FAA Airline Transport Pilot (ATM)Navigation, Air Traffic Control and ProceduresMedium
An airway segment has a published MEA of 6,000 feet and a published MOCA of 4,000 feet. The pilot wants to descend to the lowest altitude that guarantees both obstacle clearance and reliable navigation signal reception for the entire length of the segment. Which altitude should the pilot use?
- A6,000 feet, the MEA
- BWhatever altitude ATC happens to assign
- C4,000 feet, the MOCA
- D5,000 feet, splitting the difference
Show answer & explanationAnswer & explanation
Correct answer: A. 6,000 feet, the MEA
The MOCA only guarantees acceptable navigation signal coverage within 22 NM of the VOR; beyond that, signal reception is not assured. The MEA guarantees both obstacle clearance and navigation signal reception for the entire route segment, so 6,000 feet must be used.
Why the other options are wrong
- B. ATC assigns altitudes but the pilot must still comply with published minimums.
- C. MOCA only assures signal reception within 22 NM of the station, not the whole segment.
- D. Splitting the altitude has no regulatory basis and may not clear obstacles.
MEA vs. MOCA
MEA (Minimum Enroute Altitude) ensures obstacle clearance and navigation signal reception along an entire airway; MOCA (Minimum Obstruction Clearance Altitude) ensures obstacle clearance but only guarantees signal reception within 22 NM of a VOR.
- MEA applies for the whole route segment
- MOCA reception guaranteed only within 22 NM of VOR
- MOCA is typically lower than MEA
- Charted with 'MOCA' notation below MEA on IFR charts
Memory trick: 'MOCA is a Mini-signal, only close to home (22 NM)'