Slaving autopilot to a VOR?

A one axis autopilot is a wing leveler. It may have features that allow it
to track a radial or GPS course or even to follow a heading bug or all
three. Even then it's a one axis autopilot. A two axis autopilot does that
plus holds altitude. A three axis autopilot will also control yaw. You see
these on a lot of V tail Bonanza's or any plane that is not that stable in
yaw. Some of these planes may have two separate autopilots. The first is a
typical two axis and a second totally separate autopilot to control yaw. A
buddy of mine has that setup on his Bo.



"Jay Honeck" wrote in message
news:tossc.53968$gr.5228519@attbi_s52...
I suspect what you have is something like a Piper Autocontrol? Two axis?
You
mean it has altitude-hold?

Hmm. I thought 3-axis was altitude-hold? Whatever, all mine does is
hold
the wings level, and follow the bug...

Thanks for the tips! I'd be interested to hear from folks who have these
things -- do they hunt all over, or can that be damped?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Newps" wrote in message
...
A one axis autopilot is a wing leveler. It may have features that allow
it
to track a radial or GPS course or even to follow a heading bug or all
three. Even then it's a one axis autopilot. A two axis autopilot does
that
plus holds altitude. A three axis autopilot will also control yaw. You
see
these on a lot of V tail Bonanza's or any plane that is not that stable in
yaw. Some of these planes may have two separate autopilots. The first is
a
typical two axis and a second totally separate autopilot to control yaw.
A
buddy of mine has that setup on his Bo.



A yaw damper is a separate autopilot? Hmmm...I can see that!

On 24-May-2004, "Jay Honeck" wrote:

I suspect what you have is something like a Piper Autocontrol? Two axis?
You mean it has altitude-hold?

Hmm. I thought 3-axis was altitude-hold? Whatever, all mine does is
hold the wings level, and follow the bug...

Thanks for the tips! I'd be interested to hear from folks who have these
things -- do they hunt all over, or can that be damped?
--


Jay,

My Arrow IV has the Autocontrol III (single axis) with nav coupling
(switchable between the 2 VHF Navs). There are actually four Nav modes that
can be selected. One is standard VOR. In this setting, the AP will "chase
the needle," resulting in gentle hunting in heading when the VOR signal is
not strong. A second nav mode also does VOR tracking, but with considerable
damping of the input signal. This results in much less hunting, and thus
this mode works best when the VOR signal is not very strong. There are also
LOC and LOC Backcourse (reversed sensing) modes that do a very good job of
intercepting and tracking the localizer during ILS approaches. In all
cases, the heading bug on the DG must be set to the intended course to give
the AP a datum for intercepting and tracking the nav signal.

Even IFR, I rarely use the VOR tracking feature of the AP. Instead, I use
heading hold and monitor the VOR needle. Actually, I primarily monitor the
moving map display of our non-IFR GPS (strictly for situational awareness,
of course) and adjust the heading bug to nail the exact course. I then
verify that he VOR needle is in agreement. So far, it always has been. If
there were ever a disagreement, I would have to rely on the VOR (after
verifying with the second Nav receiver, of course).

--
-Elliott Drucker

Dave Butler wrote:
: ...but (assuming all my assumptions above are true) I predict you won't like it.
: If there's any unsteadiness at all in the VOR signal, the autopilot will
: follow the swinging CDI. There's some damping built into the coupler, but
: still... Even when the VOR signal is rock-steady, all (well, OK, 2) the
: installations I've seen will "hunt" back and forth across the centerline of the
: signal. There might be a sensitivity adjustment that will correct this.

I also predict that Jay won't like it. I have an "Autoflite I" with the NAV
coupler. When coupled to the NAV (NAV1, FWIW), the needle stays dead centered.
But, look at the ground track on the GPS! It's moving all over! Who's flying
this thing?

Seriously, unless you're right on top of the VOR, or it's a Doppler VOR
(DVOR), the radials move around. A lot, in fact. The only steady one that
I routinely fly over is JFK.

When the autopilot is coupled up to the GPS following a radial, the VOR
needle moves around. The GPS guides the airplane where the radial is
supposed to be! This can get a bit nerve-wracking, especially if you're
flying, say, V3 in the gauntlet between ORL's "B" and Cape Canaveral's
restricted areas.

--
Aaron Coolidge

Jay,
if you are thinking about hooking up a VOR why not a GPS? The outputs
can be the same depending on the head configuration.
Michelle

Jay Honeck wrote:

My autopilot (2-axis, Piper) is hooked up to my DG, via a "heading bug."
Otherwise, it's just a wing leveler.

I've been told that this autopilot has the capability of being connected to
my VORs.

Can anyone outline what's involved with connecting the two?

Thanks!



--

Michelle P ATP-ASEL, CP-AMEL, and AMT-A&P

"Elisabeth" a Maule M-7-235B (no two are alike)

Volunteer Pilot, Angel Flight Mid-Atlantic

Volunteer Builder, Habitat for Humanity

if you are thinking about hooking up a VOR why not a GPS? The outputs
can be the same depending on the head configuration.

How can I hook up my autopilot to my AvMap's outputs?

Now THAT would be useful.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay,
There are so many possibilities that only a qualified avionics person
can answer if your GPS can be hooked up to your particular Autopilot.
I can tell you how the CRJ FMS works though ;-)
Michelle

Jay Honeck wrote:

if you are thinking about hooking up a VOR why not a GPS? The outputs
can be the same depending on the head configuration.



How can I hook up my autopilot to my AvMap's outputs?

Now THAT would be useful.



--

Michelle P ATP-ASEL, CP-AMEL, and AMT-A&P

"Elisabeth" a Maule M-7-235B (no two are alike)

Volunteer Pilot, Angel Flight Mid-Atlantic

Volunteer Builder, Habitat for Humanity

"Jay Honeck" wrote in message news:Esysc.1914$eT4.92@attbi_s54...
if you are thinking about hooking up a VOR why not a GPS? The outputs
can be the same depending on the head configuration.

How can I hook up my autopilot to my AvMap's outputs?

Now THAT would be useful.

If your autopilot supports nav coupling (ie has CDI L/R input pins and
some kind of a mode button to bring this into the control loop), you
can get a converter that generates the standard CDI voltages from an
NMEA RS-232 data stream, see the Smart Coupler on
http://www.porcine.com. Looks like it could be installed in a portable
manner via some panel jack, or get the "LE" model and hide it under
the panel good ;-)

I thought about doing this for the ARC 200A Fail-o-Matic in my
Cardinal, its not much of an autopilot, but it does work fairly well
in the VOR/LOC tracking mode, so the GPS input would make it slightly
more useful in the typical VFR GPS direct-to flying. I understand
people have done this with mixed results, however, the dampening
circuits in these units were designed for twitchy VHF nav, not the
ultra-steady GPS corrections. May need to use the "high-sens" mode for
that, if it has one (the ARC units have a button for that, used when
tracking a localizer).

Martin

Martin,

How can I hook up my autopilot to my AvMap's outputs?

Now THAT would be useful.

If your autopilot supports nav coupling (ie has CDI L/R input pins and
some kind of a mode button to bring this into the control loop), you
can get a converter that generates the standard CDI voltages from an
NMEA RS-232 data stream, see the Smart Coupler on
http://www.porcine.com. Looks like it could be installed in a portable
manner via some panel jack, or get the "LE" model and hide it under
the panel good ;-)

But even it's possible technicaly, I guess nobody would let you do it, just
because the AvMap is a handheld unit (even if Jay straps it on his knee ;-)

Regards

Kai

"Kai Glaesner" wrote in message ...
Martin,

How can I hook up my autopilot to my AvMap's outputs?

Now THAT would be useful.

Porcine Smart Coupler Info snip

But even it's possible technicaly, I guess nobody would let you do it, just
because the AvMap is a handheld unit (even if Jay straps it on his knee ;-)

Yeah, this is one of those things you probably don't want to ask
about, just install the box in a semi-portable way (quick-disconnect,
zip-tied) and be done with it. Remove before annual.