Autopilot Question

[Jay Honeck]

We have the Piper Autocontrol IIIB in our '74 Pathfinder. It has worked
fairly well since Day One, failing only when our vacuum instruments each
went Tango Uniform, in the space of six weeks.

However, the "heading bug" on our DG has always off by about 10 degrees. If
we wanted to fly 180 degrees, we had to set the bug to 170 on the DG. This
was mildly annoying, but easy to work around.

When the DG died, and we got our newly rebuilt unit (from the Gyro House), I
was expecting the heading bug to be PERFECT. Well, imagine my surprise when
the NEW heading bug is ALSO off -- by exactly the same amount! We *still*
have to set the bug on 170 to fly 180!

It's apparent that there is some other adjustment out of whack. But what?

Even my A&P (who admits he's no autopilot expert) was completely surprised
that our new DG didn't fix the problem.

What the heck is up? What needs to be adjusted, if not the DG?

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

[Aaron Coolidge]

Jay Honeck > wrote:
: However, the "heading bug" on our DG has always off by about 10 degrees. If
: we wanted to fly 180 degrees, we had to set the bug to 170 on the DG. This
: was mildly annoying, but easy to work around.

Jay, did you try asking the folks at Autopilots Central? There are numerous
adjustments on the Autocontrol autopilot, some on the autopilot unit with
the on/off switch, and some on the input selector (Nav/Loc/BC/Hdg switch).

--
Aaron Coolidge (N9376J)

[JimC]

Jay,

You can adjust the bug centering. I posted a note several months back
(maybe more than a year) regarding the Autocontrol IIIB and its various
adjustments. Do a search on "Autopilot Oscillation Fixed" and you'll find
the whole posting. I've attached part of the post below covering the
location of the bug centering adjustment potentiometer.

JimC

<start>
Making the Adjustments:

The adjustments required access to 4 potentiometers located on the
front of the autopilot, behind the faceplate. Removal of the
faceplate required two tools. One Allan wrench to first remove the
roll knob, and a small screwdriver for the faceplate screws. The roll
knob screw is on the bottom of the knob, and the two faceplate screws
are visible after the roll knob is off.

The potentiometers are quite small, arranged horizontally, and are
found directly under the right rocker switch. These pots will not be
visible if you are of normal height and are sitting up in the pilot
seat. A small jeweler-type flat screwdriver is required to adjust
these pots. The pots are 20 turns for full range.

From left to right, the potentiometers adjust the following functions:
gain/threshold, left roll, heading bug centering, right roll.
<end>


"Jay Honeck" > wrote in message
news:dtuzb.213271$Dw6.776220@attbi_s02...
> We have the Piper Autocontrol IIIB in our '74 Pathfinder. It has worked
> fairly well since Day One, failing only when our vacuum instruments each
> went Tango Uniform, in the space of six weeks.
>
> However, the "heading bug" on our DG has always off by about 10 degrees.
If
> we wanted to fly 180 degrees, we had to set the bug to 170 on the DG.
This
> was mildly annoying, but easy to work around.
>
> When the DG died, and we got our newly rebuilt unit (from the Gyro House),
I
> was expecting the heading bug to be PERFECT. Well, imagine my surprise
when
> the NEW heading bug is ALSO off -- by exactly the same amount! We *still*
> have to set the bug on 170 to fly 180!
>
> It's apparent that there is some other adjustment out of whack. But what?
>
> Even my A&P (who admits he's no autopilot expert) was completely surprised
> that our new DG didn't fix the problem.
>
> What the heck is up? What needs to be adjusted, if not the DG?
>
> Thanks!
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>
>

[John Clonts]

Great post JimC-- do you know where I could get the same information about
my Century 2000?

Thanks!
John Clonts
Temple, Texas
N7NZ

"JimC" > wrote in message
...
> Jay,
>
> You can adjust the bug centering. I posted a note several months back
> (maybe more than a year) regarding the Autocontrol IIIB and its various
> adjustments. Do a search on "Autopilot Oscillation Fixed" and you'll find
> the whole posting. I've attached part of the post below covering the
> location of the bug centering adjustment potentiometer.
>
> JimC
>
> <start>
> Making the Adjustments:
>
> The adjustments required access to 4 potentiometers located on the
> front of the autopilot, behind the faceplate. Removal of the
> faceplate required two tools. One Allan wrench to first remove the
> roll knob, and a small screwdriver for the faceplate screws. The roll
> knob screw is on the bottom of the knob, and the two faceplate screws
> are visible after the roll knob is off.
>
> The potentiometers are quite small, arranged horizontally, and are
> found directly under the right rocker switch. These pots will not be
> visible if you are of normal height and are sitting up in the pilot
> seat. A small jeweler-type flat screwdriver is required to adjust
> these pots. The pots are 20 turns for full range.
>
> From left to right, the potentiometers adjust the following functions:
> gain/threshold, left roll, heading bug centering, right roll.
> <end>
>
>
> "Jay Honeck" > wrote in message
> news:dtuzb.213271$Dw6.776220@attbi_s02...
> > We have the Piper Autocontrol IIIB in our '74 Pathfinder. It has worked
> > fairly well since Day One, failing only when our vacuum instruments each
> > went Tango Uniform, in the space of six weeks.
> >
> > However, the "heading bug" on our DG has always off by about 10 degrees.
> If
> > we wanted to fly 180 degrees, we had to set the bug to 170 on the DG.
> This
> > was mildly annoying, but easy to work around.
> >
> > When the DG died, and we got our newly rebuilt unit (from the Gyro
House),
> I
> > was expecting the heading bug to be PERFECT. Well, imagine my surprise
> when
> > the NEW heading bug is ALSO off -- by exactly the same amount! We
*still*
> > have to set the bug on 170 to fly 180!
> >
> > It's apparent that there is some other adjustment out of whack. But
what?
> >
> > Even my A&P (who admits he's no autopilot expert) was completely
surprised
> > that our new DG didn't fix the problem.
> >
> > What the heck is up? What needs to be adjusted, if not the DG?
> >
> > Thanks!
> > --
> > Jay Honeck
> > Iowa City, IA
> > Pathfinder N56993
> > www.AlexisParkInn.com
> > "Your Aviation Destination"
> >
> >
>
>

[Tom Jackson]

Jim,
Sounds like you know a thing or two about autopilots.

I have a '74 Warrior, with an Autocontrol IIIB. I find the unit to be
somewhat intermittant at times, when slaved to the heading bug (I don't have
the piece that ties it into the VOR.)

Sometimes, it holds for a while, then "lets go" and the plane starts a very
slow circle to the right. If I cycle the autopilot switch on/off several
times, sometimes it starts to hold again (sometimes it doesn't.) It also
seems that the more I use it, the more reliable it gets.

I made a similar post once before, and about the only real comment I
received was someone thinking it may be in the connector on the back of the
DG.

Would any of these potentiometer adjustments help here (specifically the one
that has to do with gain/threshold?) Any other ideas?

Thanks



"JimC" > wrote in message
...
> Jay,
>
> You can adjust the bug centering. I posted a note several months back
> (maybe more than a year) regarding the Autocontrol IIIB and its various
> adjustments. Do a search on "Autopilot Oscillation Fixed" and you'll find
> the whole posting. I've attached part of the post below covering the
> location of the bug centering adjustment potentiometer.
>
> JimC
>
> <start>
> Making the Adjustments:
>
> The adjustments required access to 4 potentiometers located on the
> front of the autopilot, behind the faceplate. Removal of the
> faceplate required two tools. One Allan wrench to first remove the
> roll knob, and a small screwdriver for the faceplate screws. The roll
> knob screw is on the bottom of the knob, and the two faceplate screws
> are visible after the roll knob is off.
>
> The potentiometers are quite small, arranged horizontally, and are
> found directly under the right rocker switch. These pots will not be
> visible if you are of normal height and are sitting up in the pilot
> seat. A small jeweler-type flat screwdriver is required to adjust
> these pots. The pots are 20 turns for full range.
>
> From left to right, the potentiometers adjust the following functions:
> gain/threshold, left roll, heading bug centering, right roll.
> <end>
>
>
> "Jay Honeck" > wrote in message
> news:dtuzb.213271$Dw6.776220@attbi_s02...
> > We have the Piper Autocontrol IIIB in our '74 Pathfinder. It has worked
> > fairly well since Day One, failing only when our vacuum instruments each
> > went Tango Uniform, in the space of six weeks.
> >
> > However, the "heading bug" on our DG has always off by about 10 degrees.
> If
> > we wanted to fly 180 degrees, we had to set the bug to 170 on the DG.
> This
> > was mildly annoying, but easy to work around.
> >
> > When the DG died, and we got our newly rebuilt unit (from the Gyro
House),
> I
> > was expecting the heading bug to be PERFECT. Well, imagine my surprise
> when
> > the NEW heading bug is ALSO off -- by exactly the same amount! We
*still*
> > have to set the bug on 170 to fly 180!
> >
> > It's apparent that there is some other adjustment out of whack. But
what?
> >
> > Even my A&P (who admits he's no autopilot expert) was completely
surprised
> > that our new DG didn't fix the problem.
> >
> > What the heck is up? What needs to be adjusted, if not the DG?
> >
> > Thanks!
> > --
> > Jay Honeck
> > Iowa City, IA
> > Pathfinder N56993
> > www.AlexisParkInn.com
> > "Your Aviation Destination"
> >
> >
>
>

[Jay Honeck]

> You can adjust the bug centering. I posted a note several months back
> (maybe more than a year) regarding the Autocontrol IIIB and its various
> adjustments.

Jim, you da MAN!

I'm curious, however: You say you can't see the adjusters while sitting in
the pilot's seat, yet you also say that you adjusted them in flight, with a
safety pilot flying.

How'd you see what you were doing? I'm 6 feet tall, and less flexible
every day -- so I don't want to try anything potentially dangerous.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[James M. Knox]

"Tom Jackson" > wrote in
news:Qexzb.408939$HS4.3307083@attbi_s01:

> Sometimes, it holds for a while, then "lets go" and the plane starts a
> very slow circle to the right. If I cycle the autopilot switch on/off
> several times, sometimes it starts to hold again (sometimes it
> doesn't.) It also seems that the more I use it, the more reliable it
> gets.
> Would any of these potentiometer adjustments help here (specifically
> the one that has to do with gain/threshold?) Any other ideas?

"Let's go"? Does it actually drop off line, or just stop holding the
heading? If the former, it's probably a problem with the electromagnet
behind the switch. It can build up enough crud to keep the pull plate from
making good contact. Then the slightest vibration can sometimes cause it
to switch HDG mode off.

But I suspect that you mean that it just sometimes starts "going it's own
way." If so, and coupled with the "the more I use it the more reliable it
gets" comment, then I suspect you have an electrolytic that is shot (a very
common problem with these older units). That's going to need standard
electronic troubleshooting skills - i.e. figure out which one and replace
it.

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

[JimC]

All the information I shared came directly from those knowledgeable and
helpful folks over at Autopilots Central in Tulsa. I wish I could remember
the name of the gentleman that helped me over the phone so I could give
credit where it is due.

Give them a call and they'll likely help you out.

JimC

"John Clonts" > wrote in message
.. .
> Great post JimC-- do you know where I could get the same information about
> my Century 2000?
>
> Thanks!
> John Clonts
> Temple, Texas
> N7NZ
>
> "JimC" > wrote in message
> ...
> > Jay,
> >
> > You can adjust the bug centering. I posted a note several months back
> > (maybe more than a year) regarding the Autocontrol IIIB and its various
> > adjustments. Do a search on "Autopilot Oscillation Fixed" and you'll
find
> > the whole posting. I've attached part of the post below covering the
> > location of the bug centering adjustment potentiometer.
> >
> > JimC
> >
> > <start>
> > Making the Adjustments:
> >
> > The adjustments required access to 4 potentiometers located on the
> > front of the autopilot, behind the faceplate. Removal of the
> > faceplate required two tools. One Allan wrench to first remove the
> > roll knob, and a small screwdriver for the faceplate screws. The roll
> > knob screw is on the bottom of the knob, and the two faceplate screws
> > are visible after the roll knob is off.
> >
> > The potentiometers are quite small, arranged horizontally, and are
> > found directly under the right rocker switch. These pots will not be
> > visible if you are of normal height and are sitting up in the pilot
> > seat. A small jeweler-type flat screwdriver is required to adjust
> > these pots. The pots are 20 turns for full range.
> >
> > From left to right, the potentiometers adjust the following functions:
> > gain/threshold, left roll, heading bug centering, right roll.
> > <end>
> >
> >
> > "Jay Honeck" > wrote in message
> > news:dtuzb.213271$Dw6.776220@attbi_s02...
> > > We have the Piper Autocontrol IIIB in our '74 Pathfinder. It has
worked
> > > fairly well since Day One, failing only when our vacuum instruments
each
> > > went Tango Uniform, in the space of six weeks.
> > >
> > > However, the "heading bug" on our DG has always off by about 10
degrees.
> > If
> > > we wanted to fly 180 degrees, we had to set the bug to 170 on the DG.
> > This
> > > was mildly annoying, but easy to work around.
> > >
> > > When the DG died, and we got our newly rebuilt unit (from the Gyro
> House),
> > I
> > > was expecting the heading bug to be PERFECT. Well, imagine my
surprise
> > when
> > > the NEW heading bug is ALSO off -- by exactly the same amount! We
> *still*
> > > have to set the bug on 170 to fly 180!
> > >
> > > It's apparent that there is some other adjustment out of whack. But
> what?
> > >
> > > Even my A&P (who admits he's no autopilot expert) was completely
> surprised
> > > that our new DG didn't fix the problem.
> > >
> > > What the heck is up? What needs to be adjusted, if not the DG?
> > >
> > > Thanks!
> > > --
> > > Jay Honeck
> > > Iowa City, IA
> > > Pathfinder N56993
> > > www.AlexisParkInn.com
> > > "Your Aviation Destination"
> > >
> > >
> >
> >
>
>

[JimC]

That could be caused by a number of factors. Someone else already pointed
out the capacitors going bad with age. I usually try to start with the
least expensive "fixes" and work my way up if the problem persists. The
first thing I'd do in your situation is remove and clean all the connectors
to make sure you aren't getting intermittent connections. I have see the
IIIB do what you described due to a dirty connector on the AI. I've also
seen worn cables so that intermittent shorts were developing. If you can
reach under the panel and affect the autopilot performance by wiggling wires
you should carefully inspect the cabling.

JimC

"Tom Jackson" > wrote in message
news:Qexzb.408939$HS4.3307083@attbi_s01...
> Jim,
> Sounds like you know a thing or two about autopilots.
>
> I have a '74 Warrior, with an Autocontrol IIIB. I find the unit to be
> somewhat intermittant at times, when slaved to the heading bug (I don't
have
> the piece that ties it into the VOR.)
>
> Sometimes, it holds for a while, then "lets go" and the plane starts a
very
> slow circle to the right. If I cycle the autopilot switch on/off several
> times, sometimes it starts to hold again (sometimes it doesn't.) It also
> seems that the more I use it, the more reliable it gets.
>
> I made a similar post once before, and about the only real comment I
> received was someone thinking it may be in the connector on the back of
the
> DG.
>
> Would any of these potentiometer adjustments help here (specifically the
one
> that has to do with gain/threshold?) Any other ideas?
>
> Thanks
>
>
>
> "JimC" > wrote in message
> ...
> > Jay,
> >
> > You can adjust the bug centering. I posted a note several months back
> > (maybe more than a year) regarding the Autocontrol IIIB and its various
> > adjustments. Do a search on "Autopilot Oscillation Fixed" and you'll
find
> > the whole posting. I've attached part of the post below covering the
> > location of the bug centering adjustment potentiometer.
> >
> > JimC
> >
> > <start>
> > Making the Adjustments:
> >
> > The adjustments required access to 4 potentiometers located on the
> > front of the autopilot, behind the faceplate. Removal of the
> > faceplate required two tools. One Allan wrench to first remove the
> > roll knob, and a small screwdriver for the faceplate screws. The roll
> > knob screw is on the bottom of the knob, and the two faceplate screws
> > are visible after the roll knob is off.
> >
> > The potentiometers are quite small, arranged horizontally, and are
> > found directly under the right rocker switch. These pots will not be
> > visible if you are of normal height and are sitting up in the pilot
> > seat. A small jeweler-type flat screwdriver is required to adjust
> > these pots. The pots are 20 turns for full range.
> >
> > From left to right, the potentiometers adjust the following functions:
> > gain/threshold, left roll, heading bug centering, right roll.
> > <end>
> >
> >
> > "Jay Honeck" > wrote in message
> > news:dtuzb.213271$Dw6.776220@attbi_s02...
> > > We have the Piper Autocontrol IIIB in our '74 Pathfinder. It has
worked
> > > fairly well since Day One, failing only when our vacuum instruments
each
> > > went Tango Uniform, in the space of six weeks.
> > >
> > > However, the "heading bug" on our DG has always off by about 10
degrees.
> > If
> > > we wanted to fly 180 degrees, we had to set the bug to 170 on the DG.
> > This
> > > was mildly annoying, but easy to work around.
> > >
> > > When the DG died, and we got our newly rebuilt unit (from the Gyro
> House),
> > I
> > > was expecting the heading bug to be PERFECT. Well, imagine my
surprise
> > when
> > > the NEW heading bug is ALSO off -- by exactly the same amount! We
> *still*
> > > have to set the bug on 170 to fly 180!
> > >
> > > It's apparent that there is some other adjustment out of whack. But
> what?
> > >
> > > Even my A&P (who admits he's no autopilot expert) was completely
> surprised
> > > that our new DG didn't fix the problem.
> > >
> > > What the heck is up? What needs to be adjusted, if not the DG?
> > >
> > > Thanks!
> > > --
> > > Jay Honeck
> > > Iowa City, IA
> > > Pathfinder N56993
> > > www.AlexisParkInn.com
> > > "Your Aviation Destination"
> > >
> > >
> >
> >
>
>

[JimC]

If you crunch down a little you will be able to see the openings in the
metal that align with the potentiometers. You can fit the screwdriver, have
the safety pilot confirm that you have the correct slot, have the safety
pilot assist with flying as you make the adjustments.

Good luck,

Jim

"Jay Honeck" > wrote in message
news:cGHzb.424935$Fm2.427640@attbi_s04...
> > You can adjust the bug centering. I posted a note several months back
> > (maybe more than a year) regarding the Autocontrol IIIB and its various
> > adjustments.
>
> Jim, you da MAN!
>
> I'm curious, however: You say you can't see the adjusters while sitting in
> the pilot's seat, yet you also say that you adjusted them in flight, with
a
> safety pilot flying.
>
> How'd you see what you were doing? I'm 6 feet tall, and less flexible
> every day -- so I don't want to try anything potentially dangerous.
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>
>