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ADS-B with non-certified GPS

ADS-B with non-certified GPS


The British Microlight Aircraft Association and Light Aircraft Association are set to take over verification of Mode S Extended Squitter ADS-B installations with non-certified GPS sources, otherwise known as ADS-B Out, following the successful conclusion of NATS trials to review the technology.

As part of the development of tools to help improve flight safety by enhancing situational awareness, last year NATS conducted a General Aviation ADS-B Trial in Southern England, which was supported by the CAA, LAA, BMAA and FASVIG. Data recorded over the six-month trial saw GA pilots transmitting sufficiently accurate ADS-B position information from their transponders when connected to non-certified GPS sources.

This allowed other airspace users to track their aircraft in real-time on apps such as Planefinder and FlightRadar24. Linked with an additional ADS-B receiver technology such as Pilot Aware, it is helping to increase awareness of nearby ADS-B equipped aircraft making the UK’s busy airspace even safer.

Now the trial is complete, the BMAA and LAA have agreed they will continue to approve Mode S Extended Squitter ADS-B installations with non-certified GPS devices. From 18th March, BMAA and LAA’s Avionics Modification Approval processes will take over the ADS-B verification service from NATS.

BMAA members wishing to transmit ADS-B from a non-certified GPS source connected to an Extended Squitter-capable Mode S transponder, should contact the BMAA Technical Office (technical.office@bmaa.org).

In support of ADS-B Avionics Modification Approvals by the BMAA and LAA, NATS has been providing an email service to supply verification that the correct ADS-B operational status messages are being broadcast by applicant’s Mode S ES transponders. When used with an uncertified GPS device, the most important part of the modification is to ensure the GPS data is tagged as being of low/no integrity. In this situation the Surveillance Integrity Level (SIL) and System Design Assurance (SDA) values being broadcast must be zero. Following the trial the BMAA and LAA will take over this work in continuing to verify Mode S ES ADS-B avionics installations with uncertified GPS devices.

NATS, LAA, BMAA and FASVIG view the voluntary adoption of ADS-B electronic conspicuity equipment by GA as an important enhancement to flight safety and encourage Association members to implement ADS-B where possible. Further information on the setup of Mode S ES transponders to broadcast ADS-B is available on the FASVIG website (www.fasvig.org). Note that not all Mode S ES transponders are capable of being configured for use with an uncertified GPS.


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