What is a major disadvantage of TCAS systems?

TCAS, or Traffic Collision Avoidance System, is designed to enhance situational awareness and prevent mid-air collisions by providing pilots with information about nearby aircraft. A major disadvantage of TCAS systems is that they rely on active transponders to receive data. This means that aircraft equipped with TCAS can detect other aircraft only if those aircraft are actively transmitting their position information via their transponders. Therefore, any aircraft that does not have an operational transponder cannot be detected by TCAS. This limitation poses a safety risk, as the system may not provide full situational awareness in airspace where non-transponder-equipped aircraft may be present.

Other options may propose issues such as reliance on satellite communication or altitude limitations, neither of which accurately describes TCAS functionality. TCAS operates independently of satellite communications, relying instead on transponder signals for its operations, and it is designed to function at various altitudes. Similarly, while it does not detect weather variations, this aspect does not correspond with the primary operational limitations associated with aircraft transponders, which is the critical factor in TCAS's effectiveness.