KFC 150 Problems

[PTK]

It will fly any couse in APP mode. It will not fly an actual approach course in NAV mode.

Sometimes flying along tracking what seems to me perfectly the course with wind correction applied in NAV mode just for fun I'll put it in APP. It's pretty cool to watch uncle Otto sit up and listen and tweak to track what it now thinks is an approach course!

 

[Releew]

Wanted to provide an update.  Several weeks and I am still fighting this problem.  I have been in discussions with Auto Pilot Central who BTW are GREAT folks to deal with and have a DEEP understanding of this system.  

Long story short.....I took the plane to the local Avionics Shop.  Tech was amazed the AP computer did not have an access port to plug into for troubleshooting so in essence we either had to get out the Fluke or replace a few parts.  Fortunately, they had a spare trim servo available.  In a nutshell, just about everything pointed to the Trim Servo......BUT after swapping to a KNOWN GOOD Servo the same problem was present....4 pulses on the motor but no audible tones to indicate all good to engage the AP.  At that point I decided to pull the AP head as AP central was going to send me a loaner to troubleshoot with.  REALLY GREAT PEOPLE.  I had to remove the 530 and DME in the stack above the 150 first. When I backed out the AP head and placed a light on the connection bus-bar I noticed minor oxidation on the terminals.  I did not remove the unit as it was a PITA to get the static hose off the back of the unit.  I carefully cleaned the terminals and replaced the equipment back in the rack.  EVERYTHING worked the first time and several test afterwards!  I HATE to say this was the problem......  More test tomorrow!

Rick

[flyboy0681]

14 hours ago, Releew said:

When I backed out the AP head and placed a light on the connection bus-bar I noticed minor oxidation on the terminals.  I did not remove the unit as it was a PITA to get the static hose off the back of the unit.  I carefully cleaned the terminals and replaced the equipment back in the rack. 

Well, you know what Piloto always says.

[Andy95W]

58 minutes ago, flyboy0681 said:

Well, you know what Piloto always says.

Put WD-40 on everything?

[flyboy0681]

Just now, N1395W said:

Put WD-40 on everything?

Almost. Spray contact cleaner on everything.

[Releew]

You forgot Marvel Mystery Oil too...............  

No fix on the AP.....  Once again, sometimes it passes the pre-flight test, sometimes doesn't.  Generally good for the first flight.  Trim light blinks but no audible confirmation..... SOMETIMES!

Flew today with a different twist.  It passed all tests but wandered a few degrees past the heading (heading hold) hunting and oscillating.  Never did that before!  Changing the computer next!

Someone out there has to had experienced this problem.  Any input is appreciated.

Rick

[ZFD]

I had a similar problem earlier this summer on my 1989  M20J.  The electric trim failed and the autopilot could not hold any vertical mode.  On the ground the autopilot test failed.  The problem was intermittent.  With help from info posted mostly on this forum, I was able to trace the problem to a failed autopilot disconnect switch mounted on the pilot yoke.  Mooney was also very helpful by providing the autopilot wiring diagrams.  Switch can be ordered from Digikey, or if you prefer your local Honeywell dealer.

[kortopates]

There are just two many failure modes ranging from poor connections at the back of your tray, not including the oxidation on units card that slides in, to switch problems on the yoke and on and on.... I've been down this road before with an intermittent trim failure/disconnect. I sent my computer and both pitch and trim servos into AP Central and they were never able to find the source. After several months of ongoing effort to resolve it I finally flew to Executive Autopilots at Sacramento, CA; only after there bench testing also didn't find fault. In the end with the plane there, they found the problem pretty quickly but it wasn't something that any bench test would have resolved. They have all the specialized BendixKing test gear that enables them to plug in their test harness to the units while they are in the aircraft - then problems can be found very quickly. If I had just bit the bullet much earlier on I could have saved myself lots of $$$.

But another well learned lesson.

Sent from my iPhone using Tapatalk

[Releew]

Thanks for the info....  I did send in the AP head to AP central.  I was told it had an error trapping routine built in the firmware that could be read by a diagnostics device.  There is a port on the right side of the unit.  I did change the Trim Servo and was getting the same intermittent problem.  I am concerned it is a connector or wire on the back of a pin or harness. Waiting to see what the error report says.   I am hoping it is something very definitive in the motherboard.  AP central told me there are three different voltages required to pass the system check and they have seen this to be a problem with a few of the capacitors that were right on the boarder of being bad.

Thanks for the input.

Rick

[Releew]

To close the book on this chapter......  The problem was on the motherboard.  The Roll-Check Relay was bad.  I guess the only good that came out of this was I gained a deep understanding of the AP system!

Rick

[flyboy0681]

4 minutes ago, Releew said:

To close the book on this chapter......  The problem was on the motherboard.  The Roll-Check Relay was bad.  I guess the only good that came out of this was I gained a deep understanding of the AP system!

Rick

Other than the expense, thank goodness parts are still available for these units.

[kortopates]

1 hour ago, flyboy0681 said:

Other than the expense, thank goodness parts are still available for these units.

I am glad Rick got it fixed as well. But many critical parts are not readily available; basic electronics parts are. The Achilles heal of these systems are the electric servo motors. When the electrical motor's armature wears out you'll learn Bendix-King/Honeywell doesn't sell or produce replacement armatures. You'll need a new motor when the armature is gone. Luckily I don't need one yet, but AP Central quoted $5200 to overhaul/remanufacturer the motor. I know a couple years ago they didn't even have that option. They consider that progress but at over $5K for a little servo that's hard to fathom! 

[jonhop]

On 1/23/2016 at 5:20 PM, kortopates said:

I am glad Rick got it fixed as well. But many critical parts are not readily available; basic electronics parts are. The Achilles heal of these systems are the electric servo motors. When the electrical motor's armature wears out you'll learn Bendix-King/Honeywell doesn't sell or produce replacement armatures. You'll need a new motor when the armature is gone. Luckily I don't need one yet, but AP Central quoted $5200 to overhaul/remanufacturer the motor. I know a couple years ago they didn't even have that option. They consider that progress but at over $5K for a little servo that's hard to fathom! 

 

On 12/24/2015 at 4:26 PM, kortopates said:

 

There are just two many failure modes ranging from poor connections at the back of your tray, not including the oxidation on units card that slides in, to switch problems on the yoke and on and on.... I've been down this road before with an intermittent trim failure/disconnect. I sent my computer and both pitch and trim servos into AP Central and they were never able to find the source. After several months of ongoing effort to resolve it I finally flew to Executive Autopilots at Sacramento, CA; only after there bench testing also didn't find fault. In the end with the plane there, they found the problem pretty quickly but it wasn't something that any bench test would have resolved. They have all the specialized BendixKing test gear that enables them to plug in their test harness to the units while they are in the aircraft - then problems can be found very quickly. If I had just bit the bullet much earlier on I could have saved myself lots of $$$.

But another well learned lesson.

Sent from my iPhone using Tapatalk

Paul,

Are you back from your winter trip? I would love to stop by and discuss your lessons learned. My KAP-150 is misbehaving intermittently. Message me when you get back, so I can swing by your hanger the next time you are there...

[kortopates]

17 minutes ago, jonhop said:

 

Paul,

Are you back from your winter trip? I would love to stop by and discuss your lessons learned. My KAP-150 is misbehaving intermittently. Message me when you get back, so I can swing by your hanger the next time you are there...

Hi Jon,

Yes I am back. Iam there a lot and should be there most every day this week but text me before you make the trip to be sure. I am most likely there in the afternoons. 'll PM you with contact info. 

Edited February 9, 2016 by kortopates