19SAB11 NAT LATERAL ASEPS

Safety Bulletin

19SAB11 01 October 2019 NAT Lateral ASEPS Note: This publication is based upon ALPA, International Operations Bulletin 2019-04, Atlantic Oceanic: Space-Based ADS-B Lateral Separation and MicroSLOP. ALPA-I has also updated its NAT webpage at www.alpa.org/nat which also includes web links to each of the NAT Operations Bulletins for the changes described below.

On March 2019, longitudinal separation standards were reduced based on the availability of Space-Based ADS-B in the Shanwick (EGGX), Gander (CZQX), and Santa Maria (LPPO) Oceanic Control Areas in the North Atlantic (NAT), as part of the Advanced Surveillance Enhanced Procedural Separation (ASEPS) trials.

The NAT region will be commencing the second phase of the ASEPS trials to include reduced lateral separation starting on or about 10 October 2019. If your aircraft is appropriately equipped and filed with Communication, Navigation, and Surveillance equipment, Air Traffic Control may apply 19 NM lateral spacing between parallel or non-intersecting tracks, instead of the 23NM minimum lateral separation in use now. This is in addition to the reduced longitudinal separation implemented in the first phase.

The revised in-flight contingency procedure introduced on 28 March 2019 is still in effect, and with the reduced lateral separation, it is critical that the new procedures be followed in the NAT region and New York Ocean West (WATRS), including Gander, Shanwick, Santa Maria, NY Ocean East and NY Ocean West (KZWY), Bodø (ENOB), Reykjavik (BIRD), and Nuuk (BGGL).

For those aircraft whose Flight Management Systems (FMSs) are capable, an enhancement to the Strategic Lateral Offset Procedure (SLOP) is authorized in the entire NAT region. The NAT region has used the SLOP for several years, to provide additional protection against the effects of a Gross Navigational Error with precision navigation. SLOP authorized the flight crew to randomly select either a 1.0 or 2.0 NM offset right-of-course.

Effective 7 August 2019, the new “Micro-SLOP” procedure provides additional protection by authorizing aircraft with capable FMSs to fly increments of 0.1 NM between 0.0 and 2.0 NM right-of-course. By allowing 0.1 NM offsets, this further reduces the possibility of a near mid-air collision by providing more offset distance options for flight crews to choose at random.

Micro-SLOP is currently authorized throughout the NAT region. The latest information available to ALPA is that the most recent Boeing B737s (NG, Max), B787s, and the B777X (when it enters service) have Micro-SLOP capability. Airbus is planning an enhancement across their product offerings in the 2022+ timeframe. There is no hazard introduced by this mixed implementation of Micro-SLOP.

Execution of SLOP is ALWAYS right of course and NEVER left of course. Application of SLOP can be dynamic in response to factors such as wake turbulence avoidance.

ALPA advises flight crews to follow company guidance for the lateral ASEPS trial, for SLOP, and in which airspace to use Micro-SLOP if capable.

If you have any questions, please contact ALPA Engineering & Air Safety at eas@alpa.org or

• 800.424.2470.

©2019 The International Federation of Air Line Pilots’ Associations. This publication is provided for information purposes only, in all cases pilots should follow their company’s guidance and procedures. In the interest of flight safety, reproduction of this publication in whole or in part is encouraged. It may not be offered for sale or used commercially. All reprints must credit IFALPA.