ENR 7.12 Reduced Separation Climb/Descent Procedures

  1. Automatic Dependent Surveillance- Broadcast (ADS-B) In-Trail Procedure (ITP)
    1. The ITP is designed for use in non-surveillance oceanic airspace to enable appropriately equipped ADS-B In aircraft to perform flight level (FL) changes previously unavailable with procedural separation minima applied. The improved traffic information available to ADS-B In-equipped aircraft allows ITP maneuvers to occur safely with reduced separation minima applied. ITP will enable flight crews to execute FL changes to improve ride comfort, avoid weather, or obtain more favorable winds to improve fuel economy and arrival times. The ITP is only available within the Anchorage, Oakland, and New York Oceanic Flight Information Regions (FIR).
    2. FAA air traffic procedures for the ADS-B ITP mirror those contained within ICAO Document 4444 (Doc. 4444), Procedures for Air Navigation Service- Air Traffic Management (PANS-ATM), Section 5.4.2.7, Longitudinal Separation Minima Based on Distance Using ADS-B In-Trail Procedure (ITP), with one difference. Section 5.4.2.7.3.2 of Doc. 4444 states, “A controller may clear an aircraft for an ITP climb or descent provided the following conditions are satisfied: d) both the ITP aircraft and reference aircraft are either on; 2) parallel or same tracks with no turns permitted during the manoeuvre.” The FAA's Advanced Technology and Oceanic Procedures (ATOP) automation platform is designed to ensure that separation will not decrease below required minima for same track aircraft should either the reference or maneuvering aircraft turn during the ITP. FAA Order JO 7110.65, Air Traffic Control, states that an aircraft may be cleared for an ITP climb or descent if both the ITP aircraft and reference aircraft are on the “same tracks with no turns permitted that reduce required separation during the ITP.”
    3. Equipment specifications and guidance for pilot procedures is available in FAA Advisory Circular (AC) 90-114, Automatic Dependent Surveillance-Broadcast (ADS-B) Operations, Appendix 2, ADS-B In-Trail Procedure.
    4. Additional information is also available in ICAO Circular 325, In-Trail Procedure (ITP) Using Automatic Dependent Surveillance-Broadcast (ADS-B).
  2. Automatic Dependent Surveillance- Contract (ADS-C) Climb Descend Procedure (CDP)
    1. The ADS-C CDP is designed to improve service to properly equipped aircraft by allowing an oceanic air traffic controller to have an option for granting an altitude change request when other standard separations (such as ADS-C distance-based 30 NM longitudinal separation minima) do not allow for a climb or descent through the altitude of a blocking aircraft. It is an air traffic control tool to be applied between maneuvering and blocking aircraft pairs. The CDP is only available within the Anchorage, Oakland, and New York Oceanic FIRs.
    2. FAA air traffic procedures, published in FAA Order JO 7110.65, Chapter 8, mirror those in ICAO Document 4444 (Doc 4444), Procedures for Air Navigation Service-Air Traffic Management (PANS-ATM), Section 5.4.2.8, Longitudinal Separation Minima Based on Distance Using ADS-C Climb and Descend Procedure (CDP), and in ICAO Circular 342, Automatic Dependent Surveillance – Contract (ADS-C) Climb and Descend Procedure (CDP). The FAA's ATOP automation platform is designed to alert the controller before separation decreases below the required minima. Aircraft pair distance verification is performed by the ground automation system, using near simultaneous ADS-C demand reports.
    3. The implementation of the ADS-C CDP is intended to facilitate increased access to optimum flight levels for aircraft operating in airspace where no ATS surveillance service is available. It is similar to the ADS-B ITP [see ICAO Circular 325, In-Trail Procedure (ITP) Using Automatic Dependent SurveillanceBroadcast (ADS-B)] in that it is a climb or descend through procedure. Unlike the ITP, however, the pilots involved in an ADS-C CDP may not be aware of which separation minima a controller is utilizing.