Basic Aerodynamics Flashcards by C MC

Bernoulli principle

What is the basic definition of Bernoullis therom?

Air forced through a restriction speeds up
As space decreases, flow speed increases
Mass airflow remains constant but as mass flow increases, temperature and pressure decrease

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What is the Dynamic Pressure equation?

q = 1/2 p V^2

q = Dynamic pressure
p = rho
V = velocity

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dynamic pressure + static pressure = ?

Total Pressure

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Total pressure = ? + ?

dynamic pressure + static pressure
SAME AS:
Ps + 1/2 p V^2

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What type of airflow is defined below?

Successive molecules of air follow the same steady path

Streamline flow

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What type of airflow is defined below?

Molecules of air do not follow a steady path

Turbulent flow

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Airflow above the wing is deflected TOWARDS or AWAY from the fuselage?

TOWARDS

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Airflow below the wing is deflected TOWARDS or AWAY from the fuselage?

AWAY

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What is the definition of vortex wake

Spanwise flow above and below the wing meet and create a vortice

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What is the definition of the boundary layer

The layer of decreasing airspeed caused by skin friction
At surface, airflow is stationary
As distance increases from aerofoil, air molecule speed increases

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What is the speed of air molecule flow at the surface of an aerofoil

Stationary

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What happens to airflow the further higher the molecules are in the boundary layer?

Increase until they reach the relative airflow (99%)

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What direction does the Transition Point move in relation to the leading edge as speed increases

FORWARD towards the leading edge

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What are the 2 flows within the boundary layer

Laminar Flow
Turbulent Flow

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What is the definition of laminar flow

Air molecules sliding over each other
Thin layer
Low skin friction

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What is the definition of turbulent flow

Air molecules bumping into each other
Thick layer (cm)
High skin friction

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How prone are the airflows to flow seperation

Laminar flow - MORE or LESS
Turbulent flow - MORE or LESS

Laminar - MORE
Turbulent - LESS

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Assume asymmetric aerofoil

What is the name of the straight line that joins the leading edge to the trailing edge

CHORD LINE

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Assume asymmetric aerofoil

What is the name of the curved line that joins the leading edge to the trailing edge

CAMBER LINE

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What is the equidistant line between the upper and lower surface of an aerofoil known as

MEAN CAMBER LINE

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What is the maximum distance between the chord line and the mean camber line known as

MAXIMUM CAMBER

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What is the following

Maximum thickness divded by chord

Thickness/Chord Ratio

What is the angle of incidence

Angle between the chord and longitudinal centre line of aircraft fuselage

Lift Factors

The amount of lift produced is influenced by which factors

Air speed
Air density
Angle of attack
Aerofoil Shape

Lift = 1/2 p V^2 S CL

The Centre of Pressure (CoP) moves FORWARD or AFT from the leading edge with an increased AoA

FORWARD

Which direction does the stagnation point move with an increase of AoA

Moves down the leading edge to the underside of the aerofoil and aft ## Footnote Presents high pressure air to the stall warning device

If airspeed increases, MORE or LESS lift is produced

MORE lift means MORE or LESS drag

CLcrit is the point of what

Stalling AoA

The best glide speed is determined by what

The maximum Lift/Drag ratio

How many feet in 1nm

6080 ft = 1nm

An aircraft has a L/D ratio of 10:1 Given a height loss of 6000 ft, how far will the aircraft travel in nautical miles (nm)

**9.87 nm** 6000 ft x 10 = 60,000 ft travelled 6080 ft in 1nm 60,000 / 6080 = 9.87 nm ## Footnote For every 1 ft of height loss, the aircraft travels 10 ft, ratio 10:1

What are the 2 types of drag represented in the drag curve

Parasite (Form) Drag (Dp) Induced Drag (Di)

Induced drag is caused by what

LIFT Induced drag only exists once lift is being created

Form (Zero lift) drag is made up from what

Non aerodynamic parts; Examples; Interference drag (i.e. wing meets the fuselage) Fuselage rivets Aerials

What is the Zero Lift Drag (Form) formula

Dp = 1/2 p V^2 S CD0 ## Footnote Drag = half x rho x V squared x surface area x Form Drag coefficient

# D0 = 1/2 p V^2 S CD0 If airspeed doubles, what happens to drag?

Quadruples ## Footnote Airspeed is squared. So doubling airspeed will quadruple drag Airspeed vs Drag 1 = 1 2 = 4 3 = 9 4 = 16

# As airspeed increases Form drag INCREASES or DECREASES Induced drag INCREASES or DECREASES

Form drag = INCREASES Induced drag = DECREASES

# As airspeed decreases Form drag INCREASES or DECREASES Induced drag INCREASES or DECREASES

Form drag = DECREASES Induced drag = INCREASES

Induced Drag INCREASES or DECREASES with an increase in AoA

INCREASES

For aircrafts at same speed and altitude; Higher weight needs MORE or LESS lift

MORE ## Footnote For aircrafts at same speed and altitude; MORE weight needs MORE lift LESS weight needs LESS lift

For a given speed, high altitude implies MORE or LESS induced drag

MORE ## Footnote Air pressure is less at high altitude. For the same aircraft with the same TAS at higher altitude, to maintain lift, an increase in AoA is required. An increase in AoA impies MORE induced drag

What is a typical wing design type if the wing is a high aspect ratio

Long and thin Glider ## Footnote Glider AR - 30:1 MRJ AR - 10:1 Fighter Jet AR - 2:1

What is a typical wing design type if the wing is a low aspect ratio

short and thicker Delta Wing Fighter Jet ## Footnote Glider AR - 30:1 MRJ AR - 10:1 Fighter Jet AR - 2:1

a low aspect ratio wing has MORE or LESS induced drag

MORE ## Footnote The more wing tip length there is, the more air that can spill from lower to upper aerofoil surface, which means more induced drag

What is the definition and effect of washout

AoA at wing tip is lower than at the root REDUCED vorticies REDUCED induced drag

What is the Aspect Ratio (AR) formula

span / mean chord OR; span^2 / area

What is ground effect

Ground "gets in the way" of upwash and downwash Typical within 1x wing span height from the ground

What effect does ground effect have on wing tip vorticies

REDUCES their strength

What effect does ground effect have on effective air flow

REDUCES the angle EAF becomes more like RAF

What is the relationship between airspeed and induced drag

Drag increases at a rate of the inverse square of the square of the airspeed ##FOOTNOTE More speed means less AoA needed for lift Less AoA means less vortices = Less inducted drag As speed increases, induced drag decreases

A SEP aircraft accelerates in flight. To maintain constant lift (i.e. straight and level flight), what must the pilot do

REDUCE AoA ## Footnote Refer to lift formula. If Speed is increased, this is squared. V^2 is therefore increased If an element is increased, lift increases. To maintain a constant, another element must be decreased Reduce AoA reduces the Coefficient of lift (CL) meaning lift remains constant

Which direction does aerodynamic drag act in, in relation to an aircraft in motion

OPPOSITE DIRECTION