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EASA Principle of Flight > Forces, weight, lift, drag, thrust > Flashcards

Forces, weight, lift, drag, thrust Flashcards

1
Q

Four forces

A

Weight, lift, thrust and drag

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2
Q

Equilibrium

A

All forces are balanced

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3
Q

L/D abbr meaning

A

Lift / drag ratio

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4
Q

In a cruise flight, what’s the approximate L/D ratio

A

10 to 1, 10 lift, 1 drag

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5
Q

MTOW

A

Maximum takeoff weight

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6
Q

MATOW

A

Maximum allowable takeoff weight

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7
Q

All-up weight

A

The general weight of the aircraft including fuel, passengers and load. Should be equal or less than MTOW

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8
Q

Wing loading

A

The load that the wings carry in a straight in level flight

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9
Q

Wing loading formula

A

Weight of the airplace / Wing area

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10
Q

An aircraft weighs 1220kg and wing area of 20 square meters. what is wing loading

A

=(1220/20)
=61kg /square meter

also written as: kgm^-2

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11
Q

Venturi effect

A

High flow velocity = low static pressure
(Like an air flowing through a tube, which is narrower at the center, so at the center the flow will be faster, with lower static pressure)

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12
Q

Boundary layer

A

The layer of airflow closest to the surface of the aerofoil. It causes friction of air with surface, which can make this layer relative velocity zero. The relative velocity in general is less in the boundary layer. And after it, the layer thickens.

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13
Q

Transition point

A

The point at which the boundary layer becomes turbulent.

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14
Q

Streamline flow

A

The desirable flow around aircrafts aerofoil

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15
Q

Separation point

A

The point at which the boundary layer separates from the surface of an erofil, causing the airflow to break and become turbulent.

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16
Q

Bernoulli principle

A

Anything in motion has energy.
Static pressure energey; and
dynamic pressure energy (kinetic energy due to motion)
Sum of them will give total energy

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17
Q

a fluid in motion will have

A

static pressure energy + dynamic pressure energy = constant totsl energy

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18
Q

Dynamic pressure two variables:

A
  • the speed of the body relative to the air
  • the density of the air
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19
Q

dynamic pressure equation

A

1/2 * rho * velocity squared

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20
Q

if velocity increaes, static pressure

A

decreases. and vice versa

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21
Q

upwash

A

a stream of air that hits the wing and being forced into a constricted area. its velocity increases above the wing

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22
Q

after an upwash, veloicity is increased above the wing, therefore:

A

decreasing static pressure above the wing according to bernoulli principle

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23
Q

cambered surface

A

a curvature causing the airflow over it to accelarate more ans generate more lift at the same AoE

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24
Q

mean camber line

A

a line drawn halfway between the upper and lower surface (its not straight in a cambered surface)

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25
Q

chord line

A

a straight line joining the leading edge and tralining edge, in other words, a straight line joining the ends of mean camber lines

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26
Q

camber

A

the distance between mean camber line and chord line

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27
Q

well cambered wing is associated with

A

low speed, high lift

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28
Q

total reaction (tr)

A

consists of the lift and drag components from the center of pressure (the total reaction)

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29
Q

AoA

A

angle between chord line and relative airflow

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30
Q

Is relative airflow parallel to horizon?

A

no

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31
Q

Pitch angle

A

The angle relative to the horizon

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32
Q

IMPORTANT the airflow and pitch angle and AoA,

A

refer to page 18

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33
Q

Angle of incidence

A

the angle which the wing is fixed to the airframe relative to the longitudinal axis

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34
Q

Stagnation point

A

Airflow come to rest at this point. Occurs at the leading edge and trailing edge.

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35
Q

What happens to the coLift and centre of pressure when increasing AoA

A
  1. The lifting ability of the wing (coLift) increases
  2. The centre of pressure moves forward
36
Q

What happens to CP (center of pressure) when reaching a stalling AoA

A

Moves backwards

37
Q

Lift formula

A

cL 1/2 ρ V^2 S
Explained:
(coefficient of lift) * (1/2*air density) * (velocity sqaured) * (wing surface)

38
Q

What lift depends on?

A

Angle of attack and indicated airspeed

39
Q

A difference in location between center of pressure and center of gravity

A

Will make the airplane pitch up / down. We can counteract this by using the tailplane controls (elevator controls)

40
Q

In symmetrical aerofoil, at AoA 0 what is the lift?

A

0, since the mean camber line and chord line are the at the same position.

41
Q

What’s called The angle at which laminar flow over the upper wing surface breaks into eddies and sepearates?

A

Crticial angle

42
Q

Purpose of tailplane

A

To balance the MOMENT created by the differing positions of the CP and CG

43
Q

When AoA increased, where on a low speed aerofoil will flow separation start?

A

On the upper surface towards teh trailing edge

44
Q

In a cambered wing surface, when AoA is -4 degrees approx

A

Lift is 0

45
Q

Drag is parallel to?

A

relative airflow. acts opposite of it

46
Q

Total drag

A

the total resistance sum of all drag acting opposite of the aircraft movement

47
Q

Two types of drags

A

Induced drag
Parasite drag

48
Q

Parasite drag 3 children

A

Skin friction
Form drag
Interference drag

49
Q

Induced drag small explanation

A

Drag forces associated with the production of lift. I.e. vortices at the trailing edge and wing tips

50
Q

Parasite drag small explanation

A

Drag forces not directly associated with lift.

51
Q

Skin friction drag

A

Friction between an object the air, depends on:
- Surface area of the aircraft
- If the boundary layer airflow is laminar or turbulent
- Roughness of the surface (like ice)
- Airspeed, more airspeed more skin friction drag
- Aerofil thickness, more thickness more drag
- AoA, more AoA more drag

52
Q

Form drag

A

When the airflow spearates from the surface, eddies are formed and streamline is distrubed.
Like landing gear

53
Q

Difference between form drag and skin friction drag

A

Imagine a flat plate, at 0 AoA is all skin friction drag and at 90 AoA its all form drag as the air behind it is trubulent

54
Q

What is streamlining

A

Making a “shape” (such as landing gear) more streamline friendly to delay the separation point and reduce form drag. Like putting fairings on the landing gear.

55
Q

Interference drag

A

The drag generated due to the “junctins” of various surfaces, like the wing junction.

56
Q

Parasite drag and airspeed

A

As airspeed increases, parasite drag increases, by V-squared. (Square rule)

57
Q

Induced drag

A

By-product of the production of lift and is closely related to angle of attack

58
Q

Wing tip vortices (induced drag)

A

As the air flows rearwards, some airflow will “leak” around the wingtip from underneath, joining the eventually both the high pressure below and low preure above. Creating vortices.

59
Q

When wings are producting high value of cLift, the wingtip vortices

A

Are stronger, since the pressure difference is greater as well

60
Q

Newton’s third law

A

For every action there’s an opposite reaction

61
Q

Induced downwash

A

The overall downflow of the air behind the trailing edge behind forced down after a wing

62
Q

High aspect ratio wings when (span / chord)

A

Induced drag is reduced

63
Q

Tapered wings

A

Wings that at the tip has less “width” and therefore induced drag is less since less vortices are created

64
Q

Washout

A

Wing is built such that the AoA at the wing tip is less. It means the wing in general will produce less lift, but also less induced drag

65
Q

The slower the airspeed

A

The more vortices, more induced drag. Since the pilot will want to stay on a straight flight, so he increases the AoA.

66
Q

Induced drag is most significant at

A

Slow speeds, high AoA

67
Q

Increased lift efficieny means

A

More induced drag.

68
Q

The greater the airspeed

A

Less induced drag, more parasite drag

69
Q

Minimum drag speed (Vmd)

A

The point at which parasite drag and induced drag are balanced, creating the lowest of total drag

70
Q

Low airspeed is associated with

A

High angle of attacks. To keep the plane lifted

71
Q

How to calculate lift/drag ratio

A

Lift / drag (or the equations)

72
Q

What approx is the best angle of attack to give the best lift/drag ratio

A

4 degrees

73
Q

Blade angle

A

The angle at which the chord line of apropeller section makes with the plane of rotatio

74
Q

Name of the cambered side of the blade

A

Blade back

75
Q

Name of the flat side of the blade

A

Blade face

76
Q

Helical path

A

When airplane moves forward, the propeller secgtion follows a cockscrew path through the air called helix

77
Q

Two velocity components affecting a propeller

A

Rotational velocity
Forward velocity (when aircraft is moving forward)

78
Q

Propeller torque

A

The resistance to motion in the plane of rotation

79
Q

If the aeroplane is into a dive, what can we see on the RPM?

A

Increase. Even if we didnt open more throttle

80
Q

Slipstream effect

A

When propeller is rotating to the right (from the cockpit view), will make a clockwise (right) slipstream around the body of the aircraft, reaching the left side of the fin, causing the tail to be pushed to the right and the nose to yaw left

81
Q

Propeller torque reaction

A

If rotates to the right, the torque reaction will tend to rotate the aircraft anti-clockwise and roll it to the left. On the ground the left wheel stops this motion, but makes the airplace yaw to the left

82
Q

At fixed-pitch propeller the blade angle

A

is constant

83
Q

Angle of attack of the propeller blade is

A

Between the resultant velocity (Down velocity due to rotation, and forward velocity due to motion on the aircraft) and chord line.
Imagine a triangle

84
Q

More forward velocity with same RPM, the blade AoA is

A

reduced

85
Q

More rotational velocity (more RPM) with same forward velocity, the AoA is

A

higher

EASA Principle of Flight (6 decks)

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