Definition
A traffic alert and collision avoidance system resolution advisory (TCAS RA) is an onboard system-generated instruction that directs the pilot to perform a specific vertical maneuver—such as climb, descend, or maintain vertical speed—to avoid a predicted midair collision with another transponder-equipped aircraft. When issued, the resolution advisory takes precedence over ATC instructions, and the pilot is required to respond promptly while notifying ATC of the deviation as soon as practicable.
Plain English
It is an automatic cockpit warning that tells the pilot to climb, descend, or hold a vertical rate right now to avoid hitting another aircraft. The pilot follows the warning first and tells the controller about it afterward.
Context Anchor
A pilot may encounter this on aircraft equipped with a traffic alert and collision avoidance system, usually as a visual message and a spoken cockpit command such as “Climb” or “Descend.”
Derivation
"Resolution" comes from the Latin resolvere, meaning to loosen or settle. In this context the system is not just warning of traffic—it is resolving the conflict by telling the pilot exactly what vertical action will separate the two aircraft.
Why Pilots Care
It supplies immediate, specific guidance that prevents a mid-air collision when visual contact or air traffic control instructions are insufficient.
Grounding Statement
When the system gives a resolution advisory, it is telling the pilot what vertical action is needed now to increase separation from another aircraft.
Intuition Check
Do not read “advisory” as a casual suggestion here. In this aviation use, a resolution advisory is urgent safety guidance that the pilot is expected to respond to unless doing so would make the situation unsafe.
Example Sentence 1
When the crew received a resolution advisory to descend, they disconnected the autopilot, followed the commanded vertical rate, and then advised ATC of the deviation.
Example Sentence 2
A traffic alert and collision avoidance system resolution advisory directed a descent that safely increased separation from the crossing traffic.