Altimetry for air traffic controller[PDF]
When controlling his airspace, an air traffic controller can give instruction in order to change aircraft altitude.
- Altimeter set on local QNH
- Altimeter set on standard pressure 1013hPa (29.92inHg)
- Altimeter set on local QFE (forbidden in some areas and airport but still used in some regions)
Q code definition
|QNH||Atmospheric pressure at mean sea level (may be either a local, measured pressure or a regional forecast pressure (RPS)).|
|QFE||Atmospheric pressure at a specified datum such as airfield runway threshold.|
Altimeter setting change
- ATC gives clearance using altitude based upon local QNH at and below sector’s transition altitude.
- ATC gives clearance using flight level based upon standard pressure at and above sector’s transition level.
When in a climbing flight, passing through the transition altitude the altimeter setting will be changed from QNH to STD. The transition altitude (TA) is the highest altitude that will be assigned to an aircraft.
When in a descending flight, passing through the transition level the altimeter setting will be changed from STD to QNH. The transition level (TRL) is the lowest available FL, depending on the local pressure, that will be assigned to an aircraft.
The first assignable flight level for IFR aircraft by ATC should be in that case the next IFR flight level above transition level which ensure a minimum of 1000ft separation.
- ICAO documentation Annex 2 - Rules of the Air - 10th Edition July 2005
- VID 150259 - Creation
- VID 150259 - Wiki integration
DATE OF SUBMISSION
- 00:17, 14 May 2021
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