The industry had been monitoring Traffic Collision Avoidance System (TCAS) II 7.0 events for a number of years, and the crash investigation reports contained a number of recommendations concerning TCAS software upgrades, better training and clearer instructions to the pilots.
TCAS and Airborne Collision Avoidance System (ACAS) are designed to reduce mid-air collisions between aircraft by monitoring the airspace around an aircraft for other aircraft equipped with a corresponding transponder, independent of air traffic control.
One of the results of the investigation was the recommendation to develop TCAS/ACAS version 7.1 following the discovery of two safety issues ─ one relating to the performance of the Resolution Advisory (RA) reversal logic and the other involving incorrect responses to “Adjust vertical speed” RAs.
Development was undertaken jointly by U.S. and European technical regulatory organizations with support from the entire industry and the Minimum Operation Performance Standards (MOPS) were thereupon revised.
In December 2011, the European Union Commission published regulation EU No 1332/2011 mandating ACAS version 7.1 within European airspace. At this time, the FAA has authorized but not required operators in U.S. airspace to upgrade to TCAS 7.1. FAA InFo 12010 TCAS II Version 7.1.
TCAS Time Line
ADS B Time Line
The version 7.1 solutions consist of a call out of “Level off, level off” and improved reversal logic. Level-off logic is designed to prevent incorrect pilot responses. In version 7.0, the “Adjust vertical speed; adjust” RA has been replaced by a new "level off,level off" RA which requires a reduction of vertical rate to 0 ft/min.
Improved reversal logic has been added to version 7.1 which monitors RA compliance in coordinated encounters. When it is detected that an aircraft is not responding correctly to an RA, a reversal RA will be issued to the aircraft which maneuvers in accordance with the RA.
The new Honeywell family of TCAS products provides all the enhanced capabilities for current and future TCAS/ACAS requirements.
The additional safety benefits that come with new TCAS/ACAS 7.1 software and ADS-B transponders are smart additions to aircraft and meet global mandate requirements. The added safety features will provide another layer of situational awareness and safety for the passengers and cockpit crew. Honeywell has certified solutions available through our dealer and OEM networks.