European airspace authorities have moved closer to resolving a shortage of secondary surveillance codes, after the approval of new Single European Sky rules on aircraft identification.

From next year, at least half the flights in core European airspace will be subject to the new coding rules, said air safety organisation Eurocontrol, requiring air navigation services to use downlinked aircraft data for identification, without relying solely on secondary "squawk" codes.

The squawk system is based on limited numerical technology, and only permits 4,096 distinct four-digit codes.

Eurocontrol said this could result in code allocation confusion, given the daily workload of 33,000 flights across the continent.

To ease the problem three code-management processes will be integrated by February 2012, including the use of Mode-S radar surveillance and more efficient centralised squawk allocation.

Use of downlinked data to identify aircraft will mean air navigation services will have to replace the older Mode A/C radars with systems capable of detecting this alternative information - such as Mode-S radar or automatic dependent surveillance.

From January 2020, the new regulations will apply across the whole Single European Sky region.

Source: Flight International