UK Trial of 978MHz UAT ADS-B Obstruction Beacons for gliding, hang gliding, paragliding, and model flying sites

UK Trial of 978MHz UAT ADS-B Obstruction Beacons for gliding, hang gliding, paragliding, and model flying sites2022-10-26T09:25:39-05:00

Project Description

uAvionix is participating in a Civil Aviation Authority-endorsed large-scale trial using ground-based ADS-B obstruction beacons operating on 978MHz Universal Access Transceiver (UAT) in the UK. A first-ever trial to use ADS-B to enhance the safety of glider, hang gliding, paragliding, and model flying operations, the trials will commence in the autumn of 2022 at various sites throughout the UK, supported by the UK Civil Aviation Authority (CAA) Airspace Modernisation Strategy (AMS).

Collision risks associated with hazardous overflight of winch launch gliding sites are well known to operators, yet frequent incidents continue to be reported. As part of the AMS, the CAA is seeking to implement measures to mitigate this and similar risk utilizing underutilized 978Mhz spectrum, commonly used in the USA as a secondary ADS-B frequency and for Traffic Information System Broadcast (TIS-B) and Flight Information System – Broadcast (FIS-B).

As the global market leader in UAT ADS-B devices, uAvionix is supporting the trials by providing purpose-built powered obstruction beacons that will be placed at 13 club sites throughout the UK, enabling the sites to be visualized when operational on any Electronic Flight Bag (EFB) utilizing ADS-B IN devices such as the uAvionix skyEcho2. The obstruction beacons will be switched on and broadcast only when flying activities are underway at the participating club sites.

The project will trial new airspace safety functionality built upon ground-based ADS-B obstruction beacons broadcasting on 978MHz UAT ADS-B protocols. Approved by the CAA, the project will be undertaken between September 1st and October 31st, 2022. The trials are a collaboration between uAvionix, the CAA, Association Head Office and member clubs of the British Gliding Association (BGA), British Hang Gliding & Paragliding Association (BHPA), and the British Model Flying Association & Large Model Association (BMFA & LMA).

Suitably equipped General Aviation pilots flying within the vicinity of these Beacons will be alerted in real-time to these aerial activities to enhance their situational awareness and safety. Other airspace users and interested parties may also benefit. The project will be seeking feedback from all relevant stakeholders.

The trial is approved by the CAA to evaluate digital Flight Information Service provision as part of the Airspace Modernisation Strategy.

UPDATE: Trial Extended

At the request of the UK CAA, the Trial has been extended by one month and will now run until 30th November 2022.


Feedback on airspace user’s experience of the trial is welcome and may be submitted here.

Club Sites Participating in the Trial

Club Lat/Long Beacon ID Beacon Alt AMSL (ft)
Burn Gliding Club 534707N 0010551W UKWLBURN 3100
Cambridge Gliding Club 521109N 0000640W UKWLCAMB 3300
The Gliding Centre, Husbands Bosworth 522626N 0010238W UKWLHUSB 3500
Lasham Airfield 511118N 0010152W UKWLEGHL 3625
Derbyshire & Lancashire Gliding Club 531817N 0014345W UKWLDLGC 3400
Challow Paragliding Club 513629N, 0012843W UKHPCHAL 1300
Wessex HGPG 505229N 0021728W UKHPWESS 2800
Avon HGPG 513715N 0024325W UKHPAVON 2800
Cambridge Aerotow Club 523839N  0000641E UKHPCAMB 2000
LMA North West Site 532646N 0022821W UKMFLMNW 475
BMFA Buckminster 524650N 0004242W UKMFBUCK 1950
Wimbourne Model Aero Club 505532N 0020117W UKMFWIMB 1850
Phoenix Model Flying Club 514259N 0001541W UKMFPHOE 1775
Why this Trial is important – A real-life situation2022-08-26T09:47:37-05:00

Ian McFarlane of Burn Gliding Club provided this example:

“I was at Burn Gliding Club yesterday (25th August 2022) and took a student on a winch launch sortie (we were typically gaining about 1200ft AGL in light winds). As I flew the downwind leg (in an ASK-21 Glider) I observed a small GA aircraft approximately 500ft above me crossing the airfield. As part of my downwind call I alerted the launch point team to the traffic stating my height QFE as 650ft. They had already seen the traffic themselves and were observing. My aircraft had a SkyEcho unit installed and functioning and there was another glider on the ground with SkyEcho installed too; both gliders also had Flarm installed and active. The winch driver also observed the aircraft and reported “it appeared to be below cable height”. The winch driver continued to observe the flight expecting it to descend into nearby Sherburn in Elmet but it didn’t.

I never felt that the safety of my flight was compromised – we had ample separation, but the overflying traffic came dangerously close to a potential winch launch, only recently in a stronger wind on this runway I was seeing over 1600ft on the winch launch – with a 6mm diameter steel wire!

 If we ever needed a timely example of why this trial is important, this would be it!”

How the Beacons will operate2022-08-26T09:47:49-05:00

CAA have specified that the Beacons will broadcast 978MHz UAT ADS-B messages with an Emitter Category of ‘Point Obstacle’. The location broadcast by the Beacon will be based on the geographical position of the Beacon as reported by the Beacon’s built-in GNSS position source. The altitude broadcast will be a fixed altitude in feet above mean sea level (AMSL) defined based on the operating procedures for the site, e.g. as defined in the AIP (rounded to the nearest 25ft as per the UAT standard). Placement of the Beacon will be the responsibility of the site operator.

The Beacons, presenting electronically at a fixed point in space, will be there to provide pilots and other airspace users with situational awareness of the risk of collision with aerial activities at the site in the vicinity of that fixed point in space. ‘In the vicinity’ can mean above, below and in the area around that fixed point in space. For example, for glider winch launch sites the altitude AMSL of the Beacon broadcast will be the maximum altitude of the winch launch cable, though gliders usually hope to climb higher than this after release from the cable. Model aircraft flights will typically remain within the site boundaries. Hang gliders and paraglider flights may remain in the vicinity of the site or may choose to fly further afield. So the Beacons will be there to offer helpful real-time situational awareness of live activities but do not depict the full volume of airspace occupied by those flying activities.

Receiving the Beacon Broadcasts2022-08-26T09:48:00-05:00

Airspace users equipped with 978MHz UAT ADS-B IN and within range of these broadcasts should be able to receive real-time alerting of site activity from the ADS-B Obstruction Beacon if their avionics/Electronic Flight Bag application receives 978MHz UAT ADS-B IN data and supports the display of 978Mhz UAT ADS-B Point Obstacles. Some avionics/Electronic Flight Bag applications may not yet correctly display ADS-B Point Obstacles. Gathering feedback on such matters is one objective of the trial.

ADS-B transceivers/receivers, such as the uAvionix SkyEcho 2 or Garmin GDL 50, which are dual-band, receiving ADS-B IN on 1090MHz and 978MHz, will be able to receive these new Obstruction Beacon broadcasts. The SkyEcho 2’s second receivers must be set to receive 978Mhz UAT. See SkyEcho 2 Setup screen below.

CAA Guidance to GA Pilots2022-08-26T09:48:09-05:00

CAA has provided the following guidance for GA pilots:

“Pilots observing the electronic depiction of an ADS-B Obstruction Beacon during the trial, should recognise that associated flying activities are underway, assess the location and vertical extent of the activity, avoiding the immediate vicinity of the beacon in accordance with their avoidance techniques when observing the depiction of such activities on a chart or via NOTAM notification.”

Technical Characteristics of the Beacon’s 978MHz UAT ADS-B Messages2022-08-26T09:48:17-05:00

Address Qualifier Field Encoding

In accordance with DO-282, Beacons will broadcast an Address Qualifier value of 5, meaning the Address Type is ‘Fixed ADS-B Beacon’, using a non-ICAO, state assigned unique 24-bit address.

24-bit Address Field

As qualified by the above, each Beacon will broadcast a fixed non-ICAO 24- bit address (Hex Code). These will be assigned on a fixed basis for the duration of the trial. The values that will be used will be 000001 – 00000D (1 – 13 decimal).

Beacon IDs

Each Beacon will broadcast its own unique ID. All Beacon IDs will be 8 characters long. IDs will conform to the format described in the following table.

Character PositionsValueDescription
1 & 2“UK”United Kingdom
3 & 4“WL”Beacon for Gliding Winch Launch Site
3 & 4“HP”Beacon for Hang Gliding and Paragliding Site
3 & 4“MF”Beacon for Model Flying Site
5 – 84 Alphanumeric charactersIndicative of the site name
FAQ for the 978MHz UAT ADS-B Obstruction Beacon Trial2022-09-23T09:59:14-05:00

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:

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:

Further Information

Further information will be made available on the uAvionix website, where future updates will be posted. This will be shared as widely as possible to raise awareness with all stakeholders.

Notifications will also be published via official aviation channels, such as NOTAMs and AIS.

“The trial of functionality such as ADS-B Obstruction Beacons helps us understand and evaluate the benefits of deploying digital Flight Information Services as part of the Airspace Modernisation Strategy.  We are pleased to fund this trial via the Airspace Modernisation Strategy Support Fund (AMSSF) and that uAvionix have chosen to work with some of our key General Aviation stakeholders to improve the promulgation and awareness of their activities at the trial locations, to deliver a safety benefit.”

Stuart Lindsey, Head of Airspace Modernisation Strategy at Civil Aviation Authority

“The BGA has for several years recorded and raised awareness of hazardous overflights of glider winch launch sites by aeroplanes and helicopters. These sites are depicted on ½ mil charts and described within the AIP. Participating in the obstruction beacon trial will contribute to an understanding of the effectiveness of using technology to highlight a fixed airspace hazard during flight and in doing so reduce mid-air conflict risk. It is important too that the equipment is reliable and affordable. We’re pleased to be working with others to identify the wider benefits of voluntary equipage of electronic conspicuity.”

Pete Stratten, CEO of the BGA

“The BMFA and LMA are excited to be involved in this trial. We see it as an important stepping stone on the route to integrated airspace, where all manned, unmanned and autonomous aircraft can safely coexist, especially at low altitudes. We are looking for the trial to show how model aircraft will practically continue to fly while being in electronically conspicuous airspace that is visible to other traffic, increasing situational awareness and improving safety.”

Rob Buckley, BMFA/LMA

“For many years the BHPA has sought to raise awareness amongst the UK aviation industry of the extent of UK hang glider and paraglider flights made by its membership operating in excess of 7500 aircraft. Operating far from established airfields in most cases, often from sites not marked on air charts, these aircraft can be foot-launched from hills or towed from flat ground into the air by winch or behind a microlight. They can also launch using a power unit from any reasonably flat area. The activities are described within the UK AIP as operating anywhere in the open FIR.

Unpowered thermal flights take place from ground level to cloudbase, which even in the UK, can occasionally be up to 10,000 feet. Flights of hundreds of km can, routinely, be made using thermals (the current UK distance record for an unpowered paraglider stands at 317km from Elan Valley, mid Wales, to Scarborough). A significant proportion of soaring and circuit flight activity takes place within 500ft of the ground and remains within a mile or so of a take-off area. It is common for fifty or more gliders to be flying soaring patterns above a ridge and or an area of hillside.

The very low airspeed of hang gliders and paragliders enables them to fly in close proximity to each other using ‘see and avoid’ as an effective means of collision avoidance. However, they lack the manoeuvrability to take significant collision avoidance action against faster heavier aircraft. On-board ADS-B has not yet been demonstrated to be fully effective and compatible with the open-cockpit nature of hang gliders and paragliders. The BHPA hopes that its participation in the ADS-B Obstruction Beacon trial will provide a means of evaluating how ground-based electronic conspicuity can assist pilots in identifying local areas of high intensity hang gliding and paragliding activity, and will ultimately lead to the development of an effective system allowing all air users to ‘see and avoid’ our comparatively stationary aircraft.“

Marc Asquith, BHPA Chairman

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