A pilot is flying an IFR flight at 7,000 feet MSL. The en route low-altitude chart shows an airway segment with a Minimum En Route Altitude (MEA) of 6,000 feet and a Minimum Obstruction Clearance Altitude (MOCA) of 5,500 feet. The grid Minimum Off-Route Altitude (MORA) for the area is 8,000 feet. The pilot's GPS receiver fails. What is the lowest altitude the pilot can descend to while remaining on the airway, assuming VOR reception is adequate?
- A6,000 feet MSL.
- BMaintain 7,000 feet MSL until further instruction from ATC.
- C8,000 feet MSL.
- D5,500 feet MSL.
Show answer & explanationAnswer & explanation
Correct answer: A. 6,000 feet MSL.
The MEA (Minimum En Route Altitude) guarantees both obstacle clearance and navigation signal reception along the entire segment. The MOCA only guarantees obstacle clearance and navigation signal reception within 22 nautical miles of the VOR. Since the pilot's GPS failed, they must rely on VOR navigation and therefore must maintain the MEA to ensure both obstacle clearance and signal reception along the entire airway segment.
Why the other options are wrong
- B. While maintaining current altitude is generally a good initial response to equipment failure, the pilot must comply with published minimum altitudes for obstacle clearance and navigation, which would be the MEA in this case.
- C. MORA is for off-route navigation and does not apply when on a published airway.
- D. MOCA only guarantees signal reception within 22 NM of the VOR, which is insufficient for entire airway segment navigation.
MEA vs. MOCA (En Route)
MEA (Minimum En Route Altitude) guarantees obstacle clearance and navigation signal coverage along the entire airway segment. MOCA (Minimum Obstruction Clearance Altitude) guarantees obstacle clearance and navigation signal coverage only within 22 NM of the VOR.
- MEA: full segment obstacle clearance + nav coverage.
- MOCA: obstacle clearance + nav coverage within 22 NM of VOR.
- MEA is generally higher or equal to MOCA.
- MORA: off-route obstacle clearance only.
Memory trick: MEA: 'Maintains Entire Airway' coverage.