Minimum Obstruction Clearance Altitude (MOCA)
Minimum Obstruction Clearance Altitude (MOCA) is the lowest published altitude in effect between radio fixes on VOR airways, airways, and routes that meets obstacle clearance requirements for the entire route segment. Unlike MEA, MOCA guarantees navigation signal coverage only within 22 NM of the defining VOR.
When to Use MOCA
MOCA can be used by ATC to assign altitudes below the MEA when radar monitoring is available to ensure obstacle clearance. Pilots may use MOCA for descent when they need the flexibility to descend before reaching the VOR, provided they remain within 22 NM of the facility.
MEA vs. MOCA
The MEA is always ≥ MOCA. The difference between them reflects the additional altitude needed to guarantee VOR reception along the full segment. In mountainous terrain, MEA and MOCA may differ by thousands of feet.