• 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.