wrote:
OK, here's a question for those familiar with use of an IFR
certified GPS in
non-GPS approaches. The approach plate for the ILS at my home
airport (PAE)
plainly states "ADF REQUIRED". The reason is that the missed
approach
procedure calls for intercepting and tracking inbound on a specific
heading
to the LOM. In looking over a bunch of approaches it is clear to me
that
there are a number of ILSs that carry the ADF REQUIRED indication.
My
question is, can an approach certified GPS (legally) be used in lieu
of an
ADF for navigational guidance in a segment of an ILS procedure that
nominally requires an ADF? If so, how?

From the AIM 1-1-20 f.:
6. Restrictions
(a) GPS avionics approved for terminal IFR operations may be used in
lieu of ADF and/or DME....
[snip]
(f) Charted requirements for ADF and/or DME can be met using the GPS
system, except for use as the principal instrument approach navigation
source. [unless, of course, the approach is charted as an "overlay"
approach].

To do this in the case you describe, I would press the the "direct"
button on the KLN-90B and enter the identifier for the LOM as the
waypoint. I would then have to press "enter" twice, set the GPS to OBS
mode, set the CDI scale to one mile and turn the OBS to the missed
approach course setting on the approach plate.

If I were really flying this approach, I would have already done this
stuff before I ever commenced the approach. It's really the same thing
as tuning in a VOR and setting the OBS on a conventional NAV radio.
More accurate than using the ADF and easier to fly. Oh yeah, and I
would *still* have my ADF tuned to the LOM and be watching it, too.
--
Dan
C172RG at BFM