This regulation comes into force on the day after its publication and cancels the previous regulation NfL I 189/97.
Transition height and transition area:
- For flights under instrument flight rules, a transition altitude of 5000 ft MSL (Mean Sea Level) is specified. Below this altitude, the pilot must set the altimeter to the QNH value transmitted by the responsible air traffic control centre. QNH is the air pressure at sea level, corrected to the current temperature, and enables the pilot to accurately measure the altitude above sea level.
- Above the transition altitude, the standard altimeter setting must be used, which is based on a standardised air pressure (1013.25 hPa).
- In addition, a transition area is defined that is at least 1000 ft above the transition altitude. This area corresponds to the flight level for instrument flight rules, taking into account the applicable QNH value.
Altimeter settings:
- Before take-off, the altimeter must be set to the transmitted QNH value. When flying through the transition altitude, switch to the standard altimeter setting, which is retained during the cruise flight.
- For approaches under instrument flight rules where the standard altimeter setting was previously used, the altimeter must be reset to the QNH value when flying through the transition area.
Communication of the altimeter setting:
- The respective air traffic services unit is obliged to transmit the current altimeter setting to the aircraft as soon as the first clearance for a flight altitude below the transition area is issued.
This control ensures that the altitude measurement is consistent and accurate during flight by providing the correct settings based on the flight phase and current altitude. The use of QNH below the transition altitude enables precise altitude measurement in relation to the actual altitude above sea level, while the standard altimeter setting above this altitude creates a uniform basis for altitude measurement in the high flight range.
Source references:
NFL (the link requires a subscription to Eisenschmidt)
