GM1 ATS.TR.155(f) ATS surveillance services

• ED Decision 2020/008/R found in: ATM/ANS Provision of Services (2017/373) (Feb 2023)

GM1 ATS.TR.155(f) ATS surveillance services ED Decision 2020/008/R ERRONEOUS LEVEL INFORMATION IN AIR TRAFFIC CONTROL SERVICE PROVISION (a)       If the displayed level information is not within the approved tolerance value or when a discrepancy in excess of the approved tolerance value is detected subsequent to verification, the pilot should be advised accordingly and requested to check the pressure setting and confirm the aircraft’s level. (b)       If, following confirmation of the correct pressure setting, the discrepancy continues to exist, the following actions should be taken by the air traffic controller according to circumstances: (1)       request the pilot to stop Mode C or ADS-B altitude data transmission, provided this does not cause the loss of position and identity information, and notify the next control positions or air traffic control unit concerned with the aircraft of the action taken; or (2)       inform the pilot of the discrepancy and request that the relevant operation continue in order to prevent loss of position and identity information of the aircraft and, when so prescribed by the local instructions, override the label-displayed level information with the reported level. In addition, the air traffic control unit should notify the next control position or air traffic control unit concerned with the aircraft of the action taken. (c)       It should be highlighted that the airborne collision avoidance system (ACAS) will accept Mode C replies that are erroneous, and it is possible to issue a resolution advisory (RA) based on these inputs. When the measures described in point (b)(1) cannot be implemented, the air traffic controller should take into account the likelihood of generating ACAS RA in the air traffic services provision. GM1 ATS.TR.155(f) ATS surveillance services ED Decision 2020/008/R ERRONEOUS LEVEL INFORMATION IN AIR TRAFFIC CONTROL SERVICE PROVISION (a) If the displayed level information is not within the approved tolerance value or when a discrepancy in excess of the approved tolerance value is detected subsequent to verification, the pilot should be advised accordingly and requested to check the pressure setting and confirm the aircraft’s level. (b) If, following confirmation of the correct pressure setting, the discrepancy continues to exist, the following actions should be taken by the air traffic controller according to circumstances: (1) request the pilot to stop Mode C or ADS-B altitude data transmission, provided this does not cause the loss of position and identity information, and notify the next control positions or air traffic control unit concerned with the aircraft of the action taken; or (2) inform the pilot of the discrepancy and request that the relevant operation continue in order to prevent loss of position and identity information of the aircraft and, when so prescribed by the local instructions, override the label-displayed level information with the reported level. In addition, the air traffic control unit should notify the next control position or air traffic control unit concerned with the aircraft of the action taken. (c) It should be highlighted that the airborne collision avoidance system (ACAS) will accept Mode C replies that are erroneous, and it is possible to issue a resolution advisory (RA) based on these inputs. When the measures described in point (b)(1) cannot be implemented, the air traffic controller should take into account the likelihood of generating ACAS RA in the air traffic services provision.