11.1 High Speed Flight

Question 1

What are the two types of shock waves that are formed at supersonic flight?

Answer 1

Normal and oblique

Question 2

What happens to air temperature behind a shock wave?

Answer 2

The temperature rises

Question 3

How does the area rule effect an aircraft’s transonic flight performance?

Answer 3

It reduces wave drag

Question 4

In dry air at 20 degrees C what is the speed of sound?

Answer 4

343.2 metres per second

Question 5

Speed of sound varies depending on its substance, what does it travel the fastest an£ slowest through?

Answer 5

Fastest through a solid object
Slowest through a gas

Question 6

What are the three region of aircraft speeds?

Answer 6

. Subsonic
. Transonic
. Supersonic

Question 7

Define transonic

Answer 7

Some speeds around the aircraft are below the speed of sound and some are above the speed of sound

Question 8

As an aircraft approaches the speed of sound, what is formed after the leading edge?

Answer 8

A shock wave

Question 9

What is the Mach number for subsonic flight?

Answer 9

<0.8 Mach

Question 10

What is the Mach number for transonic flight?

Answer 10

0.8-1.2 Mach

Question 11

What is the Mach number for supersonic flight?

Answer 11

1.2-5.0

Question 12

How do you calculate the Mach number?

Answer 12

It’s aircraft’s speed divided by speed of sound

Question 13

What is the critical Mach number?

Answer 13

The highest possible Mach number that you can reach without turning to supersonic flight

Question 14

When does a normal shock wave take place?

Answer 14

At 1.2 Mach

Question 15

What is wave drag?

Answer 15

It is the portion of total drag that is caused by shock waves

Question 16

What are the two ways to reduce wave drag?

Answer 16

. Area rule
. Vortex generators

Question 17

What is the disadvantage of a vortex generator?

Answer 17

It increases parasite drag

Question 18

How does area rule effect the aircraft transonic flight performance?

Answer 18

Decreases the amount of wave drag

Question 19

When speed is increased to 0.8 Mach, we get shock waves. Therefore for fast aircraft you must have a what profile?

Answer 19

Thin profile

Question 20

Most modern aircraft have a sweep back wing of what?

Answer 20

30 degrees

Question 21

What is the main advatange of having a movable swept wing?

Answer 21

High performance at both low and high speed flight

Question 22

What are the three characteristics for an aircraft that flies at transonic flights?

Answer 22

. Flatter upper surface
. More curved leading edge
. Thinner trailing edge

Question 23

What can a wing with a transonic profile also be called?

Answer 23

Rear loaded wing

Question 24

What is the main advatange of a transonic wing profile?

Answer 24

It uses the skin as the torque box, therefore lighter and has greater fuel capacity. Therefore reducing drag.

Question 25

What is a flow separation on a wing also called?

Answer 25

Shock stall

Question 26

When the aircraft passes critical Mach was is its reaction?

Answer 26

Nose down - tuck under effect

Question 27

How can the tuck under effect be corrected?

Answer 27

By the horizontal stabiliser as it has the Mach trim system

Question 28

When a supersonic airflow passes through a shock wave, what happens to temperature?

Answer 28

Temperature increases

Question 29

When a supersonic airflow passes through a shock wave, what happens to pressure and density?

Answer 29

They increase

Question 30

When a supersonic airflow passes through a shock wave, what happens to velocity?

Answer 30

Decrease

Question 31

What are the two main types of WAVES formed in supersonic flow?

Answer 31

. Shock waves . Expansion waves

Question 32

What are the two types of shock waves?

Answer 32

. Normal . Oblique

Question 33

Where is a normal wave formed in conjunction to the object?

Answer 33

In front of the object

Question 34

Where is a oblique wave formed in conjunction to the object?

Answer 34

Formed above and below the object

Question 35

When a supersonic airstream passes through a normal shockwave what happens?

Answer 35

The velocity of airflow is decreased to subsonic (but not direction change)

Question 36

When a supersonic airstream passes through a oblique shockwave what happens?

Answer 36

Change in airflow direction and speed decreases but Stays at supersonic.

Question 37

When is an expansion wave formed?

Answer 37

Where the supersonic air stream turns away from preceding flow direction

Question 38

When a supersonic airstream passes through an expansion shockwave what happens?

Answer 38

The velocity increases Direction stays same as long as no flow separation

Question 39

What are the two typical supersonic profiles?

Answer 39

. Double wedge profile . Circular arc profile

Question 40

When flying a supersonic flight, the air entering the engine inlets must be slowed to what?

Answer 40

Subsonic range without wasting energy

Question 41

What is the correlation between Mach number and temperature?

Answer 41

At Mach number increases so does temperature