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PPL - PoF > Basic Aerodynamics > Flashcards

Basic Aerodynamics Flashcards

1
Q

Bernoulli principle

What is the basic definition of Bernoullis therom?

A

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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2
Q

What is the Dynamic Pressure equation?

A

q = 1/2 p V^2

q = Dynamic pressure
p = rho
V = velocity

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3
Q

dynamic pressure + static pressure = ?

A

Total Pressure

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4
Q

Total pressure = ? + ?

A

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

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5
Q

What type of airflow is defined below?

Successive molecules of air follow the same steady path

A

Streamline flow

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6
Q

What type of airflow is defined below?

Molecules of air do not follow a steady path

A

Turbulent flow

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7
Q

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

A

TOWARDS

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8
Q

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

A

AWAY

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9
Q

What is the definition of vortex wake

A

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

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10
Q

What is the definition of the boundary layer

A

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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11
Q

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

A

Stationary

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12
Q

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

A

Increase until they reach the relative airflow (99%)

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13
Q

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

A

FORWARD towards the leading edge

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14
Q

What are the 2 flows within the boundary layer

A

Laminar Flow
Turbulent Flow

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15
Q

What is the definition of laminar flow

A

Air molecules sliding over each other
Thin layer
Low skin friction

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16
Q

What is the definition of turbulent flow

A

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

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17
Q

How prone are the airflows to flow seperation

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

A

Laminar - MORE
Turbulent - LESS

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18
Q

Assume asymmetric aerofoil

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

A

CHORD LINE

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19
Q

Assume asymmetric aerofoil

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

A

CAMBER LINE

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20
Q

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

A

MEAN CAMBER LINE

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21
Q

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

A

MAXIMUM CAMBER

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22
Q

What is the following

Maximum thickness divded by chord

A

Thickness/Chord Ratio

23
Q

What is the angle of incidence

A

Angle between the chord and longitudinal centre line of aircraft fuselage

24
Q

Lift Factors

The amount of lift produced is influenced by which factors

A

Air speed
Air density
Angle of attack
Aerofoil Shape

Lift = 1/2 p V^2 S CL

25
Q

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

A

FORWARD

26
Q

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

A

Moves down the leading edge to the underside of the aerofoil and aft

Presents high pressure air to the stall warning device

27
Q

If airspeed increases, MORE or LESS lift is produced

A

MORE

28
Q

MORE lift means MORE or LESS drag

A

MORE

29
Q

CLcrit is the point of what

A

Stalling AoA

30
Q

The best glide speed is determined by what

A

The maximum Lift/Drag ratio

31
Q

How many feet in 1nm

A

6080 ft = 1nm

32
Q

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)

A

9.87 nm
6000 ft x 10 = 60,000 ft travelled
6080 ft in 1nm
60,000 / 6080 = 9.87 nm

For every 1 ft of height loss, the aircraft travels 10 ft, ratio 10:1

33
Q

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

A

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

34
Q

Induced drag is caused by what

A

LIFT
Induced drag only exists once lift is being created

35
Q

Form (Zero lift) drag is made up from what

A

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

36
Q

What is the Zero Lift Drag (Form) formula

A

Dp = 1/2 p V^2 S CD0

Drag = half x rho x V squared x surface area x Form Drag coefficient

37
Q

D0 = 1/2 p V^2 S CD0

If airspeed doubles, what happens to drag?

A

Quadruples

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

38
Q

As airspeed increases

Form drag INCREASES or DECREASES
Induced drag INCREASES or DECREASES

A

Form drag = INCREASES
Induced drag = DECREASES

39
Q

As airspeed decreases

Form drag INCREASES or DECREASES
Induced drag INCREASES or DECREASES

A

Form drag = DECREASES
Induced drag = INCREASES

40
Q

Induced Drag INCREASES or DECREASES with an increase in AoA

A

INCREASES

41
Q

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

A

MORE

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

42
Q

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

A

MORE

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

43
Q

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

A

Long and thin
Glider

Glider AR - 30:1
MRJ AR - 10:1
Fighter Jet AR - 2:1

44
Q

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

A

short and thicker
Delta Wing
Fighter Jet

Glider AR - 30:1
MRJ AR - 10:1
Fighter Jet AR - 2:1

45
Q

a low aspect ratio wing has MORE or LESS induced drag

A

MORE

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

46
Q

What is the definition and effect of washout

A

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

47
Q

What is the Aspect Ratio (AR) formula

A

span / mean chord OR;
span^2 / area

48
Q

What is ground effect

A

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

49
Q

What effect does ground effect have on wing tip vorticies

A

REDUCES their strength

50
Q

What effect does ground effect have on effective air flow

A

REDUCES the angle
EAF becomes more like RAF

51
Q

What is the relationship between airspeed and induced drag

A

Drag increases at a rate of the inverse square of the square of the airspeed

More speed means less AoA needed for lift
Less AoA means less vortices = Less inducted drag
As speed increases, induced drag decreases

52
Q

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

A

REDUCE AoA

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

53
Q

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

A

OPPOSITE DIRECTION

PPL - PoF (9 decks)

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