A pilot is flying an IFR flight at 7,000 feet MSL. The en route low-altitude chart for the current segment shows an MEA of 6,000 feet and a MOCA of 5,000 feet. The aircraft's navigation receiver indicates full signal strength. What is the lowest safe altitude the pilot can descend to while maintaining IFR requirements for this segment?
- A7,000 feet MSL, as it is the current altitude.
- B6,000 feet MSL, as it is the MEA.
- CThe pilot must remain at 7,000 feet as no lower altitude has been cleared by ATC.
- D5,000 feet MSL, as it is the MOCA.
Show answer & explanationAnswer & explanation
Correct answer: B. 6,000 feet MSL, as it is the MEA.
The Minimum En Route Altitude (MEA) ensures both obstacle clearance and navigation signal reception along an airway segment. While the MOCA provides obstacle clearance, it only guarantees navigation signal reception within 22 NM of the VOR. Since the pilot is flying IFR and needs continuous navigation signal, the MEA of 6,000 feet is the lowest altitude that meets all IFR requirements (obstacle clearance and navigation signal coverage). However, the pilot cannot descend to 6,000 feet without an ATC clearance.
Why the other options are wrong
- A. While the pilot must maintain 7,000 feet unless cleared lower, the question asks for the lowest *safe* altitude *for the segment* per IFR requirements, not the cleared altitude.
- C. While true that the pilot must remain at 7,000 feet without clearance, the question is asking what the lowest *safe* altitude *for the segment* is, considering chart data, not what they are currently cleared to do.
- D. Incorrect. While MOCA provides obstacle clearance, it only guarantees navigation signal reception within 22 NM of the VOR, which may not cover the entire segment.
MEA vs. MOCA (En Route)
The Minimum En Route Altitude (MEA) provides obstacle clearance and guarantees navigation signal coverage. The Minimum Obstruction Clearance Altitude (MOCA) provides obstacle clearance but only guarantees navigation signal coverage within 22 nautical miles of a VOR.
- MEA: Guarantees obstacle clearance (1000/2000 ft) and navigation signal coverage.
- MOCA: Guarantees obstacle clearance (1000/2000 ft) but only nav signal within 22 NM of VOR.
- Pilots must fly at or above MEA for an entire segment to ensure signal coverage.
- MOCA can be used if within 22 NM of the VOR and ATC clearance is received.
Memory trick: MEA means 'Everywhere' for nav, MOCA is 'Close' to the VOR.