If no Minimum Reception Altitude (MRA) is published for an airway, what is the relationship between MEA and MRA?

The concept of Minimum Enroute Altitude (MEA) and Minimum Reception Altitude (MRA) is essential for safe navigation in instrument flight. If no MRA is published for an airway, the relationship between MEA and MRA can be understood in terms of their functions.

MEA is designed to ensure adequate obstacle clearance for aircraft operating along a route and also provides a reliable signal for navigation aids. In scenarios where no MRA is established, the MEA effectively serves to guarantee the same level of navigational reliability that would typically be provided by the MRA. Thus, the absence of a specific MRA means that the MEA must maintain enough altitude to ensure that navigation aids are receivable.

As a result, the MEA must be at least equal to the MRA because it guarantees minimum navigational signal reception as well as obstacle clearance. This equivalency helps pilots maintain safety during flight in controlled airspace, relying on available instrumentation even when specific MRA values are not published for the airway.