What is the effect on density altitude from a temperature decrease and pressure altitude increase when going from 90°F at 1,250 feet to 55°F at 1,750 feet?

Density altitude is a crucial concept in aviation that represents the altitude at which the air density is equal to the standard atmospheric conditions. It is influenced by temperature and pressure. As temperature decreases or pressure increases, density altitude decreases, leading to better aircraft performance due to higher air density.

In this question, the scenario describes a decrease in temperature from 90°F to 55°F and an increase in pressure altitude from 1,250 feet to 1,750 feet. The decrease in temperature directly lowers the density altitude because cooler air is denser. At the same time, the increase in elevation (pressure altitude), which typically results in lower air pressure, should also contribute to a lower density altitude.

To assess the combined effects of these changes, it is essential to recognize that the decrease in temperature has a significant impact on air density and therefore reduces density altitude effectively. On the other hand, the increase in pressure altitude has a lesser effect compared to the influence of temperature. The net result of these two changes leads to a substantial decrease in density altitude, calculated in this case as a decrease of approximately 1,700 feet.

Thus, considering the changes in temperature and pressure altitude, the correct answer is indeed that there is a 1,700-foot decrease