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KAP 140 trouble



 
 
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  #1  
Old June 24th 07, 02:49 PM posted to rec.aviation.owning
Dan Luke
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Posts: 678
Default KAP 140 trouble

The B/K KAP 140 autopilot in my 2006 Cessna T-182T has a problem that is
baffling the avionics shop. The altitude capture/hold function does not work.
Here are the symptoms:

o All other functions work, including +/- vertical speed control.

o It will accept and correctly execute a vertical speed setting, but will
fly right through the target altitude.

o If Altitude Hold is engaged in level flight, it will not maintain
altitude.

o If Vertical Speed is engaged in level flight and set to "0", it will do
a fair job of maintaining altitude.

o According to the tech, the KAP 140 perpetually believes it is at 13,000
ft, and nothing will convince it otherwise. The unit has its own barometric
setting, independent of the G1000. However, the latest theory at the shop is
that it is a Garmin problem.


The tech's have spent a lot of time on the phone with Garmin and B/K,
listening to a lot of finger-pointing back and forth. They currently have
over 20 hours labor charged to the job--thank goodness it's warranty. I'm
able to fly the plane this weekend, but it goes back in the shop Monday.

Anybody have any ideas?

--
Dan

"You spend money to buy aggravation."
-Chinese proverb


  #2  
Old June 24th 07, 03:06 PM posted to rec.aviation.owning
Peter Clark
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Posts: 538
Default KAP 140 trouble

On Sun, 24 Jun 2007 08:49:05 -0500, "Dan Luke"
wrote:

The B/K KAP 140 autopilot in my 2006 Cessna T-182T has a problem that is
baffling the avionics shop. The altitude capture/hold function does not work.
Here are the symptoms:

o All other functions work, including +/- vertical speed control.

o It will accept and correctly execute a vertical speed setting, but will
fly right through the target altitude.

o If Altitude Hold is engaged in level flight, it will not maintain
altitude.

o If Vertical Speed is engaged in level flight and set to "0", it will do
a fair job of maintaining altitude.

o According to the tech, the KAP 140 perpetually believes it is at 13,000
ft, and nothing will convince it otherwise. The unit has its own barometric
setting, independent of the G1000. However, the latest theory at the shop is
that it is a Garmin problem.


The tech's have spent a lot of time on the phone with Garmin and B/K,
listening to a lot of finger-pointing back and forth. They currently have
over 20 hours labor charged to the job--thank goodness it's warranty. I'm
able to fly the plane this weekend, but it goes back in the shop Monday.


Sounds like the AP computer. Did the code download come up with any
codes? The shop did hook a laptop up to the KAP140, right?

There is no connection between the G1000 and the KAP140 outside of the
GPSS and HDG outputs. Altitude modes are all internal to the KAP140
which is why it's got a static input and you need to enter the
altitude (again) and baro (again) when making changes. Is there a
blockage in the static line heading towards the KAP140? Any other
wierd readings on the primary or secondary instruments?
  #3  
Old June 24th 07, 04:26 PM posted to rec.aviation.owning
Dan Luke
external usenet poster
 
Posts: 678
Default KAP 140 trouble


"Peter Clark" wrote:


Sounds like the AP computer. Did the code download come up with any
codes?


Don't know.

The shop did hook a laptop up to the KAP140, right?


Yes.


There is no connection between the G1000 and the KAP140 outside of the
GPSS and HDG outputs. Altitude modes are all internal to the KAP140
which is why it's got a static input and you need to enter the
altitude (again) and baro (again) when making changes.


That's what I thought. I don't see how the G1000 could have anything to do
with it.



Is there a blockage in the static line heading towards the KAP140?


Evidently not.

Any other wierd readings on the primary or secondary instruments?


Nope, all fine.

Thanks for your input. I'm looking for help asking questons when I see the
avionics shop guys tomorrow.

--
Dan
T-182T at BFM


  #4  
Old June 24th 07, 05:02 PM posted to rec.aviation.owning
Matt Barrow[_4_]
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Posts: 1,119
Default KAP 140 trouble

"Peter Clark" wrote in message
...

Sounds like the AP computer. Did the code download come up with any
codes? The shop did hook a laptop up to the KAP140, right?

There is no connection between the G1000 and the KAP140 outside of the
GPSS and HDG outputs. Altitude modes are all internal to the KAP140
which is why it's got a static input and you need to enter the
altitude (again) and baro (again) when making changes. Is there a
blockage in the static line heading towards the KAP140? Any other
wierd readings on the primary or secondary instruments?


The King A/P's, after the KFC200, have had probems with the computers.
http://avionicswest.com/articles/kno..._autopilot.htm




  #5  
Old June 24th 07, 05:17 PM posted to rec.aviation.owning
Peter Clark
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Posts: 538
Default KAP 140 trouble

On Sun, 24 Jun 2007 10:26:53 -0500, "Dan Luke"
wrote:


Thanks for your input. I'm looking for help asking questons when I see the
avionics shop guys tomorrow.


Yea, unless there's a block from the back of the T into the KAP140
(since unlike the 172 the 182 plumbs it off the back of the main
static system) there are only two things it could be, the computer, or
the pitch servo. Since it holds vertical speed modes fine, then it
seems that there's A) in fact no blockage since it wouldn't be able to
process the proper vertical speed, and B) no problem with the
pitch/trim servos. From what I can tell, they really should have just
ordered you a new KAP140 computer by now. I've not run into this
particular problem with the KAP140 but have gone through enough servos
and AP computers that this would be the only logical item left. King
sends them out without requiring the core be returned first when it's
a warranty claim. It should take about 1.5 hours to install,
including resetting the roll offsets and loading the new cert files
when the computer arrives.

Good luck.
  #6  
Old June 25th 07, 12:41 AM posted to rec.aviation.owning
Dan Luke
external usenet poster
 
Posts: 678
Default KAP 140 trouble


"Dan Luke" wrote:


Anybody have any ideas?



John Jones, a fellow Cessna Pilots Ass'n member, has put me on the right
track, I believe. The autopilot receives its altitude information via Gray
code from the Garmin transponder. If a particular line is grounded, it would
hold the autopilot at 13,000 ft.

Tomorrow I'll take this information to the avionics shop and see what they
say.

--
Dan
T-182T at BFM


  #7  
Old June 26th 07, 12:06 PM posted to rec.aviation.owning
Dan Luke
external usenet poster
 
Posts: 678
Default KAP 140 trouble


John Jones, a fellow Cessna Pilots Ass'n member, has put me on the right
track, I believe. The autopilot receives its altitude information via Gray
code from the Garmin transponder. If a particular line is grounded, it
would hold the autopilot at 13,000 ft.

Tomorrow I'll take this information to the avionics shop and see what they
say.


That wasn't it. The incorrect altitude Gray code is definitely coming from
the Garmin side.


  #8  
Old June 26th 07, 06:04 PM posted to rec.aviation.owning
Peter Clark
external usenet poster
 
Posts: 538
Default KAP 140 trouble

On Tue, 26 Jun 2007 06:06:23 -0500, "Dan Luke"
wrote:


John Jones, a fellow Cessna Pilots Ass'n member, has put me on the right
track, I believe. The autopilot receives its altitude information via Gray
code from the Garmin transponder. If a particular line is grounded, it
would hold the autopilot at 13,000 ft.

Tomorrow I'll take this information to the avionics shop and see what they
say.


That wasn't it. The incorrect altitude Gray code is definitely coming from
the Garmin side.


If the gray code coming in from the transponder was wrong it would
hold the wrong altitude, not be unable to hold altitude....
  #9  
Old June 26th 07, 06:11 PM posted to rec.aviation.owning
Matt Barrow[_4_]
external usenet poster
 
Posts: 1,119
Default KAP 140 trouble


"Peter Clark" wrote in message
...
On Tue, 26 Jun 2007 06:06:23 -0500, "Dan Luke"
wrote:


John Jones, a fellow Cessna Pilots Ass'n member, has put me on the right
track, I believe. The autopilot receives its altitude information via
Gray
code from the Garmin transponder. If a particular line is grounded, it
would hold the autopilot at 13,000 ft.

Tomorrow I'll take this information to the avionics shop and see what
they
say.


That wasn't it. The incorrect altitude Gray code is definitely coming
from
the Garmin side.


If the gray code coming in from the transponder was wrong it would
hold the wrong altitude, not be unable to hold altitude....


As a really new (four months) G1000 owner, I must thank you for your
excellent running analysis here.

Matt
--
Matt Barrow
Performance Homes, LLC.
Cheyenne, WY


  #10  
Old June 26th 07, 06:26 PM posted to rec.aviation.owning
Peter Clark
external usenet poster
 
Posts: 538
Default KAP 140 trouble

On Tue, 26 Jun 2007 10:11:22 -0700, "Matt Barrow"
wrote:


"Peter Clark" wrote in message
.. .
On Tue, 26 Jun 2007 06:06:23 -0500, "Dan Luke"
wrote:


John Jones, a fellow Cessna Pilots Ass'n member, has put me on the right
track, I believe. The autopilot receives its altitude information via
Gray
code from the Garmin transponder. If a particular line is grounded, it
would hold the autopilot at 13,000 ft.

Tomorrow I'll take this information to the avionics shop and see what
they
say.

That wasn't it. The incorrect altitude Gray code is definitely coming
from
the Garmin side.


If the gray code coming in from the transponder was wrong it would
hold the wrong altitude, not be unable to hold altitude....


As a really new (four months) G1000 owner, I must thank you for your
excellent running analysis here.


Perhaps to complete my reasoning - the original post says it drifts
off altitude when in level flight clicking ALT. AFAIK the only time
the KAP140 cares about the altimeter setting and the preselected
altitude is when it's in a capture mode, and it uses it's internal
pressure transducer to maintain altitude. Course, wouldn't be the
first time I've been wrong about the internal workings of the box, but
it's really not that big a deal to replace it and see - it's not like
there's no known history of the KAP140 computers being problematic...
 




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