Definition
The lowest published altitude on a Victor airway, off-airway route, or route segment that meets obstacle clearance requirements for the entire segment, and which assures acceptable navigation signal coverage only within 22 nautical miles of a VOR.
Plain English
The lowest altitude you can fly on a given route segment and still be guaranteed clearance over terrain and obstacles, but where the navigation signal is only reliable when you are within 22 nautical miles of the VOR station.
Context Anchor
Seen on IFR low en route charts, often marked with an asterisk next to an altitude on an airway or route segment.
Derivation
Minimum' (least), 'obstacle clearance' (room above terrain and structures), 'altitude' (height). The name reflects the priority of the value: it guarantees obstacle clearance first, while signal coverage is a secondary, limited consideration.
Why Pilots Care
Allows descent below the MEA when navigation signal coverage is not required while maintaining terrain safety.
Grounding Statement
On an instrument route where you may not be able to see the ground, this altitude is a published floor that keeps the airplane above known obstacles for that segment.
Intuition Check
Do not read “minimum” as “best” or “normal.” Here it means the lowest published altitude that still gives obstacle clearance for that exact segment, with navigation signal limits that still matter.
Example Sentence 1
ATC cleared us to descend to the MOCA of 4,500 feet, which kept us above the ridges along the airway.
Example Sentence 2
On the low altitude chart the minimum obstacle clearance altitude for the airway segment was shown as 4500 feet.