ED-57A supersedes ED-57 “MPS for Distance Measuring Equipment (DME/N and DME/P) (Ground Equipment)”, issued in December 1986.
This document contains the Minimum Operational Performance Standards (MOPS) for Distance Measuring Equipment (DME/N and DME/P) (Ground Equipment).

The standard has been updated to bring it in line with equipment capabilities of DME/N while maintaining compatibility with ICAO Annex 10. The update reflects the capabilities of the airborne equipment that allow the reversion to RNP procedures using DME/DME positioning. This would allow to continue using the RNP procedures even during an outage of the GNSS. The specifications related with DME/P have not been changed.

A DME ground equipment conforming with this minimum performance specification will be compliant with the International Civil Aviation Organisation Standards and Recommended Practices of Annex 10, Volume I, paragraph 3.5. This compliance with ICAO Annex 10 also ensures compliance with ITU spectrum regulations.

The MOPS covers performance requirements, system characteristics, equipment characteristics, and general guidelines, test set-ups and application notes that may be helpful to define procedures to demonstrate compliance with requirements. The document lists the main changes introduced in ED-57A in comparison to the first edition of ED-57 published in December 1986.