Traffic information service – broadcast explained

Traffic information service – broadcast (TIS–B) is an aviation information service that allows pilots to see aircraft that are not emitting ADS-B data but have a basic transponder.

As aircraft are discovered by primary radar and respond with encoded altitude information, this information is broadcast over ADS-B. These near real time positions and ground tracks of other nearby aircraft are provided for the purpose of collision avoidance. It presents to the pilot a combined representation of aircraft positions derived from GPS satellite and ground-based radar data, specifically: aircraft's replies to ATC interrogations (i.e., they are responses to queries as sent to the aircraft from air traffic controller on the ground).^{[1] [2]}

TIS-B is broadcast to aircraft using both the 1090 MHz extended squitter (1090 ES) and the universal access transceiver (UAT) band of Automatic Dependent Surveillance–Broadcast (ADS-B).^[3] Currently the service mainly benefits general aviation (GA) aircraft equipped with ADS-B "in" hardware by providing a traffic information relay to a screen in the cockpit.

At this time TIS–B is meant to be only a supplement to visual separation from other aircraft when operating in visual meteorological conditions (VMC) and as a backup to radar, which in remote areas only updates every 13 seconds, when operating under instrument flight rules (IFR).^[4]

Notes and References

1. Web site: Ins and Outs . faa.gov . 15 April 2022 . 18 June 2022 . To qualify as a TIS-B target, an aircraft must be equipped with a transponder, and be within radar coverage. .
2. Web site: AC 900114B Automatic Dependent Surveillance-Broadcast Operations . faa.gov . 30 December 2019 . 18 June 2022 . 2 TIS-B. TIS-B is the broadcast of transponder-based Mode C or Mode S traffic information derived from ATC surveillance systems. TIS-B provides ADS-B In-equipped aircraft with a more complete picture of surrounding traffic in situations where not all aircraft are equipped with ADS-B. An aircraft or vehicle that is ADS-B Out and is receiving TIS-B service is known as a TIS-B client. A non-ADS-B-equipped aircraft or vehicle that has its position transmitted in TIS-B reports is known as a TIS-B target. See paragraph 2.3.5 for TIS-B client qualification criteria. .
3. Web site: New Technology – ADS-B, TIS-B, and FIS-B. FAA - Air Traffic Bulletin - Special. 2005-3. August 2005. https://web.archive.org/web/20120921045525/https://www.faa.gov/air_traffic/publications/bulletins/media/atb_aug_05.pdf. 21 September 2012.
4. Web site: Mysteries of ADS-B - FLYING Magazine . Tom Benenson . FLYING Magazine . 30 October 2005 . 18 June 2022 . The uplink of non-ADS-B traffic is referred to as Traffic Information Service-Broadcast (TIS-B). Because the uplinked radar information is not as accurate as the ADS-B targets, the icon on the cockpit display for “degraded” non-ADS-B traffic looks a bit like a Pacman that’s had a bite taken out of its backside; the ADS-B traffic is displayed as a chevron or arrow head pointing in its direction of movement.. }