single pilot ifr trip tonight

Of course, the "synthetic TC" is just the GPS taking the course change delta
and displaying it graphically in a familiar way. It knows that a 3
degree/sec turn should be painted as a TC showing a standard rate turn .
You can do the same thing in your head, it's just somewhat less precise.
During the last dual flight before my ASEL checkride, my instructor failed
the instruments one by one until all I was left with was a non-moving-map
GPS, which was displaying my course as a digital readout. Even just using
this, it was possible to keep flying the plane in smooth air with the hood
on, pretty much indefinitely.

"Snowbird" wrote in message
om...
Roy Smith wrote in message
...
A friend of mine and me tried an experiement once. I put our Archer
into some unusual attitudes, and he recovered using just the synthetic
instruments on his handheld GPS (Garmin something-or-other, might have
been the 295 but I'm not sure). Conditions were night VFR, no
turbulence.

I haven't tried this yet, and I really should.

What I can say is that IME it's significantly easier to fly
a full approach partial panel at night with either my panel
moving map, or my handheld moving map, than it is with both
failed, and that this is not because it's easier to navigate
per se, but because it's easier to *keep the wings perfectly
level* in TB or chop by using the track info on either GPS
to hold a steady track. (Basically, I would hold that navigation
at its most fundamental is simply the ability to hold heading,
and that the ability to hold heading at its most fundamental
is simply the ability to keep the wings level).

Our CFI has absolutely no regard for the FAA's views on
which instruments to fail or how many *g* and we did this
very deliberatly as an emergency exercise, in order to learn
exactly how much info we extract from the moving maps and
the best setup to extract it from our particular equipment.

If he ignored pitch (let the trim take care of it)
and just used rudder to zero out rate of turn on the synthetic TC, he
did pretty well.

I don't have a "synthetic TC", but it sounds analogous to what
I learned to do in the way of zeroing the change on the track.

I'll have to see about trying it with unusual attitudes.

Best,
Sydney

In article , Dave Butler
writes:

I've owned one of the manifold-driven backup vacuum systems, and it's
marginally
OK, but I wouldn't buy one again.

I've had one pump failure and the manifold vacuum was worth twice the price!

Chuck

In article , "Ron Natalie"
writes:

Gee, my corollary was "When someone famous crashes and non-aviation oriented
people find out that you are a pilot, they're going to ask you about it."

I flew up to my family reunion in Mass. a few weeks after the JFKJr crash.
I got
asked that every time I turned around.


And they didn't like my explaination that he was mostly to blame and that you
could "get behind" and spiral and believe you were level.

Chuck

"Jeremy Lew" wrote:
Of course, the "synthetic TC" is just the GPS taking the course change delta
and displaying it graphically in a familiar way.

Of course that's all it's doing. Same with all the other synthetic
instruments it displays.

I suppose it might be mixing in some higher-order derivitives to try and
simulate the mixed yaw-roll behavior of a real TC, but I suspect there's
not enough useful resolution in the data to make that feasable.

Andrew Gideon wrote in message gonline.com...
Dan Truesdell wrote:
Thanks for the heads-up on those. I was figuring on about $2K, but $4K
would mean asking the other 4 owners to kick in $1000 for an item that
they won't use. For a 172, it's probably just as good then to get a
manifold-driven backup vacuum. Too bad the electronic AI's are not
certified for IFR (the $1500 ones, not the $6000 ones.)

Well, I'd kind of like to know whether people other than NewPS's
shop have had trouble with the RC Allen electrical AIs. I
know several pilots who have them, IIRC there are several pilots
on these groups who have them, and this is the first I've heard
that they're so incredibly shoddy that the majority of them are
useless. The people I know who have them seem to find them OK.

As far as manifold-driven backup vacuum, my issue is: between us,
DH and I have about 1000 hrs. Our collective tally is:
AI failure (new instrument, less than 1 yr old) --- one
DG failue (overhauled instrument, age 4 yrs) --- one
vacuum pump failue (about 700 hrs best guess) --- one

So backup vacuum would have helped with only 1/3 failures. Whether
this is typical overall I can't say -- wish ASF or someone would do
a survey. Hmmm, maybe I'll start on on that avionics swap Yahoo
group.

One of our club airplanes has something like this. But someone told me that
it works least well under full throttle...which means down low executing a
missed approach.
Was I told correctly?

Pretty much, but it still may be useful.

It depends upon the differential between atmospheric pressure and
manifold pressure to work. For your gyros to function happily, they
need about
4" of pressure. So if you're powered back, *shooting* an approach, it
should be helpful. If you're at 8,000 ft with atm. pressure about
22",
you may not be able to throttle back enough to get it to work
adequately
and maintain altitude. Likewise full throttle, going around on a
missed
approach, it may not work well at all (but, it may give you a better
chance to shoot an approach you can land from).

IIRC part of the installation (and the later AD) is to establish a
chart of power settings for adequate operation in the plane in which
its installed. Your club plane should have this lurking around in the
paperwork, and it should give you a good understanding of when and
to what degree it's likely to be helpful.

HTH,
Sydney

"Roy Smith" wrote in message
...
"Jeremy Lew" wrote:
Of course, the "synthetic TC" is just the GPS taking the course change
delta
and displaying it graphically in a familiar way.

Of course that's all it's doing. Same with all the other synthetic
instruments it displays.

Well, the fake altimiter and fake "airspeed" indicator are not concerned
with the course delta, but your point is (I think) that everything is
derived from the 2D or 3D position data over time. I wonder too how much
intelligence they have tried to give those fake instruments. They must be
smoothed, if nothing else, to make up for position error jitters. Does WAAS
make them any better? Dunno. It seems like someone should be combine a GPS
with a cheap accelerometer and come up with a servicable backup panel.

"Jeremy Lew" wrote:
Well, the fake altimiter and fake "airspeed" indicator are not concerned
with the course delta, but your point is (I think) that everything is
derived from the 2D or 3D position data over time.

Yes, obviously. My apologies for being sloppy.

It seems like someone should be combine a GPS
with a cheap accelerometer and come up with a servicable backup panel.

Given that I can buy a Garmin eTrex for $100, I have to assume the basic
GPS sensor engine is pretty cheap. The obvious next step would be a GPS
in each wingtip and one in the tail and trying to derive pitch, bank,
and heading from those three 3D data points.

Some day, we'll all be flying GPS/INS/FMS/FADEC computer planes. I
suppose by that time all the fun will be gone :-)

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

Newps wrote in message news:govqb.129678$Fm2.107682@attbi_s04...
Dan Truesdell wrote:
the few short
forays into the clouds lead me to investigate an electric AI. Although
we were only in the bumpy stuff for a few minutes at a time,

Now that the FAA has finally relented and allowed you to throw away your
turn coordinator and get a second AI I went and talked to my local
avionics shop about the RC Allen electric AI that I see advertised for
about $1800. They said don't bother as 90% of them come back because
they are so horribly built. They told me to get the reliability of a
vacuum AI it's gonna take about $4000.

Why are the electric AI's so poor? I hear this frequently on the
newsgroup.

OTOH, one rarely hears about people complaining of TCs.

Is it the extra dimension of rotation that causes the problem? Or is
just RC Allen's design/mfg?

-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