AMC1 ATS.TR.155(g) ATS surveillance services

• ED Decision 2020/008/R found in: ATM/ANS Provision of Services (2017/373) (Mar 2025)

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)](#_DxCrossRefBm647742572), 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). 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)](#_DxCrossRefBm1726555395), 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).