Minimum safe altitude warning (MSAW) is an automated warning system for
air traffic controller
An Air traffic controller (ATC) is a person responsible for the coordination of traffic in their assigned airspace. Typically stationed in area control centers or control towers, they monitor the position, speed, and altitude of aircraft and c ...
s (ATCO). It is a ground-based safety net intended to warn the controller about increased risk of
controlled flight into terrain
In aviation, a controlled flight into terrain (CFIT; usually ) is an aviation accidents and incidents, accident in which an airworthy aircraft, fully under pilot control, is unintentionally flown into the ground, a body of water or other obstac ...
accidents by generating, in a timely manner, an alert of aircraft proximity to terrain or obstacles.
Description
International Civil Aviation Organization
The International Civil Aviation Organization (ICAO ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sch ...
Doc 4444 requires that radar systems should provide for the display of safety-related alerts including the presentation of minimum safe altitude warning.
The radar equipment predicts an aircraft’s position in 2 minutes based on present path of flight, and the controller issues a safety alert if the projected path encounters terrain or an obstruction. An unusually rapid descent rate on a
non-precision approach
In aviation, an instrument approach or instrument approach procedure (IAP) is a series of predetermined maneuvers for the orderly transfer of an aircraft operating under instrument flight rules from the beginning of the initial approach to a lan ...
can trigger such an alert.
[ ]
It is worth mentioning that ICAO Doc 4444 does not provide a definition of the term MSAW. Instead the term MSAW is ambiguously used in
ATC community to identify such warnings as well as for data processing systems providing the alert function.{{CN, date=January 2025
References
External links
SKYbrary article on MSAW
Aviation safety
Air traffic control
Warning systems