Instrument Rating Checkride Practice Test

What is the definition of Minimum Obstruction Clearance Altitude (MOCA)?

1. The lowest altitude for IFR flights that provides clearance for obstacles

2. The minimum altitude that guarantees navigation signal coverage within a specific distance of a VOR

3. The lowest published altitude for non-radar environments

4. The minimum altitude when crossing certain NAVAIDs

The correct answer is: The minimum altitude that guarantees navigation signal coverage within a specific distance of a VOR

The definition of Minimum Obstruction Clearance Altitude (MOCA) is primarily associated with the minimum altitude that ensures adequate navigation signal coverage for aircraft flying under Instrument Flight Rules (IFR) within a certain distance of a VOR (VHF Omnidirectional Range) navigation aid. Specifically, MOCA guarantees obstacle clearance for the route segment under consideration while also ensuring that the aircraft is within the acceptable range where the navigation signals from the VOR are reliable. This is crucial for maintaining safe navigation in non-radar environments, particularly in mountainous terrain or areas with significant obstacles. The other options describe different altitudes related to navigation and safety but do not capture the full scope of the MOCA definition. For instance, while the lowest altitude for IFR flights that provides obstacle clearance pertains to overall safety, MOCA specifically identifies the altitude that combines obstacle clearance with the validity of navigation signals. Therefore, the emphasis on the relationship with the VOR’s navigation coverage is what makes this definition of MOCA accurate and essential for IFR operations.