AMC1 ATS.TR.155(g) ATS surveillance services
ED Decision 2020/008/R
VERIFICATION
OF LEVEL OCCUPANCY
(a) In accordance with AMC1 ATS.TR.155(f), the criterion which should be used to determine that a specific level is occupied by an aircraft should be ±60 m (±200 ft) in RVSM airspace. In other airspace, this criterion should be ±90 m (±300 ft), except that the competent authority may specify a smaller criterion, but not less than ±60 m (±200 ft), if this is found to be more practical.
(b) Aircraft maintaining a level
An aircraft should be considered to be maintaining its assigned level as long as the pressure-altitude-derived level information indicates that it is within the appropriate tolerances of the assigned level, as specified in point (a).
(c) Aircraft vacating a level
An aircraft cleared to leave a level should be considered to have commenced its manoeuvre and vacated the previously occupied level when the pressure-altitude-derived level information indicates a change of more than 90 m (300 ft) in the anticipated direction from its previously assigned level.
(d) Aircraft passing a level in climb or descent
An aircraft in climb or descent should be considered to have crossed a level when the pressure-altitude-derived level information indicates that it has passed this level in the required direction by more than 90 m (300 ft).
(e) Aircraft reaching a level
An aircraft should be considered to have reached the level to which it has been cleared when the elapsed time of three display updates, three sensor updates or 15 seconds, whichever is the greater, has passed since the pressure-altitude-derived level information has indicated that it is within the appropriate tolerances of the assigned level, as specified in point (a).
EASA aviation regulations define aircraft level occupancy for air traffic surveillance. Level verification uses pressure-altitude data. Occupancy tolerance is ±60m in RVSM airspace, ±90m elsewhere (minimum ±60m if specified). Vacating/passing levels require a 90m change. Reaching a level requires sustained tolerance for 15 seconds or three display/sensor updates.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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