What does density altitude indicate?

Density altitude is an important concept in aviation that refers to the altitude in the standard atmosphere where the air density is the same as the current air density at the given altitude and temperature. Specifically, it indicates how high the air density is compared to what would be expected at a given pressure altitude, adjusted for nonstandard temperature.

When the temperature is higher than standard (which is 15 degrees Celsius at sea level), the density of the air decreases. Consequently, to determine how the performance of an aircraft is affected by these variations in temperature, pilots adjust the pressure altitude for temperature deviations to derive the density altitude. This allows for better predictions of aircraft performance, as lower air density means less lift and poorer engine performance.

In contrast to other options, this understanding emphasizes that density altitude takes into account both pressure altitude and temperature to reflect the actual performance conditions that an aircraft will experience during takeoff, climb, and landing. This makes it a critical metric for pilots when assessing aircraft capabilities under varying atmospheric conditions.