<< If the approach requires a DME arc or DME distance fixes and does not have an
approved GPS or GPS/ARNAV (advanced area navigation, to be required at the
upper FL's in 2005), you're stuck. >>

Thanks for the response, Eric, but I disagree. The 2003 AIM specifically says that an en route IFR GPS can be used for flying a DME arc ( page 1-1-42 ).

Also, the following is from AOPA Safety Advisor: (http://www.aopa.org/asf/publications/sa01.pdf)

"In mid-1998, the FAA approved broad use of IFR-certified GPS as a substitute for VOR, DME, and ADF. Essentially, GPS can be used in place of DME in any situation, with just a few exceptions. You can use GPS in lieu of DME in the named fix appears in the GPS database or if the datum upon which the fix is based is in the GPS database. In other words, in you were flying a VOR-DME approach without DME aboard, the GPS can substitute if the required fixes are named and included in the GPS database or if the VOR upon which the approach is based can be found in the GPS database.

You can use GPS in lieu of ADF on an ILS for a stepdown fix or when ADF is required in a special equipment note. The only exception is this: If you don't have ADF aboard, you can't use GPS to fly an NDB approach that isn't overlaid. In other words, no ADF -- no NDB approach, unless it's also an overlay.

As long as conventional nav equipment is aboard, pilots can use an IFR-approved GPS receiver for direct IFR routings and can substitute GPS when the ground-based part of the system is off the air. The minimum condition for GPS substitution is a TSO C129 GPS receiver approved for en route or A2 operations."

I'm just an IFR student, but I interpret the above to mean that I can use my TSO C129 A2 GPS as a substitute for DME, including a step down fix on an approach, subject to the limitations. Anyone see where I am wrong?

Mike Reinath
LNC2
N3602M