Service outage at Swanwick 12 Dec

A technical fault with the flight data system used by air traffic controllers at Swanwick on 12 Dec led to a service interruption.

At 1444 UTC on Friday 12 Dec 2014 the main and standby System Flight Servers (SFS) for London Area Control (LAC) failed. These servers store and distribute flight data to the controller working positions in Area Control. Without SFS updating the workstations, the data on flights approaching the sectors and departing from airfields in the UK starts to become out of date. In order to maintain safety until such time as the failure could be understood and the system returned to operation and confirmed to be stable, NATS applied pre-defined fall-back procedures and traffic management plans. As a result, safety was not compromised at any time. Contrary to media reports, at no time was UK airspace closed, but rather capacity and flow rates were reduced whilst the system was recovered to normal operating conditions.

A number of actions were taken as soon as the root cause was established to prevent re-occurrence including a physical limitation on the number of workstations that could be opened and operational procedures and monitoring of the system. A permanent software fix was introduced on the night of 7/8 January 2015.

There have been no instances of a dual SFS failure in 13 years of operation and the failure is unrelated to that of a previous service delivery impact on December 7th 2013.

NATS has carried out a preliminary internal investigation of the facts surrounding the failure of the System Flight Server on 12th December 2014, including what happened and the cause and impact together with immediate recommendations. This will be followed up with an independent enquiry led by Admiral Sir Robert Walmsley KCB. The terms of reference of the enquiry have been reviewed by BATA and AOA. Sir Robert will produce an interim report at the end of January 2015 with the full report being released on the 14th May 2015.

Overall the enquiry will consider:

• The causes of the failure
• The handling of the event within NATS and more widely within the UK and European network
• NATS past and future investments in resilience
• What level of resilience is reasonable to expect
• CAA oversight of NATS regulatory operations