Density altitude
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Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation. "Density Altitude" is the pressure altitude adjusted for non-standard temperature.
Both increase in temperature and increase in humidity cause a reduction in air density. Thus in hot and humid conditions the density altitude at a particular location may be significantly higher than the geometric altitude.
Density altitude can be calculated from atmospheric pressure and temperature (assuming dry air).
[\mathrm = 145426 \left[1-left(frac}/T_}right)^bright]]
where
[\mathrm=] density altitude
[P_0=] atmospheric (static) pressure
[P_=] standard sea level atmospheric pressure (1013.25 hpa)
[\mathrm=] true (static) air temperature
[T_=] standard sea level air temperature(288.15 K)
[b=] 0.235
Simpler less acurate method
Another simpler less acurate method to calculate density altitude is:DA = ( 29.92 - A) x 100 + 100 ( T - ( 15 - ( 2 x H ) / 1000 ) )
A is the altimeter setting in inches of mercury T is the temperature in degrees Celsius H is the height of the airfield, or aircraft
References
- Langley Flying School, 2005 Groundschool Manual, page 97, located at Langley Regional Airport
See also
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