Operational safety study on impact on ATC from a loss of aircraft transponder function

This paper aims at providing input material into the “EUROCONTROL NM top 5 safety priorities” for the topic of “operation without a transponder or with a dysfunctional one”.

The paper proposes an approach for the safety assessment of the impact on ATC from the loss of the aircraft transponder function, i.e. an Aircraft Surveillance Function (ASF) continuity failure. It addresses the case of an aircraft subject to Area Control Service and Approach Control Service. The paper proposes a set of generic operational elements for both the Aircraft and the Ground Domains, as well as recommendations for future work by appropriate stakeholder bodies.

Regarding the generic operational environments, the presence of both Independent Non-Cooperative Surveillance (INCS) and Cooperative Surveillance (CS) has been assumed in high density TMA whereas only CS has been assumed in the other airspace types (namely, low to high density En-route and low/medium TMA). This paper addresses ASF continuity failure in Area Control Service and Approach Control Service, but excludes Aerodrome Control Service.

Moreover, in this paper, the notion of a “Continuity” failure is applied only to an aircraft that is receiving an ATC Surveillance Service at the time the failure occurs. Therefore, ASF continuity failure prior to entering a sector or infringement cases are out of scope of this paper.

This paper covers both cases where the failure is either “detected” or “not detected” by the ATCo, and this for various situations of system “notification” (or not) on the ATCo surveillance interface (display). For this purpose, a display logic for system notifications to support ATCo detection has been assumed (including coasting mechanism and symbology).

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Operational safety study on impact on ATC from a loss of aircraft transponder function