FAA Aircraft Dispatcher (ADX)Navigation and ATCHard
A dispatcher is briefing a captain on the Minimum Safe Altitude (MSA) circle depicted on an instrument approach chart. What is the primary purpose of the published MSA?
- ATo provide the minimum altitude for normal approach navigation within the terminal area
- BTo provide 1,000 feet of obstacle clearance within a specified radius of a reference facility for emergency use
- CTo designate the altitude at which the missed approach procedure must be initiated
- DTo establish the minimum altitude at which ATC may issue radar vectors
Show answer & explanationAnswer & explanation
Correct answer: B. To provide 1,000 feet of obstacle clearance within a specified radius of a reference facility for emergency use
The MSA depicted on approach charts provides 1,000 feet of obstacle clearance within 25 NM (or as otherwise specified) of the reference navigation facility or fix, and is intended for emergency use only, not for normal approach navigation or ATC vectoring altitudes.
Why the other options are wrong
- A. MSA is not used for normal approach navigation, only emergency reference.
- C. Missed approach altitudes are separately published on the approach procedure, not tied to MSA.
- D. Minimum Vectoring Altitude (MVA), not MSA, governs ATC radar vector altitudes.
Minimum Safe Altitude (MSA)
An altitude depicted on instrument approach charts providing 1,000 feet of obstacle clearance within a specified radius (typically 25 NM) of a reference facility, intended for emergency use only.
- Provides 1,000 ft obstacle clearance, not navigation guidance
- Typically based on a 25 NM radius from a facility or fix
- For emergency use only — not for normal approach or vectoring
- May be divided into sectors if terrain/obstacles vary
Memory trick: 'MSA = My Safety Anchor' — emergency backup, not a flight plan altitude