Slaving autopilot to a VOR?

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!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

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!

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

Well, anyway, I think what you need is something like this MITCHELL RADIO
COUPLER FOR CENTURY III AUTOPILOT
http://cgi.ebay.com/ebaymotors/ws/eB...m=2479416 829

....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.

When I had one, I nearly always used it in heading (not NAV) mode, except for
the occasional coupling with a localizer for instrument practice. Actually, I
always felt guilty using it on the localizer. It made the approach too easy.

Dave

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"

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...

You're right. In common usage, wing-leveler plus heading mode equals a two-axis
autopilot. I've always rebelled against that usage. To me an axis is
roll-pitch-yaw. Unless the autopilot controls two of those, it's a one-axis
autopilot... but I'm swimming against the tide.


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?

Dave
Remove SHIRT to reply directly.

lets see.. wing leveler and heading control... sounds close to roll and
yaw..

BT

"Dave Butler" wrote in message
...
To me an axis is
roll-pitch-yaw. Unless the autopilot controls two of those, it's a
one-axis
autopilot... but I'm swimming against the tide.

BTIZ wrote:

lets see.. wing leveler and heading control... sounds close to roll
and
yaw..

"Dave Butler wrote:

To me an axis is
roll-pitch-yaw. Unless the autopilot controls two of those, it's a
one-axis
autopilot... but I'm swimming against the tide.

Dave is correct here. The # of axes in an autopilot refers to how many
axes of _controls_ it has feedback for - i.e. one for roll/ailerons (for
wing leveling and/or heading via roll), two for pitch/elevator (for
altitude and/or climb/descent rate) and three for rudder/yaw. Almost no
small GA autopilots are more than two axis, and many are only one axis.

With one axis, you can easily control heading - when you're at cruise
speed in most small GA aircraft, and you change direction with the
ailerons in anything less than a 30 degree roll, you hardly use the
rudders at all (I said MOST). Now consider that the autopilot generally
will roll no more than 5-10 degrees, and you can see that rudder control
is not required.

Pitch as a second axis, however, is nice to have.....

--
Marc J. Zeitlin
http://marc.zeitlin.home.comcast.net/
http://www.cozybuilders.org/
Copyright (c) 2004

BTIZ wrote:
lets see.. wing leveler and heading control... sounds close to roll and
yaw..

The ones I've seen have only one servo - the ailerons. They track heading by
controlling roll.


BT

"Dave Butler" wrote in message
...
To me an axis is

roll-pitch-yaw. Unless the autopilot controls two of those, it's a

one-axis

autopilot... but I'm swimming against the tide.

Jay Honeck writes:

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?

I have a single axis autopilot (Navaid) in my homebuilt. I have it
hooked up to my Garmin 195 GPS or to my Narco 122A NAV (via a switch).
Tracking the GPS is rock solid - no hunting whatsoever. Tracking the
VOR is a roller coaster. I watch the CDI needle, and it's always
jumping around a bit, and the AP tries to follow it, even when it goes a
dot to the left, and then two seconds later, a dot to the right.

The problem is in the VOR, not the AP - if your VOR CDI needle is
jumping around a bit, so will the AP when trying to track it. If your
VOR needle stays stuck (no clue if this jumping is a function of MY
receiver or of the inaccuracy of the basic system), then you'd probably
be OK tracking with the AP.

If I track an ILS/LOC, which never jumps around on my CDI, the AP is
solid, so I know it's not the VOR/AP combination.

At any rate, if it's easy to connect, give it a try. If not, don't
bother, especially if your needle is jumpy.

--
Marc J. Zeitlin
http://marc.zeitlin.home.comcast.net/
http://www.cozybuilders.org/
Copyright (c) 2004

My STEC 20 is slaved can be slaved to my #1 VOR or to my Loran. It has front
panel selection of high and low sensitivity modes. Normally, for VOR's you'd
use the low sensitivity mode to minimize the manuevering to stay on a scalloped
signal. It flies a VOR radial just fine, no obvious hunting. It is a single
axis autopilot.

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 Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

In article tossc.53968$gr.5228519@attbi_s52, "Jay Honeck"
writes:

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

The Autocontrol III in my Archer has switches that allow it to track a VOR, the
LORAN, or the GPS. The LORAN and the GPS (Garmin 430) do a better job of
flying a heading and not wandering but I wouldn't say the the VOR is bad. If
you are tracking a VOR that is distant and the signal is weak, you might be
better to watch the needle and use the heading bug, but if you are close (30
miles) and have a good signal, there isn't much of a problem. Get a 430 though
and you will think that you are on rails!

Chuck