I have been trying to understand the AIM guidelines for substituting GPS for DME. My GPS is an en route and terminal IFR GPS (Apollo GX 65).

One of the restrictions says (AIM 1-1-43): "Charted requirements for ADF and/or DME can be met using the GPS system, except for use as the principal instrument approach navigation source."

It seems fairly clear that I can substitute GPS for DME during the en route and terminal phase of the flight. Where I am unclear is for the approach. For example, can I use my GPS as a substitute for DME (I do not have a DME receiver) for a VOR DME approach (assuming that I can load the fix from the data base, have a procedure if the RAIM occurs, etc.)? I am thinking yes, because the GPS is not the principal navigation source. Can anyone clear this up for me? Thanks.

Mike Reinath
360 Std. Build
N3602M