Communications, Navigation, and Surveillance (CNS) equipment (sometimes referred to collectively as navigational aids) is the infrastructure located on and around airports, and is vital for safe air traffic management. They are used collectively across the aviation industry to share information, facilitate precise aircraft positioning, and monitor airspace activities, all of which play an important part in ensuring that complex airspace is managed safely and efficiently.
In this series, we will delve deeper into each of the three functions, outline their purposes, and explore how they can be affected by new developments.
Communications, Navigation, Surveillance
Before we get started, this article provides some useful background information and terms to aid in future understanding of the series. Naturally the first place to start is the definition of each function of CNS. Definitions and systems examples for each function are provided in the table below.
CNS definitions and examples.
The above examples show that there are many different CNS equipment types, though a single airport is more likely to have a selection of systems rather than all. Th equipment present will depend on the activities, location, and complexity of the airport, with unlicensed airfields often only having Ground to air radio and international airports having almost all of them.
It is common for the most complex international airports to have over 20 ‘facilities’ (individual radio equipment locations) located across the airport, and beyond. In fact, some systems are made up of multiple facilities, such as an Instrument Landing System, which can even be on opposite sides of the airport to one another!
Building Restricted Areas
Another important concept in this series, particularly when understanding how to assess the impact of new development, is the concept of Building Restricted Areas (BRAs). BRAs are 3D zones defined around CNS facilities where buildings have the potential to cause unacceptable interference to the facility. They are defined differently depending on the country in which the airport is located; however, the primary source for defining these areas is within International Civil Aviation Organization (ICAO) guidance – ‘ICAO EUR DOC 015 – European Guidance Material on Managing Building Restricted Areas’.
The typical formation of a BRA includes a zone immediately surrounding the facility where new obstacles are prohibited. The rest of the zones are typically taller or sloped such that new obstacles can be taller the further they are from the facility.
BRAs also look different depending on whether the facility is omni-directional or directional – the generic BRA shapes for omni-directional and directional facilities are shown in Figure 1 and Figure 2, respectively.
Figure 1: Omni-directional facility BRA shape.
Figure 2: Directional facility BRA shape.
Where a new obstacle infringes the BRA, further assessment is required to determine whether there will be unacceptable interference to the facility. This can be through a review of the level of infringement in the context of the facility purpose and whether there is already existing infringement.
Sometimes further modelling is required to fully understand the impact upon the facility, which is typically undertaken by the equipment supplier. Construction of the BRA is, however, almost always the most appropriate first step to determine whether CNS equipment can be affected.
Next in the Series
Stay tuned for the articles in this ‘CNS Equipment Deep Dive’ series over the next few months. The next in the series will cover each CNS function in turn where we will take a closer look into the system examples provided in this article.
Pager Power
Pager Power has experienced constructing Building Restricted Areas around CNS equipment at airports around the world to determine whether they could be impacted by new obstacles.
If you are working on a project where concerns have been raised in relation to CNS equipment, please reach out on +44 (0) 1787 319001 or email michael@pagerpower.com.
Thumbnail image accreditation: Pascal Meier (April 2019) from Unsplash.com. Last accessed on 17th February 2025. Available at: https://www.pagerpower.com/news/introducing-cns-equipment-deep-dive/
