Bruce E. Haddad wrote:
The following is from
http://www.airweb.faa.gov/Regulatory...B?OpenDocument
(sorry for the long link). It's the GPS that's certified for IFR
operations. As such - the regulations controlling pilots simply states that
the equipment must be IFR certified. This circular starts to define the
certification process. You can dig further into the science for more
information.
...

AC 20-130A has come up already in response to my question. It presents
one way to install an IFR panel-mount GPS unit and get IFR approval for
it. But it says nothing about handhelds. I don't think you can
conclude that just because IFR approved installations exist that they
are required and necessary for all IFR operations.

You mentioned all sorts of stuff in you message about apporaches and
GPSs getting behind. I think all of the discussion here has only dealt
with enroute flying, not approaches.

GPS lag is also not the big deal you make it seem. Especially when
you're mostly traveling enroute in a straight line. Besides, most
modern GPSs have about a one second update rate. That's way faster
than the 12 second sweep of enroute radar and even faster than the 4.5
second sweep of approach radar. So you could make the same argument
about radar vectors.

And then you talk about errors in the GPS system. But all navaids have
errors. GPS is, in general, quite a bit more accurate than anything
but a localizer. Sure it can go bad, but all navaids have multiple
failure modes.

Peter