Minimum Sector Altitudes provide obstacle clearance within what radius according to MSA?

Minimum Sector Altitudes (MSA) are designed to ensure that aircraft have obstacle clearance within a specified radius from a navigation facility or point on the ground. The correct answer indicates that MSA provides obstacle clearance within a 25 nautical mile (NM) radius.

This range is significant, as it allows pilots to have a safe altitude during their approach, especially when navigating through areas that may harbor terrain or obstacles that could pose a risk to flight safety. By using a 25 NM radius, the MSA accounts for any unexpected deviations in flight, ensuring a margin of safety that supports the safe operation of the aircraft.

The MSA is particularly important for pilots during the initial stages of approach or in areas where terrain may not be well-lit or marked. This altitude serves as a critical reference for maintaining safety while navigating through potentially challenging airspace.

In contrast, the other options do not represent the standard or commonly used radius for obstacle clearance provided by MSA, which is firmly established at 25 NM.