VT-10 Primary INAV Ground School Instrument 3 Practice Test

Minimum Safe Altitude provides a guaranteed obstacle clearance. Specifically, it ensures at least 1000 feet of terrain or obstacle clearance within 25 nautical miles of a navigational aid (with 2000 feet in some mountainous areas). This altitude is published on IFR charts to give you a safe buffer when flying near a VOR, especially if you must navigate by instruments and you’re within that 25 NM radius.

The other altitudes serve different purposes: a Minimum Vectoring Altitude is the altitude ATC uses to ensure safe radar-vectored navigation within a sector, and it can vary by sector rather than being a fixed 25 NM/1000 ft rule; a Minimum Crossing Altitude is the altitude you must cross a fix or airway intersection at; a Minimum Reception Altitude is the height needed to receive a VOR/VHF signal, not a terrain clearance value.