Flying into an airfield in Africa the other day
Was a DME Arc onto the ILS
Approaching the field I noticed the DME was U/S. Pointed this out to the captain, he acknowledged it, mentioned it to ATC, no further discussion.
GPS was Primary and the aircraft few the arc perfectly (as it was programmed to do) intercepted the ILS landed, went to the hotel. Didn't think twice about what we had just done.
A while later I realized that we had just done a DME Arc with no DME! Which led me to a discussion with another captain; our reliance and expectation of our FMS is such these days that we forget that except for RNAV approaches all other NPA are not meant to be flown by the FMS alone. So long as the chart says, VOR, DME, or NDB the said ground aid should be fully serviceable, even if we are going to let the box manage. Technically and legally speaking that is. I think.
Would anyone like to comment on this, i.e. the permissibility or impermisibility of flying approaches, or parts of approaches without the required ground aids working. Pros and Cons,
the reality vs. what the book says. 