EASA, the European Aviation Safety Agency, has approved the Trig Avionics TT31 Mode S transponder for ETSO C166a, the ADS-B technical standard for 1090 MHz extended squitter transmission.

The TT31 is the world’s first transponder to receive this European approval, and provides a cost effective route to next generation ATC surveillance. All TT31 transponders are ADS-B capable – Trig make no charge for this feature, although some older units will require a software update.

ADS-B stands for Automatic Dependent Surveillance Broadcast, and is a system to automatically transmit aircraft identity, altitude, position and velocity to ground users and to other aircraft. The international standard data link for these transmissions is based on Mode S transponder technology, and the transmission mechanism is called “Extended Squitter” or ES. The Trig TT31 is a Mode S transponder which also supports this extended squitter function. Not only does the TT31 satisfy current Mode S requirements, but by connecting a suitable GPS position source, the aircraft can also report all the required parameters to comply with current and proposed future ADS-B requirements.

Today ADS-B is used as a tool for providing ATC surveillance in areas where conventional radar surveillance is not technically possible, such as over water in the North Sea, the Mediterranean, the Hudson Bay and the Gulf of Mexico, or in the Australian outback. In future, ADS-B is seen as an enabling technology for better airspace utilisation, for example by supporting in-trail procedures and higher density operations, and as a way of providing affordable collision avoidance for light aircraft.