Roy,

You need to always be sure to give the aircraft a heading
that will actually provide an intercept else it will never go
from ARM to CPLD. Sounds like there is a small offset
in that detector given that you got a couple soon as you
cycled NAV. It is very rate sensitive... it will go to
CPLD when the needle is not nearly centered if the needle is moving
fast
toward the center. If the needle is moving slowly, it will have
to be centered or even a bit past center. The reason is that
the crosswind integrator is only sort of shorted out during
this ARM- capture phase of flight.

When you go to CPLD, the yellow arrow
becomes the course datum.

Note that you can even intercept from FD-APR-ARM mode--wing
leveling only. Heading does not have to be selected to effect the
coupling--but the airplane needs to be aimed so as to
acheive an intercept.

The tip of the day is to always use APR mode when coupling to
your GPS, even enroute. NAV mode is dumbed down
considerably to make crossing over VOR stations less
traumatic. APR doesn't suffer that, and since the GPS
course needle is rock solid APR works great with sharp,
precise coupling. You can fly a T shaped GPS approach
without ever decoupling it-- just feed the new headings in as
cued by the cnx-80.

There's a lot to learn about the KFC-200. Maybe the POH smart-
asses know what it does when the HSI is failed:
answer is that it will either cancel everything or just ignore
the heading bug, depending on how it's wired. Most cancel
everything if heading reference is lost and any mode requiring
heading is selected. But you can turn
FD and ALT modes back on and it will wing-level at a constant
altitude which can be very useful if you are trying to figure
out what to do after a gyro failure. Explore this by pulling
out the HSI breaker.

Have you completely figured out the pitch modes?

Bill Hale BPPP instructor.




Roy Smith wrote:
My club just got a very nicely equipped Bonanza with a King KFC-200
A/P system installed (along with a CNX-80 GPS). I think I've got most
of it figured out, but yesterday something happend which I didn't
understand.

The active leg in the GPS was a course of about 230, with a stiff wind
from the south. I was about 2.5 miles right of course, and 30 miles
from the next waypoint. I put the course pointer on 230, the heading
bug on 190, and selected FD, HDG, ALT, and AP-ON, and watched the
cross-track error on the GPS; it was decreasing slowly, so I figured I
had a nice shallow intercept angle set up. I then hit the NAV
button. The NAV and ARM lights came on, as expected.

Eventually, Otto intercepted the desired course (as indicated by the
GPS XTE going to zero and the HSI course deviation bar centering.
What I expected to happen at this point was that the HDG and ARM
lights would go out and the CPLD light would come on, and Otto would
start tracking the course. Instead, it just stayed in heading mode
with ARM lit up, slowly taking us left of course. When I recycled the
NAV button, it instantly went into coupled mode and started tracking.

Is my understanding of how ARM/CPLD works in error? Is it possible
that the very shallow intercept angle I had set up (just a couple of
degrees) had somehow fooled the coupling trigger circuitry?