Introduction to Pressure, Temperature, and Density

Temperature, Pressure, and DensityDanielle Hettmann and Chris SalehSYST460 Fall 2011

Static temperature: measure of the temperature at the surface of the aircraftAmbient temperature: measure of the temperature of the air in the region surrounding the aircraft

rule of thumb: ambient temperature drops 1 C for every 1000 feet increase in altitudeAmbient temperature varies with altitude: Below 36,089 feet: ambient temperature (R) = -3.566 * (altitude/1000)Above 36,089 feet: ambient temperature (R) = 389.988Temperature RatioBelow 36,089 feet, Tamb/TSeaLevel = = 1 (6.8753 X 10^-6) * pressure altitudeAbove 36, 089 feet, Tamb/TSeaLevel = = 0.7519Delta ISA = (Tamb + ISA) / (TSeaLevel + ISA)

Static Pressure:Measure of the pressure at the surface of the aircraft Ambient Pressure: Measure of the pressure of the air in the region surrounding the aircraft

Pressure Ratio :

=Pamb / PSeaLevelBelow 36,089 feet, the Ambient Pressure (lb/ft2) = (1 - * 6.88 X 10-6 * Pressure Altitude)5.26Above 36,089 feet, the Ambient Pressure (lb/ft2) = 0.223360 e ( (36.089 Pressure Altitude)/20.8057)

Ambient Density: Measure of the density of the air in the region surrounding the aircraftDensity Ratio:

= (Slugs/ft3) = amb / SeaLevelBoyles Law: Density (), pressure (), temperature () = /