Definition
A function of the air traffic control radar system that alerts the controller when a tracked aircraft is below, or is predicted to descend below, a predetermined minimum safe altitude. When the alert triggers, the controller issues a low altitude alert to the pilot.
Plain English
A safety feature in the controller's radar system. If your aircraft drops too low, or looks like it's about to, the system warns the controller, who then warns you.
Context Anchor
Pilots encounter MSAW in discussions of air traffic control safety alerts and radar-based services, especially when an aircraft may be close to terrain or obstacles.
Why Pilots Care
Gives controllers immediate notice to issue a safety alert, reducing the chance of controlled flight into terrain.
Grounding Statement
Picture an aircraft descending at night near rising terrain: MSAW is the controller-side alert that may warn air traffic control that the aircraft is getting dangerously low.
Intuition Check
MSAW is not a warning displayed in every cockpit. It is primarily an air traffic control alert, and it does not replace the pilot’s responsibility to maintain safe altitude.
Example Sentence 1
Approach control issued a low altitude alert after MSAW triggered on the descending traffic.
Example Sentence 2
MSAW coverage is especially important when flying near high terrain at night.