"Peter Clark" wrote in message
...

OK, I'm not trying to be obtuse here, I'd really like to understand
what I'm doing wrong. I'm flying along using the GPS head to tell me
I'm on an arc (X) miles from (Y) transmitter, twisting the VOR head
every 10deg or so until I hit the leadin radial and then turn inbound
(or in the case of the DC approach see the runway or go missed). The
manual documents this scenario. The AOPA article seems to document
the same usage. Yet it's not allowed by the substitution rules?


AIM para 1-1-19.f.1.(b)(6):

"Charted requirements for ADF and/or DME can be met using the GPS system,
except for use as the principal instrument approach navigation source.

What serves as the principal instrument approach navigation source for the
ILS/DME RWY 2 at DRO? What serves as the principal instrument approach
navigation source for the VOR/DME RWY 15 at MTN?