What is pressure altitude?

Pressure altitude is defined as the altitude indicated when the barometric pressure scale is set to the standard atmospheric pressure of 29.92 inches of mercury (Hg). This standardization is important for pilots because it allows for a consistent reference point for aircraft performance calculations and navigation, regardless of current local atmospheric pressures.

When the altimeter is set to 29.92 inches of mercury, it reads pressure altitude, which is crucial when flying at higher elevations or under varying atmospheric conditions. It provides a way to express altitude in relation to a standard atmosphere, allowing pilots and air traffic controllers to maintain safe separation between aircraft.

The other options refer to different altitude concepts that do not align with the definition of pressure altitude. For instance, adjusting altitude for temperature considers atmospheric variations rather than a standardized pressure. Similarly, the altitude indicated by the altimeter presumes standard conditions, which are different from the specific adjustment made when setting to 29.92 inches. Ground level altitude pertains to the height above the terrain, rather than a defined atmospheric reference.