FAA releases updated AC on collision avoidance systems

An updated advisory circular has been released by the FAA focusing on the operational use of Airborne Collision Avoidance Systems (ACAS), including Traffic Alert and Collision Avoidance Systems (TCAS).

The update to Advisory Circular (AC) 90-120 “aims to standardize practices, improve compliance, and enhance safety during in-flight collision risk scenarios,” according to FAA officials.

ACAS technology has become a critical component for preventing midair collisions, offering alerts and resolution advisories (RAs) to help pilots maintain safe separation.

The circular, released Nov. 20, 2024, provides a detailed explanation of ACAS technology, its variants (ACAS I, ACAS II, ACAS Xa), and how these systems function to prevent mid-air collisions.

It also clarifies the differences between Traffic Advisories (TAs) and Resolution Advisories (RAs), and how pilots should respond to each.

Why does this matter to pilots?

As airspace grows increasingly congested, understanding and utilizing ACAS capabilities effectively can significantly enhance safety. This circular provides the tools to train pilots, manage ACAS events, and comply with evolving regulations, ensuring seamless operation in complex airspace, according to FAA officials.

For general aviation, ACAS can reduce near-miss incidents, particularly in busy terminal environments. By adopting the guidance in this circular, pilots can improve situational awareness and respond accurately to collision threats, FAA officials noted.

In addition, the AC covers:

• Operational Approval and Procedures: The circular outlines the process for obtaining operational approval from the FAA for ACAS use. It covers the necessary amendments to operational manuals, MELs, training programs, and other documentation.
• Training Requirements: AC 90-120 emphasizes the importance of comprehensive ACAS training, encompassing both ground and flight instruction, including simulator exercises. It stresses the need for pilots to demonstrate proficiency in interpreting ACAS displays and responding correctly to TAs and RAs.
• Reporting Procedures: The AC details the different reporting requirements for various ACAS events. It clarifies the mandatory reporting requirements for RAs under specific conditions and outlines other reporting channels, such as the FAA Hotline and NASA ASRS, for voluntary reporting of significant events.

For more information: FAA.gov