Select Committee on Environment, Transport and Regional Affairs Appendices to the Minutes of Evidence

Supplementary memorandum by the Institution of Professionals, Managers and Specialists (NAS 07A)

What proportion of NATS' capacity to deal with air traffic is lost when staff are forced to revert to manual procedures?

  The extent of lost capacity is variable, depending on the extent and timing of the computer failure. If automated "flight progress strip" production and aircraft code/callsign paring is lost, the impact on operations is severe, with a potential reduction in safety. Such large-scale failures are, thankfully, very rare.

  The first reaction is to prevent any further aircraft entering the system. This is done by stopping aircraft departures from domestic airfields. Flow restrictions are immediately applied, which may require aircraft already airborne in neighbouring sectors or countries to divert away from their intended airfield.

  Traffic is "run-down" to manageable levels. The loss of capacity under the worst system failure, (such as occurred on 17 June), would be a guess on our part of as much as 75 per cent. That again would be variable depending upon sector or airport. (Actual figures for demand before the failure, reduced capacity and sector delays are with the Central Flow Management Unit, Brussels). Service provision in terms of route flexibility and level allocation would also decline.

Should NATS have back up computer systems to deal with failures, rather than reverting to manual procedures?

  NATS could carry out a fundamental review of whether the National Airspace System computer (NAS) is becoming too critical a single failure point, and perhaps whether the functions it performs ie radar and data processing should be separated, so that, in the event of failure of one system, the effect is minimised. A NAS replacement strategy could also consider whether separate autonomous, but interconnected, flight data processing systems should be located at the New En-route Centre, Swanwick, and the current or New Scottish Centre, Prestwick, and whether these could provide a contingency service for each other, and to other users apart from the two Centres.

  Consideration also needs to be given to ensuring the appropriate quality and quantity of work required to fully develop and test software, particularly for the current NAS. There should be an avoidance of "over duplication" however, and potentially just doubling workload.

What was the impact of those failures on delays and on staff?

  Exact figures should be available from NATS or the Central Flow Management Unit, (CFMU), Brussels. Delays will vary across airports, sectors and other air traffic units.

  There is an impact on staff. "Clearance Delivery Planner" controllers have the difficulty of dealing with frustrated pilots, and there is safety critical pressure on radar controllers, who need timely and accurate information. Morale is affected because no staff member wishes to see additional delay to any aircraft.

  However, the safety and service ethos and culture amongst NATS staff is a major asset in dealing with such contingencies.

What benefits will the New Scottish Centre bring, in terms of increased capacity in the airspace it covers, or in terms of reduced delays?

  It is a question of "when" rather than "if" UK airspace capacity becomes limited to the point of major delays to every user, civil and military.

  To handle projected air traffic in the latter part of this decade, NATS will have to bring in new technology and ideas for automated traffic handling. The present generation of ATC systems cannot support this level of automation, and need long term development.

  The UK is one of the few countries involved in this type of future research and planning. It is not being done to increase NATS profitability, but to allow equal access to UK airspace to all users, and not access limited by capacity and, consequently, ability to pay.

  The benefits can be summarised thus—

    —  Future Capacity: NERC is too small to accommodate all UK ATC en-route functions, an additional modern expansion capability is required. NERC will also require development after "O" (operational) date to cater for the continuing large traffic growth. The NSC programme will provide a cost-effective development route without disrupting "live" operations at NERC. The programme would be an ideal proving ground for the new technology and systems, allowing quicker introduction, and, therefore, the capacity increases that will be required. In addition, the NSC should ensure the UK maintains an European/world lead in ATC provision.

    —  In addition, NSC would also ensure a retention of regional expertise, and a boost to the local economy.

    —  Contingency for the New En-route Centre, (NERC): Aviation, most notably in and out of the London airports, provides vital links from the UK/Europe with the rest of the world, and is essential to the wellbeing of the UK economy. Contingency to cover any failure of NERC must be a priority, and could only be adequately provided by a New Scottish Centre.

What has caused the marked improvement in the reliability of the current system at the Oceanic Centre?

  Oceanic Centre: The Oceanic Flight Data Processing System computer (FDPS1) is a long-term programme by NATS. When installed in the mid 1980s, it was the most advanced automated ATC system in the world. It has continued to be developed and enhanced "in-house" by NATS, and still has features and function, which other oceanic air traffic service providers do not have in the systems they are currently installing. There are very few delays in the most densely packed portion of the world oceanic airspace.

  Through experience, improved procedures and NATS own developmental team, many of the faults that previously caused unreliability have been identified, removed, rectified or accommodated.

  There is no room for complacency, however. Further improvements are being planned and implemented, (eg new processors), to increase capacity, improve service provision, and to exploit new technologies.

Will further improvements be made in future?

  Improvement will be required to cope with future traffic growth. It is certainly hoped that system stability and capacity will be further improved with planned developments.

What caused the other software failures at LATCC in June and August this year?

  The 17 June failure was the result of a new software build interacting with a latent software bug.

  We understand that the August failure was caused by an erroneous user input at the Scottish Area Control Centre, (SCACC).

  The National Airspace System Computer hardware has proved reliable, new processors are about to be introduced. The software, though relatively old, is updated by NATS once or twice a year, following testing.


24 November 2000

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