This figure is published on instrument approach charts to guarantee at least 1,000 feet of vertical clearance over all objects within a 25-nautical-mile radius of a navigation aid. Pilots use it as a baseline safety reference during emergency descents or when they lose situational awareness. While it keeps the aircraft from hitting terrain, it does not guarantee navigational signal reception.
Heard on the job
If we lose the glideslope out here, climb immediately to the MSA of four thousand five hundred feet.
Insider tip
Historically, this abbreviation also stood for the defunct airline Malaysia-Singapore Airlines.
Also heard as
- minimum safe altitude