What is density altitude?

Density altitude is defined as the vertical distance above mean sea level in the standard atmosphere where a given atmospheric density would be found. It is a crucial concept in aviation because it impacts aircraft performance; as density altitude increases, the air becomes less dense, which affects lift, engine performance, and propeller efficiency.

For instance, at higher density altitudes, aircraft may need longer distances to take off and climb, due to reduced engine power and lift generated by the wings.

The other provided definitions do not accurately capture the importance and implications of density altitude. For example, the definition that refers to vertical distance above sea level at a specific temperature does not address how density altitude relates to atmospheric density and performance. The mention of equal temperature and pressure describes a different atmospheric phenomenon, while temperature increase with altitude pertains to the lapse rate, which is another aspect of atmospheric science but is not relevant to understanding density altitude.