DenAlt

DenAlt is a utility app for the calculation of density altitude.

Density Altitude Calculator for iPhone gives a convenient way to include the effects of non standard pressure, temperature and humidity on aircraft performance. This utility app provides the at hand ease of accounting for the real world consequences of non-standard air in the preflight phase.

The concept of density altitude expresses the aerodynamic effects in a compelling manner by the artiface of using a ficticious altitude. By thinking in terms of the density altitude the actual aircraft performance is more readily envisioned. One appreciates that the aircraft performs as if it was at that higher altitude instead of the actual altitude.

The theory, formulae, and on-line calculators are those due to Richard Shelquist and found at his site: http//:wahiduddin.net.

Input data consisting of actual field elevation, air temperature, altimeter setting, and dew point are entered in the appropriate input fields on the Main View.

A touch in a field brings the keyboard up. When all the input data are entered, the "RESULTS" button removes the keyboard and calculates the results. This action brings up a graphic view which shows the relationship of the actual altitude and the density altitude.

This presentation offers a more intuitive understanding of the actual aircraft performance at the atmospheric conditions relative to what it would be at the actual altitude on a standard day. Pressing the Main View button returns to the MainView which now has the "RESULTS" fields filled in with the complete parameters of density altitude, absolute pressure, relative air density, and relative humidity.

It is noted that DenAlt app results will differ from those obtained from denalt chart, E6B, or ASOS/AWOS broadcast when humidity is significant. That is because these sources do not include the effect of humidity but only those for temperature and pressure. The DenAlt app results are therefore more accurate. These effects can greatly affect the aircraft performance by decreasing the lift and the engine power output due to decreased air density.

The Info View contains switches for units selection and a ready to hand reference to the information presented here.

The selected settings take effect when the "Done" button is touched. This action also returns user to the Main screen where the just selected units are now shown. It's noted that millibars and hectopascales are equivalent.

Marcus Staloff, Copyright 2010.