Learn what QNH means, how to set it manually or with the B key in Microsoft Flight Simulator 2020, and fix wrong altimeter readings.
QNH is the local barometric pressure corrected to mean sea level. Set it in Microsoft Flight Simulator 2020 by pressing the default B key for automatic adjustment, or turn the aircraft’s BARO/altimeter knob until the displayed value matches ATIS or ATC. On the ground, the altimeter should then show airfield elevation.
What does QNH mean?
QNH makes an aircraft altimeter indicate altitude above mean sea level rather than height above the runway. When the correct QNH is set while parked, the indicated altitude should be close to the published elevation of the airfield.
Pressure changes with weather and location, so QNH is not a permanent setting. A rough rule is that an error of 1 hPa changes indicated altitude by about 27 feet. Flying from high pressure towards lower pressure without updating the setting makes the aircraft lower than the altimeter suggests.
In US-style ATIS and ATC phraseology, QNH is usually called the altimeter setting and given in inches of mercury. Elsewhere, it is commonly given in hectopascals.
| Pressure format | Typical spoken example | Value entered |
|---|---|---|
| Inches of mercury | “Altimeter two niner niner two” | 29.92 inHg |
| Hectopascals | “QNH one zero one three” | 1013 hPa |
| Standard pressure | “Standard” | 1013.25 hPa or 29.92 inHg |
How do I set QNH in Microsoft Flight Simulator 2020?
- Obtain the local pressure. Listen to the destination or departure airport’s ATIS, or use the altimeter setting supplied by MSFS ATC.
- Set it automatically. Press
Bwith the default keyboard bindings. This invokes the Set Altimeter command and adjusts the pressure setting to the simulated local conditions. Our MSFS keyboard and control-command reference covers this shortcut and other useful bindings. - Set it manually when required. Find the knob labelled BARO, ALT or a similar abbreviation beside the altimeter or primary flight display. Rotate it until the pressure window shows the ATIS or ATC value. Glass cockpits normally display the setting along an edge of the primary flight display.
- Cross-check the result. Before take-off, compare indicated altitude with airfield elevation. A small difference can result from rounded pressure reports, but a large discrepancy usually means the pressure or units are wrong.
The exact knob differs between aircraft. For a familiar example, our explanation of the Cessna 172’s altimeter and other cockpit instruments shows how the pressure setting relates to indicated altitude.
When should I use QNH instead of standard pressure?
Use local QNH below the applicable transition altitude, then select standard pressure when climbing above it. On descent, restore the destination QNH when passing the transition level so that approach, circuit and minimum altitudes are referenced correctly.
Transition altitudes vary by country and region; 18,000 feet is used in the United States but is not a worldwide rule. Follow the applicable procedure rather than changing to standard pressure at one fixed altitude everywhere.
For visual circuits, QNH lets you compare indicated altitude with published airfield elevation and circuit altitude. Our guide to using airfield elevation and altitude in a simulator traffic pattern explains that relationship.
Why is the altimeter still wrong after pressing B?
The most common causes are an altered control binding, the wrong pressure units, standard pressure being left selected, or an aircraft with independently controlled altimeters.
- Check the binding: open Controls Options and search by command name for
Set Altimeter. Reassign it ifBhas been changed or removed. Xbox users can bind the same command to a controller button combination. - Check hPa versus inHg: a report of 1013 belongs in an hPa display; 29.92 belongs in an inHg display. Some glass cockpits allow the units to be changed.
- Leave STD mode: pressing or turning a BARO control may toggle standard pressure. Confirm that the display shows a numerical local setting before landing.
- Set every required instrument: airliners and some add-on aircraft can have separate captain, first-officer and standby altimeters. One may remain on a different pressure.
- Use the cockpit control in custom aircraft: a sophisticated add-on may handle its barometric controls separately and ignore the general simulator shortcut.
If no pressure report is available while parked, turn the setting until the altimeter approximately matches the known airfield elevation. That is a useful fallback on the ground, but it is not a substitute for obtaining updated destination QNH before an approach.