KAP150 Autopilot/servo repair

[300AS]

I'm sure this topic has been covered, but I couldn't find a thread...  The pitch on my KAP 150 is going bad (pitches up for no reason and won't pitch down to capture a glideslope).  I'm not sure if it's the unit or a servo.  Can someone please recommend a shop that can troubleshot and repair the box and/or the servos? I'm in SC, so would prefer somewhere in the SE.

[M016576]

59 minutes ago, 300AS said:

I'm sure this topic has been covered, but I couldn't find a thread...  The pitch on my KAP 150 is going bad (pitches up for no reason and won't pitch down to capture a glideslope).  I'm not sure if it's the unit or a servo.  Can someone please recommend a shop that can troubleshot and repair the box and/or the servos? I'm in SC, so would prefer somewhere in the SE.

Autopilots central in Tulsa.  They are the masters- highly recommended.

I’d call them before you take your mooney anywhere- they will recommend a solid course of action that won’t break the bank.

edit- I think you might have a broken pin (feeds into the tray), or have a bad contact (between tray and unit).  You might be able to fix the issue by removing the KAP150 from the tray and cleaning the contacts (most use a pencil erasure for this).  I’d start by googling the install manual for the KAP150, and see what pins control what- then look at any potential problem contacts (pitch related) to see if it’s dirty- if you’re up for troubleshooting in this manner.

I am not an avionics tech, or an A&P, but I have dealt with some auto pilot troubleshooting over the years. 

Edited December 2, 2018 by M016576

[carusoam]

Some insight to servo motor overhaul...

https://mooneyspace.com/search/?q=Autopilot Servo overhaul&sortby=relevancy&search_and_or=and

 

and here...

 

 

[300AS]

Thank you both for some great input!

[CaptRJM]

Sparkchasers at KJNX, just south of Raleigh, is pretty darn good with BK autopilots. They have my KFC 200 humming as good as humanly possible. Call and ask for Mark, he’s the autopilot guru. 

[LANCECASPER]

11 hours ago, 300AS said:

I'm sure this topic has been covered, but I couldn't find a thread...  The pitch on my KAP 150 is going bad (pitches up for no reason and won't pitch down to capture a glideslope).  I'm not sure if it's the unit or a servo.  Can someone please recommend a shop that can troubleshot and repair the box and/or the servos? I'm in SC, so would prefer somewhere in the SE.

Before you spend a dime, call Bob Weber

https://www.beechtalk.com/forums/viewtopic.php?f=21&t=152259

 

[Diesel 10]

++ on Autopilots Central.  I have had my KFC150 down there a couple of times without the whole plane needing to be there.  There don't seem to be many remaining places in the US (or the world!) that can still service this equipment!

[carusoam]

Does APcentral have servo motor services as well?

Or where do BK servos go when their clutch is worn out?

I get the feeling... that the main elevator servo gets the most work and has the opportunity to show clutch wear first....

Following the MS theory... the most simple thing that can go wrong, will go wrong first... (What was that guy’s name?)

Best regards,

-a-

 

[M016576]

3 minutes ago, carusoam said:

Does APcentral have servo motor services as well?

I get the feeling... that the main elevator servo gets the most work and has the opportunity to show clutch wear first....

Following the MS most simple thing that can go wrong, will go wrong.... (What was that guy’s name?)

Best regards,

-a-

 

Yes- they can exchange, replace or overhaul servo motors.  The reason why I think it’s electrical is because the issue is only manifesting in one direction on a single axis- not both directions (which would indicate a worn clutch to me).  But I’m no autopilot expert... just a thought from a pilot.

could also be a gyro issue, I guess..

Edited December 3, 2018 by M016576

[carusoam]

And two-way clutches, at the end of their life, behave strangely and less predictably as well...

Nice if there were a checklist on how to inspect for wear before sending out...  

Best regards,

-a-

[Davidv]

I thought I'd just use this thread rather than starting another.  I'm also having an issue with my KAP150.  On an ILS or LPV the autopilot does a very good job of picking up the lateral but not the vertical.  As I intercept the GS the "GS" light on the AP does not come on and it does not pitch down.  Any ideas?  I was thinking a pitch servo since I get some quirkiness sometimes when setting a descent or climb with my preselect.  However, the fact that the GS light does not illuminate has me thinking it may be something else?

[carusoam]

For servo motor concerns... Beven Rabel gets mentioned a lot....

There are two servos for attitude... coarse (pitch) and fine (trim).

Let us know what you find...

Best regards,

-a-

[Davidv]

Thanks @carusoam, also curious if anyone else has had the GS not illuminate and what the outcome was?  It's connected to my Sandel 3308.

[PT20J]

2 hours ago, Davidv said:

I thought I'd just use this thread rather than starting another.  I'm also having an issue with my KAP150.  On an ILS or LPV the autopilot does a very good job of picking up the lateral but not the vertical.  As I intercept the GS the "GS" light on the AP does not come on and it does not pitch down.  Any ideas?  I was thinking a pitch servo since I get some quirkiness sometimes when setting a descent or climb with my preselect.  However, the fact that the GS light does not illuminate has me thinking it may be something else?

If MET works, the trim servo is working.

If it holds pitch when not in ALT, or altitude when in ALT, the the pitch servo is working. 

The servos, logic and lights get tested during self test.

Not getting GS light probably means that it’s not getting a glideslope signal. Since you mentioned LPV, you must have a WAAS navigator. Good place to start is to check the output of that. If you have an Aspen, the signal will come from the ACU.

Skip

[Awful_Charlie]

Do you get the GS indicator on an ILS? If so, and you consistently fail to get the GS indicator on a GNSS, then you are most likely missing a wire - from memory I think it is the 'ILS Energise' signal.

If it is intermittent then a bit more troubleshooting is going to be required to work out what it is that makes the difference between ok and not ok

[Davidv]

Thanks @Awful_Charlie, it doesn’t come on in either mode.

[Davidv]

9 hours ago, PT20J said:

If MET works, the trim servo is working.

If it holds pitch when not in ALT, or altitude when in ALT, the the pitch servo is working. 

The servos, logic and lights get tested during self test.

Not getting GS light probably means that it’s not getting a glideslope signal. Since you mentioned LPV, you must have a WAAS navigator. Good place to start is to check the output of that. If you have an Aspen, the signal will come from the ACU.

Skip

Thanks, I’ll also call Sandel and see if I’m missing a setting with them.

[Bob Weber]

14 hours ago, Davidv said:

I thought I'd just use this thread rather than starting another.  I'm also having an issue with my KAP150.  On an ILS or LPV the autopilot does a very good job of picking up the lateral but not the vertical.  As I intercept the GS the "GS" light on the AP does not come on and it does not pitch down.  Any ideas?  I was thinking a pitch servo since I get some quirkiness sometimes when setting a descent or climb with my preselect.  However, the fact that the GS light does not illuminate has me thinking it may be something else?

I can help you with this, I don't believe you have servo issues. There are some tests and questions that may help you, 616 822 1999 8am-8pm eastern time

Bob Weber

Autopilot consulting

webairconsulting.com

[PT20J]

8 hours ago, Awful_Charlie said:

Do you get the GS indicator on an ILS? If so, and you consistently fail to get the GS indicator on a GNSS, then you are most likely missing a wire - from memory I think it is the 'ILS Energise' signal.

If it is intermittent then a bit more troubleshooting is going to be required to work out what it is that makes the difference between ok and not ok

The ILS Energize signal tells the autopilot to enable the glideslope when in APR mode, so it could be a cause of the problem also. Regardless of whether it's the ILS Energize or the GS signal, it is most likely a problem of the signal getting to the autopilot.

Although it doesn't seem to fit this case, there is a possible installation goof when changing a GNS 430 to a GNS 430W. On the 430, the ILS Energize output is connected to the KC 191 ILS Energize input. On the 430W, the ILS/GPS Approach output should be connected to the ILS Energize input on the autopilot or the glideslope will only work on ILS approaches and not GPS approaches.

Skip

[Davidv]

Thanks Skip, my HSI is a Sandel 3308.  My NAV 1 is a KX-155 which feeds the ILS info to the Sandel and my GNX-375 sends the RNAV data.  Both seem to be working well visually.

[PT20J]

5 minutes ago, Davidv said:

Thanks Skip, my HSI is a Sandel 3308.  My NAV 1 is a KX-155 which feeds the ILS info to the Sandel and my GNX-375 sends the RNAV data.  Both seem to be working well visually.

It's been a few years since I flew a 3308. When  you select the Nav source on the 3308, does it also control which source feeds the autopilot? If so, there may be a problem with the connection between the HSI and the autopilot. I assume you had the GNX 375 installed recently -- did the GS ever work correctly on both ILS and GPS after installation? It's a little tricky since you have separate units for ILS and GPS and the Sandel in the mix and it might be an issue with the installation. I'd take it back to the shop that installed the 375 and have them troubleshoot it.

[Davidv]

I just spoke with Sandel and they told me that the heading bug is the only piece transmitted by their unit to the AP.  Everything else comes directly from either the radios or the GPS to the AP.  I’m going to call my installer who put in the 375 and see what they say.  

I’ll let you know what I find out.

[PT20J]

1 hour ago, Davidv said:

I just spoke with Sandel and they told me that the heading bug is the only piece transmitted by their unit to the AP.  Everything else comes directly from either the radios or the GPS to the AP.  I’m going to call my installer who put in the 375 and see what they say.  

I’ll let you know what I find out.

OK, so there has to be a switch somewhere to select the autopilot NAV input between the KX 155 or the GNX 375. It should also switch the ILS Energize input to the KC 191.

[bcbender10]

Hi all, picking up on this thread for a trim servo issue. 

Situation: Outbound leg: Power trim worked fine, KFC150 passed the a/p test. All appeared fine on climb out, but A/P failed to capture altitude set in altitude preselect. Then held altitude when I set using "ALT" on the KFC150 controller. On descent, noticed issues again. With A/P off, noticed electric trim was not working. Used manual trim which was smooth and fine to land.

Return leg: on start up, electric trim didn't work in either direction. A/P would not pass its self check. 

Seems like a trim servo issue to me. Perhaps it died? 1998 Mooney Encore. Likely given 24 years of service...

[LANCECASPER]

28 minutes ago, bcbender10 said:

Hi all, picking up on this thread for a trim servo issue. 

Situation: Outbound leg: Power trim worked fine, KFC150 passed the a/p test. All appeared fine on climb out, but A/P failed to capture altitude set in altitude preselect. Then held altitude when I set using "ALT" on the KFC150 controller. On descent, noticed issues again. With A/P off, noticed electric trim was not working. Used manual trim which was smooth and fine to land.

Return leg: on start up, electric trim didn't work in either direction. A/P would not pass its self check. 

Seems like a trim servo issue to me. Perhaps it died? 1998 Mooney Encore. Likely given 24 years of service...

@Jake@BevanAviation is the master.