Final answer:
Pressure altitude is the height above a standard datum plane (SDP) where the weight of the atmosphere is considered. It is commonly used in aviation to determine an aircraft's position in relation to the surrounding air pressure.
Step-by-step explanation:
Pressure altitude is the height above a standard datum plane (SDP) where the weight of the atmosphere is considered. It is commonly used in aviation to determine an aircraft's position in relation to the surrounding air pressure. The pressure at a particular altitude is determined by the weight of the air above that altitude.
For example, at sea level, the average atmospheric pressure is 1 atmosphere (atm) or 101 kPa. As you go higher in altitude, the pressure decreases because there is less weight of air above you. This is why people may experience difficulty breathing at high altitudes, as there is less oxygen available due to the lower atmospheric pressure.
Understanding pressure altitude is important for pilots, as it helps them calculate performance metrics, such as aircraft climb rates and fuel efficiency, which are affected by changes in atmospheric pressure.