Final ABC Notes

Aerodynamics

Branch of Fluid Mechanics

studing Air in Motion

(Main science that Aviation is Based on)

Pressure (Atmospheric or Barometric)

Weight of an Air Column measured

from Surface to the Top of the Atmosphere.

Which is (the Force per unit Area Exerted on a body Above an Atmospheric Column)

Density

Mass per unit Volume

when d↑, performance ↑

Typical density values with increasing altitude would be:

20,000 ft. Density is 50% of the surface value.

40,000 ft. Density is 25% of the surface value.

60,000 ft. Density is 10% of the surface value.

Newton's 1st Law of Motion: “Inertia”

A body at rest tends to remain in rest

and a body in motion tend to remain in motion

@ Constant Speed & Same Direction

Newton's 2nd Law of Motion

F = M x A

when a force acts on a body, its

Resulting Acceleration is

Directly proportional to Force,

Inversely proportional to Mass

Newton's 3rd Law of Motion

Actions have Reactions,

Equal in force & Opposite in Direction

Continuity Equation

Area X Velocity is Constant

‘smaller area makes air speed up,

larger area makes air slow down

because the same mass must pass through’

Leading to Bernoulli’s Equation.

Bernoulli's Princple

As Velocity⬆ Increase

Press. ⬇ Decreases

Lift

Upward Force created by

Difference in Air Pressure

Above (⬆ Velocity, ⬇Pressure)

Below (⬇ Velocity,⬆Pressure) the Wing.

equation; ½ρ×V²×CLxS

at High altitudes lift Decreases

Coefficient of Lift (CL)

Lift Variation depending on

Shape & Inclination of the airfoil.

Coefiecent of Lift Max (CLmax)

Highest point in CL & AoA Curve.

the highest value of lift coefficient (CL) a wing can produce at a given airspeed

just before the stall.

Angle Of Attack (AoA)

angle between

Chord line & Relative wind

Opposing it

Relative Wind

Air moving across the airfoil.

Critical Angle of Attack

(Critical AoA)

Highest point in CL & AoA Curve.

where CLmax is reached which is:

the highest value of lift coefficient (CL) a wing can produce at a given airspeed

just before Stall.

Chord

Distance Between,

Leading and Trailing edges

Chord Line

Imaginary Straight line

connecting between Leading and Trailing edges of the wing.

Leading edge

Part of the wing that meets the air First

Trailing edge

Part of the wing that meets the air Last

Mean Line

Imaginary Equidistant line

between Upper & Lower surfaces of the wing

Camber

Distance from

Straight Chord-line to Equidistant Mean-line

Center of Pressure (CP)

Point on Chord line where the Aerodynamic Force Acts.

Center of Gravity (CG)

Point at which your aircraft would Perfectly

Balance if it were Suspended from it.

Drag

Any force

Opposing airfoil in its

Forward Motion.

Induced Drag

Portion of the total drag

Created by Production of lift

Due to Downward Deflection of air

Happens at Low Speeds & High AoA

creating Wing Tip Vortices

Down wash

Wake Turbulence

function of an aircraft Producing lift, resulting in the formation of

2 counter-rotating vortices trailing behind the aircraft.

greatest vortex strength on climb out when jet is

Slow, Clean, Heavy with High (AoA).

Wing Tip Vortices

Circular patterns of rotating air

created at the tips of wings due to pressure differences above and below the wing.

must be Heavy, Slow,

with High AoA

Winglets

Vertical Extension of the wing

Reducing induced drag and

Solving wing tip vortices problem

Parasite Drag

Created by Any part of the airplane

Not Contributing to Production of Lift

Form drag

Parasite drag Resulted from Turbulent wake.

Caused by the Separation of airflow from Structure

fixed by Streamlining

Interference Drag

parasite drag from Varied Currents of Airflow Interaction

with any 2 Parts in conjunction

(Drag due to the interaction of individual boundary layers at the junction of aircraft major components)

Skin-friction Drag

type of parasite drag due to airplane's surfaces Roughness

Structural Drag

Type of parasite drag Acting on

Any Structure of the plane

Profile Drag

Type of parasite drag Acting on the Wing

(Combination Form + Skin friction)

Wave Drag

due to Shock wave Formation

Only in Transonic and Supersonic

Total Drag

Sum of Induced and Parasite drag

Lift to Drag Ratio

The amount of lift generated by a wing compared to its drag.

L/Dmax (best Lift to Drag ratio)

Point where Total Drag is at its Minimum.

Providing Best:

Endurance Speed &

Fuel Flow (minimum fuel consumption per hour)

Indicated Airspeed (IAS)

speed Observed on the airspeed Indicator

Not corrected for Position Errors

Calibrated Airspeed (CAS)

Indicated airspeed corrected for Positioning errors

Equivilant Airspeed (EAS)

Calibrated airspeed corrected for Compressibility errors

True Airspeed (TAS)

Equivalent airspeed corrected for

Density variation

Ground Speed (GS)

True airspeed corrected for Wind variation

used in Navigation

Stall

Rapid Decrease in lift caused by separation of airflow from wings surface

Factors Affecting Aerodynamic Forces of a Wing (3eS,@,MAD)

Divided into 3 parts,

1st; Wing's

1. Surface Area (S)

2. Span

3. Sweep Back Angle

Then

1. Aspect ratio

2. Taper ratio

3. Thickness to chord ratio

Lastly,

1. Mean aerodynamic chord (Mac)

2. Angle of incidence

3. Diherdral angle

Wings Surface Area

directly proportional to Lift

if increased can

1. Better Stability@Lower Speeds

Sweepback angle ‘λ’

Angle between airplane wing’s

Lateral axis in Leading edge,

and its Quarter Chord

Allowing airplanes to fly at higher speeds without facing Shock Wave 🍩

Wing Span

Tip-to-Tip dimension of the airplane wing,

regardless of its geometric shape

Aspect Ratio

Ratio Between Span divided by Average Chord of the wing.

Taper Ratio

Ratio between Root chord and Tip chord

Approx: 2:1 Ratio

Thickness to Chord Ratio

Ratio between wing's Camber and its Chord.

Mean Aerodynamic Chord 'MAC'

Average chord of the Entire Wing.

(CP) concentrates on it.

Used in weight and balance calculations

Angle of Incedence

Angle between Wing’s

Chord Line & a line Parallel to plane's Longitudinal axis.

Slightly ⬆Increasing AoA during Cruise

Dihedral Angle

Upward angle between Plane's

Wing & Ground.

Anhedral Angle

Downward angle between Plane’s Wing &

Ground.

Compressibility

Increase in the Volume of matter

when External Force is Applied

Speed of Sound

Distance traveled per Unit time

as sound wave Propagates

Directly ∝ to Temp.

(SoS= 39 × √(273 ±SAT))

Speed of sound Equation

= 39 × √(273 ±SAT)

Shock Wave 🍩

Boundry Layer between

Compressed & Undisturbed air

Shoke Wave Characteristics

1-⬆increase in TPD

"Temp., Press, Denisty"

1- sudden ⬇decrease in ‘Velocity'

Mach Tuck (Tuck Under)

Due to Shock wave Formation.

(CP) move Aft

causing Nose of airplane to Drop Down.

MACH Trim

used for Mach Tuck Avoidnance

by sending Signals to

Pitch Control surfaces (Elevator)

Resisting Airplane Nose Down tendency

MACH number

Ratio Between

True Airspeed & Speed of Sound

Critical MACH number

Speed at which Coefficient of DRAG increase by 0.002%⬆

Factors Increasing Critical MACH number (SVL)

1- Swept Back wing

2- Vortex Generator

3-Less thickness to chord ratio

Vortex Generator

Small aerodynamic device delaying Airflow Separation.

Dutch Roll

Swept Back wings Planes Encounter them more often;

due to Uncoordinated Rudder Defliction which is

Combination of Continuous

Rolling & Yawing Oscillation

occurs when:

⬆Dihedral effect

is more Powerful than

⬇Directional Stability

the advancing wing is at a higher angle of attack (dihedral effect) and presents a greater span to the airstream, which is why the roll is so pronounced

Yaw Damper

Automatic flight control system on the Vertical axis

Counterattacks

Rolling & Yawing Oscillations

produced by Dutch roll by controlling Rudders

lift to drag ratio (L/D)

Relation between lift generated by wings to drag opposing it

Best lift to Drag ratio

Point where Total Drag is at its Minimum

Washout

⬇ Angle of Incidence

from Root to Tip

this is usually to ensure that @Vs

Root stalls before the Tip,

providing the aircraft with

(CAC) Continued Aileron Controllability

Aircraft's Speed Margines

(1)Vs

(2)Vmo/Mmo

(3)Vdf/Mdf

Vmo/Mmo 'Maximum Operating speed'

Indicated airspeed to be

Intentionally flown,

in knots or in Mach number,

Ensuring safe Operation of the aircraft

Vdf/Mdf 'Maximum Demonstrated Flight Speed'

Highest airspeed

planned to be flown

in Knots and Mach number

Achieved in Certification Testing

aircraft speed Regimes

1. Subsonic:Below 0.75

2. Transonic: From 0.75 To 1.20

3. Supersonic: From 1.20 To 5.00

4. Hypersonic: Above 5.00

1. Subsonic:

Mach numbers Below 0.75

2. Transonic

Mach numbers From 0.75 To 1.20

3. Supersonic

Mach numbers From 1.20 To 5.00

4. Hypersonic

Mach numbers Above 5.00

Performance Calculations

to know Weight and Calculate Profit from payload

Payload

Weight of Pax, Baggage, & Cargo.

Basic Parameters affecting aircraft's performance

(1/∝)Temperature
(1/∝)Altitude
(∝)Speed

Temprature benefits in aviation

Performance Calculations.
Determining Icing Conditions.
Airspeed and Altitude Correction,
for Obtaining True Calculations

Ram Rise

increase Temperature due to
Compressibility.

Negligible Until: 0.3 Mach speed

Static Air Temprature (SAT) (or) Outside Air Temprature (OAT)

temperature of

Free moving, Undisturbed Air Around an aircraft

corrected for Instrument & Compressibility Errors

Total Air Temprature (TAT)

“SAT”+ 100% of Ram Rise

Determines N1/EPR limits
obtained by TAT Probes

Ram Air Temperature (RAT)

SAT + Specific % of Ram Rise.

Altitude

Elevation with respect to an assumed reference level

Barometric Altitude

reduction in air pressure with an increase in altitude

QFE (Height)

Altimeter setting that indicates height Above Ground Level (AGL)

Absolute Altitude

Height Above Terrain
Measured by RA

not exceeding 2500 feet

QNH ‘Local Altimeter Settings’

Altimeter setting used Below Transition Layer
when aircraft's fly with reference to

Mean Sea Level, Giving Indicated Altitude
Indicating Elevation, Provided by ATC

Indecated Altitude

Altitude on the altimeter when set to QNH
indicates the aircraft height above MSL

Transition Altitude

Highest available to use below the transition layer.
where transition from QNH To QNE

if Climbing should begin

Transition Layer

1000ft layer between

transition altitude & level

ensuring Vertical Separation of aircraft

Operating on Different Altimeter Settings

Transition Level

Lowest available for use Above the transition Layer.
where transition from QNE to QNH

if Descending should begin

QNE

Altimeter setting used Above Transition Layer
when aircraft fly with reference to Flight Level
@ Standard Pressure 1013.25Hpa

and “Pressure Altitude”

Pressure Altitude

Altitude on the altimeter when set to QNE
@ISA
which is 1013.25 hectopascals (hPa)
or 29.92 inches of mercury (inHg).

Density Altitude

Pressure altitude corrected for non-standard Temp.

used for (Perf. Calculations)
DA=[Non stndr temp. - 15°c] x120+PA

True Altitude

Actual Height of an object above Sea Level
not indicated by any instruments.

in ISA conditions, MSL = SL, so True Alt.= Indecatied Alt.