MSA provides obstacle clearance within what radius?

• A. It provides obstacle clearance outside a 25 NM radius
• B. It provides obstacle clearance within a 25 NM radius
• C. It is 50 NM radius
• D. It does not relate to terrain elevation

Answer: (B)

MSA defines the altitude needed to guarantee obstacle clearance inside a specific circle around a navigation aid. That circle has a radius of 25 nautical miles. Within this 25 NM zone, the minimum altitude shown as MSA ensures you have safe clearance over terrain and obstacles, making it a reliable reference when flying near the nav aid. It’s not about a larger radius or outside the circle, and it does relate to terrain elevations because the purpose is to maintain obstacle clearance.