Originally Posted by
alaskabob
Critical DME has to do with your RNAV Capabilities and availability for the STAR/SID. Japan has not quite embraced pure GPS navagation so for RNAV aircraft you must also have ground based navaids for backup position recognition.
That's not the way I understand it. If your FMS uses GPS you can ignore the note. But, if your FMS doesn't have GPS (old RNAV airframe), and instead uses DME/DME, then the critical DME must be operative to use the STAR or SID. KSLC, for example has the same restriction. Most of the time the terminal area has sufficient DME geometry that the note isn't required for the old pre-GPS RNAV airframes.