ENR 7.5 Operational Policy ADS-C Distance-Based Separation

  1. Introduction
    1. Distance-based longitudinal separation minima using Automatic Dependent Surveillance-Contract (ADS-C) is implemented in Oakland Oceanic airspace as specified in TBL ENR 7.5-1.

      TBL ENR 7.5-1
      Minima

      Minima

      Standard

      RNP

      RCP

      RSP

      Maximum ADS-C Periodic Reporting
      Interval

      50 NM

      10

      240

      180

      27 minutes

      50 NM

      4

      240

      180

      32 minutes

      30 NM

      4

      240

      180

      14 minutes

    2. Distance-based longitudinal separation minima using ADS-C is implemented in the Anchorage Oceanic and New York Oceanic airspace as specified in TBL ENR 7.5-2.

      TBL ENR 7.5-2
      Minima

      Minima

      Standard

      RNP

      RCP

      RSP

      Maximum ADS-C Periodic Reporting
      Interval

      50 NM

      10

      240

      180

      27 minutes

      50 NM

      4

      240

      180

      32 minutes

      30 NM

      4

      240

      180

      10 minutes

    3. Aircraft Future Air Navigation System (FANS) 1/A communications, navigation and surveillance (CNS) capabilities, interfaced with Advanced Technology and Oceanic Procedures (ATOP), are required for ADS-C distance based separation to be applied.

      NOTE-

      1. ADS-C distance based separation standards may not be applied to aircraft utilizing High Frequency Data Link (HFDL).
      2. ADS-C distance based separation is not currently authorized in the Anchorage Arctic FIR.
  2. Application
    1. Oakland, New York and Anchorage ARTCCs will apply the following policies to the use of ADS-C distance based separation:
      1. The separation will be applied to pairs of suitably equipped pairs of aircraft;
      2. Published ATS routes and other tracks (e.g. PACOTS) will continue to be laterally separated by a minimum of 50 NM;
      3. Minimum ADS-C based lateral and longitudinal separation between 30 NM eligible aircraft and 50 NM eligible aircraft is 50 NM; and
      4. Lateral and longitudinal separation standards applied between RNP 10 and non-RNP 10 aircraft remains unchanged.
  3. Aircraft and Operator Eligibility for Performance-Based Separation
    1. The aircraft and operator must be authorized by the State of the Operator or the State of Registry, as appropriate, for 50 NM: at a minimum, RNP 4 or RNAV 10, RCP 240, and RSP 180; and for 30 NM: at a minimum, RNP 4, RCP 240, and RSP 180 operations;
    2. The aircraft must be equipped with a minimum of two approved long range navigation systems that will enable the aircraft to maintain RNP 4 for the duration of flight in the applicable airspace;
    3. The aircraft must be equipped with a FANS1/A package (or equivalent) that includes satellite Controller Pilot Data Link Communication (CPDLC) and ADS-C that meet the standards of RTCA Document 258, Interoperability Requirements for ATS Applications Using ARINC 622 Data Communications;
    4. Satellite CPDLC communications and ADS-C surveillance must be conducted in accordance with the ICAO Global Operational Data Link Document (GOLD), as amended, and maintained for the duration of the flight in the applicable Pacific FIRs; and
    5. Pilots and, if applicable, dispatchers must be trained on policies and procedures applicable to ADS-C distance based separation, including the use of Satellite CPDLC and ADS-C in Pacific oceanic airspace.
    6. Operators should use the ICAO GOLD to develop policy and procedures for CPDLC and ADS-C operations.
      1. Operators must use one of the following documents to develop policy and procedures for RNP 4 operations:
        1. FAA Advisory Circular (AC) 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace;
        2. Australian Civil Aviation Safety Authority (CASA) Advisory Circular 91U3(0); or
        3. ICAO Performance-Based Navigation (PBN) Manual ( ICAO Document 9613), Volume II, Part C, Chapter 1.
        4. ICAO Performance-Based Communication and Surveillance (PBCS) Manual ( ICAO Doc 9869).
  4. Flight Planning Requirements See ENR 7.1, Paragraph 2, Flight Plan Filing Requirements.

    NOTE-

    Other than the flight plan requirements discussed in ENR 7.1, Paragraph 2, Flight Plan Filing Requirements, application of distance based separation does not affect operator planning processes or procedures for filing flight plans. Operators that have filed and flown User Preferred Routes (UPRs) may continue to do so.

  5. In-Flight Contingency Actions/ Procedures and Emphasis on Situational Awareness
    1. Pilots should be aware that ADS-C distance based separation can be applied to their aircraft. They should use all available tools to maintain an awareness of other aircraft in their proximity in case an inflight contingency occurs (e.g., aircraft or ATC system malfunction).
    2. Pilots must advise ATC of a loss of CPDLC and/or ADS-C capability or an inability to continue to meet RNP 4. ATC will transition the aircraft to another form of separation as expeditiously as possible.
    3. If there is a known malfunction of the CPDLC or ADS-C system, ATC will contact aircraft and transition the aircraft to another form of separation as expeditiously as possible.
    4. Pilots should use the guidance in ENR 7.3, Special Procedures for In-Flight Contingencies in Oceanic Airspace. This reflects current ICAO guidance calling for a 15 NM track offset when unable to obtain ATC clearance prior to executing maneuvers for contingencies such as rapid descent, turn back, or diversion. This is of particular importance for aircraft to which 30 NM separation can be applied.
    5. Pilots are required to maneuver (deviate) around convective weather on a regular basis in the course of Pacific operations. The enhanced CNS requirements and capabilities aid pilots and controllers in situations where aircraft are required to maneuver around convective weather. For weather avoidance maneuvers in areas where ADS-C distance based separation is applied, operators should emphasize the following items in pilot training programs:
      1. Pilots should not assume the ATOP system will automatically quickly detect significant changes to the aircraft flight path. Unlike radar, the ATOP system does not receive aircraft position updates in real-time. Aircraft position is updated to the ATOP system at intervals of up to 27 minutes. Controllers may change the update intervals as the situation warrants.
      2. It is imperative that pilots keep ATC advised via CPDLC (or HF voice, if necessary) of their intentions (including significant airspeed changes) during the initial weather avoidance maneuver and any subsequent maneuvers to avoid convective weather.
      3. Pilots must be aware that other aircraft could be approximately 30 NM ahead or behind on the same track, and inform ATC expeditiously of changes to flight path or airspeed that could erode longitudinal separation.
      4. Pilots must be familiar with ENR 7.3, Special Procedures for In-Flight Contingencies in Oceanic Airspace.

        NOTE-

        In particular, pilots should be aware of the provision to climb or descend 300 feet (depending on the direction of flight and direction of deviation from track) to mitigate the chance of conflict with other aircraft when forced to deviate without a clearance.

      5. It is recommended that ACAS be operational for aircraft to which 30 NM separation can be applied. ACAS provides a valuable tool to alert the pilot to the presence and proximity of nearby aircraft in weather deviation situations.
      6. In accordance with ICAO Document 4444, pilots are reminded that, regardless of the magnitude of a deviation from assigned route, whenever possible, clearance should be requested in advance from ATC. Prior coordination with ATC will help prevent the aircraft generating unnecessary alerts to ATC for lateral deviation events.

        NOTE-

        This does not apply to SLOP.

      7. Operators should consider adopting guidance for pilots to use heading mode to maneuver around areas of convective weather. Use of heading mode will prevent transmission of unnecessary lateral deviation event alerts that some flight management systems (FMS) automatically transmit to ATC when the FMS automatic lateral offset feature is used for weather avoidance. It should be emphasized that, when using heading mode, pilots should monitor cross track and heading and return to track when weather avoidance maneuvering is complete.
      8. Aircraft navigation errors and system malfunctions will be monitored and documented. Operators should cooperate in follow up investigation of these events.