One of the key aims of the Airspace Modernisation Strategy is to make airspace more efficient – saving time and fuel and
reducing emissions.Key to achieving this is improving the accuracy of where aircraft fly and a move to use satellite
based navigation rather than ground-based navigation aids.
The level of accuracy, safety and integrity that these satellite navigation systems must reach is set out in the
international requirements for Performance-based Navigation (PBN).
PBN is being adopted world wide and countries are expected to develop their airspace to apply it. Therefore as
airspace and the routes aircraft fly are re designed they will move to PBN.
This will affect both the high level airways and the lower level arrival and departure routes into and out of
airports. In many cases as the change to PBN happens the routes will remain very similar to those flown under the old
ground-based navigation system but in some cases when the route moves to PBN there may be some structural changes to
the airspace.
Route spacing
An essential component supporting PBN is the definition of route spacing between proximate departure and/or arrival
routes and approach transitions.
The CAA and NATS have worked collaboratively to develop a Loss of Separation Risk Model (LSRM) which assesses the
safe spacing between PBN routes in a tactically controlled airspace environment based on the predicted number of losses
of separation.
Based on this work, CAP 1385 'Enhanced route spacing guidance' provides the
background, assumptions and constraints in applying route spacing for nine standard airspace design scenarios. These
scenarios are intended to be applied within a terminal airspace design as building blocks. As further data is collected
and analyses, additional scenarios will be developed and the guidance document updated.
Noise mitigation considerations
A Noise Task Force was established to consider the issues associated with the negative impacts of PBN. They produced
a guidance document that explores the impacts and possibilities of using PBN
routes to mitigate noise impacts. It covers a range of design options, and provides guidance on the potential benefits
and impacts, technical requirements and constraints, and potential solutions.
The solutions presented are drawn from existing designs, emerging concepts generated by the aviation industry, and
suggestions from environmental groups; so we intend to update this guidance regularly as new knowledge and experience
of PBN deployment is gained.