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Mark the altitude which is defined as the lowest altitude between radio navigation fixes that assures acceptable navigation signal coverage and meets obstacle clearance requirements between those fixes.
  • A
    Minimum En-route Altitude (MEA).
  • B
    Minimum Off Route Altitude (MORA).
  • C
    Minimum Sector Altitude (MSA).
  • D
    Minimum Obstacle Clearance Altitude (MOCA).

ICAO Doc 8168
The Minimum En-route Altitude (MEA) is the altitude for an en-route segment that provides adequate reception of relevant navigation facilities and ATS communications, complies with the airspace structure and provides the required obstacle clearance.

Pilots should know that MEA will assure:

  • proper reception of the navigation aids
  • two-way communication with the ATC
  • safe clearance or margin from the obstacles
  • adherence to the ATC or local procedures

"Minimum Off Route Altitude (MORA)." INCORRECT
The minimum off route altitudes named MORA is an altitude which provides 2 000 feet of terrain clearance in mountainous areas and 1 000 feet in non-mountainous regions, at the same time it provides a reference point of clearance of 10 nm from the route centreline.

"Minimum Sector Altitude (MSA)." INCORRECT
Minimum Sector Altitude named MSA is the lowest altitude which may be used which will provide a minimum clearance of 300 m (= 1000ft) above all objects located in the area contained within a sector of a circle of 46 km (=25 NM) radius centred on a radio aid to navigation.

"Minimum Obstacle Clearance Altitude (MOCA)." INCORRECT
Minimum Obstacle Clearance Altitude named MOCA is the minimum altitude for a defined segment that provides the required obstacle clearance.

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