What should a pilot do when given an ACAS resolution advisory?

When a pilot receives an ACAS (Airborne Collision Avoidance System) resolution advisory, the appropriate response is to comply with the advisory and maneuver according to its instructions. The ACAS system is designed to enhance safety by providing timely alerts to avoid potential mid-air collisions. It generates resolutions based on the current flight path and position of the aircraft in relation to other traffic.

Choosing to maneuver as per the advisory ensures that the pilot is actively responding to a potential threat rather than waiting for further confirmation or instruction. This immediate action is crucial as it can greatly increase the safety of the flight. After executing the maneuver, it is appropriate for the pilot to inform Air Traffic Control of any actions taken and report any deviation from the previously cleared flight path. This helps maintain awareness of the aircraft's current situation after resolving the potential conflict.

The rationale behind the other choices is less aligned with the principles of safety encapsulated in the ACAS system. While keeping Air Traffic Control informed is important, prioritizing immediate action based on the advisory takes precedence. Following the advisory only when no conflicting traffic has been reported neglects the fundamental purpose of the ACAS, which is to alert the pilot to potential hazards regardless of prior reports.