QFE and QNH Altimeter
QFE and QNH Altimeter Settings
Generally it can be said that:
When setting the QFE (FE = Field Elevation) value the altimeter will show 0 feet because it simply shows height above the airfield.
When setting the QNH (NH = Nautical Height) value, the altimeter will show the altitude above mean sea level. So in UUWW, runway 01 it will show approx. 630 feet.
In Russian Airspace at or above transition altitude / height / level the same Flight Levels (FL) in [ft] system is used.
Below transition altitude / height / level the procedure depends on whether or not you can actually set the QFE value in the FCU.
Aircraft that do not have a QFE setting avaible for the altimeters, a conversion of the reported QFE value into the corresponding QNH value has to be made.
In the example we will use the airport UUWW/Vnukovo. The threshold for runway 01 is 630 [ft] above Sea Level.
Lets assume the reported QFE is 997. On Lido charts you might find a published QFE/QNH conversion value. On Jeppesen (Navigraph) you do not. You will need to calculate the QNH value yourself. What you come up with? (Click to open)
Knowing that 1 hPa equals 27 [ft] difference, we take the threshold elevation and divide it by 27.
So: 630 divided by 27 equals a pressure difference (between QNH and QFE) of 23 hPa.
Now we can derive the QNH by adding 23 hPa from the QFE: 997 + 23 = 1020 hPa QNH.
When you set this value in the Altimeters, they will show a value of 630 feet, i.e. The height above MSL.
Please download the PDF for the full walkthrough (sadly outdated in current Navdata).
ONLY for Flight-Simulation!