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This glossary is written for virtual airline and flight simulation use within Virtual Air Canada Airline. It is not intended as a real-world aviation reference.
The Minimum Sector Altitude is the lowest altitude that provides at least 1,000 feet of clearance above all obstacles within a defined area, typically a 25 nautical mile radius sector centered on a navigational aid or a prominent fix associated with an approach procedure. MSAs are divided into compass sectors (usually four quadrants), and each sector has its own altitude value depending on the terrain within that slice of the circle. MSA is published on instrument approach charts as the “MSA circle” in the plan view, and its purpose is to provide a safe emergency reference altitude in the event of navigation uncertainty, communications failure, or an unexpected need to maneuver in the terminal area. MSA is an emergency safe altitude reference, not a regularly used operating altitude. It does not guarantee navaid reception and is not a substitute for published procedure altitudes or ATC clearances. When a crew is uncertain of their position or has lost communications, descending to or maintaining the applicable MSA sector altitude provides a baseline level of obstacle clearance while the situation is resolved. In some circumstances, the MSA may be the only available reference if primary navigation systems have failed and the crew needs to determine a safe holding altitude near the destination.

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In Virtual Airline Operations

The MSA circle on approach charts is a useful reference for Virtual Air Canada Airline crews flying into unfamiliar airports, particularly those surrounded by terrain. Checking the MSA before beginning a descent ensures that any maneuvering altitude used during vectors or unexpected holds will provide adequate terrain separation. In simulation, consulting the MSA adds procedural discipline to approach briefings and reflects real-world practice for mountainous destinations such as those found on Canadian and international routes.
  • MEA - Minimum Enroute Altitude
  • IAF - Initial Approach Fix
  • ILS - Instrument Landing System