FINAL REPORT - Stakeholders - Ofcom

3.2.3 Operational Requirements
3.2.3.1 Introduction
The study has reviewed the future operational requirements for primary radar on the
grounds that it is necessary to determine the service requirements as a prerequisite to
consideration of spectrum requirements. This is particularly true given the long term
nature of changes in ATC procedures and also the lead time involved in changes to
spectral allocations. Furthermore, in the case of primary radar, a small change in
operational requirements could result in a relatively large change in spectrum utilisation.
3.2.3.2 Users
The study is principally concerned with the civil ATC use of primary radar for the control of
aircraft. This can include commercial aircraft, military aircraft and general aviation. The
study has not included military defence aspects but the military ATC services are a joint
operation with UK NATS and these joint civil/military requirements are included. Primary
radar provides services to these customers in most of the bands considered. Exceptions
include civil airport surface movement radars, which generally are not involved in
providing services to military aircraft.
NATS Approach/TMA Radar and En Route radar data is provided to additional users such
as local airports. This ensures that maximum use is made of a given radar service.
3.2.3.3 Approach/TMA Surveillance Radar
Primary radar is used at airports and terminal areas to provide independent radar
coverage. Larger airports use primary radar as a non co-operative aid which provides
coverage in the event of SSR failure, non SSR transponder equipped aircraft and
intruders. Smaller airports are often equipped with primary radar only as their main source
of radar information. Primary radar for approach/TMA use is an accepted requirement
throughout Europe and elsewhere. In the US, the FAA has announced a plan to renew
primary radar in terminal areas with timescales extending to 2015.
Generally such radars are characterised by a short range capability and a high data
update rate (the result of a high antenna rotation rate). The high data update rate
provides precision surveillance in the approach phase. These services are normally
dedicated to a specific airport/TMA and are designed to provide good short range
performance to runway thresholds. S band radars tend to be the preferred option for this
application with 34 civil radars currently deployed. There are also 7 short range approach
radars operating in the X band.
Approach radars normally have ranges of less than 80nm with 60nm being a typical
figure. Minimum range is typically 0.25 nm – this can be an important parameter because
it dictates the maximum pulse width that can be used.
Good low cover is of prime importance in the specification of an approach/TMA radar with
the following requirement being typical:
• Ground level from 0 to 2nm;
• 300ft from 2nm to 15nm;
• 2000 ft from 15nm to 40nm;
• 5000ft from 40nm to 50nm.
High level coverage is normally set at a ceiling of 30000 ft for all ranges. Turning speeds
of 15 RPM are required if operating in a three nautical mile separation standard
environment.
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