The purpose of this AIC is to disseminate to the Data Link users in Brazil detailed information regarding the migration of the VHF Base frequency in Brazil from 131.550 MHz to 131.825 MHz, planned for March 2024.
This Circular applies to all users of VHF Data Link services in Brazil.
Means of communication that enables digital message exchanges between aircraft and ground systems.
2.1. Data Link services in Brazil are under a Concession Agreement between the Brazilian Department of Airspace Control (DECEA) and SITA. Within this concession, SITA implemented and operates a dedicated Data Link Service Processor and the ground stations covering Brazilian airspace. For the Plain Old ACARS (POA) operation, the VHF Base frequency of 131.550 MHz has been adopted, as assigned by DECEA.
2.2. As the roll-out of Brazilian ground stations increased, the coverage along the border regions became denser. Consequently, transmissions on 131.550 MHz are now being picked up by Brazilian ground stations operated by SITA as well as by ground stations operated by Rockwell Collins, which use 131.550 MHz as their Base Frequency in South America, resulting in service degradation.
2.3. In order to address this issue and improve the Data Link service performance in the Brazilian border regions, DECEA and SITA worked together to have a new VHF Base frequency assigned. DECEA, as the Brazilian Aeronautical Authority, has allocated the new Base frequency of 131.825 MHz.
3.1.1. As aligned with DECEA, SITA will migrate the VHF Base frequency, for all VHF sites in Brazil, from 131.550 MHz to 131.825 MHz, on March 21, 2024.
3.1.2. The updated list of ground stations was distributed on 21 August 2021 by SITA to avionics vendors and airframe manufacturers, adding the new 131.825 MHz frequency to the current 131.550 MHz frequency, so that the correspondent geographical databases can be updated to include both frequencies in their next releases.
3.1.3. SITA will perform a hard cutover, from the old (131.550 MHz) to the new (131.825 MHz) Base frequency, on March 21, 2024. Therefore, both Base frequencies will not be simultaneously supported at any given VHF site in Brazil.
3.1.4. Once the migration has been completed, SITA will again update its ground station list for the avionics vendors and airframe manufacturers to remove the 131.550 MHz frequency, so that in their next geographical database release after March 2024 only the 131.825 MHz VHF Base frequency will be available for Brazilian sites.
NOTA: There is no change to the Brazilian VDL Common Signaling Channel (CSC) frequency of 136.975 MHz.
NOTA: There is no change to the Brazilian VDL Common Signaling Channel (CSC) frequency of 136.975 MHz.
3.2.1. An action is required to ensure all aircraft avionics are properly configured to operate with the new Base frequency in Brazil before March 2024.
NOTA: It is recommended to contact the Original Equipment Manufacturer (OEM) or avionics vendor, irrespective of whether your avionics use Geographical Filters or a Flat Scan Table, to ascertain which changes are required in the aircraft avionics to support the rollout of the new Base frequency in Brazil.
NOTA: It is recommended to contact the Original Equipment Manufacturer (OEM) or avionics vendor, irrespective of whether your avionics use Geographical Filters or a Flat Scan Table, to ascertain which changes are required in the aircraft avionics to support the rollout of the new Base frequency in Brazil.
3.2.2. AVIONICS WITH FLAT SCAN TABLE
3.2.2.1. Aircraft avionics using a Flat Scan Table typically have a list of worldwide VHF frequencies and associated Service Provider identifications. Each frequency in the list can be either Enabled or Disabled.
3.2.2.2. Even if frequency 131.825 MHz is present in the scan table, it is currently associated with a Service Provider Id XA and hence will not enable the aircraft to reliably use the Data Link service in Brazil, which uses Service Provider Id XB, which is the code of the DECEA Data Link Network, operated by SITA.
3.2.3. AVIONICS WITH GEOGRAPHICAL FILTERS
3.2.3.1. Some aircraft avionics use Geographical Filters (Geo-Filters). This means that only certain frequencies are configured to be used in certain geographical locations. This approach enables the customer to select the Service Provider per specified geographic area. Hence, aircraft using Geo-Filters need to have these filters updated to include frequency 131.825 MHz in Brazil geographic area.
3.2.3.2. Some avionics Geo-Filters only allow the user to specify one VHF frequency per geography. This may be problematic, because if the Geo-Filter is updated in advance, then the aircraft will not be able to use the VHF Data Link service until the frequency migration is completed. Conversely, if the Geo-Filter is updated after the base frequency migration, then the aircraft will be in NO COMM in VHF frequency from the time of the migration until the time of the avionics update. If the aircraft has such avionics, the operator should contact the OEM or avionics vendor and establish an avionics upgrade plan that minimizes impacts to operations.
3.2.3.3. If the aircraft is also equipped and configured to use the VDL frequency in Brazil or is equipped and configured to use SATCOM, it will be able to use these other Data Link communications until the avionics migration and update is completed.
3.2.3.4. Geo-Filters that allow two frequencies per region can be updated prior to the migration to include both 131.550 MHz and 131.825 MHz. In this case, the aircraft will be able to use either frequency and normal service over VHF will be maintained. If the aircraft has such avionics, operators will need to contact the avionics OEM or avionics vendor and ensure a copy of the updated database and that it is loaded on the aircraft in advance so that the updated database is uploaded before March 2024.
4.1. Criticisms and/or suggestions are welcome and should be sent via Contact Us – SAC-DECEA, on the Internet, at www.decea.gov.br, or Intraer, at www.decea.intraer.
4.2. Unforeseen cases will be resolved by the Head of the DECEA Technical Subdepartment.
4.3. This AIC republishes the AIC A 19/23.