single pilot ifr trip tonight

(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.

This information is very valuable as a cross-check to the flight
instruments.

Agreed, but I don't think I'm a good enough pilot to use it safely in
a partial-panel situation, where I'm already under a great deal of
stress. I'd probably keep the GPS just on a basic navigation display,
and even then, only if I wasn't able to talk to ATC. My preference
(of course) would be vectors with nice shallow no-gryo turns, so all I
had to worry about was basic flying.

In IMC - I'll take any clue available that indicates something is
wrong with the gryo instruments. I'm confident I can fly partial
panel, but detecting the failure mode is the difficult part...

My only vacuum failure so far was in night VMC, but it was impossible
to miss the big orange annuciator light right above the altimeter --
even my passenger saw it immediately. I never thought of the
importance of having altimeter/oil/vacuum annunciators inside my main
scan when I was shopping for planes, but I'm certainly glad now that I
have it in my Warrior.

Of course, the best insurance is just keeping all the primary
instruments in your scan. Annunciator bulbs can burn out (though I
test them in every preflight).

I have flown approaches under the hood with reference to only the GPS
(this is in a PA28 which is a reasonably stable aircraft). While not
easy it is do-able as long as the plane is trimmed before the approach
and control inputs are kept minimal.

How rough was the air? I wouldn't mind trying it in nice, smooth
stratus or even in light chop, but I wouldn't have wanted to count on
it in some of the cumulus I was flying through this weekend.

Regarding the distraction of setting up a GPS upon the failure. I
think it is significant. I've had a similar situation - an electrical
failure at night (fortunately in MVFR conditions). This was in class
D airspace. Tower called and let me know they lost the transponder.
When I keyed the mic to transmit, the panel went black. This happened
directly over the field. By the time I got the flashlights setup,
grabbed the handheld radio (backseat), plugged in the headset, turned
on, tuned in, and let tower know what was going on - I was 5-6 miles
North (about 3 minutes in the Cherokee).

If or when I'm ever in an emergency, I won't appreciate being
second-guessed afterwards, so I'll try not to do that now, but I do
like to learn from people who have been in real emergency situations.
At the time, what was your motivation for plugging in the handheld,
etc., rather than just landing NORDO? Would you make the same
decision again?

The workload during these few minutes was relatively high.
Significant enough that I revamped how I approach IFR flying. I do
not fly hard IFR at night, and I always keep the handheld charged and
ready to go in the side pocket.

I'm starting to wonder if my handheld was worth the money, since its
transmission range is so small without an external antenna. I'm
thinking of getting a pass-through cell-phone headset adapter instead,
since I'll be able to reach help much quickly (and can keep ATC and
FSS emergency numbers on the speed-dial).


All the best,


David

"David Megginson" wrote:
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.

May I suggest that you try it under the hood? I've found that it makes
flying my airplane no-gyro very easy. That may not be true of higher
performance airplanes, I haven't tried it in one.

This information is very valuable as a cross-check to the flight
instruments.

Agreed, but I don't think I'm a good enough pilot to use it safely in
a partial-panel situation, where I'm already under a great deal of
stress.

Try it. I think you'll find it reduces the stress.
--
Dan
C172RG at BFM

"Dan Luke" writes:

May I suggest that you try it under the hood? I've found that it makes
flying my airplane no-gyro very easy. That may not be true of higher
performance airplanes, I haven't tried it in one.

Personally, the only time I've found flying under the hood or foggles
useful was on cloudy nights over relatively unpopulated terrain --
otherwise, the light and shadows in the airplane make the hood even
less effective at simulating IMC flight than a flight simulator on my
home computer. I recognize that other pilots may have different
experiences, of course, but that's one of the reasons I took my IFR
flight test in IMC, so that I would know if the examiner thought I was
safe in the real thing.

Agreed, but I don't think I'm a good enough pilot to use it safely
in a partial-panel situation, where I'm already under a great deal
of stress.

Try it. I think you'll find it reduces the stress.

I'm worried that it might reduce the stress a little too much, causing
me to fixate on it and ignore the TC and ASI, but I will try it some
time with an instructor or safety pilot anyway.


Thanks, and all the best,


David

I think the point of Dan's question was to inquire whether you have tested
your theory that a GPS-derived HSI's lag is 'dangerous' or not. Everything
I've read suggests that it's perfectly possible to keep the plane upright
using this, although you'll tend to oscillate around your intended attitude
a bit because of the lag. I have a Garmin 196 which has this kind of setup,
but I have not really tried to use it as my primary instrument. I'm going to
do that test soon.

"David Megginson" wrote in message
...
"Dan Luke" writes:

May I suggest that you try it under the hood? I've found that it makes
flying my airplane no-gyro very easy. That may not be true of higher
performance airplanes, I haven't tried it in one.

Personally, the only time I've found flying under the hood or foggles
useful was on cloudy nights over relatively unpopulated terrain --
otherwise, the light and shadows in the airplane make the hood even
less effective at simulating IMC flight than a flight simulator on my
home computer. I recognize that other pilots may have different
experiences, of course, but that's one of the reasons I took my IFR
flight test in IMC, so that I would know if the examiner thought I was
safe in the real thing.

Agreed, but I don't think I'm a good enough pilot to use it safely
in a partial-panel situation, where I'm already under a great deal
of stress.

Try it. I think you'll find it reduces the stress.

I'm worried that it might reduce the stress a little too much, causing
me to fixate on it and ignore the TC and ASI, but I will try it some
time with an instructor or safety pilot anyway.


Thanks, and all the best,


David

"Jeremy Lew" wrote in message ...
I think the point of Dan's question was to inquire whether you have tested
your theory that a GPS-derived HSI's lag is 'dangerous' or not. Everything
I've read suggests that it's perfectly possible to keep the plane upright
using this, although you'll tend to oscillate around your intended attitude
a bit because of the lag. I have a Garmin 196 which has this kind of setup,
but I have not really tried to use it as my primary instrument. I'm going to
do that test soon.

I've heard good things about it, but IMO a simple
GPS moving map is very helpful partial panel,
especially if a 'direct to' button has set up
a courseline. It is not a primary instrument,
and I would not want to depend upon it to keep
the plane upright, but in any kind of rough air
where the compass and TC are bobbing a mad dance
it is very helpful in assessing how well I am
doing at holding heading (ie, at keeping the
wings level).

Obviously other people's milage can vary, and does

Sydney

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

(Nathan Young) writes:

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.

The lag is time, not heading. How long does it take a heading change
to register? I've heard that it's at least a second on the 196, and
sometimes two seconds or more on the 295, but I don't own either.


All the best,


David

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

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.

The lag is time, not heading. How long does it take a heading change
to register? I've heard that it's at least a second on the 196, and
sometimes two seconds or more on the 295, but I don't own either.

It is probably a 1 or 2 sec update rate. That is often enough to
detect and display heading changes of a degree or two (as long as bank
angle is kept reasonable). The 'lag' is roughly equivalent to the
update rate. Ie, the GPS updates every second, and is showing you
position, heading, velocity derived from the t and t-1 epoch.

Most GPS engines are running faster than the display rate. GPS
engines from 5-10 years ago operated on 1 or 2 sec position updates.
Newer engines are more granular, with 5Hz operation being common.
That means the display data shown is typically derived from the
velocity/heading calculated from the time 1 and 1.2 seconds in the
past.

-Nathan

(Nathan Young) writes:

It is probably a 1 or 2 sec update rate. That is often enough to
detect and display heading changes of a degree or two (as long as bank
angle is kept reasonable). The 'lag' is roughly equivalent to the
update rate. Ie, the GPS updates every second, and is showing you
position, heading, velocity derived from the t and t-1 epoch.

The reason I'm skeptical is that the mag compass also works fine for
holding heading in smooth air with very shallow turns: it doesn't go
to hell in a handbasket until the air gets rough, precisely the same
time the update lag in a handheld GPS could potentially also make it
difficult to use. That's why I'm interested in hearing from people
who've used it successfully in rough air, preferably at night (where
there are fewer visual cues like shadows moving over the panel).

Note that I love GPS's -- so much so, that I collect GIS data just for
fun, and have even hacked a way to get DAFIF data into a Magellan 315
from Linux.


All the best,


David

David Megginson wrote:

The reason I'm skeptical is that the mag compass also works fine for
holding heading in smooth air with very shallow turns: it doesn't go
to hell in a handbasket until the air gets rough, precisely the same
time the update lag in a handheld GPS could potentially also make it
difficult to use. That's why I'm interested in hearing from people
who've used it successfully in rough air, preferably at night (where
there are fewer visual cues like shadows moving over the panel).

And that's why I'm looking for a device that acts - effectively - as a
backup AI.

I saw a couple of devices at the Expo. Both were "boxes" that plugged into
different "computers". One was a large box that plugged into what I think
was and Ipaq, and one was a small box that plugged into a "Cheeta" portable
MFD device.

I really liked the Cheeta, but I think it was the most expensive of the
solutions I saw.

Anyone have other thoughts about this?

What was the price of a panel-mounted electric AI? 4K? I wonder if I could
get the club to consider such an investment on our aircraft.

- Andrew