What is the definition of pressure altitude?

• A. The height of the aircraft above mean sea level
• B. The altitude indicated when the barometric pressure scale is set to 29.92 inHg
• C. The pressure exerted by the atmosphere at sea level
• D. The altitude at which the air density is standard

Answer: (B)

Pressure altitude is defined as the altitude indicated when the barometric pressure scale is set to 29.92 inches of mercury (inHg). This measurement is crucial for understanding various performance parameters of an aircraft, as it provides a standardized reference for altitude regardless of local weather conditions. By setting the altimeter to this standard pressure value, pilots can determine their aircraft's altitude in a manner that is consistent and comparable across different locations and conditions.

This standardization is essential in aviation, as it allows for clear communication and ensures that altitude readings are understood universally, aiding safety and navigation. Other altitude measurements, such as true altitude or indicated altitude, can be influenced by varying local pressures, but pressure altitude remains constant when referenced to standard atmospheric conditions at sea level.