Definition
An emergency-use altitude depicted on an instrument approach chart that provides at least 1,000 feet of obstacle clearance within a defined radius (typically 25 nautical miles) of a specified navigation facility or airport reference point. MSA is for emergency use only and does not necessarily guarantee acceptable navigation signal coverage.
Plain English
A safe altitude shown on an approach chart that you can climb to in an emergency, knowing you'll clear all obstacles within a circle around the airport or navigation aid.
Context Anchor
Seen in the plan view of an instrument approach chart, usually near the airport or navigation point the approach is built around.
Derivation
Altitude comes from the Latin altus, meaning high. In this term, it helps to think of MSA as the lowest published height that still gives obstacle clearance in the stated area.
Why Pilots Care
It supplies a reliable altitude floor that protects against terrain and obstacles during instrument flight when the pilot is relying on the chart.
Grounding Statement
If you are near the approach area and need one quick number to stay above surrounding terrain and towers, the MSA is that emergency number.
Intuition Check
“Safe” does not mean safe for every purpose. MSA mainly protects you from terrain and obstacles in the stated area; it does not automatically guarantee radio reception, navigation signal coverage, or permission to descend.
Example Sentence 1
After losing the glideslope, the pilot climbed to the published MSA shown on the approach chart while sorting out the next step.
Example Sentence 2
The approach chart showed an MSA of 3,200 feet within the 25-mile radius of the VOR.