KAP140 autopilot and a KLN94 GPS question

I got my IFR rating 1 month ago and now have a license to learn.



Pont of confusion.



I enter a "direct-to" in the GPS and fly the desired track (DTK) heading
with the Heading Bug and the autopilot in heading mode to the IAF. As I
approach the IAF and engage the "APR" mode (with a flight plan and approach
loaded). The autopilot does not track the DTK (my current heading), but in
fact wants to intercept the course stored in the GPS active flight plan
(which is a different heading than I am currently tracking with DTK).



Am I correct in assuming the Autopilot wants to fly the GPS loaded flight
plan/approach in the NAV/APR mode and NOT the DTK I selected in "direct to"
in the GPS?



I am flying a C172S/G with a KAP140 autopilot and a KLN94 GPS. Assume I load
a short flight plan loaded with the first waypoint as the IAF for a GPS
approach to the destination airport. I am doing a Tower Enroute with a
Departure Procedure. I takeoff, start the DP and is handed-off to Departure
Control. I request the GPS approach and "direct" to the IAF. I am assigned
the "direct". I enter into the GPS the "direct to IAF" and get a DTK. When I
engage the APR on the autopilot, it navigates to the flight plan loaded in
the GPS and not the desired track (DTK) I am flying.

"STICKMONKE" wrote in message ...
I got my IFR rating 1 month ago and now have a license to learn.



Pont of confusion.



I enter a "direct-to" in the GPS and fly the desired track (DTK) heading with the Heading Bug and the
autopilot in heading mode to the IAF. As I approach the IAF and engage the "APR" mode (with a flight plan and
approach loaded). The autopilot does not track the DTK (my current heading), but in fact wants to intercept
the course stored in the GPS active flight plan (which is a different heading than I am currently tracking
with DTK).



Am I correct in assuming the Autopilot wants to fly the GPS loaded flight plan/approach in the NAV/APR mode
and NOT the DTK I selected in "direct to" in the GPS?



I am flying a C172S/G with a KAP140 autopilot and a KLN94 GPS. Assume I load a short flight plan loaded with
the first waypoint as the IAF for a GPS approach to the destination airport. I am doing a Tower Enroute with
a Departure Procedure. I takeoff, start the DP and is handed-off to Departure Control. I request the GPS
approach and "direct" to the IAF. I am assigned the "direct". I enter into the GPS the "direct to IAF" and
get a DTK. When I engage the APR on the autopilot, it navigates to the flight plan loaded in the GPS and not
the desired track (DTK) I am flying.



Indeed this does not sound "right"! When you say it "navigates to the flight plan", do you mean it turns to
intercept the flight plan leg instead of following the direct-to course? Which one is purple, the direct-to
course or the flight plan leg (it should be the direct-to course). I fly with a KLN94 but not the KAP140, mine
is a Century 2000. But doesn't your A/P track based on the external CDI (HSI or VOR--which do you have BTW?) ?
If it does, what does your external CDI say while this is going on-- does it agree with your GPS' CDI (and
therefore navigate with respect to the purple direct-to line)?
--
Cheers,
John Clonts
Temple, Texas
N7NZ

Yes, the autopilot appears to want to intercept the flight plan leg instead
of following the direct-to course when I engage NAV or APR on the autopilot
(heading bug and CDI set to DTK desired track). The bug and OBS is set to
the indicated DTK heading. I was told by my instructor to fly "with the bug"
in heading mode until I get very close to the DTK waypoint before I engage
NAV or APR. Is it possible that when I disengage HEADING MODE and engage NAV
or APR the autopilot is simply correcting my DTK. I have been either
disengaging the autopilot or re-engaging the heading mode when the autopilot
appears to be making a noticeable course correction.

"John Clonts" wrote in message
...

"STICKMONKE" wrote in message
...
I got my IFR rating 1 month ago and now have a license to learn.



Pont of confusion.



I enter a "direct-to" in the GPS and fly the desired track (DTK) heading
with the Heading Bug and the autopilot in heading mode to the IAF. As I
approach the IAF and engage the "APR" mode (with a flight plan and
approach loaded). The autopilot does not track the DTK (my current
heading), but in fact wants to intercept the course stored in the GPS
active flight plan (which is a different heading than I am currently
tracking with DTK).



Am I correct in assuming the Autopilot wants to fly the GPS loaded flight
plan/approach in the NAV/APR mode and NOT the DTK I selected in "direct
to" in the GPS?



I am flying a C172S/G with a KAP140 autopilot and a KLN94 GPS. Assume I
load a short flight plan loaded with the first waypoint as the IAF for a
GPS approach to the destination airport. I am doing a Tower Enroute with
a Departure Procedure. I takeoff, start the DP and is handed-off to
Departure Control. I request the GPS approach and "direct" to the IAF. I
am assigned the "direct". I enter into the GPS the "direct to IAF" and
get a DTK. When I engage the APR on the autopilot, it navigates to the
flight plan loaded in the GPS and not the desired track (DTK) I am
flying.



Indeed this does not sound "right"! When you say it "navigates to the
flight plan", do you mean it turns to intercept the flight plan leg
instead of following the direct-to course? Which one is purple, the
direct-to course or the flight plan leg (it should be the direct-to
course). I fly with a KLN94 but not the KAP140, mine is a Century 2000.
But doesn't your A/P track based on the external CDI (HSI or VOR--which do
you have BTW?) ? If it does, what does your external CDI say while this is
going on-- does it agree with your GPS' CDI (and therefore navigate with
respect to the purple direct-to line)?
--
Cheers,
John Clonts
Temple, Texas
N7NZ

Is your NAV/GPS input selector switch in NAV or GPS?
Does your aircraft have a DG or a HSI?

In my experience the NAV/GPS selector in GPS mode will attempt to get
to the purple line when you select NAV. HDG mode obviously just flies
the bug.

I believe that you should have the NAV/GPS button in GPS, and use the
autopilot's NAV mode to have it fly the flight plan (or direct-to).
It's a lot of extra work having it tell you the track to fly and then
keep fiddling with the bug to maintain it when the unit will do that
itself. The only time mine goes out of GPS-input-is-NAV-button mode
is when I'm getting vectored for an ILS and I need it to get ready to
fly the localizer, or if I'm really flying a radial.

Just out of curiosity, where are you based?

On Tue, 8 Nov 2005 21:05:54 -0800, "STICKMONKE"
wrote:

Yes, the autopilot appears to want to intercept the flight plan leg instead
of following the direct-to course when I engage NAV or APR on the autopilot
(heading bug and CDI set to DTK desired track). The bug and OBS is set to
the indicated DTK heading. I was told by my instructor to fly "with the bug"
in heading mode until I get very close to the DTK waypoint before I engage
NAV or APR. Is it possible that when I disengage HEADING MODE and engage NAV
or APR the autopilot is simply correcting my DTK. I have been either
disengaging the autopilot or re-engaging the heading mode when the autopilot
appears to be making a noticeable course correction.

"John Clonts" wrote in message
.. .

"STICKMONKE" wrote in message
...
I got my IFR rating 1 month ago and now have a license to learn.



Pont of confusion.



I enter a "direct-to" in the GPS and fly the desired track (DTK) heading
with the Heading Bug and the autopilot in heading mode to the IAF. As I
approach the IAF and engage the "APR" mode (with a flight plan and
approach loaded). The autopilot does not track the DTK (my current
heading), but in fact wants to intercept the course stored in the GPS
active flight plan (which is a different heading than I am currently
tracking with DTK).



Am I correct in assuming the Autopilot wants to fly the GPS loaded flight
plan/approach in the NAV/APR mode and NOT the DTK I selected in "direct
to" in the GPS?



I am flying a C172S/G with a KAP140 autopilot and a KLN94 GPS. Assume I
load a short flight plan loaded with the first waypoint as the IAF for a
GPS approach to the destination airport. I am doing a Tower Enroute with
a Departure Procedure. I takeoff, start the DP and is handed-off to
Departure Control. I request the GPS approach and "direct" to the IAF. I
am assigned the "direct". I enter into the GPS the "direct to IAF" and
get a DTK. When I engage the APR on the autopilot, it navigates to the
flight plan loaded in the GPS and not the desired track (DTK) I am
flying.



Indeed this does not sound "right"! When you say it "navigates to the
flight plan", do you mean it turns to intercept the flight plan leg
instead of following the direct-to course? Which one is purple, the
direct-to course or the flight plan leg (it should be the direct-to
course). I fly with a KLN94 but not the KAP140, mine is a Century 2000.
But doesn't your A/P track based on the external CDI (HSI or VOR--which do
you have BTW?) ? If it does, what does your external CDI say while this is
going on-- does it agree with your GPS' CDI (and therefore navigate with
respect to the purple direct-to line)?
--
Cheers,
John Clonts
Temple, Texas
N7NZ

STICKMONKE wrote:

I enter a "direct-to" in the GPS and fly the desired track (DTK) heading
with the Heading Bug and the autopilot in heading mode to the IAF. As I
approach the IAF and engage the "APR" mode (with a flight plan and approach
loaded). The autopilot does not track the DTK (my current heading), but in
fact wants to intercept the course stored in the GPS active flight plan
(which is a different heading than I am currently tracking with DTK).

I used to fly a lot in a C172S/G with the KAP140 and B/K KLN94. However my
memory of these units is clouded by time and a few hundred hours behind a
Garmin GNS430 and an S-TEC AP with which I now currently fly.

First off, I am confused as to why you are choosing the APR mode to fly a
GPS approach. Normally, one would use the NAV mode and be sure the NAV/GPS
switch is set to GPS.

Secondly, there are different combinations of AP key pressing that result
in the AP capturing the desired course differently. Depending on what
lateral course guidance mode (NAV or HDG) the AP has selected prior to you
hitting the APR button, your intercept will vary.

Given the potential for life-threatening mistakes, I recommend that you
take a half hour or so and read the chapter out of the KAP140 manual
discussing how to use the AP for instrument approaches. If you don't have
the manual, you can download it for free from Bendix-King. I would then
recommend that you launch with a safety pilot one CAVU day and practice
several coupled approaches.

I did this a few times to get familiar with the S-TEC/GNS430 combination of
my new aircraft and a few months later was able to confidently use the
S-TEC to fly an actual IFR approach right to minimums one night for an
Angel Flight mission.

--
Peter
























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I'm going to have to pull out the book so don't take this as gospel.
But, in your situation I would first load the approach for the
destination airport and select vectors if not doing the full approach.
This will allow you to use the heading bug for the early part of the
approach. You could also select the approach with the proper IAF fix.
This will load the waypoints you will need (IAF, FAF, Missed Approach
holding waypoint). These will display on your GPS. So, if you now want
to go to the IAF, activate the cursor, highlight the IAF and press the
direct to button. You will need to press APR on your autopilot. You
should see APR and Nav ARM. You are set up at that point. Once at the
IAF, it will capture NAV and put you on course and then capture the ILS
if that's what you are shooting. If not an ILS (ie the GPS approach),
then you will select a missed altitude, deactivate the alt button and
select a desired rate of descent by pressing the down button until you
see the negative number you want (say -700).

Don't try this alone. Like another poster, I've been off this system
for almost a year and this is from memory. Go out with an instructor
and play until you know it cold. Once that happens you will begin to
appreciate how good the KLN 94 and KAP 140 really are.

Mike