Reduced Spacing ADS-B Trials To Start in NAT Airspace

 - March 27, 2019, 10:49 AM

Three North Atlantic Track (NAT) air navigation service providers will begin trials tomorrow of new reduced longitudinal separation minima using ADS-B surveillance data. The trials will be available to approved ADS-B-equipped aircraft flying throughout the NAT in the Shanwick, Gander, and Santa Maria Oceanic Control areas.

Called Advanced Surveillance-Enhanced Procedural Separation (ASEPS), the trials will initially apply to longitudinal separation. Specifically, 17-nm longitudinal separation of aircraft operating on the same track or intersecting tracks provided that the relative angle between the tracks is less than 90 degrees and 14 nm provided the relative angle between the tracks is less than 45 degrees.

No special LOA or other approval is needed for ASEPS operations, but participating aircraft must be RVSM/HLA approved and ADS-B Out (1090 MHz) equipped, as well as meet specifications for RNP 4, RCP 240, and RSP 180.

Starting simultaneously with the ASEPS trial will be changes to contingency and weather and weather deviation procedures for NAT operators. Outlined in NATS Bulletin 2018-05, the revised procedures apply when there is an inability to comply with the assigned clearance due to weather; diversion across the prevailing traffic flow; loss of, or significant reduction in, the required navigation capability; or pressurization failure.

The FAA published these procedures as Notams on February 28 and also released more details in an Information for Operators bulletin.