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