New GI275 install; problem with KAP150 integration

[Alangj]

We’ve just had 2 Garmin 275’s installed in our M20J 201, in the AI and HSI positions. Existing avionics at the time of the install were: KAP150, GTN650 and GTX345. Since the install, the 275’s seem to perform as expected, providing nav guidance, including glide slope and all other 275 functions, including the auto-slew. However, whenever the KAP150 is engaged, and put into heading mode, it will briefly respond to the HDG bug correctly (i.e HDG bug is moved to the left and a left turn is initiated), but it quickly assumes a much greater than standard rate turn (in excess of 30 degrees) and continues past the assigned HDG bug bearing without hesitation. It also begins a rapidly increasing descent in the turn, ignoring the altitude hold function, leading to a descending spiral. Turning the HDG bug back to counteract the turn, does not seem to correct the problem once it has been initiated. To say the least, this can be a startling development, that would be catastrophic in IMC. I was wondering if anybody has experienced anything like this after 275 install. Any suggestions would be welcome, as the plane has been essentially grounded for weeks and weeks as our installer tries to troubleshoot the problem. 

[wombat]

I don't have an answer for you, but wow, that's too bad.    Sounds like it's probably one of three things:

• A misconfiguration in the GI-275
• A wiring issue
• A tuning/thresholds issue in the KAP-150

If you had the KFC-150 it'd be easier because you'd have the flight director to check it against

 

[midlifeflyer]

Best I can offer is to discuss it with your installer. The KAP150 is not natively designed to work with the GI275s. That doesn’t mean it won’t; just that there are opportunities for miscommunication between them.

One other thing comes to mind. Is the GI275 adding GPSS capability to the 150? If so, if GPSS is on, HDG mode its looking for instructions from the 650, not following the HDG bug at all. If it has no GPS instructions, it doesn’t know what to do. That could account for the heading issues. The failure of altitude hold suggests this is not the case, but I thought it worthwhile to toss out.

[Alangj]

Thanks for the input. We wish we had the KFC150 also. We’ve tried it both with and without the GPSS function turned on in the 275 and it doesn’t seem to respond appropriately either way. Still goes into a steep turn that requires dis-engaging the AP. I am under the impression that our installer has done this exact install on other Mooneys with the KAP150, but he’s stumped too. 

[Fly Boomer]

18 hours ago, midlifeflyer said:

The KAP150 is not natively designed to work with the GI275

 

[Pinecone]

Well he DID say that the KAP150 was not designed to work with the GI-275, because the GI-275 did not exist for some 40 years or more after the KAP-150 was designed.

But this is the case with a lot of new products.  And these cases, you make the new product work with the legacy products.

So while is is true that the KAP-150 was NOT designed to work with the GI-275, it IS TRUE that the GI-275 was designed to work with the KAP-150.

 

[midlifeflyer]

49 minutes ago, Fly Boomer said:

 

I didn’t say it wouldn’t. Just that it’s not designed to natively work with a non-digital autopilot and that the ways it does work can introduce the opportunity for installation errors. That’s why I said I would discuss problems with the installer.

[LANCECASPER]

1 hour ago, midlifeflyer said:

I didn’t say it wouldn’t. Just that it’s not designed to natively work with a non-digital autopilot and that the ways it does work can introduce the opportunity for installation errors. That’s why I said I would discuss problems with the installer.

The KAP 100 & 150 and KFC 150 were some of the first digital autopilots for GA.

http://www.testflysundance.org/documents/aircraft/Cherokee/kap100-pilot-guide.pdf           page 4

[Jake@BevanAviation]

Anytime the system is over banking there is a issue with the AI information or the alignment of the system.  For example, if you rotate the heading bug 45deg right of the lubber line the aircraft should go into a 20-22 deg right bank and hold the bank until the HDG bug is approaching the lubber line.  Without the AI information the system will continue to turn to the right until you tell it to stop.  This is situation can lead to a dangerous attitude if you are not watching the bank attitude of the aircraft.  All the interconnect drawings for the system and the alignment procedure are listed in the Garmin IM.  If the shop is knowledgeable about how the GI275 is interconnected to the legacy system they will know how to test the attitude response on the ground.

The GI275 ADAHRS +AP unit is perfectly capable of driving the legacy autopilot system.  The key is knowing what information the system wants and how to get it to the system.

[OR75]

i wired several old analog system to new digital systems (DAC or G5)

i found it difficult to link the symptom to the cause. It either works or it does not.  Check that the settings are configured correctly. If they are, the harness will need to be checked and maybe rebuild if they cannot trace every single wire to the right pin       

[Bob Weber]

On 6/10/2024 at 6:44 PM, Alangj said:

We’ve just had 2 Garmin 275’s installed in our M20J 201, in the AI and HSI positions. Existing avionics at the time of the install were: KAP150, GTN650 and GTX345. Since the install, the 275’s seem to perform as expected, providing nav guidance, including glide slope and all other 275 functions, including the auto-slew. However, whenever the KAP150 is engaged, and put into heading mode, it will briefly respond to the HDG bug correctly (i.e HDG bug is moved to the left and a left turn is initiated), but it quickly assumes a much greater than standard rate turn (in excess of 30 degrees) and continues past the assigned HDG bug bearing without hesitation. It also begins a rapidly increasing descent in the turn, ignoring the altitude hold function, leading to a descending spiral. Turning the HDG bug back to counteract the turn, does not seem to correct the problem once it has been initiated. To say the least, this can be a startling development, that would be catastrophic in IMC. I was wondering if anybody has experienced anything like this after 275 install. Any suggestions would be welcome, as the plane has been essentially grounded for weeks and weeks as our installer tries to troubleshoot the problem. 

The GI 275 most certainly was designed specifically for interface with many legacy Autopilots, when properly aligned they shine!

I can assist your shop in troubleshooting this, Have them give me a call and I can point them in the right direction. 616 822 1999 mon-fri 9am-5pm Eastern.

This should be simple to correct, the GI 275 is a wonderful upgrade from the KI 256 and this is certainly not the first attempt at interfacing one to a KC 19(x) computer..

 

 

[Alangj]

Thanks everyone. Turns out my shop got it sorted out. It was a matter of calibration settings that Garmin had to supply. Test flight today a complete success. Love the new 275 units!

[Aerodon]

I might have a spare 28V KFC150, is there any merit in replacing a KAP150 with the GI275?

 

Aerodon

[drstephensugiono]

On 6/22/2024 at 8:12 AM, Aerodon said:

I might have a spare 28V KFC150, is there any merit in replacing a KAP150 with the GI275?

 

Aerodon

Aerodon , what KFC accessories do u have for sale?  Has it been verified to work 100 percent?  I may need head unit.  I’m also replacing my Sandel for 2 GI275s

[Bob Weber]

I have a fresh tagged by Bevan Aviation KC 192 -03 with rack.