KAP 150 not cooperating

[WaynePierce]

I've just installed two GI 275s and I'm currently working on my IR. Yesterday I took my CFII out to lunch and flew under the hood for a little more than an hour to KCMD for lunch since my CFII is leaving to begin flying the larger planes. Anyway I did great and I said we would fly back with the AP on just to enjoy the flight. I did the normal test before take-off and everything was fine. I engaged the AP on the climb out and it was fine but after a couple thousand feet the plane started a bank to the right, and we noticed that the AP had dis-engaged. I did the AP test again and it went through everything but it would never engage again, we did this a couple of times and got the same results. I pulled the C/B and tried again with the same results. I do have issues with this A/P not being able to fly in the Nav or App mode but heading and alt hold have been flawless. It has worked every time since installing the GI 275's in both heading mode and GPSS.

Does anyone have any idea as to what to check or what to ask be checked when it goes in to annual next week? I was planning on replacing the A/P with a G 500 in the Spring when I can sell the Harley for the amount of the install but it looks like, unless one of you has something in mind that might work until then. I'm a little cash strapped after the VERY recent install of the dual GI 275s and my retirement income would love a rest in airplane spending...

[AnAngryGoose]

Was the KAP 150 reprogrammed after installing the Gi 275?

When changing from a analog HSI to a 275, you generally need to reprogram the KAP 150 using a terminal software provided by BK. It is easy to overlook in the manuals. Give me a few and I will try to find it.

[AnAngryGoose]

Also, be sure your setting for HSI Type on the 275 is "King KI 525" and NOT "NSD 360 DC"

 

This should be your other settings:

Edited October 19, 2022 by AnAngryGoose

[WaynePierce]

1 minute ago, AnAngryGoose said:

Was the KAP 150 reprogrammed after installing the Gi 275?

When changing from a analog HSI to a 275, you generally need to reprogram the KAP 150 using a terminal software provided by BK. It is easy to overlook in the manuals. Give me a few and I will try to find it.

I think so the avionics shop was setting potentiometers and discovered that the pot you get to from the front of the panel was missing and they replaced it there were two ( I think) cards for the nav and approach that would not adjust to the recommended settings. They suggested having it sent out for rebuild but at nearly half the cost of a new, modern A/P it would make sense to go new. Like I said Heading and altitude worked fine both before and afterward. 
 

[WaynePierce]

4 minutes ago, AnAngryGoose said:

Also, be sure your setting for HSI Type on the 275 is "King KI 525" and NOT "NSD 360 DC"

 

This should be your other settings:

I’ll check with the shop to be sure. I went here first before I contact them. Thank you for your guidance. 

[AnAngryGoose]

You would most likely need to adjust the pots, yes.

 

On a KAP 140 at least (not 100% on  a 150) you have to change a few settings on the KAP config module using a laptop. Potentially the pots aren't aligned quite right but not entirely sure. Definitely check in with your shop and I'd be glad to help more if needed.

[Z W]

Our KAP150 started doing something similar, at least, the immediate hard bank to the right when engaged.  The avionics shop said shipping the computer off to a specialist shop was the only option, with fixes starting at $2500+ (probably would be more in today's dollars, this was probably 3 years ago).  Put the money towards a GFC500 install instead and have been very happy with the choice.  The KAP150 is a really capable and neat autopilot until it breaks.  Then the costs quickly make it hard to justify.  The GFC500 is just a completely different class of equipment.

Hope your experience is different and it's just a setting somewhere.

[carusoam]

Nice work AAG!

It is great to see your participation on this topic!

Thanks for sharing the details!

Go MS!

Best regards,

-a-

[carusoam]

 

 

 

[carusoam]

Two threads sharing a similar topic…

-a-

[Jake@BevanAviation]

For the KAP 140 when changing from a DG to HSI they have to be reprogrammed via a laptop.  The KAP/KFC150 has sealed resistor modules that can not be re-strapped.  They are specific for the air-frame installation and the flight computer options (FD or no FD, DG or HSI).  If you went from a DG to a HSI the top resistor module would have to be changed.  Any time you change the attitude source you have realign the flight computer to the new attitude source.  This is even mentioned in the installation manual for the GI275.

When you were doing the PFT test in flight did you get the proper sequencing of lights (4 flashes of trim, 12-13 flashes of AP)?  If you did not get the sequence listed below there is something missing that the computer wants during PFT.

Things that could cause a disconnect in flight are listed below.

• Faulty disconnect switch
• Faulty return springs in the MET switch assembly not returning the switches to center.
• Faulty gyro valid relay in the GI275
• Activation of MET (manual electric trim) switch with the AP on
• Failure of the power supply monitor circuit in the KC191
• Loss of compass valid from the GI275

[carusoam]

Let’s invite @WaynePierce and @VA FLYER to see Jake’s response above…

Best regards,

-a-

[WaynePierce]

On 10/19/2022 at 8:22 AM, Jake@BevanAviation said:

For the KAP 140 when changing from a DG to HSI they have to be reprogrammed via a laptop.  The KAP/KFC150 has sealed resistor modules that can not be re-strapped.  They are specific for the air-frame installation and the flight computer options (FD or no FD, DG or HSI).  If you went from a DG to a HSI the top resistor module would have to be changed.  Any time you change the attitude source you have realign the flight computer to the new attitude source.  This is even mentioned in the installation manual for the GI275.

When you were doing the PFT test in flight did you get the proper sequencing of lights (4 flashes of trim, 12-13 flashes of AP)?  If you did not get the sequence listed below there is something missing that the computer wants during PFT.

Things that could cause a disconnect in flight are listed below.

• Faulty disconnect switch
• Faulty return springs in the MET switch assembly not returning the switches to center.
• Faulty gyro valid relay in the GI275
• Activation of MET (manual electric trim) switch with the AP on
• Failure of the power supply monitor circuit in the KC191
• Loss of compass valid from the GI275

I'm heading out to the hangar later today, I will go through the test sequence again and count flashes. This is the first time I've seen where the number of flashes actually meant something. Thank you.

[Jake@BevanAviation]

@WaynePierce if you are able to get a video of the PFT sequence that would be very helpful. 

[WaynePierce]

5 hours ago, Jake@BevanAviation said:

@WaynePierce if you are able to get a video of the PFT sequence that would be very helpful. 

I'm seeing this upon my return home from the hangar... A Millennial would have thought about doing this without being prompted, alas I am neither, a Millennial nor someone that thinks about my phone when doing things like this...

The good news is I found where this information is in my KAP 150 Pilots manual and you are exactly correct AND when I pushed the test button i got 4 trim flashes and then the AP beeped for 5 lights and it went on to flash for 8 1/2 flashes for a total of 12.5 (the .5 because it was a much shorter flash). Also, after the sequence was over I pushed the AP engage button just to see what it would do (in the hangar) and it flashed another 12.5 times then went out. So the Auto Pilot thinks everything is correct, evidently.

[Jake@BevanAviation]

@WaynePierce 12-13 flashes of the AP light should indicate a pass.  If the compass valid is inop on the GI275 it will not allow you to select any lateral guidance mode.  Basic roll only mode should still work for wings level.  On the side of the unit should be a red 4 digit stamp.  Typically it is on the back of the unit around the transducer static port.  For example 4685 would be the 46 week of 1985. 

Units made from 1993-1998 have capacitor leakage problems.  This can cause issues with the unit passing PFT or allowing it to engage.  There is also a current sense resistor in the computer that has very tight tolerance, if it falls out of tolerance it can cause issues with intermittent disconnects.  Any time I get a KC19X unit in for repair I always replace the current sense resistor as preventive maintenance.

Thom Duncan Avionics in Fayetteville is pretty sharp on the KAP/KFC150 system.  If you need a shop to troubleshoot the aircraft that would be my suggestion.  Another option would be a loaner unit, I might have something available but I would need to know what your dash number is.  If you have any questions or concerns just give me a call.

[WaynePierce]

1 hour ago, Jake@BevanAviation said:

@WaynePierce 12-13 flashes of the AP light should indicate a pass.  If the compass valid is inop on the GI275 it will not allow you to select any lateral guidance mode.  Basic roll only mode should still work for wings level.  On the side of the unit should be a red 4 digit stamp.  Typically it is on the back of the unit around the transducer static port.  For example 4685 would be the 46 week of 1985. 

Units made from 1993-1998 have capacitor leakage problems.  This can cause issues with the unit passing PFT or allowing it to engage.  There is also a current sense resistor in the computer that has very tight tolerance, if it falls out of tolerance it can cause issues with intermittent disconnects.  Any time I get a KC19X unit in for repair I always replace the current sense resistor as preventive maintenance.

Thom Duncan Avionics in Fayetteville is pretty sharp on the KAP/KFC150 system.  If you need a shop to troubleshoot the aircraft that would be my suggestion.  Another option would be a loaner unit, I might have something available but I would need to know what your dash number is.  If you have any questions or concerns just give me a call.

Well, you can't get any better guidance than this! Thank you so much. It goes in to annual next Monday, I'll check the A/P again on the way to annual and if it doesn't connect I'll figure out what my next steps are... I know the KAP 150 has some issues with at least two adjustments that the avionics shop could not get to adjust properly, he gave me the paperwork of what it should be adjusted to and what he was able to get out of the unit. I assumed these adjustments would have had something to do with the NAV and APP modes since they haven't worked since I bought the plane. The HDG and Alt. Hold have been flawless since the beginning. I just installed the two GI 275s two weeks ago and Monday was the first time the A/P hasn't worked in HDG mode.