Ruy L. Brandao

Using TCAS surveillance to enable legacy ADS-B transponder use for in-trail procedures

In-Trail Procedures (ITP) is an application of Automatic Dependent Surveillance-Broadcast (ADS-B) that allows aircraft to change flight levels in areas where current non-radar separation standards would prevent desirable altitude changes. The ITP avionics receive ADS-B Out position reports from aircraft at intermediate flight levels that could be blocking the desired climb or descent maneuver. The most recent standard for ADS-B broadcast is RTCA/DO-260B [1]. This is also known as Version 2. Equipage is mandated by 2020 in the US for the same aircraft that carry transponders. Equipage is mandated in Europe by 2015 for forward fit aircraft and by 2017 for retrofit aircraft. Standards have been developed for the ADS-B data accuracy requirements for ITP [2, 3]. The standards are straightforward to apply to aircraft equipped with transponders certified to DO-260B [1]. The standards are less straightforward to apply for aircraft equipped with transponders certified to the earlier standards of ADS-B, which are known as Version 0 or Version 1 [4, 5]. This paper shows that crosschecking ADS-B data with Traffic Alert and Collision Avoidance System (TCAS) data is an effective mitigation technique for uncertain ADS-B horizontal position accuracy and integrity for legacy Version 0 and Version 1 ADS-B transponders.

Validation of Extended Hybrid Surveillance

Extended Hybrid Surveillance is a surveillance technique allowing TCAS to track some intruders using ADS-B reports and thus considerably reduce utilization of the 1090 MHz channel. This new surveillance method can be used if the intruder is not projected to be near collision threat and is qualified according to specific criteria. Unlike previously defined Hybrid Surveillance, Extended Hybrid Surveillance may not use active interrogations to validate the passive data. This paper presents first validation results of the system (implemented to meet the recently published standard), which combines using Active (conventional), Hybrid, and Extended Hybrid Surveillance. The validation objective was to assess the overall system behavior as well as evaluate the achievable benefits in terms of saved Mode S interrogations. The presented work is outcome of SESAR project 9.47 entitled “TCAS Evolution”. Data used for validation was recorded during a set of first worldwide flight tests of this capability performed during 2014.