5.13.1.2 Communication aspects in multiple mode of operation

The ATS provider should conduct an in-depth evaluation of the communication aspects of any multiple mode of operation implementation, as part of the local safety assessment. The related operational procedures should be designed and established, and the necessary system support should be defined accordingly. The validation activities performed in the framework of the SESAR JU programme ([33], [36], [38]) have examined different ways of handling communication in a multiple mode of operation context, i.e. in dealing with frequencies/radio traffic for several aerodromes at the same time as well as dealing with an increased number of telephone lines to other ATS units and entities (compared to single mode of operation). With regard to the radio communication aspect, based on the validation results, some preferences can be noted, as discussed below. For aeronautical mobile service (air-ground communications), two obvious possibilities exist. Either the respective aerodrome frequencies are handled separately or cross-coupled (as e.g. commonly used when combining sectors in an ACC). If treated separately, the ATCO/AFISO would be able to hear all transmissions for all aerodromes; however, the pilots would only hear the aircraft transmissions related to their ‘own’ aerodrome. The ATCO/AFISO may respond/transmit to aerodromes separately, or may choose to respond/transmit to all aerodromes under their responsibility. One benefit of this method would be a reduced risk for pilot confusion, as a result of lowered risk to misinterpret transmissions on frequencies of other aerodromes. On the other hand, pilots may try to transmit on the frequency when the ATCO/AFISO is occupied with radio traffic at another aerodrome, as they will not necessarily hear transmissions of the other aerodrome(s). In addition, the ATCO/AFISO would need to select the correct transmitter/frequency, which could lead to the possibility of a mix-up of transmitters/frequencies (transmitting on the wrong aerodrome frequency). If the different aerodrome frequencies are cross-coupled, pilots (as well as the ATCO/AFISO) would hear all transmissions related to all aerodromes under the responsibility of the ATCO/AFISO. The benefit of this method would be that pilots at all times would be aware of the ATCO/AFISO occupancy and the risk for simultaneous transmissions (affecting the ATCO/AFISO) would be reduced. Also, the risk for ATCO transmitter/frequency mix-up (transmitting on the wrong aerodrome frequency) will be eliminated. On the other hand, confusion may arise from pilots hearing transmission(s) at other aerodromes. Based on the SESAR JU programme validation results ([33], [36], [38]), the preferred method seems to be frequency cross-coupling across the aerodromes. Some specific recommendations can be given with regard to aeronautical mobile service: When performing multiple mode of operation and when there is a possibility of confusion due to aerodromes having the same or similar runway designators, and if transmissions are not performed to individual aerodromes, the inclusion of aerodrome names in clearances/radio transmissions should be considered as a standard procedure. In addition, the ATS provider may also consider, as part of the local safety assessment, the inclusion of aerodrome names/ATS unit call sign for all transmissions (i.e. not only for the first contact) between pilots and ATCOs/AFISOs in multiple mode of operation. If this procedure is to be implemented, it should be published in the AIP for the particular aerodrome, together with any other specific communication methods as deemed necessary. For surface movement control service (communications for the control of vehicles other than aircraft on manoeuvring areas at controlled aerodromes), based on the SESAR JU programme validation results ([33], [36], [38]), the preference seems to be to keep the frequencies of different aerodromes separate. A recommendation in this regard can also be made: For aerodromes provided with (or to potentially be provided with) multiple mode of operation, it is recommended to consider the introduction of different call sign/number series for the vehicles at the respective aerodrome. For instance, vehicles at aerodrome A to use a call sign/number series starting with ‘A’ or ‘1’, vehicles at aerodrome B to use a call sign/number series starting with ‘B’ or ‘2’, etc.). This could be a simple way to support and facilitate the ATCO/AFISO recognition of vehicle radio calls from different aerodromes, as well as to avoid misinterpretations of clearances/transmissions. Another possibility could be to include the aerodrome name or its shortened form into the call sign/number of the ground vehicles. Using different position symbols for different aerodromes might be also an option. For further guidance on interdependencies, see Section 5.10.