Lesson 2

Question 1

Lift is a pressure gradient pushing…

Answer 1

upwards

Question 2

Pressure drag is?

Answer 2

an aerodynamic force created downstream of an object in the aerofoil

Question 3

C_L represents

Answer 3

Coefficient of lift

Question 4

C_{L MAX} describes?

Answer 4

Max lift an aerofoil can produce

Question 5

α_CRIT describes?

Answer 5

AoA critical = stall

Question 6

C_L / α graph:
line crosses zero alpha and zero Coefficient of lift
would be what type of aerofoil?

Answer 6

symmetrical

Question 7

C_L / α graph:
line crosses +4 alpha and zero Coefficient of lift
would be what type of aerofoil?

Answer 7

positive camber aerofoil

Question 8

C_L / α graph:
line crosses -4 α and zero C_L
would be what type of aerofoil?

Answer 8

negative camber aerofoil

Question 9

What is the lift equation

Answer 9

Lift = 1/2 x Density x Velocity² x Surface area x Coefficient of lift

Lift = ¹⁄₂ ρ V² S C_L

Question 10

Air is fluid, How would you describe its compressibility?

Answer 10

Incompressible

Question 11

Equation of continuity:
Mass flow and a streamtube
tell me more

Answer 11

Mass flow of incompressible fluid through a streamtube must be constant at all points

Question 12

Mass flow equation is:

Answer 12

m = ρ (density) x velocity x cross-sectional area of the flow

Question 13

P_TOT represents

Answer 13

Total pressure

Question 14

P_STAT represents

Answer 14

Static pressure

Question 15

the letter
‘q’
represents

Answer 15

Dynamic pressure

Question 16

When streamlines converge static pressure does what?

Answer 16

Decreases

Question 17

A pressure gradient is…

Answer 17

A change in static pressure over a distance

Question 18

Describe the pressure gradient force

Answer 18

Acts on an object inside a pressure gradient. The force acts in the high to low direction.

Question 19

Which two things determine the pressure gradient force strength?

Answer 19

The difference in the static pressure
The distance over which that difference is acting.

Question 19

Drag acts in the opposite to which direction.

Answer 19

Flight.

Question 20

2D airflow works in which two dimensions?

Answer 20

Up and down
forward and aft

Question 21

3D air flow ads which dimension?

Answer 21

Left to right
Spanwise flow

Question 22

What are the two types of two dimensional drag?

Answer 22

Form (pressure drag)
Skin friction drag

Question 23

What causes form drag

Answer 23

Form drag is caused by asymmetry in the areas of high pressure in front of and behind the aerofoil. The static pressure to the rear is lower than the static pressure around the front stagnation point. This causes a net force rearwards dash the ultimate cause of form drag.

Question 24

How do you minimise form drag

Answer 24

Reduce frontal surface area Minimised by changing shape of the object

Question 25

In which direction does form drag act?

Answer 25

Opposite to the direction of flight.

Question 26

Turbulent flow behind an object is indicative of which type of drag?

Answer 26

Form drag

Question 27

How would you define freestream airspeed?

Answer 27

The Airflow completely unaffected by the aerofoil and aircraft

Question 28

What is the name of the layer which changes the speed of the free stream air up to 99%?

Answer 28

The boundary layer

Question 29

Is skin friction drag a large value?

Answer 29

Negative, but it acts over the entire aircraft so can become significant.

Question 30

What are the two types of boundary layer?

Answer 30

Laminar boundary layer Turbulent boundary layer

Question 31

Does the laminar boundary layer or the turbulent boundary layer present a smooth velocity increase?

Answer 31

laminar

Question 32

Does the laminate boundary layer or the turbulent boundary layer present a steep velocity gradient?

Answer 32

Turbulent boundary layer

Question 33

Turbulent boundary layer or laminar boundary layer resist separation more?

Answer 33

turbulent boundary layer

Question 34

Which of these is more prone to separation [stall ] Laminar boundary layer or turbulent boundary layer

Answer 34

Laminer boundry layer

Question 35

would the laminar boundary layer be measured in millimetres or centimetres

Answer 35

millimetres

Question 36

would the turbulent boundary layer be measured in millimetres or centimetres

Answer 36

centimetres

Question 37

The transition point of an aerofoil marks the difference between what?

Answer 37

Laminar and turbulent boundary layers

Question 38

The separation point marks the difference between what?

Answer 38

Turbulent and a stalled condition Where the boundary layer separates from the surface

Question 39

Where on the aerofoil are you most likely to see laminar flow

Answer 39

On the top front edge

Question 40

At what point of the aerofoil is laminar flow physically unable to pass?

Answer 40

The thickest point of the aerofoil

Question 41

The adverse pressure gradient describes the pressure gradient in which location of an aerofoil

Answer 41

The adverse pressure gradient is caused because of the static pressure distribution, it causes pressure to flow against the direction of for air flow over the air of foil, it prevents the laminate flow going past the thickest point.

Question 42

What happens to the energy of the air flow once it moves aft of the adverse pressure gradient

Answer 42

Loses energy

Question 43

Which type of boundary layer requires a smooth clean surface forward of the thickest point?

Answer 43

laminar boundary layer

Question 44

How can you extend the laminar boundary layer on the top front of an aerofoil

Answer 44

Move the thickest point of the aerofoil aft

Question 45

What type of aircraft are you more likely to see turbulent boundary layer on

Answer 45

Slower training aircraft

Question 46

Role operates about which axis

Answer 46

Longitudinal

Question 47

Pitch operates about which axis

Answer 47

Lateral

Question 48

Yaw Operates about which axis

Answer 48

Normal

Question 49

An aircraft will pitch roll and yaw about which point?

Answer 49

Centre of gravity

Question 50

What word describes the top down shape of the wing

Answer 50

Planform

Question 51

Give four examples of wing shape

Answer 51

Rectangular Tapered elliptical swept

Question 52

What is used for the taper ratio of a wing

Answer 52

Tip chord divided by root chord

Question 53

What is used for the aspect ratio of a wing

Answer 53

Span divided by chord

Question 54

What is used for the thickness of a wing

Answer 54

Maximum thickness divided by chord length multiplied by 100 to get a percentage

Question 55

How would you describe the mean geometric chord

Answer 55

The average chord length

Question 56

The mean aerodynamic chord could be described as what

Answer 56

The cord of an imaginary rectangular wing with the same span as the swept or tapered wing that creates the same pitching moment as the wing. The position of things like scent of gravity and scent of pressure are given as percentages of MAC

Question 57

Describe sweep angle of a wing

Answer 57

The angle between the leading edge and a line perpendicular to the fuselage

Question 58

Describe rigging angle when it comes to a wing

Answer 58

Rigging angle for the angle of incidence is the angle between the aircraft's longitudinal axis and the wing cord at the wing root

Question 59

Describe a dihedral wing

Answer 59

The wing tips are higher than the wing root

Question 60

And describe a dihedral wing

Answer 60

The wing tips are lower than the wing root

Question 61

Why does span wise flow occur in three dimensional aerodynamics?

Answer 61

The elliptical lift distribution across the span of the wing

Question 62

What direction to spanwise flow run in

Answer 62

Towards the tip of the wing beneath and then towards the root on top. This creates a port clockwise rotation when viewed from behind and they starboard anticlockwise rotation

Question 63

What causes tip vortices

Answer 63

The combination of forward motion through the air and the span wise flow

Question 64

What affects wing tip vortices

Answer 64

Tip chord length Aircraft speed(A lower speed allows the spam wise flow to add a greater vortex to the incoming air flow)

Question 65

Where do vortices come from

Answer 65

Wing tip Trailing edge

Question 66

What is the effect of spoilers on the angle of attack and stall speed at a constant mass

Answer 66

with increasing spoilers both the angle of attack and stall speed increase