Why is this Obstruction Beacon trial being undertaken?

The CAA’s Airspace Modernisation Strategy (AMS) outlines a range of new digital flight information services, including FIS-B and TIS-B (Flight Information Service – Broadcast and Traffic Information Service – Broadcast). ADS-B Obstruction Beacons are another element of these digital flight information services. Several GA representative organisations have requested that CAA investigate additional methods of promulgating their particular activity.   The CAA and DfT have welcomed the trial of ADS-B Obstruction Beacons as a potential method of enhancing safety around these operations.

Why are ADS-B Obstruction Beacons being considered in support of particular operations?

Notifications of winch cables continue to be missed or ignored by pilots despite existing methods of promulgation. The British Gliding Association (BGA) have requested that the CAA attempt to seek addition means of warning of the presence of winch cables.

Large model flying sites are not routinely depicted on charts but may be listed in the AIP. Notification of planned activity at these sites is normally subject to a NOTAM but again is occasionally missed or ignored by other airspace users. In the case of large models operating in close proximity to a single location, it is not necessary or desirable to make each individual model electronically conspicuous and therefore a generic electronic warning of the presence of these air systems (obstruction) at a point location is what is being evaluated by the use of an ADS-B Obstruction Beacon in these circumstances.

Some hang glider/paraglider launch sites are notified and depicted on the charts but the actual use of the location may not be subject to individual NOTAM. The deployment of a beacon in this case is to act as a notification that launching is taking place at that location and time. Again, it is not intended to replace or supplement electronic conspicuity on individual air systems. 

What is the aim of deploying ADS-B Obstruction Beacons and the aim of the trial?

The aim of deploying an ADS-B Obstruction Beacon would be to supplement and support the existing notification and promulgation of a range of activities at fixed locations with an additional electronic marking.

The aim of the trial is to test and evaluate the practicalities and performance of deploying and operating a battery powered ADS-B Obstruction Beacon in support of a number of different use cases.

Is this ADS-B Obstruction Beacon trial being conducted by the CAA?

No. The trial is being conducted by uAvionix to evaluate one aspect of digital Flight Information Service provision as part of the AMS Concept of Operations. This is not a CAA trial but is supported by and forms part of the evaluation and deployment of the Airspace Modernisation Strategy. 

Each trial location is NOTAM’d. Each NOTAM references an AIS Briefing Sheet giving a basic overview of the trial and contains links to detailed information including the purpose and objectives of the trial hosted by uAvionix. The site also hosts an opportunity to provide feedback/user experience which will be gratefully received.

How can I access the AIS Briefing Sheet for the Trial?

The AIS Briefing Sheet for the Trial is available here:

Who is funding the trial?

The trial is being funded via the CAA’s Airspace Modernisation Strategy Support Fund. 

The Airspace Modernisation Strategy Support Fund is funded through the UK State overflight charging mechanism (en-route unit rate) for commercial air transport. It was established as part of the UK RP3 performance plan, and we expect provision to continue in to a new UK performance plan for the period 2023 to 2027, known as “NR23”.4 The fund will be collected through the CAA element of the en-route unit rate and administered by the CAA through suitable governance arrangements.

Who do you want feedback from?

We want feedback form any and all relevant stakeholders, no matter who they are. Feedback on the trial may be provided here: https://uavionix.com/projects/ukobsbeaconfeedback/

Besides light aircraft and microlights, who are the ADS-B Obstruction Beacons aimed at?
The tactical real-time electronic notification of these ‘obstructions’ may be useful to a whole variety of operators and systems including low level military operators, emergency services helicopters, and other air systems wholly or partially reliant on detect and avoid to integrate with other airspace users.

Why are the beacons operating on 978MHz UAT?

To avoid saturation of 1090 MHz these new (to the UK) digital services, together with certain new categories of air system, are likely to be assigned an alternative frequency.

For the purposes of this trial, and pending any other formal announcement, this frequency/mode of operation is 978/UAT. The eventual range of services and air systems utilising the alternate frequency/mode is going to be far broader than just electronic obstruction beacons.

How were the Trial sites selected?

The Trial sites were nominated by the participating General Aviation organisations.

Why are the Trial sites NOTAM’d?
Each trial site location has been NOTAM’d purely for the purposes of the trial, i.e. to provide notification of a radio transmission within the aviation spectrum that may, when received, generate an alert and/or depiction on existing aviation systems. It is for this reason that these NOTAMs have been issued.

If widely adopted, would use of ADS-B Obstruction Beacons be NOTAM’d?

No. Should the concept of ADS-B Obstruction Beacons be widely adopted then the location of each beacon would be notified in the AIP. The operation of that beacon would not be supported by issuing of a NOTAM.

The issuing or not of a NOTAM to support promulgation of an activity would be very much as it is today. Daily activity at a winch launching site is not currently, generally subject to a NOTAM whereas occasional activation of a large model flying site is. The operation of a beacon in support of that activity is an additional electronic safety net to support existing promulgation.

Are these beacons intended to replace electronic conspicuity of aircraft operating at the trial sites?
No, they are not. These beacons are Obstruction Beacons. They are not intended to replace electronic conspicuity of individual aircraft where this is desirable or required. 

In the case of glider winch launching sites, the ADS-B Obstruction Beacon is providing an additional means of situational awareness that the site is the location of a 6mm steel cable that is being raised potentially over 2000ft into the air. The beacon doesn’t necessarily indicate the presence of one or multiple gliders in the immediate vicinity of the beacon or replace individual electronic conspicuity of those gliders.

Who is responsible for operating the ADS-B Obstruction Beacons?

The Trial site operators/clubs are responsible for the installation and operation of the ADS-B Obstruction Beacons.

Are all Electronic Conspicuity receivers capable of picking up the ADS-B Obstruction Beacon broadcasts?

Only those receivers that receive 978MHz UAT will be able to pick up the ADS-B Obstruction Beacon broadcasts. Receivers need to be within range and have line-of-sight of a beacon.

Which Electronic Conspicuity devices support reception of 978MHz UAT?

This is a non-exhaustive list:

  • uAvionix SkyEcho, SkyEcho2, SkySensor, pingUSB
  • Foreflight Scout, Sentry Mini, Sentry, Sentry Plus
  • Avidyne SkyTrax100B
  • Dynon DRX, SV-ADSB-470, SV-ADSB-472
  • GRT Discovery
  • iLevil 3 & iLevil Astrolink
  • Appareo Stratus 1, 2, 2S, 3
  • Garmin GDL 39, 39R, 50, 50R, 52, GNX 375, GTX 345
  • Dual XGPS170D
  • Stratux Dual Band ADS-B receiver

Do all Electronic Flight Book (EFB) navigation apps present the ADS-B Obstruction Beacons?

Currently, most but not all EFB applications will present the Obstruction Beacons, IF they are correctly connected to, and being fed traffic data by a 978MHz UAT ADS-B receiver that is in receipt of Obstruction Beacon broadcasts. Some EFBs may not yet use an appropriate symbol representing an Obstacle. Prior to this Trial, with no ADS-B Obstruction Beacons in use in the UK, some EFB providers had not implemented specific support for ADS-B Obstacles. Due to the trial, EFB providers that do not yet fully support ADS-B Obstacles are looking to add the required updates to their EFB applications.

Which EFBs support ADS-B Obstacle Beacons?

It has been confirmed that the current version of SkyDemon presents ADS-B Obstruction Beacons (Point Obstacles) as an obstacle. Foreflight have advised that they present ADS-B Obstruction Beacons but do so using a default symbol (not as an obstacle), however they have it on their development list. Prompted by the trial, EasyVFR, SafeSky and RunwayHD have all advised they are adding full support for ADS-B Obstruction Beacons (Point Obstacles). As can be seen, this is a developing area.

Is this Trial about the ADS-B receivers and EFBs?

Although we are interested in the reception and display of the ADS-B Obstruction Beacon broadcasts – the entire system entails transmission, reception and presentation of the Obstacle Beacon data – the reception and presentation elements of the system are entirely outside the control on the project (except for the site operators who have been provided with the capability to verify transmissions). With 978MHz UAT currently being so new and little used in the UK, we are aware that understanding of UAT is limited, ability to receive the broadcasts is limited and those that can potentially receive the broadcasts may not be setup to do so. Therefore, the main focus of the Trial is on the transmission side, on the setup and use of the beacons.

Where can I find further information about the Trial?

Further information about the Trial may be found here: https://uavionix.com/projects/ukobsbeacon/