"CriticalMass" wrote in
:


"Michael" wrote in message
om...
If this a/p is anything like the one I had in my prior PA-28, and my
current PA-24 before I installed the Stec system, the adjustments I
remember are behind the faceplate on the a/p head, not at the coupler.

Both have adjustments. The NAV Coupler basically sits in series with
the DG (HDG) and, if in anything but HDG mode, combines the DG error
with the CDI error (from VOR or LOC receiver, or from GPS) into a single
signal that the AP "computer" sees as a DG heading bug offset.

As I recall (and my recall is a little fuzzy), two of them are left
and right roll limit adjustments, one sets heading center, and I think
the fourth was for sensitivity of some kind. It's been a long time.

Actually, you remember pretty accurately, long time or not. That last
one is the hysterisis adjustment. It sets the "dead band" on the servo
motor (yes, in effect, making the unit more sensitive to error sooner).
Set it too low and the aircraft will wander either side of the course
line. Set it too high and you will get wing rock. In theory, there is
a correct setting in between the two. G

The "B" units have this fourth trimpot. The earlier units just used a
couple of diodes... no adjustment.

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