Successful GPS trial allows general aviation to use full functionality of transponders

A trial to enable general aviation (GA) pilots to use the full functionality of their Mode S Extended Squitter transponders has proved successful.

Data recorded over the six-month trial saw GA pilots transmitting sufficiently accurate Automatic Dependent Surveillance-Broadcast (ADS-B) position information when their transponders were connected to non-certified GPS sources.

Using a non-certified source meant they could track their aircraft in real-time on apps such as Planefinder and FlightRadar24. And with an additional ADS-B receiver it will help increase awareness of nearby ADS-B equipped aircraft making the UK’s busy airspace even safer.

Mark Watson, Head of Research and Development at NATS, said: “This trial has successfully shown we can use non-certified GPS sources with capable transponders to provide ADS-B and therefore increase visibility and situational awareness of GA pilots.

“The GA community using visual flight rules will look out the aircraft window to see and avoid other traffic. The trial showed that they could transmit position data to enhance pilots’ situational awareness, which supports the “see, be seen and avoid” concept.”

The trial was supported by the Civil Aviation Authority (CAA), the Aircraft Owners and Pilots Association (AOPA), the British Microlight Aircraft Association (BMAA), the Light Aircraft Association (LAA) and the Future Airspace Strategy VFR Implementation Group (FASVIG).

Now the trial is complete, the BMAA and LAA, in conjunction with FASVIG, have announced they will continue to approve Mode S Extended Squitter ADS-B installations with non-certified GPS sources.

NATS believes that the GA community should continue to be encouraged to connect non-certified sources so they can benefit from this additional safety tool. To do so, a minor aircraft modification must be approved by either the CAA or EASA, or other delegated authority like the LAA or BMAA. From 18 March the BMAA and LAA’s Avionics Modification Approval processes will take over the ADS-B verification from NATS.

Steve Hutt, FASVIG Programme Coordinator, said: “FASVIG support the voluntary adoption of ADS-B by GA. ADS-B offers great potential for improved traffic situational awareness and flight safety. We want to make installing ADS-B as quick, simple and low cost as possible to ensure that adopting ADS-B is an obvious and easy decision for GA pilots. FASVIG has been working closely with NATS, CAA, BGA, BMAA, LAA, AOPA, transponder manufacturers and the GA community to advance this cause, and especially the acceptance of non-certified GPS as the position source for ADS-B.”

The trial was part of a wider project called ‘EVA’ – Electronic Visibility via ADS-B – where NATS is working with AOPA UK, Trig Avionics, Funke Avionics and Eurocontrol to validate the use of ADS-B by the GA community. The project is co-funded by the SESAR Joint Undertaking.

As part of Project EVA, NATS and Funke Avionics have been developing a new prototype device called the Low Power ADS-B Transceiver (LPAT), which is a portable, battery powered and affordable device that will provide the minimum functionality needed to make a GA pilot visible to other airspace users. It will also provide proximity warnings against other suitably equipped aircraft.

Mark added: “Transmitting GA position via ADS-B is just part of the story here. We are enabling the capability of GA aircraft to send and receive information about each other.

“This could provide the capability in the future to allow air traffic control to have enhanced awareness of the surrounding GA traffic, making it a safer environment for all to use.”

LPAT can send and receive 1090MHz ADS-B signals allowing pilots to have greater awareness of the traffic around them; however it does not match a full transponder in terms of functionality. For example, it is not currently interoperable with Traffic Collision Avoidance System (TCAS) and its use will not allow access to some airspace if a transponder is mandatory.

Read the full report of the non-certified GPS trial here