Coupled approach?

"Roy Smith" wrote in message
...



Roy, my Saratoga has an Altiimatic IIIC autopilot. It's heading bug is
active in NAV mode also. I believe the a/p sums the bug vs DG error and the
nav error input, and attempts to null the sum. Mine also oscillates if a
sudden change is made, but not too bad for a 10 degree bug change. I have
flown only a few coupled approaches so I don't really know how it behaves on
a localizer. I remember turning it off because I could hand fly it better.

In cruise using the GPS nav input, before I engage the NAV function, I first
get established on the course in heading mode and then engage the a/p. If
there is a strong crosswind, it will still oscillate some as it hunts for
the correct heading and track offset. If I have to make a substantial turn,
I sometimes will disengage the a/p or go back to heading mode, then reengage
NAV when established.

For your specific question about correcting the 10 degree bug error, I would
probably disengage the a/p and hand fly it. If I wanted to continue the
coupled approach, I would either ignore it or just slowly tweak it back.
The way you said would probably work fine, a couple of degrees at a time.
The thing is, in a crosswind, it will fly an offset from the track (at least
mine does) to null out the bug vs heading error. So the tweaking of the bug
setting has to be slow enough so that the nav offset gets established in
addition to the heading offset. It may take too much attention to be worth
it, just make the correction when you break out and disengage the a/p.
Maybe not too good at ILS minimums, but OK for higher.

Stan