FAA Ground School Practice Test

What is density altitude?

1. The altitude indicated by the altimeter reading

2. The altitude above ground level

3. The pressure altitude corrected for nonstandard temperature

4. The vertical distance of the aircraft above sea level

The correct answer is: The pressure altitude corrected for nonstandard temperature

Density altitude is defined as the pressure altitude corrected for nonstandard temperature. This measurement is crucial for pilots because it directly affects aircraft performance. Aircraft performance is influenced by the density of air, which changes with temperature and pressure. As temperature increases, the air density decreases, leading to a higher density altitude. At standard atmospheric conditions, pressure altitude and density altitude can be the same; however, when temperatures deviate from the standard, density altitude must be calculated to understand how well the aircraft will perform. For example, on a hot day, the air is less dense, and the density altitude will be higher than the actual pressure altitude, adversely affecting engine performance, climb rates, and wing efficiency. Understanding density altitude helps pilots make informed decisions about takeoff distances, climb rates, and overall flight safety, especially in varying weather conditions and elevations.