The use of a handheld GPS for
IFR enroute navigation in US controlled
airspace is not going to cause a
mountain to appear in front of you

Well, actually it could. Any navigation system which tells the pilot he
is in one place when he is actually in another, which is used by a pilot
who is in IMC, could cause the pilot to place himself in a position from
which a collision with a mountainous surprise is unavoidable. While it
is true that the navigation system did not move the mountain, the effect
on the pilot is the same.

I suppose the real risk of using^H^H^H^H^Hrelying on a VFR GPS is not
one of collision (this is a risk inherent in any navigation system) but
one of paperwork. If a pilot uses an IFR GPS and it misleads him into a
mountain of granite (or sandstone, or shale), the dead pilot can claim
that the fault does not lie with him. OTOH, if relying on a VFR GPS
causes him meet the same fate, a mountain of paperwork sufficient to
delay his appearances at the pearly gates will appear before him.

It may be that a VFR GPS which is clipped to the right part of the yoke
will provide better guidance in and among ridges than an IFR ADF. But
there is a risk, not present with an IFR installation of anything, that
the highly accurate VFR GPS unit will fall off the yoke at the wrong
moment, perhaps while outside of radar coverage, or on an approach.
There is a risk (present in VFR and IFR units) that the data displayed
is incorrect - it has happened in our aircraft (Danbury moved four
hundred miles without giving any notice to Ridgefield); IFR units are
(presumably, though only the manufacturer really knows) tested to higher
standards. There is a risk that the pilot will be unable to maintain
the more challenging scan required by certain VFR GPS "installations"
and thus will end up elsewhere than where he thought he was. Outside of
a radar environment, in hostle terrain, this could activate the ELT.

As for relying on controllers to "nudge" the aircraft back on course in
a radar environment, this would be true primarily in airspace controlled
by Steven P. McNicoll, who mever nakes mistakes. Merely human
controllers might, for any number of reasons incomprehensible to Steven,
miss something, allowing the pilot's error to terminate the flight
prematurely.

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.