FAA Aircraft Dispatcher (ADX)Navigation and ATCMedium
A dispatcher is planning a route that uses a VOR airway segment published with a Minimum Obstruction Clearance Altitude (MOCA) of 6,000 feet and a Minimum Enroute Altitude (MEA) of 7,000 feet. What is the primary limitation of operating at the MOCA rather than the MEA on this segment?
- AMOCA is only usable during VFR conditions
- BMOCA does not guarantee obstacle clearance
- CMOCA only guarantees acceptable navigation signal coverage within 22 NM of the VOR
- DMOCA provides no communication reception guarantee at any distance
Show answer & explanationAnswer & explanation
Correct answer: C. MOCA only guarantees acceptable navigation signal coverage within 22 NM of the VOR
MOCA provides obstacle clearance for the entire route segment but guarantees acceptable navigational signal coverage only within 22 nautical miles of the VOR. Beyond that distance, navigation signal reliability is not assured, even though obstacle clearance still is.
Why the other options are wrong
- A. MOCA is an IFR altitude designation and is unrelated to VFR/IFR conditions.
- B. MOCA does guarantee obstacle clearance; the limitation is signal reception distance.
- D. MOCA relates to navigation signal reception, not voice communication.
MEA vs MOCA
MEA guarantees both obstacle clearance and navigation signal reception along the entire route; MOCA guarantees obstacle clearance for the full segment but navigation signal only within 22 NM of the VOR.
- MEA: obstacle clearance + full-route signal reception
- MOCA: obstacle clearance for full segment, signal reception limited to 22 NM of VOR
- MOCA is charted with an asterisk on IFR enroute charts
Memory trick: MOCA = Only 22 miles of Clear Airwaves