Properties of air Flashcards
What percentage of the atmosphere is composed of Carbon Dioxide?
Less than 1%
Density is maximum or minimum at sea level
Maximum
Aircraft performance is best in an atmosphere of high density or Low density.
Aircraft performance is best in an atmosphere of high density.
Define the term Pressure
The total force acting on a given surface area.
Define the term Temperature
The kinetic energy of the substance. (How fast they vibrate)
What atmospheric conditions will result in best aircraft performance
Low Temperature, High Pressure
ISA
International Standard Atmosphere
What is the pressure lapse rate until 5000 ft?
1 hPa per 30ft
statements regarding ISA conditions. With an increase in altitude……
Temperature slowly decreases steadily by 1.98 degrees per thousand feet,
Temperature decreases until the tropopause,
Temperature stops decreasing once it reaches -56.4 degrees.,
Density decreases (Quickly at first),
Pressure decreases by 30 ft per hPa (then slower past 5000ft)
What is the ISA temperature lapse rate until the tropopause?
The ISA temperature at sea level is 15°C. It decreases with altitude at a rate of 1.98 degrees every 1000 ft until the temperature is -56.4 degrees
What is the ISA Pressure at sea level?
The ISA pressure at sea level is 1013.2hPa. It decreases with altitude at a rate of 1hPa every 30 ft until 5000 ft, and then at a lower rate higher up.
Aircraft performance is highest when density altitude is high(True/False)
False
Pressure altitude Formula
Aircraft elevation + (30 x (1013-QNH)
Density altitude Formula
Density altitude = Pressure Altitude + (120 x (Actual temperature - ISA temperature at pressure altitude))
Two locations at sea level have the same temperature and pressure, but one location is very dry and one is very humid. Aircraft performance will be BEST at which location.
The humid atmosphere has water particles that replace the dry air particles. These water particles have less mass, meaning the air will be less dense.
An atmosphere with a reduced density will result in lower aircraft performance.
The correct answer is: Very dry location
What percentage of the atmosphere is composed of Oxygen?
21%
Assuming that the temerature of the gas remains constant in these situations,
The greater the density of the air, the greater the number of molecules there are colliding with the surface. This creates a greater force on a given area, meaning higher pressure.
The correct answers are: Increased density means an increased pressure, Increased volume means an decreased pressure
Density can be measured directly and is indicated in the cockpit.
As a property, it’s very difficult, if not impossible to measure density directly, due to the difficulty in measuring the mass of a gas, imagine trying to count the number of molecules of air floating around in an empty glass.
The correct answer is ‘False’.
Select the correct statement.
a. Pressure remains constant regardless of altitude because density and temperature cancel each other out
b. Pressure reduces with altitude. Slowly initially, and then at a larger rate higher up
c. Pressure reduces with altitude. Quickly initially, and then at a lower rate higher up
d. Pressure reduces at a constant rate with altitude
Pressure reduces with altitude. Quickly initially, and then at a lower rate higher up
In a flexible container that can expand or contract, is a gas substance. Select the correct statement(s) for the gas that is heated.
Density reduces, Pressure will remain equal to the surrounding air
What atmospheric conditions will result in poorest aircraft performance
High Temperature, Low Pressure
When the pilot selects 1013 hPa on their altimeter subscale, the altimeter reading will indicate…..
Pressure altitude
What is the ISA density at sea level?
The ISA density at sea level is 1.225kg/m³. It decreases with altitude rapidly at first then at a lower rate higher up.
What is the ISA temperature at sea level?
15°C.
If the pressure altitude was 10,000 ft and the corrosponding temperature was 9°C, what is the temperature deviation from ISA?
In ISA conditions, the sea level temperature is 15°C. This temperature reduces at a lapse rate of 2° per 1000 ft. So at 10, 000 ft the temperature has dropped 20°. (15°C - 20°C = -5°C) The ISA temperature at 10,000 ft is -5°C.
The actual temperature is 9°C which is 14° hotter than ISA. The ISA deviation is Δ 14°C.
The correct answer is: Δ 14°C
What is the purpose of ISA?
a. To compare aircraft performance
b. For performance calculations
c. To judge performance on the day
Aircraft performance is highest when density altitude is high(True/False)
A low density altitude indicates a high atmospheric density. This results in higher aircraft performance.
The correct answer is ‘False’
What percentage of the atmosphere is composed of Nitrogen?
78%
For conventional flight, density is required to become airborne.
Select one:
True
False
The correct answer is ‘True’.
As an aircraft _______ the performance will reduce.
Climb
Aircraft performance is greatest when taking off from aerodromes at a _____ altitude.
Low
In New Zealand Aviation, atmospheric pressure is measured in……
HectoPascals (hPa)
In a sealed container that cannot expand or contract, is a gas substance.
Select the correct statement(s) for the gas that is heated.
Density remains the same,
Pressure increases
What is the pressure lapse rate until 5000 ft?
1 hPa per 30ft
When the pilot selects 1013 hPa on their altimeter subscale, the altimeter reading will indicate…..
Pressure altitude
a. Density reduces at a constant rate with altitude
b. Density remains constant regardless of altitude because pressure and temeperature cancel each other out
c. Density reduces with altitude. Quickly initially, and then at a lower rate higher up
d. Density reduces with altitude. Slowly initially, and then at a larger rate higher up
The correct answer is: Density reduces with altitude. Quickly initially, and then at a lower rate higher up
Density can be measured directly and is indicated in the cockpit.(True/False)
‘False
Select the correct statement regarding aircraft performance.
Select one:
a. Aircraft performance is best in an atmosphere of minimal density
b. Aircraft performance is not affected by atmospheric density.
c. High density means aircraft can take off and land from longer runways
d. Aircraft performance is best in an atmosphere of high density
The correct answer is: Aircraft performance is best in an atmosphere of high density
Aircraft performance is greatest when taking off from aerodromes at a _____ altitude.
Low
As an aircraft _______ the performance will reduce.
Climb
Select the correct statement.
Select one:
a. Pressure reduces with altitude. Slowly initially, and then at a larger rate higher up
b. Pressure remains constant regardless of altitude because density and temeperature cancel each other out
c. Pressure reduces at a constant rate with altitude
d. Pressure reduces with altitude. Quickly initially, and then at a lower rate higher up
The correct answer is: Pressure reduces with altitude. Quickly initially, and then at a lower rate higher up
Assuming that the temerature of the gas remains constant in these situations, select the correct statement(s).
Select one or more:
a. Increased volume means an decreased pressure
b. Increased density does not affect pressure
c. Increased density means an decreased pressure
d. Increased density means an increased pressure
e. Increased volume means an increased pressure
f. Increased volume does not affect pressure
The greater the density of the air, the greater the number of molecules there are colliding with the surface. This creates a greater force on a given area, meaning higher pressure.
The correct answers are: Increased density means an increased pressure, Increased volume means an decreased pressure
In a flexible container that can expand or contract, is a gas substance. Select the correct statement(s) for the gas that is heated.
Select one or more:
a. Density increases slowly at first, and then faster at higher temperatures
b. Pressure decreases a lot
c. Density reduces
d. Pressure and density changes depend on the substance itself
e. Pressure increases
f. Pressure will remain equal to the surrounding air
g. Density remains the same
If the walls of our container disappeared, the high pressure hot air will expand until its pressure is equal to the surrounding colder air. Note this results in hot air having less density.
The correct answers are: Density reduces, Pressure will remain equal to the surrounding air
