Display and use of surveillance data from unapproved systems

The CAA is aware that various electronic means are available to access live aircraft surveillance data in the public domain, with programmes and ‘Apps’ developed by a number of organisations. Aircraft surveillance data can be displayed on downloaded programmes; on internet web pages; and on various Apps that can be viewed on smart phones, tablets and laptops or other display equipment.

The CAA is mindful that some airfields in the UK that do not currently have access to assured surveillance data may wish to use these programmes and ‘Apps’ (both henceforth to be described as applications) in the provision of an air traffic service without obtaining the necessary approvals and authorisations associated with a conventional surveillance system.

In the case of ATC units the current recognised system for providing tower surveillance capability is an Aerodrome Traffic Monitor (also abbreviated as ATM), which is subject to regulation as described in CAP 670 ‘Air Traffic Services Safety Requirements’. Other airports including those already operating an ATM may be considering using other applications in the tower to supplement situational awareness, or as a back-up to an ATM.

Safety considerations

Currently there are many applications that can display aircraft data including position, time stamp, identification, flight level etc. The data displayed in such applications is supplied from various surveillance sources and include: FLARM receivers, ADS-B receivers (receiving aircraft transmissions from certified or uncertified aircraft equipment), Mode S receivers, and multilateration using multiple sensors. Radio frequencies used by these sources are either allocated for aviation use (subject to Wireless Telegraphy Act Licensing and therefore afforded a degree of protection from interference), or license-exempt. Some applications combine data from multiple sources to produce a single display.

The quality (including integrity, accuracy and latency) of such data may vary depending on the different sources of the data that are fed into the application and cannot therefore be relied upon. There are no means of verifying the quality of such data or filtering out unsuitable data.

Most of the applications are for educational or recreational purposes. They have not been developed for the purpose of providing air traffic services and are unlikely to comply with relevant Safety and Interoperability regulatory requirements.

ANSPs that may be considering the use of surveillance data from these applications, should contact CAA regional office staff to discuss this further. The CAA will be seeking assurances that ANSPs have ensured the quality and integrity of the data is sufficient for the intended purpose. While the surveillance data obtained from these applications may be considered useful as an alternative to conventional and assured surveillance data, care needs to be taken to ensure that data that cannot be assured is not used for safety-related tasks in the delivery of an air traffic service (ATS). Tasks that are not safety-related may include forward planning.

Furthermore the introduction of additional displays such as tablets, laptops or PCs into a live operational environment may itself prove a distraction and therefore human factor safety implications must also be considered.

Regulatory approval

While the CAA understands that in some circumstances, having improved situational awareness using an application that displays aircraft position information may be useful, there are safety implications in the use of such data that must be carefully considered. The introduction of such systems will need to be assessed in accordance with an ANSP’s Safety Management System and evidence of compliance with regulatory requirements for ATS equipment must be demonstrated. In the absence of information from application developers of the capabilities of their applications, it is unlikely that a case for use in a tactical air traffic service environment can be made, other than for tasks assessed as not safety-related.

The CAA reminds ANSPs that the use of any surveillance data to support the provision of an air traffic service with any of the surveillance services described in the MATS Part 1, or for the acquiring of traffic information in an ATC or Aerodrome FISO environment will only be permitted following the submission of safety assurance documentation and with approval by the relevant ATM Regional Office; and that unapproved surveillance systems can only be used for tasks that are not safety-related.