Traffic Alert And Collision Avoidance System, TCAS -  is intended for reducing the risk of aircrafts collision. The system surveys the airspace around the craft detecting others crafts appointed with TCAS. The system alerts the pilot if the aircraft collision risk appears. The TCAC systems are required to be installed on all aircrafts which weight is over 5700 kg or certificated for the transportation more than 19 passengers according to the ICAO standards.

System limits

In spite of the fact that the advantages of TCAS are incontestable, this system has a number of essential restrictions:

-TCAS can give out instructions only on vertical echelonment

- air traffic control system does not receive the instructions which have been given out TCAS to crafts, therefore air traffic controllers can not know about such instructions, and even to give contradicting instructions that is the cause of crews embarrassment.