Question; if a port has NDB and DME only, no RNAV approach, can you legally do a DME arrival using the NDB for azimuth guidance? I don't think you can if you are not current or have a rating on NDB. Or even the VOR out of service.
If your GPS is pzzzzzssst as said before or RAIM not available and have to go back to ground based navaids.
I think you would be stuffed, and as stated before good for alternate.
Craven.