Altimeter Pressure Settings
Avionics & Flight Operations · 4 specs
Direct Answer
Barometric altimeters compute aircraft height based on atmospheric pressure subscale settings: QNH (altimeter indicates true altitude above Mean Sea Level), QFE (altimeter indicates height above airport runway threshold), and QNE (standard 29.92 inHg / 1013.25 hPa for Flight Levels above transition altitude).
Specs
| Standard Pressure Setting (QNE) | 29.92 inHg (inches of mercury) = 1013.25 hPa (hectopascals/millibars) |
| US Transition Altitude | 18,000 ft MSL (Flight Level 180 / FL180) |
| European Transition Altitude | Varies by airport (typically 3,000 ft to 6,000 ft AGL) |
| Lapse Rate | 1.00 inHg per 1,000 ft (~30 ft per 1 hPa/mb) |
Q-Code Altimeter Settings Comparison
| Q-Code Setting | Barometric Reference Datum | Altimeter Reads On Ground | Primary Operational Usage |
|---|---|---|---|
| QNH | Local atmospheric pressure adjusted to Mean Sea Level | Airport Official Elevation (e.g. 5,434 ft at Denver) | Terminal departure, approach, terrain clearance below transition altitude |
| QFE | Local barometric pressure measured at runway threshold | Zero Feet (0 ft) | Soviet/military precision circuit training, aerobatics |
| QNE (Standard) | Standard ISA datum (29.92 inHg / 1013.25 hPa) | Pressure Altitude (Indicates FL) | High-altitude en-route navigation above Transition Altitude (FL180+) |