Use a density altitude chart to figure the density altitude at the departing airport. Using Figure 10-21, determine the density altitude based on the given information.
Sample Problem 1
Airport Elevation………………………………………..5,883 feet
OAT…………………………………………………………………70 °F
Altimeter…………………………………………………..30.10″ Hg
Figure 10-21. Density altitude chart.
First, compute the pressure altitude conversion. Find 30.10 under the altimeter heading. Read across to the second column. It reads “–165.” Therefore, it is necessary to subtract 165 from the airport elevation giving a pressure altitude of 5,718 feet. Next, locate the outside air temperature on the scale along the bottom of the graph on your density altitude chart. From 70°, draw a line up to the 5,718 feet pressure altitude line, which is about two-thirds of the way up between the 5,000 and 6,000 foot lines. Draw a line straight across to the far left side of the graph and read the approximate density altitude. The approximate density altitude in thousands of feet is 7,700 feet.
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