1. What is Pressure Altitude?

Pressure Altitude is the altitude in the standard atmosphere where the pressure is the same as the actual atmospheric pressure. It's a crucial parameter in aviation for aircraft performance calculations and flight planning.

2. How Does the Calculator Work?

The calculator uses the Pressure Altitude formula:

Where:

• \( PA \) — Pressure Altitude (ft)
• \( Altitude \) — Actual altitude above sea level (ft)
• \( QNH \) — Current atmospheric pressure at sea level (hPa)
• 1013 — Standard sea level pressure (hPa)

Explanation: The formula adjusts the actual altitude based on the difference between standard pressure (1013 hPa) and the current QNH value.

3. Importance of Pressure Altitude Calculation

Details: Pressure altitude is essential for determining aircraft performance characteristics such as takeoff and landing distances, rate of climb, and true airspeed calculations. It's also used for setting altimeters and ensuring proper vertical separation between aircraft.

4. Using the Calculator

Tips: Enter altitude in feet and QNH in hectopascals (hPa). Both values must be positive numbers. The calculator will compute the pressure altitude based on the standard atmospheric pressure correction.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between altitude and pressure altitude?
A: Altitude is the actual height above sea level, while pressure altitude is the altitude in the standard atmosphere where the pressure equals the current atmospheric pressure.

Q2: Why is 1013 hPa used as standard pressure?
A: 1013.25 hPa is the internationally accepted standard mean sea level pressure in the International Standard Atmosphere (ISA) model.

Q3: How does QNH affect pressure altitude?
A: When QNH is lower than 1013 hPa, pressure altitude will be higher than actual altitude. When QNH is higher than 1013 hPa, pressure altitude will be lower than actual altitude.

Q4: When is pressure altitude most important?
A: Pressure altitude is critical during aircraft performance calculations, particularly for takeoff and landing in non-standard atmospheric conditions, and for flight level assignments above the transition altitude.

Q5: Can this formula be used for all altitudes?
A: This formula provides a good approximation for lower altitudes. For very high altitudes, more complex calculations accounting for temperature variations may be necessary.