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
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,
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
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
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,
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