To get a quick idea of the potential cost go out to an open part of the
airport away from buildings and get the plane set up just like you would
be flying it, everything turned on, all the avionics on, GPS on and
booted up, etc. Tune up 121.5 on your comm and hold down the PTT for 20
seconds, no need to say anything. If at any time your GPS flags then
you're in for some expense. There are about 10-12 freqs that your
avionics guy will have to do this test on, 121.5 is one of them. A GPS
flag is not allowed on any of them, if it does then things will have to
be rearranged until it doesn't flag. Might be as simple as a filter on
the GPS coax. Might be as expensive as new comm antennas, moving
antennas, etc. Guy on the field here spent over $3K just to pass this
one test.




Matt Young wrote:
The flying club that I am in just purchased a second 172, a really nice
plane, new interior and paint and a nearly new STCd 180hp engine.
Anyway, it has a IImorrow (or Apollo?) 2001 NMS GPS installed. It is
not IFR certified, but pages I've found about it online seem to indicate
that it can be. Does anyone know what exactly is the difference between
a certified and non certified install (other than $$$)? What would be
necessary to make it certified for IFR operations?