David Megginson wrote in message ...
(Nathan Young) writes:

1. Vacuum failure -- no immediate, direct benefit from the handheld
GPS.

I disagree for several reasons. Many GPS models have the ability to
partition the main display and show an 'HSI' and groundspeed in
addition to the moving map.

That could be a nice indirect benefit, but the danger is ending up
with yet another distraction. The GPS pseudo-HSI display is much
easier to interpret but lags dangerously, while the TC and ASI are
harder to interpret but have minimal lag. I'd be nervous that in an
emergency my eyes would be drawn too much to the false security of the
GPS pseudo-HSI display instead of where they should be, on the TC and
ASI.

Your statements that the GPS lags dangerously are inaccurate (at least
wrt to the Garmin 295). The HSI updates quick enough to show heading
changes of a few degrees as long as the bank angle is kept under a
reasonable amount, say 10 degrees. Easy to do in smooth or light
turbulence.

However, I don't think you could keep the plane level (solely with
reference to the GPS) on a cumulus filled day - the kind where you
have to wrestle the airplane to stay on course/heading/altitude.

-Nathan