Pressure Altitude
Pressure altitude is the altitude indicated by an altimeter set to the standard pressure of 29.92 inHg (1013.2 hPa). It is the basis for flight level reporting above FL180, aircraft performance calculations, and density altitude determination.
How Pressure Altitude is Used
- Aircraft performance: All POH performance charts use pressure altitude — determine it before computing take-off and landing performance
- Flight levels: Above 18,000 ft in Canada, all aircraft set 29.92 inHg — the altimeter reads pressure altitude in hundreds of feet (FL350 = 35,000 ft pressure altitude)
- Density altitude: Density altitude = pressure altitude + temperature correction; the performance-critical altitude
Determining Pressure Altitude on the Ground
Set the altimeter to 29.92 inHg and read the altitude displayed. This is the pressure altitude at that location. Alternatively: pressure altitude ≈ field elevation + (29.92 − QNH) × 1,000. For each 0.01 inHg the altimeter setting differs from 29.92, pressure altitude differs from field elevation by about 10 ft.
On the TC Written Exam
Pressure altitude appears in performance, navigation, and instrument exam sections. Know: it’s the altitude with 29.92 set; it’s the reference for flight levels; it’s used to find density altitude.
Related Terms
See also: Density Altitude, Flight Level, Altimeter Setting.