Knowledge Levels Explained

Knowledge Levels

• Basic knowledge for categories A, B1, and B2 is indicated by allocating knowledge level indicators 1, 2, or 3 against each subject.
• Category C applicants are required to meet either category B1 or B2 basic knowledge levels.

Level 1

• The applicant should be familiar with the basic elements of the subject.
• The applicant should be able to give a simple description of the whole subject, using common words and examples.
• It is important for the applicant to use typical terms.

Level 2

• Possess general knowledge of the theoretical and practical aspects of the subject.
• Have an ability to apply that knowledge.
• Demonstrate an understanding of the theoretical fundamentals of the subject.
• Applicant should be able to give a general description of the subject using typical examples.
• Use mathematical formulae in conjunction with physical laws that describe the subject.
• Read and understand sketches, drawings, and schematics describing the subject.
• Apply knowledge in a practical manner using detailed procedures.

Level 3

• Requires detailed knowledge of the theoretical and practical aspects of the subject.
• A capacity to combine and apply the separate elements of knowledge in a logical and comprehensive manner.
• The applicant should know the theory of the subject and interrelationships with other subjects.
• Needs the ability to give a detailed description of the subject using theoretical fundamentals and specific examples.
• It’s important to understand and use mathematical formulae related to the subject.
• Should read, understand, and prepare sketches, simple drawings, and schematics describing the subject.
• Apply their knowledge in a practical manner using manufacturer's instructions.
• Interpret results from various sources and measurements and apply corrective action where appropriate.

Physics of the Atmosphere (8.1)

• You should be able to interpret ISA conditions for temperature, pressure, humidity, and density at sea level and identify basic changes in the atmosphere with altitude (Level 2).

Fundamentals of the Atmosphere

• An atmosphere consists of gas layers surrounding a planet.
• Weather and climatic conditions are generated within an atmosphere.

Composition of the Atmosphere

• The atmosphere comprises 78% nitrogen, 21% oxygen, and 1% other gases, including carbon dioxide.
• Gases have physical properties like pressure, density, and temperature, which vary in the atmosphere influencing aircraft performance.
• Atmospheric characteristics significantly affect the operation and maintenance of aircraft.
• Aircraft performance and forces like lift, drag, and engine power are affected by changes in densities, resulting from variations in atmospheric pressure, temperature, and humidity.

Atmospheric Regions

• The atmosphere is classified into regions that include the troposphere, tropopause, stratosphere, mesosphere, and thermosphere (ionosphere).
• This classification is based on temperature variation with altitude
• Aircraft typically fly in the troposphere and the lowest part of the stratosphere.

Troposphere

• Is where we live and where most aircraft fly
• Extends from the surface upward to the tropopause
• Contains water vapor, leading to clouds and weather
• Temperature drops approximately 2°C for every 1000 ft increase in altitude, called the lapse rate.

Tropopause

• Defined by consistent temperature regardless of altitude
• Located at the top of the troposphere and the start of the stratosphere
• Has a temperature of around -57 ⁰C
• Usually occurs at approximately 20,000 ft over the poles and 60,000 ft above the equator.
• The International Standard Atmosphere (ISA) specifies an average height of 36,000 ft

Stratosphere

• Extends above the tropopause and contains no water vapor and no weather.

Atmospheric Conditions

• The weight of air above any surface exerts pressure
• Average pressure at sea level can be represented in table form

Sea Level Atmospheric Measurement Table

• 14.7 PSI
• 29.92 inches of mercury (Hg)
• 760 mm of Hg
• 1013.25 millibars or hecto Pascal

Mercury Barometers

• Primarily used for measuring atmospheric pressure
• a device that consists of an upside-down tube filled with mercury that is in a vessel full of mercury.
• As surrounding pressure changes, the mercury rises or falls correspondingly, and it measures 29.92 in. Hg or 1013.25 mbar at sea level under standard conditions.

Air Density

• Is mass per unit of volume of a substance
• Allows all flight is possible
• Flight becomes more difficult with lower density in the surrounding atmosphere
• Air at higher altitudes with lower pressure is less dense than air at low altitudes with higher pressure
• Pressure decreases at higher altitudes

Density

• Increases if pressure increases
• Increases as temperatures decrease.

Air Temperature

• There is a gradual decrease in temperature when ascending in the atmosphere.
• In the troposphere, the temperature drops at a steady rate, and it's called the lapse rate (2°C for every 1000 feet increase in altitude).
• The rate of temperature decrease does not alter until about 36000 ft and It ceases to fall at the top of the tropopause.

Viscosity

• Viscosity of air affects aerodynamics
• Air tends to 'stick' to surfaces, slowing its motion.

Humidity

• Humidity is the moisture content of air, which is conditional based on the temperature.
• Small presence of water vapour means it's dry air
• High presence of water vapour means it's humic air
• The higher the temperature of air, the more water vapour it can absorb.
• Air density varies with humidity.
• Water vapour weighs approximately 5/8ths as much as an equal volume of perfectly dry air.

Absolute Humidity

• Absolute humidity refers to the actual amount of water vapour in a mixture of air and water.
• The higher the air temperature the more water vapour the air can hold.
• A hygrometer is an instrument used to measure the amount of water vapor in the air.

Relative Humidity

• Relative Humidity is the ratio of the amount of moisture in the air to the amount that would be present if the air was saturated.
• Relative humidity has a dramatic effect on aircraft performance because of its effect on air density.
• A relative humidity of 75% means the air is holding 75% of the total water vapour it can hold.
• Air is most dense when it is perfectly dry.
• For practical application in aviation, temperature and dew point measure the amount of water vapour in the air.

Dew Point

• Is the temperature when air must be lowered before the water vapour condenses and becomes liquid water?
• Dew point is temperature to which air must be cooled to become saturated without pressure changing.

Air Density

• Pressure, Temperature, Altitude affect air density:.
• Pressure: Air density drops as atmospheric pressure drops
• Temperature: As temperature increases, density drops due to air volume expanding.
• Altitude: As altitude increases, air temperature and pressure drops, which lowers air density.
• Air becomes less dense as altitude increases, because the drop in air pressure has a larger impact on air density than temperature.

International Standard Atmosphere (ISA)

• Has significant changes in aircraft performance based on changing atmospheric conditions.
• It develops standard conditions set to measure performance of an aircraft
• An aircraft’s performance is measured under actual atmospheric conditions.

Ideal Performance

• Ideal performance can be done by recording the parameters and correcting them to ISA conditions using graphs and charts.
• ISA conditions at Mean Seal Level:
  • Temperature of 15°C
  • Pressure of 1013.25 hPa (mb)
  • Density of 1.225 kg/m

ISA conditions

• From Mean Seal Level to 11km temperature decreases by 1.98°C per 1000ft.
• From 11 km to 20 km, temperature remains constant at -56.5°C
• From 20 km to 32 km temperature increases by 0.3°C per 1000ft.

ISA Standard Conditions

• Conditions are referenced and known as ISA Standard Day.
• Lapse rate = 2°C/1000 ft
• Tropopause height = 36 000 ft
• Sea level pressure = 1013.25 hPa = 29.92 in Hg = 14.7 psi
• Sea level temperature = 15°C
• Gravity (g) = 32.174 ft/sec² = 9.81 m/s²

Ground temperature

• Ground temperature and pressure often don't exactly match ISA standards
• The ISA+ model is implemented when the local sea level temperature exceeds 15°C.
• The complete atmosphere is increased by the temperature difference between the current sea level temperature and the standard value of 15°C
• e.g., for every 20°C day, an ISA+ model is implemented.

Pressure Altitude

• The indicated altitude occurs when an altimeter is set to 29.92 in. Hg (1013 hPa in other parts of the world).
• It can be primarily used in aircraft performance calculations and in high-altitude flight.

High Density Altitude

• Means to have decreased performance
• Published performance is based on standard atmospheric conditions of Sea level
• Density altitude is an indicator of aircraft performance.

Aerodynamics 1 (8.2)

• Should be able to describe airflow characteristics as air flows around various shapes (Level 2).
• Will be able to explain the meaning of the terms laminar flow, turbulent flow, boundary layer, free stream flow, and stagnation as it relates to airflow (Level 2).
• Be able to explain relative airflow, up wash, downwash, vortices and how vortices are formed (Level 2).
• Should be able to explain the term camber and calculate the mean camber line on a given aerofoil (Level 2).
• Has the ability to explain the term chord and identify a chord line on a given aerofoil (Level 2).
• Need to explain the terms fineness ratio, angle of attack and center of pressure (Level 2). Explain the definition of resultant force with respect to lift (Level 2).

Airflow Around a Body

• Terms and principles of airflow should be learned.
• Airflows must be made visible for observation, therefore, you need to observe airflows around object.
• Regularly spaced point sources and parallel lines spread out to visualise the airflow over the aerofoil, used to illustrate and test objects in wind tunnels
• The streamlines show if airflow is Laminar, whether they show smooth lines with little drag. Turbulent flows show more chaotic lines creating more drag. A streamline shape can be defined as producing the least possible resistance.

Laminar Flow

• Fluid maintains a uniform, parallel separation with no turbulence.
• It is shown as parallel straight lines on a flow diagram.

Turbulent Flow

• Is the random motion of fluid with unpredictable fluctuations and vortices.
• No streamlines are present.
• Laminar flow becomes turbulent flow, which is called critical velocity.

Boundary Layer

• This is a thin layer of air around surfaces of aircraft
• Air is brought to rest by the leading edge where boundary layer originates.
• This is where relative airflow begins
• This layer of air stays on the wing due to viscosity
• Layer of air tends to adhere to the wing.
• The air velocity in the boundary is from aero on surface to the velocity of the free stream edge.

Tendency of the Boundary Layer

• Is to start as laminar and then break away from the surface to become turbulent and thicker

• Particles of air on the layer are rearwards, with those closest to the top moving clockwise, and inversely to the air below.

• Transition point- the point you change from laminar to turbulent

• As speed increases, the transition point moves forward, increasing turbulent flow.

• Separation points of airflows are where turbulence can build.

Relative Airflow

• This is the movement of air relative to the aircraft.
• Relative airflow moves backward horizontally as the wing moves forward horizontally.
• Relative airflow is parallel to and opposite the flight path of the aeroplane.
• It does not depend on the aircraft’s flight attitude or on the direction and speed of the wind.
• It depends on the aircraft’s direction of travel.

Upwash

• Which is defined as an area in front of the leading edge of the foil, causing the air to move upwards.

Downwash

• Which is defined as an area behind the trailing edge, where the airflow tends to move downward.

Vortices

• Vortices form at the trailing edge.
• Vortices rotate clockwise on the left wing and counter-clockwise on the left when viewed from the rear.
• Vortices form at each wing tip while the aeroplane is flying.

Wing-tip Vortices

• Wing tip vortices exist as they originate with the higher-pressure air beneath mixing with the lower-pressure air above.
• Wake turbulence is caused by these vortices

Bernoulli's Principle

• Can explain how aircraft gain lift from the shape of the wings.
• A practical application of Bernoulli’s principle is the venturi tube

Venturi Tube

• Has an air inlet that narrows to a throat, and outlet section increases in diameter.
• Outlet and inlet diameters to equal
• Mass of entering the tube must equal exiting the tube
• Constriction increases speed of air
• Air pressure also decreases when the air speeds up
• Airflow then slows after the constriction, which increases the pressure.

Aerofoil Shape

• Helps air move faster, as its shaped that air can move faster over the top, as compared to the underside.
• Fast, slow movement of the air affects air pressure, as under the wings will increase the pressure.
• The higher pressure affects how aircraft are lifted through the lower air pressure
• Lift is generated by the motion of air past, as from Bernoulli's principle, and this result pressure differential on the upper and lower surfaces.

Aerofoil

• This section in the aircraft wing's cross section, which generates lift.

Chord Line

• A straight line and arbitrary reference line
• Used to measure angular wing position in relation to airflow

Camber

• The Aerofoil section curves from leading edge to trailing edge.
• Camber amount is stated as a ratio which varies based on which surface.
• Lower camber refers to the curve of the lower surface.
• Upper camber refers to the curve on the upper surface.

Mean Camber

• A curved line formed when taking the equal distance between the upper and lower surfaces.
• Camber is positive when the departure from the straight line is upward
• Camber is negative if its downward
• The aerofoil is symmetrical if cambers are equal

Maximum Camber

• Indicates the maximum or greatest distance between the chord line and the mean camber line.

Fineness Ratio

• Measures airfoil thickness
• length to breadthRatio

Angle of Attack

• Angle between the chord line and the free-stream flow
• Lift increases with higher angles of attack
• If stalling then the AoA will rapidly lose to zero.
• Compressor and Turbine blades use this

Angle of attack or AOA

• The acute angle, known as the angle of Incidence is a fixed degree
• Is related to the longitudinal axis
• Can only be amended during original manufacture

Aerofoil Shapes

• Symmetrical Aerofoil = same centre line shape on both airfoils\
• Non-Symmetrical = Different shape on either side of the chord line

Center of Pressure

• The total Air Reaction will occur when adding differences between top and botom surfaces of foil.
• It’s indicated as CoP or C of P
• The Resulting force will have an addition of A of A, which is the RELATIVE AIRFLOW
• The drag is lifted

Aerodynamics II (8.2) Learning Objectives

Should be able to:

• Explain terms : Induced and Parasite Drag
• Describe wing shapes and use
• aspect ratio, wash in,and wash out
• thrust and weight.
• Wing shape, lift, and lift coefficient, role of AoA, and lift coefficient use for lift generation
• Wing shape, lift, and drag coefficient, role of wing shape and drag coefficient use for drag generation
• Aerodynamic polar curve. Describe what it may be used (Level 2).
• Result of aerodynamic stall,and how they relate
• Aerofoil contamination from; frost, snow and ice

Generation of Lift

• Newtons Third Law of motion - Action and oppose reaction
• Deflected air creates lift.
• Amount of lift depends of air density/speed
• Airflow can become disturbed if AoA is too great, and stall can suddenly occur.
• According to Bernoulli, more air movement creates less pressure.

Stalling Angle

• Separation from wings upper surface results in a rapid decrease in lift. The transition point occurs where the airflow changes from laminar to turbulence, and this can move forward due to increasing of attack speeds
• A stall occurs at the same angle of attack, despite of flight weight or airspeed
• Critical Angle of Attack (Stalling is the AOA for when lift is generated.
• Airfoil loses/separates airflow
• Wing stalls
• Aircraft loses height

Generation of Drag

• Is caused by an aircraft structure that interrupts/deflects soft airflow around an area
• Both drag (and lift) increases with AoA
• Drag will limit air speed and oppose airflow direction and forward-acting force of thrust
• Drags can be classified by two main types:
  • drag or drag if by lifting
  • Parasitic drag is caused through the viscosity of wind.

Induced Drag

• Caused by lifting.
• Relates directly to wings angle of attack
• As the angle grows, drag also increases
• Airflow is slower above, as lower pressure occurs
• Air flows outwards below since the air pressure of the wing below is greater, which causes continual tipping of spiraling airflow around the wingtips.
• Air streams of above and below are joined at different angles, causing an angled meeting.
• At rear end edge of wing.
• Vortices rotate clockwise from left wing
  • Anti-clockwise from right
• Outer tip of the wing will see it when the tendencies are for the vortices to move tip as they join.
• A vortex is formed, which is called a wing tip vortex.
  • This is invisible - In very humid air, airflow is lowered, and the centre core becomes visible because the air has cooled sufficiently so condensation is possible

Parasite Drag

• All drag that is not needed to production of lift
• Caused by airflows disruption around the aeroplane's surface
• Classified in the following categories - Form Drag :Due to motion/shape - Skin Friction Drag :Smoothness or roughness of surface - Interference Drag :Surface differences. air over.

Skin Friction

• From the smoothness/roughness on aircraft parts surface. - Smoothness increases more than you think, as seen with microscope vision - Air layer has more eddy's which creates drag

Interference Drag Occurs When

    - Occurs when surfaces of mixed types meet (fuselage with a wing that has airflowed)

Jet Stream

• Drag decreases when air speeds increase
• A function of lift which max occurs when airspeed is lower.
• If airspeed or attack is increased, the drag also rises, which is induced Drag.
• Parasite increases at airspeeds squared. - The max range occurs when drag in totality is a minimum, and when theoretically is when highest range occurs. - Flight becomes less stable or if airspeed goes down there a small increase in the rate for drag, also speed is then decreases - Thrust can help you out or stall may occur.

Lift Coefficient

• Creates lift when moving through the air, by producing a low and high-pressure region on each side.
• Amount of lift is due to
  • Shape/area of airfoil
  • Air Density
  • Air speed
  • Angle of attack

Variable Definitions

• CL: Coefficient of Lift can be caused by shape of the wing and angle of attack.
• : one half times rho (density) - Relates to the air that is flying.
• Velocity that relates to speed is expressed by v2, it's relation to the airspeed. It has a major impact over generation
• The surface part of the wing: It's the square/meter area

Moving through the Air, an amount Drag force results from

• Total Drag Force (D) = Induced Drag + Form Drag + Friction Drag + Interference D.

• Variables can be rearranged

Aerodynamic Curves

• Intersects and indicates an amount of attack.
• Graph is known as its optimum.
• Creates the best lift-to-drag L/D ratio. The angle is created is called as the angle of incidence.

4 Aeroynamic Forces

• Lift/Drag/Weight/Thrust
• Flight is controlled by each
• Lift is perpendicular while relative. drag is vice area, so the relation from
• Each component can be derived from power plant, gravity and airflow

Aerodynamic

• The lift and equal weight are kept if level. Altitude is neither raised/lowered, pressures are not identical
• Designed wings can divide airflow by creating a high and low pressure around the area. This movement creates life

Weight & Force are in close Relation to Each other

• Lift is the lift power against the aircraft's weight.

Center of Gravity- Weight will always take effect due its concentration point

• Location indicates what position the center of pressure should take, depending
• Angle if aircraft is increased creates moment of balance, nose ups while angle is farther

Center Position

• Is the amount what importance gravity position will take
• Position creates high bearing related to structure. The aircraft is designed on the amount of gravity impact, and the designer will estimate the center of press to fix it so the flight remains stable.
• Ideal if requirements are both met:
  • Forward force can reduce nose pressure
  • The line thrust should be lower as compared to dragging in order.
  • Balance the other with a cancellation

Too Much Weight

• If the aircraft has to much weight , this shifts forward the aircraft.

Some Factors the May Present

• Increased fuel consumption
• More power for any given speed
• Diving tendency is more present power is not on
• Tendancy to have Oscillation
• Load on Front wheel Dangerous during flaps operations Dangerous spin features present
• Nose will harder to raise Too much to the rear
• Lift is reduced, or not as sufficient

Adverse Aft Gravity

• Lift is reduced, or not as sufficient.

Stability Effected

• As speed then reduces

• The flight is decreased, so speed in best travel isn't seen

• Pilot has increased strain or failure on instrument stall or dangerous spin characteristics Long range requires special optimum

• Landing gear may take damage.

• Aircraft weight must be distributed accordingly since both will not allow enough lift.

CG Control to Stay On Par

• Aircraft have their very-own COG, 15 and 40 amount of Chord
• Changes to weight and or cabin weight, need more/less power
• Straight Movement = the constant air must affect aircraft stability (weight, thrust )
• If thrust increased. Also , descend can be in effect.

Forces in a Climb

• Change in lift is required
• When elevator is applied, AOA are then increased and start a climb
• Climbed is entered into power then reduces or if airspeed lessens, the thrust then lessens as maintain for level flight
• The weight as component acts same direction, affecting drag as decreasing flight with some balance
• With the plane in climb, force must have more power to retain airspeed with the level flight is

A Steeper amount may result when the power is greatly set, and speed reduces.

• Steady amount needs equal portion of weight.

Descent Forces

Forces can be altered when being flighted. Descendent is entered Power stays how with. As pressured is then changed and AOA is then lessened.

Glide Forces

• Thrust has been removed, so air force is not. All must then be able to operate with the wind, drag and weight.

• Lift an drag with weight, is opposite. If wanting move than increase wind.

• The pilot has to maintain the best, can't. The the decrease rate.

• By increasing causes parasitic drag then grows less drag reduces lift

Theory to turn

• Inertia
• The turn has to be created by wind affecting the plane in the way lift. Component with lift is not with weight while others travel horizontally.
• Must increase bank thrust

Explanation of basic knowledge levels required in categories A, B1, and B2. Covers familiarity with basic elements, general knowledge, and the ability to apply knowledge. Includes understanding theoretical fundamentals and using mathematical formulas.