Definition
A free ground-based service, part of the ADS-B system, that uplinks traffic information to properly equipped aircraft. It uses radar data from FAA ground sensors to broadcast the position of nearby aircraft that are not transmitting ADS-B Out, so that ADS-B In equipped aircraft can see those targets on a cockpit traffic display.
Plain English
A free service that uses ground radar to send you the location of nearby airplanes that don't have ADS-B, so you can see them on your cockpit screen along with the ones that do.
Context Anchor
Seen in ADS-B, cockpit traffic display, and instrument flying discussions where the pilot is using electronic traffic information to improve awareness.
Derivation
‘Broadcast’ is the key word — the ground stations transmit traffic information outward to any equipped aircraft in range, rather than sending it to one specific aircraft. This distinguishes TIS-B from the older TIS, which was a directed service to a single aircraft via Mode S radar.
Why Pilots Care
It increases situational awareness by showing traffic that would otherwise remain invisible on the display.
Intuition Check
Do not assume TIS-B shows every aircraft near you. It is a useful traffic aid, but it depends on ground coverage, aircraft equipment, and what the system can detect.
Example Sentence 1
Once airborne and within ground station range, the cockpit display populated with TIS-B targets showing nearby traffic that wasn't broadcasting ADS-B Out.
Example Sentence 2
TIS-B alerted the crew to a non-equipped aircraft crossing their route at the same altitude.