Computing Pressure Altitude
You might be somewhat new to doing the pressure altitude computations, but you know the information is critical for aviation operations onboard the ship. You locate the resources to compute accurate values to give to the crew. There are pressure altitude calculators available through various sources, including the Geophysical Fleet Mission Program Library (GFMPL) and the National Oceanic and Atmospheric Administration (NOAA).
If you do not have a computer application or lookup table available, here is an example illustrating how to quickly compute pressure altitude using a mathematical formula.
pressure altitude = (standard pressure - station pressure) x 1000 + elevation
Using the formula, if you measure a station pressure of 29.45 in Hg and the standard pressure is 29.92 in Hg and your elevation is 50 feet, you can compute the pressure altitude as:
pressure altitude = (29.92 - 29.45) x 1000 + 50 = 520 feet
Based on your observations, the station pressure is 28.89 in Hg. Use the mathematical formula to compute the corresponding pressure altitude for an elevation of 30 feet.
pressure altitude = (standard pressure - station pressure) x 1000 + elevation
Choose the best answer.
The correct answer is b), 1060 feet.
pressure altitude = (standard pressure - station pressure) x 1000 + elevation
pressure altitude = (29.92 - 28.89) x 1000 + 30 = 1060 feet