Part of the 2006 “Surveillance Application Policy” work programme for the Technical and Operations Committee (TOC) included a review of IFATCA provisional Policy on ADS. This paper details the changes since the policy was last reviewed in Santiago-1999 and reports on the changes to ICAO documentation. This includes the introduction of the “Manual Air Traffic Services Datalink Applications Doc 9694” and the changes to PANS ATM Doc 4444 and Annex 11. Part of the review is to consider that ADS policy may need to be retained or modified to include ADS-B and indeed any other form of ADS that may be used in the future.

IFATCA Policy is:

Before an ADS service is introduced into operational service, the necessary system components to provide a control service and to support the control task shall be in place. Only pertinent and useful flight data should be supplied to the control team, which supports and enhances the building of human mental models and controller situation awareness.

The separation standards to be applied between ADS positions and all other surveillance targets must be subjected to an ICAO approved collision risk analysis.

ATC will require the provision of assistance tools for managing airspace where multiple separation standards apply.

The ADS system shall provide a warning to pilot and controller whenever navigation accuracy or integrity is degraded below that required to operate in the airspace, and that this will affect separation standards. Procedures must be in place to restore any loss of separation in a timely manner.

Displays of ADS information that are presented to the controller should be designed so that they meet the need of the control task and enhance the usability of the system.

ADS system design must seek to optimise the interface at the controller workstation. Control of traffic using position data derived from ADS and radar surveillance can only be used where the control system supports both types of surveillance.

Whenever a controller interface derives data from a combination of surveillance systems, the source and derivation of position data in use must be clearly and continuously evident to the controller.

Global standards and procedures must address requirements of what independent verification of position data is required before dependent position data is used for separation.

To ensure integrity of system surveillance data (not just ATC surveillance) it is essential that the automatic transmission of erroneous dependent position data can be disabled or marked as inaccurate during all stages of flight.


Definition of Automatic Dependent Surveillance (ADS):

Automatic Dependent Surveillance (ADS) is when an electromechanical device, after activation, requires no human involvement to supply dependent surveillance data.

See: WP 95 – Istanbul 2007

See also: WP 102 – Hong Kong 2004, WP 87 – Jerusalem 1995, WP 100 – Jerusalem 1995, WP 101 – Jerusalem 1995, WP 102 – Jerusalem 1995, WP 103 – Jerusalem 1995, WP 104 – Jerusalem 1995, WP 105 – Jerusalem 1995, WP 106 – Jerusalem 1995, amended by WP 94 – Santiago 1999, WP 87 (WAAS) – Tunis 1996, WP91 (ADS-B) – Tunis 1996.


Last Update: September 23, 2020  

November 3, 2019   361   Jean-Francois Lepage    AAS    

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