Introduction to Pressure, Temperature, and Density

Temperature, Pressure, and Density Danielle Hettmann and Chris Saleh SYST460 Fall 2011 Ambient temperature: measure of the temperature of the air in the region surrounding the aircraft Static temperature: measure of the temper

ature at the surface of the ai rcraft Ambient temperature varies with altitude: Below 36,089 feet: ambient temperature (R) = -3.566 * (altitude/1000) Above 36,089 feet: ambient temperature (R) = 389.988 = (Tamb rule of thumb: ambient

temperature drops 1 C for every 1000 feet increase in altitude Delta ISA + ISA) / (TSeaLevel + ISA) Temperature Ratio Below 36,089 feet, Tamb/TSeaLevel = = 1 (6.8753 X 10^-6) * pressure altitude Above 36, 089 feet, Tamb/TSeaLevel = = 0.7519

Ambient Pressure: Measure of the pressure of the air in the region surrounding the aircraft Static Pressure: Measure of the pressur e at the surface of the aircra ft

Pressure Ratio : =PPamb / PSeaLevel Below 36,089 feet, the Ambient Pressure (lb/ft2) =P (1 - * 6.88 X 10-6 * Pressure Altitude)5.26 Above 36,089 feet, the Ambient Pressure (lb/ft2) =P 0.223360 e ( (36.089 Pressure Altitude)/20.8057) Ambient Density: Measure of the density of the air in

the region surrounding the aircraft Density Ratio: =P (Slugs/ft3) =P amb / SeaLevel Boyles Law: Density (), pressure (), temperature () ) = / )