C Kingsbury wrote:
: Currently examining options for upgrading a 1979 172N with an IFR-certified
: GPS. We currently have two good nav/coms, M-1 Loran, and ADF that we want to
: replace.

: Goal is to find the most cost-efficient IFR GPS install to replace the ADF
: and add legal /G and DME capabilities. Keeping in mind that the plane is
: worth maybe 50k we are not going to spend 10-12k on a GNS-430 class box, so
: as I see it we have these options:

: - Northstar M-3 Approach
: - Garmin 155 or 155XL
: - King KLN-89B or KLN-90B
: - Apollo GX-50

The Northstar, Garmin, and Apollo units have database updates through
Jeppesen. Jeppesen has promised support for my M3 Approach for the forseeable
future (although they are reducing the number of "niceties" in the database
as the number of intersections swells uncontrollably). The King units
have database updates through King which is a pain.

On any of those units except the M3, you're going to have to buy a switch
and annunciator (and perhaps a CDI). This will run you $1200 on top of the
GPS. The install will be quite lengthy, as there are many wires that need
to be run between the GPS, switch, annunciator, and CDI.

A 430 does not need external switches or annunciators, and has a much
simpler wiring interface, so the install time may make up for its higher
cost.

I'd contact the shop that you'd like to do the install, and ask them for
their take on the matter. They may even have a used GPS!

FWIW, I put a Northstar M3 in my Cherokee 18 months ago. The GPS, CDI, and
wiring harness cost $1200, and installation/certification was $400.
--
Aaron Coolidge