Properties of air

Question 1

Why is the proportion of each of the constituent gases of air not important aerodynamically

Answer 1

All have equal value for the way in which they add to the mass of air

Question 2

What is oxygen needed for

Answer 2

To sustain the power produced by the engine and the life of the pilot

Question 3

How is density calculated

Answer 3

The total mass contained in a given volume

Question 4

Why is density important

Answer 4

Determines how well an aircraft and its engine can perform, as an aircraft climbs the density of air around it decreases and the wings of aircraft become less able to generate lift, at the same time the power output of the engine reduces

Question 5

What is the easiest way to calculate density

Answer 5

By using pressure and temperature

Question 6

What is pressure

Answer 6

The total force acting on a given area

Question 7

Units of pressure

Answer 7

n/m-2 or Pa

Question 8

What is atmospheric pressure usually measured in

Answer 8

hPa

Question 9

Relationship between pressure and density

Answer 9

The higher the density the higher the pressure

Question 10

What is tempreture

Answer 10

A measure of how much energy the molecules of a substance have or how fast they vibrate

Question 11

In masses of air with the same temperature, that with the ______ pressure has the highest density

Answer 11

Highest

Question 12

How far does the atmosphere extend from the earths surface

Answer 12

500 miles

Question 13

Why is the air nearest the earths surface the densest

Answer 13

The weight of the air in the outermost reaches bears down on the air nearer the surface and compresses it

Question 14

What happens to pressure, temperature, and density in the troposphere

Answer 14

They all decrease with altitude

Question 15

What does ISA standard for

Answer 15

International standard atmosphere

Question 16

What is the ISA

Answer 16

A hypothetical set of atmospheric conditions, which represents an average of the conditions experienced worldwide

Question 17

ISA initial sea level pressure

Answer 17

1013.2 hPa

Question 18

ISA pressure decrease rate

Answer 18

Pressure decreasing with altitude at a rapid rate initially around 1 hPa every 30ft to 5,000 ft and at a lower rate thereafter

Question 19

ISA initial sea-level temperature

Answer 19

+15C

Question 20

ISA temperature decreasing rate

Answer 20

Decreasing at a uniform rate of 1.98C/1000ft up to 36,090 ft

Question 21

ISA initial sea-level density

Answer 21

1.225kg/m3

Question 22

ISA density decreasing rate

Answer 22

Decreasing with altitude at a rapid rate initially and a lower rate thereafter

Question 23

What will a high temperature indicate

Answer 23

Low density and poorer performance

Question 24

What will a low temperature indicate

Answer 24

High density and better performance

Question 25

What will a high pressure indicate

Answer 25

High density and better performance

Question 26

What will a low pressure indicate

Answer 26

Low density and poorer performance

Question 27

What is density altitude

Answer 27

The altitude in the ISA which has the same density as the actual altitude you are trying to measure

Question 28

How is the density altitude worked out

Answer 28

Enter the temperature and pressure into the aircraft’s performance chart, use the navigation computer to work it out or do a manual calculation

Question 29

The hypothetical ISA is based on ___ air

Answer 29

Dry

Question 30

Range of average humidity in the air

Answer 30

20-80%

Question 31

How does humidity affect the density

Answer 31

Moist air is less dense than dry air as water molecules have less mass than the molecules of dry air it has replaced

Question 32

What is viscosity

Answer 32

The tendency for molecules of fluid to stick together and cling to any solid surface they come in contact with

Question 33

In masses of air with the same pressure, that with the ______ temperature has the highest density

Answer 33

Lowest