8.1 - Physics of the Atmosphere

Aerodynamics is

The study of objects in motion through the air and the forces that produce or change such motion

Aerodynamics cover the relationship between

Aircraft, relative wind and Atmosphere

The Air in the earth’s atmosphere is mostly composed of

Oxygen and Nitrogen

The compression of air is called

Atmospheric Pressure

Atmospheric pressure can be measured using

A mercury barometer

Under standard conditions, the air in a 1sq. inch column extending to the top of the atmosphere would weigh

14.7lb

The type of barometer used on-board aircrafts

Aneroid

The standard pressure at mean sea level is

20.58” of Mercury or 10.10 psi or 1013.25hPa

A hectopascal is equal to

100 pascals

At 50,000 feet the Atmospheric pressure has dropped to

almost one-tenth of the sea level value

Density is basically

weight per unit volume

The density of a gas is dependent on

Pressure (Directly)
Temperature (Inversely)

Density Altitude (Hd) is

a calculated altitude obtained by correcting pressure altitude for temperate

The troposphere is the __________ of the atmosphere

Lowest

On average the troposphere ranges from the earth’s surface to about __________ above it

38,000 feet

In the troposphere as altitude increases, temperature _________

decreases

The rate of change of temperature with altitude is somewhat constant in the troposphere which is about

-2°C or -3.5°F for every 1000 feet increase

The upper boundary of the troposphere is called

tropopause

The temperature in the tropopause is about __________

-57°C or -69°F

Above the tropopause lies the ________

Stratosphere

Temperature _________ with Altitude in the stratosphere

increases

__________ flights occur in the stratosphere

Some civilian and military

Why is it that on warm days, the take-off performance of an aircraft decreases significantly?

Since during warm days, air is less dense (Temperature and density are inversely proportional), thus less oxygen is available to readily combine with the fuel.

Humidity is the _____________

amount of water vapour in the air

Density of air and humidity are _________ proportional

inversely provided that pressure is constant

What is done to compensate for effects of Humidity during take-off (Turbine engine aircrafts)?

The allowable gross weight of an aircraft is generally reduced to compensate for less dense air generating lesser lift than usual

What is done to compensate for effects of Humidity during take-off (Reciprocating engines)?

the manifold pressure is increased in order to obtain the same output power

Dew point is the __________ to which humid air must be cooled at constant pressure to become __________

temperature, saturated

if the temperature drops below the dew point ______ occurs

condensation

Vapor pressure is expressed in

tenths of an inch of mercury