(Refer to figure 8.) What is the effect of a temperature decrease and a pressure altitude increase on the density altitude from 90 °F and 1,250 feet pressure altitude to 55 °F and 1,750 feet pressure altitude?

Figure 8, Density altitude chart: figure for "(Refer to figure 8.) What is the effect of a temperature decrease and a pressure altitude increase on the dens" — **How to read it:** Start at the outside air temperature on the bottom, go up to the pressure-altitude diagonal, then left to read density altitude. The right-hand table converts altimeter setting to pressure altitude.

1,300-foot decrease.

1,700-foot decrease.✓ Correct Answer

1,700-foot increase.

Explanation

On the Figure 8 chart, 90 degrees F at 1,250 feet pressure altitude gives a density altitude of about 3,600 feet, while 55 degrees F at 1,750 feet gives about 1,900 feet. The density altitude therefore decreases by roughly 1,700 feet: the cooler air outweighs the 500-foot increase in pressure altitude. (Check: DA is about PA + 120 x (OAT - ISA) in degrees C: 1,250 + 120 x (32.2 - 12.5) = 3,610 and 1,750 + 120 x (12.8 - 11.5) = 1,906.)

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