Plain English Meaning
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.
Full 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.
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.