MINIMUM SAFE ALTITUDE (MSA)
Altitude depicted on an instrument approach chart and identified as the minimum safe altitude which provides 1000 feet of obstacle clearance within a 25 NM radius from the navigational facility upon which the MSA is predicated. If the radius limit is other than 25 NM, it is stated. This altitude is for EMERGENCY USE ONLY and does not necessarily guarantee navaid reception. When the MSA is divided into sectors, with each sector a different altitude, the altitudes in these sectors are referred to as “minimum sector altitudes”.
MINIMUM SECTOR ALTITUDE (MSA) (ICAO)
The lowest altitude that may be used under emergency conditions that provides a minimum clearance of 300 meters (1000 feet) above all obstacles within a sector of a circle of 46 kilometers (25 NM) centered on a navigational aid.
ICAO and FAA are the same.
