is a rate that should be used in any prolonged cruise climb and is a speed the is usually 5-10 knots faster than airspeed for best rate of climb.
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Gliding Angle
Best glide angle refers to the farthest distance that an aeroplane will glide at the airspeed which results in an angle of attack that gives the maximum lift/drag (L/D) ratio.
95
Best Glide Speed for Endurance
Refers to the airspeed that is slightly less than that which gives the maximum L/D ratio and which is used to achieve minimum sink.
It is generally calculated as 1.1 times the power-off stalling speed.
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Power Approach
Normal method of landing for descent.
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Spinning
It is defined as autorotation which develops after an aggravated stall.
In a spin the airspeed is constant and low.
98
Spiral Dive
It is a steep descending turn in which the aeroplane is in an excessively nose-down attitude.
It is characterized by excessive angle of bank, rapidly increasing airspeed and rapidly increasing rate of descent. In a spiral, airspeed increases rapidly.
99
Airspeed
It is the rte of movement of an aeroplane relative to the air mass through which it is flying.
100
Never Exceed Speed / Maximum Permissible Dive Speed (Vne)
The maximum speed at which the aeroplane can be safely operated in smooth air.
101
Normal Operating Speed Limit / Maximum Structural Cruise Speed (Vno)
This is the cruise speed for which the aeroplane was designed and is the maximum safe speed at which the aeroplane should be operated in the normal category.
102
Caution Range
The speed range between the Vno and Vne.
103
Maneuvering Speed (Va)
This is the maximum speed at which the flight controls can be fully deflected without damage to the aeroplane structure.
This speed is used for abrupt maneuvers or when flying in very rough air or in severe turbulence.
104
Maximum Gust Intensity Speed (Vb)
The maximum speed for penetration of gusts of maximum intensity.
105
Maximum Flaps Extended Speed (Vfe)
This is the maximum speed at which the aeroplane may be flown with flaps lowered.
