4.1.4 Remote tower as backup facility

The remote aerodrome ATS concept could be used to support the ATS contingency arrangements for an aerodrome, as stipulated by Regulation (EU) 2017/373 [4], ATM/ANS.OR.A.070 and ATS.OR.135. A remote tower could be used as a backup facility in case the conventional tower is not available, either for planned reasons such as maintenance, or for unplanned reasons such as emergency outages. The rationale would be ATS continuity with a high level of retained safety, capacity and flexibility during contingency situations. It should be noted that, in reference to ICAO Annex 11 [16], Attachment C, point 2, referenced to in GM4 ATS.OR.135 to Regulation (EU) 2017/373 [4], any contingency arrangement is supposed to be temporary in nature, i.e. to be used only for limited time periods, until the ordinary services and facilities can be resumed. Meaning that a backup facility is not to be used as the principal means to provide the service unless properly demonstrated and approved by the competent authority. When implementing a backup facility based on the remote aerodrome ATS concept, it is recommended to define the required level of human-machine interface (HMI) commonality with respect to the conventional tower. Similarity to the ATCO/AFISO workstations and support tools provided in the conventional tower would reduce both the ATCO/AFISO familiarisation time during the transition into contingency phase as well as the need for recurrent contingency training. The use of new technical enablers should be carefully assessed. Although the introduction of such enablers has the potential to introduce operational benefits, this should be balanced against the disadvantages caused by introducing new tools and equipment which may not be available in the existing conventional tower, as well as by adding complexity to a backup facility (for which robustness would normally be a key factor). With regard to the visual presentation of RTMs used as a backup facility for a conventional tower, it would be beneficial to maximise the similarities with the OTW view of the conventional tower. On the other hand, the placement of camera(s) feeding the visual surveillance system will need careful consideration. It would not be advisable to install them on the conventional tower structure, as their purpose is to be used during an event which may have impacted the structure and the electrical/data infrastructure of the conventional tower building. Another important aspect to consider for a backup implementation is the split of infrastructure (such as for communication, uninterruptible power supply (UPS), etc.). Depending on the desired robustness of the backup solution and system, it is recommended to consider and reduce the number of common cause failures as far as practically possible. An appropriate level, depending on a local assessment, should be assessed and defined. Lastly, it is recommended to define the requirements on traffic complexity (mix of aircraft and vehicles etc.), capacity and duration of service, and switchover time for the backup facility. Contingency operations based on the remote aerodrome ATS concept have been studied in the framework of the SESAR JU programme ([22], [29], [30], [31], [32], [37]) and one related SESAR Solution has been published ().