How long before the CPA does TCAS generate a Resolution Advisory (RA) in the event of a potential collision?

TCAS, or Traffic Collision Avoidance System, is designed to enhance flight safety by providing pilots with timely warnings of potential mid-air collisions. In the event of a potential collision, TCAS generates a Resolution Advisory (RA) when it determines that another aircraft is on a collision course.

The correct answer is significant because TCAS typically generates an RA approximately 15 to 35 seconds before the calculated Closest Point of Approach (CPA). This early warning period is essential, as it allows pilots enough time to interpret the advisory and execute necessary evasive actions before the aircraft reaches the point of closest proximity to the other aircraft. This time frame is built into the system to ensure that the responses are not only timely but also safe, allowing for effective maneuvering while minimizing any risk to the aircraft and crew.

Understanding this timing is crucial for pilots, as it directly influences their response to potential threats and the overall effectiveness of TCAS in preventing mid-air collisions. The other timeframes provided do not align with TCAS's operational design and would not provide the necessary advance warning to manage an encounter safely.