1.5 DENSITY ALTITUDE
Density altitude is the air density that exists at a given altitude for a given temperature. An airfoil's
efficiency, either a wing or a rotor blade, is decreased at high altitudes by the lack of air density. All
aircraft, regardless of design, have a ceiling (limit) where the air is too thin to sustain flight. The effect
of air density on helicopter performance is vital because of the critical load limit and confined-area
operation usually required of the helicopter.
Density altitude is pressure altitude corrected for temperature. Figure 1.3 shows the density altitude
chart used in operating Army aircraft. An airfield may have a density altitude that varies several
thousand feet from the mean sea
Figure 1.3 Density Altitude Chart.