Altimeter Setting - [Transition Altitude, QNH and QNE]

Below the Transition Altitude, you have to use as an Altimeter reference the Pressure at the Mean Seal Level also called QNH.

Two Aircraft departing from 2 different airports will use the QNH, however, this value changes from one place to another depending on the Pressure on that area.

So, if you depart from an airport with a specific QNH you must change constantly the altimeter pressure reference in order to keep the Mean Sea Level as a reference.

As you can imagine this is not an easy task.

The Transition Altitude has been established in order to provide you with a clear and specific Altitude where you have to change from the Sea Level Pressure to the Standard Pressure of 1013 hpa also called QNE.

By selecting the QNE you will use the same pressure reference of all the other Aircraft flying above the Transition Altitude.

Using the QNE as a reference you will be flying FLIGHT LEVELS and not Altitudes because you are not using the QNH as a reference anymore.

Why don't we use the QNE all the time then?
Well, you need to use the Mean Sea Level Pressure as a reference until you are clear of terrain.

The terrain is expressed in Elevation which, uses the Mean Sea Level as a reference.
If you want to separate yourself from the obstacles you need to use the same reference.

So, When you take off you must use the QNH until the Transition Altitude then changes to QNE and fly FLIGHT LEVELS.

You can find the QNH from the Atis, metar, ATC.
The Transition Altitude is indicated on the AIP, ATC, ATIS, and IFR charts.

If you want to know more about IFR training watch the video below:
IFR introduction:    • IFR TRAINING (Part 1) - Instrument Fl...  
SIDs:    • Standard Instrument Departure (SID) P...  
STARs:    • Standard Arrival Route (STAR) Explain...  
Approach Chart:    • Jeppesen Approach Plates - [Bried an ...  

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Disclaimer:
THIS VIDEO IS FOR ENTERTAINMENT PURPOSES ONLY.
NOT FOR REAL-LIFE OPERATIONS.
PLEASE REFER TO THE OFFICIAL MANUAL AND DOCUMENTATION.
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