M8 new

Question 1

What does laminar flow consist of

Answer 1

Layers

Question 2

What happens during turbulent flow

Answer 2

Direction and velocity are constantly changing

Question 3

What happens during laminar flow

Answer 3

velocity can change but direction always remains the same

Question 4

What is the stagnation point

Answer 4

Is the part of the airflow that hits the airfoil at the front and comes to rest

Question 5

What is a Vortex

Answer 5

When the air try to follow the sharp edges it is not possible so a curling movement forms

Question 6

What is the Bernoulli principle

Answer 6

The relationship between potential and kinetic energy in a fluid

Question 7

Atmospheric pressure =

Answer 7

dynamic pressure + static pressure

Question 8

What is the mean camber line

Answer 8

is drawn midway between the upper and lower cambers ( one of the most important factors for identifying characteristics of an aerofoil

Question 9

Where is the chord line

Answer 9

from leading edge to trailing edge

Question 10

What is fineness ratio

Answer 10

he ratio of the length of a body to its maximum width

Question 11

What is maximum camber of a low speed airfoil

Answer 11

• Maximum camber of a typical low speed aerofoil should be 4% of the length of the aerofoil and located around 40% of the chord length behind the trailing edge

Question 12

What is the best fineness ratio

Answer 12

4 to 1

Question 13

Induced drag is due to

Answer 13

lift

Question 14

Parasite drag is caused by

Answer 14

viscosity of the air

Question 15

Wave drag during transonic and supersonic flight as a result of…

Answer 15

• Wave drag during transonic and supersonic flight as a result of shock waves

Question 16

In cruise most commercial aircraft fly between what speeds

Answer 16

0.75 to mach 0.85

Question 17

• Airflow through a shockwave experiences a rapid increase in

Answer 17

pressure and temperature

Question 18

• Wave drag can be reduced by introducing…

Answer 18

aerodynamic designs such as wing sweep and ultra thin wings

Question 19

• The centre of pressure of a subsonic airfoil is typically located somewhere around

Answer 19

30% to 40% of the chord line back from the leading edge.

Question 20

• The centre of pressure moves forward as the angle of attack increases and backwards as the angle of attack decreases

Answer 20

• The centre of pressure moves forward as the angle of attack increases and backwards as the angle of attack decreases

Question 21

• At the stall position, the wing looses lift, the airflow becomes turbulent and the centre of pressure moves

Answer 21

rearwards

Question 22

• Polar curves are diagrams in which

Answer 22

Lift and drag coefficients are plotted

Question 23

• Optimum AOA is between

Answer 23

4-6 degrees where the smallest drag is found compared to lift

Question 24

• Critical angle of attack (close to stall) is

Answer 24

15-20 degrees

Question 25

- Drag coefficient is the ratio of

Answer 25

drag pressure and dynamic pressure

Question 26

- Aspect ratio =

Answer 26

- Aspect ratio = wing span to the wing chord

Question 27

- Commercial aircraft have an aspect ratio between

Answer 27

- Commercial aircraft have an aspect ratio between 5-8

Question 28

- Mean aerodynamic chord is

Answer 28

- Mean aerodynamic chord - the average length of the chord

Question 29

- Washout is

Answer 29

- Washout - greater angle of incidence at the root than the tip (we don’t want the tip of the wing to stall first)

Question 30

- Cruise is when

Answer 30

thrust and drag are totally balanced

Question 31

- It is normal in aircraft design to have the centre of pressure

Answer 31

slightly behind the centre of gravity

Question 32

- Glide ratio is

Answer 32

Horizontal distance divided by the change in altitude

Question 33

- When supersonic air flows through a converging passage, its velocity

Answer 33

Decreases and its pressure and density both increase.

Question 34

- The speed of sound in air changes with

Answer 34

Temperature, increasing as temperature increases.

Question 35

- Mach number is

Answer 35

- Mach number is the ratio between the speed of the object and the speed of sound.

Question 36

- Mach crit or critical mach is

Answer 36

The lowest mach number at which the airflow over any part of the aircraft reaches the speed of sound

Question 37

- A shockwave occurs once...

Answer 37

Critical mach number has been exceeded

Question 38

- Transonic speed is typically between mach

Answer 38

0.8 and 1.2

Question 39

- Supersonic speed range is between mach

Answer 39

1.2 and 5

Question 40

- Normal shock wave

Answer 40

- Normal shock wave ( form perpendicular to the airstream. Velocity of the air behind a normal shock wave is subsonic and the static pressure and density of the air are higher.

Question 41

- Oblique shock waves

Answer 41

- Oblique shock waves (air behind them is lower but still supersonic. Static pressure and density are higher.

Question 42

- Expansion waves

Answer 42

- Expansion waves (when supersonic air is flowing over the top of a wing and the wing surface turns away from the direction of flow, the air will expand and follow the new direction. An expansion wave will occur at the point where the direction of flow changes.

Question 43

- For a subsonic airfoil, the aerodynamic centre or point of support is approx

Answer 43

25% back from the leading edge.

Question 44

- In supersonic flight the aerodynamic centre moves back to

Answer 44

50% aft of the leading edge

Question 45

- During high speed flight heat build up on the leading edge is cased by

Answer 45

friction

Question 46

- An aircraft tends to return to wings level flight after being disturbed and this is considered

Answer 46

Laterally stable

Question 47

- Sweepback is designed to

Answer 47

Prolong the formation of sonic shock waves on the wing caused at high speeds which cause drag

Question 48

- Dutch roll is

Answer 48

A lateral-directional oscillation

Question 49

- Torque effect is

Answer 49

The tendency for the aircraft to rotate in the opposite direction to the propeller rotation

Question 50

- Ground effect is

Answer 50

The tendency for the aircraft to ‘float’ on the cushion of air when close to the ground