Europe moves to second phase of Mode S implementation

Secondary Surveillance Radar (SSR) Mode S Elementary Surveillance (ELS) implementation in Europe has been expanded to include a much great number of flights, taking the initiative into its second phase.

The use of SSR ELS, initially applied only to flights operating on city pairs within Mode S airspace, will now include flights originating outside but then remaining within Mode S airspace. This increases the number of eligible flights from approximately 1,000 a day to nearer 4,000 flights. The next phases of implementation will encompass flights transiting Mode S airspace, and those originating within but then departing Mode S airspace. Timeframes for implementation of these subsequent phases are under negotiation.

Mode S is essentially a tool whereby an aircraft downlinks an unambiguous four-digit identification code in response to interrogation from the ground. This downlinking of aircraft identification is a feature of modern surveillance techniques, including Mode S (interrogated) and ADS-B (broadcast). 

Flights that are identified by the aircraft’s own automatically downlinked aircraft identification are assigned a Mode S conspicuity transponder code—A1000—to alert controllers, especially those using legacy systems, to the flight’s status.

SSR transponder codes are a finite resource as there are only 4,096 of them. As a result, some areas of Europe are experiencing code conflicts with potential loss of identification, frequent changes of code for a given flight, and a shortage of codes that can, at peak periods, result in aircraft being held on the ground until a suitable code becomes available.

Mode S uses the SSR radio frequency spectrum more efficiently, reducing frequency congestion, increasing radar capacity, easing delays and—by reducing garbling, mutual interference and radio reflections—improving safety.

All aircraft operating IFR/GAT in Europe are required to be compliant with ELS by Jan. 8, 2015 for new aircraft and Dec. 7, 2017 for retrofit. Aircraft with a minimum take-off mass greater than 5,700 kg. and/or with a maximum cruising true air speed greater than 250 knots are required to be compliant with Mode S Enhanced Surveillance—the second level of Mode S that provides the controller with additional information about the aircraft’s short-term intent.

Article Source : ATW Daily News