The Atmosphere

Question 1

Atmospheric density is a measure of the …… of ….. contained in a given …..

Answer 1

mass of air contained in a given volume

Question 2

When there are a large number of air molecules the density is said to be …..

Answer 2

high

Question 3

Air density affects 3 things, name them:

Answer 3

1. The lift produced at any given airspeed
2. The engine power produced at any throttle setting
3. The thrust produced by the propeller at any given RPM

Question 4

Changes in density are most noticable during ….. ….. and …..

Answer 4

take off and climb

Question 5

Low density affects all areas of an aeroplane including:

Answer 5

1. Increased landing distance due to higher TAS
2. Must accellerate to a higher TAS at take off to compensate for reduced density
3. Reduced engine power
4. Reduced thrust

All this equals a drastic reduction in performance

Question 6

In the ISA:

For every 30ft we go up we experience a reduction of …… Hpa

Answer 6

-1 Hpa for every 30 ft

Question 7

In the ISA:

Every 1000ft we ascend the standard temperature lapse rate is ….^₀C

Answer 7

2⁰C for every 1000ft

Question 8

The definition of “Pressure Height” is:

Answer 8

The height in the standard atmosphere where the pressure is the same as the sample of air being considered.

Question 9

Pressure height is not a ……

Answer 9

measure of height, it is a measure of “Pressure”

Question 10

Pressure height can have a negative value - if it does what figures do you use on the performance charts?

Answer 10

If it is less than zero, use zero but the performance will actually be a little better….

Question 11

The formula for Pressure Height =

Answer 11

Pressure Height = Elevation + [1013 - QNH] x 30

Question 12

The difference in temperature from the ISA is called …..

Answer 12

ISA deviation and is expressed as a Plus when it is hotter and a Minus when it is colder.

Question 13

What is the ISA deviation at 4500ft if it is 12^oC?

Answer 13

ISA = 15 - [2x4.5] = 6⁰C

if the temp is 12^oC @ 4500ft then the ISA deviation = +6^oC

Question 14

What is the ISA deviation at 13,000ft if it is 0^oC?

Answer 14

ISA = 15 - [2x13] = -11⁰C

If the temp is 0⁰C then the ISA deviation is +11⁰C since it is 11⁰C warmer

Question 15

What is the ISA deviation at 8500ft if it is 12^oC?

Answer 15

ISA = 15 - [2 x 8.5] = -2⁰C

Deviation = +14⁰C

Question 16

What is the ISA deviation at 4500ft if it is -4^oC?

Answer 16

ISA = 15 - [2 x 4.5] = 6⁰C

Deviation = -10⁰C

Question 17

If the pressure of a location is not standard than we must apply what?

Answer 17

The pressure and tempretature corrections

Question 18

When we have made allowances for both pressure and temperature the result is known as …..

Answer 18

Density Height

Question 19

The definition of “Density Height” is:

Answer 19

The height in the standard atmosphere where the air has the same density as the sample of air being considered

Question 20

As the air temp increases the air molecules move …… ……

Answer 20

further apart

Question 21

Temperature increases of 1⁰C will produce a density ….. quivalent to a height of …..ft

Answer 21

decrease of 120ft

Question 22

Temperature decreases of 1⁰C will produce a density ….. quivalent to a height of …..ft

Answer 22

increase 120ft

Question 23

On a hot day where the temp is 10⁰C higher than ISA the plane will perform as though it was at …..ft

Answer 23

1200ft