Which altitude concept is defined as the lowest altitude between radio fixes that ensures obstacle clearance and navigational signal coverage within 25 statute miles of a VOR?

• A. Minimum crossing altitude.
• B. Minimum en route altitude.
• C. Minimum obstruction clearance altitude.
• D. Minimum obstruction clearance altitude (MOCA).

Answer: (D)

MOCA, or minimum obstruction clearance altitude, is the lowest altitude between radio fixes that provides obstacle clearance and guarantees navigational signal coverage within 25 statute miles of a VOR. This means you’re assured of both terrain/obstacle protection and the ability to receive that VOR signal while you’re within 25 miles of the VOR, which is essential for reliable navigation on that segment. Beyond the 25-mile radius, MOCA’s signal coverage isn’t guaranteed, even though obstacle clearance still applies. The other concepts don’t fit this scenario: a crossing altitude is about crossing a fix safely, not the whole leg; a minimum en route altitude ensures obstacle clearance and nav signal reception along the route but isn’t limited to 25 miles from a VOR; and the phrase without the 25-mile coverage qualifier doesn’t capture the specific VOR signal requirement.