(Snowbird) writes:

I can see how that would be helpful, but I'm not sure I would be that
strident about it.

Suit yourself.

We've been in a couple sticky situations IMC, and I can vouch
that the handheld GPS had great value ONLY because it was turned
on and acquired.

Interestingly, this point came up yesterday morning. I was in solid
IMC and ATC cleared me direct to a VOR that was right at the limit of
my reception range for my low altitude, so I wasn't sure whether to
trust the (still wobbly) CDI yet or to ask for vectors a little
longer. I decided to get a second opinion from my handheld GPS, but I
had to reach behind my seat, open the flight bag, turn on the GPS,
acquire satellites, and then select the VOR as a waypoint. It was a
slight pain, but nothing serious -- I had everything set up in a
couple of minutes (though I did allow a brief 10-degree heading drift
at one point).

In retrospect, I would have been better just to tune in a nearby NDB
for confirmation, since it would have taken less time and effort (even
if the GPS had already been on and acquired).

How do you keep the wings level?

You HOLD HEADING

My moving map GPS is a great help in holding heading partial
panel. I can fly partial panel with the map shut off, but
it's clearly much easier with the map, especially in nasty
conditions where the compass is waving around like a bobber
with a prizewinning Bass on the hook and the TC is vibrating.

I would trust a GPS for that only if everything else failed. With a
latency of up to several seconds to register large heading changes, it
would be an awfully messy tool for trying to keep level in turbulence
(in smooth air, almost anything will work fine).

If I lost the AI and HI, I'd use the TC (of course); if I lost the AI,
HI, and TC and still had electricity, I'd use the ADF (which responds
almost instantly to heading changes); if I lost the AI, HI, TC, *and*
ADF (i.e. total vacuum and electrical failure), it would be a coin
toss between the mag compass (which overreacts) and the handheld GPS
(which lags). With my current whiskey compass, I might choose the
GPS, but if I get around to buying a vertical-card compass, I think
I'd choose that first.

So I feel you underestimate the value of GPS for fundamental
instrument flying. JMO of course.

I'm very happy to have it available, and have no desire to go back in
time. As I mentioned earlier, I think that the handheld GPS and cell
phone are extremely valuable (and cheap) insurance, and never fly
without both in my flightbag, VFR or IFR. I think we're debating only
the finer points in the middle rather than pro/anti GPS.


All the best,


David