Autopilot Question

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"