Density of Altitude

A surprisingly accurate rule of thumb (usually any error will be less than200-300 feet) for determining the density altitude is easy to remember. For each10-degrees Fahrenheit above standard temperature at any particular elevation,add 600 feet to the field elevation. (And, conversely for each 10-degrees Fbelow standard temperature, subtract 600 feet from the field elevation.)Standard temperature at sea level is 59-degrees Fahrenheit. For elevations abovesea level, subtract 3.5 degrees per thousand feet of elevation from the sealevel temperature of 59 degrees.For example, at Jackson, Wyoming the elevation is 6,444. Multiply 6.444 times3.5 for 22.55. Subtract this from 59 (59-22.55) for 36.45. The standardtemperature at Jackson is 36.5 degrees. If the existing temperature is 80degrees, subtract (80-36.5 = 43.5). Divide this difference by 10 degrees (foreach 10-degrees F above standard), and multiply 4.35 times 600 (600 feet per 10degrees) which equals 2,610. Add 2,610 to the field elevation (6,444) for adensity altitude of 9,054. Under the existing conditions (of our example), theairplane will perform as it would on a standard day at 9,054 feet elevation