101-2 Temp & Density Flashcards
ISA
International Standard Atmosphere
Worldwide averages of temp and pressures for calibrating aircraft instruments
*Warmer than standard temp decreases aircraft perf.
Average sea level temperature
15 degrees C
Average sea level pressure
1013.2 mb OR 29.92” hg
Adiabatic
Natural heat/temperature change due to compression or expansion
Ex. Air that moves up a mountain
Freezing Temperature Value
0 degrees C / 32 degrees F
Melting point of ice
Pure water can be less than 0 degrees C
Freezing Level
FRZLVL (Airmet Z)
Altitude at which air temp equals 0 degrees C
*warmer SFC temp = higher FRZLVL
*colder SFC temp = lower FRZLVL
Primary cause of all changes in weather?
Temp Variations - Variations of solar radiation
Diurnal
Changes to day to night
Seasonal
Northern Hemisphere = summer
Southern Hemisphere = winter
Latitude
Warmer at equator
Topography Characteristics
Large/deep water minimizes temp changes
Arid, barren = greatest temp changes
What happens to temp as you increase in altitude?
Typically temp decreases with increase in altitude
Lapse Rate: 2 degrees C / 1000’
What is standard temp at 20000?
-25 degrees C
What is temp deviation for -30 @ 20000’
ISA -5
20 * -2 = -40
-40 + 15 (standard) = -25 C = ISA at 20,000’
-30 - -25 = -5
(Actual) - (Standard) = ISA - 5
Inversion
Increase in temp with an increase in altitude
