OpenSky Report 2019: Analysing TCAS in the Real World using Big Data

Collision avoidance is one of the most crucial applications with regards to the safety of the global airspace. The introduction of mandatory airborne collision avoidance systems has significantly reduced the likelihood of mid-air collisions despite the increase in air traffic density. In this paper, we analyze 250 billion aircraft transponder messages received from 126,700 aircraft by the OpenSky Network over a two-week period. We use this data to quantify equipage and usage aspects of Traffic Alert and Collision Avoidance System (TCAS) as it is working in the real world. We furthermore provide an overview of the methods used by OpenSky to collect, decode and store this data for use by other researchers and aviation authorities. We observe that around 89.5% of the ADS-B-equipped aircraft have an operational TCAS. We further analyze the concrete usage of TCAS by examining several case studies where a loss of separation between aircraft has happened.