Autopilots and coupled approaches

[BDS]

I have a KFC-200 autopilot in the aircraft I fly and I have always been able
to fly a better approach by hand than the autopilot does. Just the other
day while out doing practice approaches to a runway with a 12 kt crosswind
on the surface and a pretty good wind gradient and turbulence from the FAF
down to DH I decided to try a coupled approach to see how it would go - the
autopilot did a lousy job compared to what could be done manually.

This is also true of the flight director. In other words, I can shoot a
more precise approach using the instruments as opposed to following the
flight director.

How does this compare with others' experiences using the autopilot or FD to
perform a precision approach?

BDS

[Peter Clark]

On Sun, 01 Apr 2007 13:15:37 GMT, "BDS" > wrote:

>I have a KFC-200 autopilot in the aircraft I fly and I have always been able
>to fly a better approach by hand than the autopilot does. Just the other
>day while out doing practice approaches to a runway with a 12 kt crosswind
>on the surface and a pretty good wind gradient and turbulence from the FAF
>down to DH I decided to try a coupled approach to see how it would go - the
>autopilot did a lousy job compared to what could be done manually.
>
>This is also true of the flight director. In other words, I can shoot a
>more precise approach using the instruments as opposed to following the
>flight director.
>
>How does this compare with others' experiences using the autopilot or FD to
>perform a precision approach?

My S-Tec 55X's and KAP140s fly dead-on when properly set up. I'd have
an avionics shop check the rigging on your control lines for proper
tension, and also the tension on the servo clutches and startup
voltages. I had a problem with pitch porpoise in a 55X which turned
out to be rigging being about 60% of rated tension, cleared right up
after they adjusted the cable tensions and checked the clutch torque.

[Viperdoc[_4_]]

I have a KFC-200 with FD as well. When it's gusty it does seem a little slow
on the response, and hunts a little. With smooth or constant winds it tracks
a glideslope like it's on rails.

It used to hunt a little in pitch, and I needed the cables tightened a
little, which seemed to help.

GPS approaches (LNAV/VNAV and LPV) are even smoother, but I've had some
issues capturing the GS with the KFC-200

[BDS]

"Viperdoc" > wrote

> It used to hunt a little in pitch, and I needed the cables tightened a
> little, which seemed to help.
>
> GPS approaches (LNAV/VNAV and LPV) are even smoother, but I've had some
> issues capturing the GS with the KFC-200

Ours used to hunt in pitch as well but we had some work done on taking slack
out of the cables and it fixed that problem. Over the years I've had a
couple of in-flight failures of components in the system - specifically the
pitch servo and the pressure sensor, so the system has been looked at and
adjusted more than once, the most recent was in the last 2 years when the
pressure sensor failed.

Presently ours does not track the localizer very well but it does pretty
well with the GS. In the last 12 years or so I have used it almost
exclusively for enroute ops in heading and alt hold mode, and never for
approaches, but if it could be tweaked to handle the approaches better it
would be nice to have as a backup in some situations.

Probably time to have the entire system gone over.

BDS

[TheSmokingGnu]

BDS wrote:
> I have a KFC-200 autopilot in the aircraft I fly

Original or Extra Crispy?

<ducks> It's early in the morning!

:P

TheSmokingGnu

[Kingfish]

On Apr 1, 11:13 am, TheSmokingGnu
> wrote:
> BDS wrote:
> > I have a KFC-200 autopilot in the aircraft I fly
>
> Original or Extra Crispy?
>
> <ducks> It's early in the morning!
>
> :P
>
> TheSmokingGnu

I like my duck extra crispy, thank you.

Seriously, that post reeked of Mont-posting under a nom de Usenet-black