Stuck in the airport support thread

[jpaul]

NATS report into air traffic control incident details root cause and solution implemented - NATS

NATS provides safe and efficient air traffic services and innovative solutions to UK and international airports, airlines and governments.

www.nats.aero

The report, submitted earlier this week to the Civil Aviation Authority, identified an issue with a flight plan processing sub-system called Flight Plan Reception Suite Automated – Replacement (FPRSA-R).

A small but important part of NATS’ overall air traffic control technical infrastructure, it was found to have encountered an extremely rare set of circumstances presented by a flight plan that included two identically named, but separate waypoint markers outside of UK airspace.

This led to a ‘critical exception’ whereby both the primary system and its backup entered a fail-safe mode. The report details how, in these circumstances, the system could not reject the flight plan without a clear understanding of what possible impact it may have had. Nor could it be allowed through and risk presenting air traffic controllers with incorrect safety critical information. On the day, the time taken to recover was driven by the need to identify the problem and the specific data, isolate and remove it in a controlled way, and then test it to ensure it could be returned safely into operation.

e:
The ADEXP waypoints plan included two waypoints along its route that were geographicallydistinct but which have the same designator.Although there has been work by ICAO and other bodies to eradicate non-unique waypoint namesthere are duplicates around the world. In order to avoid confusion latest standards state thatsuch identical designators should be geographically widely spaced. In this specific event, both ofthe waypoints were located outside of the UK, one towards the beginning of the route and onetowards the end; approximately 4000 nautical miles apart.
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Therefore, where there is no UK exit point explicitly included, the software logic utilises thewaypoints as detailed in the ADEXP file to search for the next nearest point beyond the UK exitpoint. This was also not present. The software therefore moved on to the next waypoint. Thissearch was successful as a duplicate identifier appeared in the flight plan.Having found an entry and exit point, with the latter being the duplicate and thereforegeographically incorrect, the software could not extract a valid UK portion of flight plan betweenthese two points. This is the root cause of the incident. We can therefore rule out any cyberrelated contribution to this incident.