The New Garmin GI 275 Attitude Indicator (AI/ADI)

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pietromarx
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Re: The New Garmin GI 275 Attitude Indicator (AI/ADI)

Post by pietromarx »

arksat wrote: Sun Jun 07, 2020 3:32 pm
pietromarx wrote: Sat Jan 18, 2020 5:44 am My airplane (G1000, 345R, TAS-600, GFC-700) is going in for its annual in late February and I'm going to see if I can't replace some of the standby units (airspeed indicator, attitude indicator or altimeter) with one or two of these units. I'll report back.
Peter, were you able to figure this out? I'm curious.
COVID intervened ... this said, I was flying up and down California this weekend and thinking it was time to restart the effort. Stay tuned.
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Tim H
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Re: The New Garmin GI 275 Attitude Indicator (AI/ADI)

Post by Tim H »

I have a non-WAAS G1000 KAP-140 and I spoke with Garmin about replacing my AI and TC with the GI 275 AI with autopilot input.

They said the KAP 140 is integrated with the G1000 system and installing a AP version of the GI 275 will not work. I explained that the G1000 provides course deviation and the TC provide the rate information to the KAP 140. I asked if I could use the rate information from the GI 275 to drive the KAP 140 and continue to use the G1000 to provide course deviation and they said no. I feel like they gave a quick "no" without fully thinking it through.

I don't think there is any communication from the G1000 and the TC. Can't I just replace the source of the TC information? Am I missing something here?
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Tim H
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Re: The New Garmin GI 275 Attitude Indicator (AI/ADI)

Post by Tim H »

So I did a little further research and according the the DA40 AMM Dwg DA4-9222-10-03 Connector J3492, the only inputs from the TC to the KAP140 are roll rate +, roll rate - and rate valid which match up with the KAP140 installation guide showing those inputs for pins 3, 21 and 10.

So...if the GI 275 can provide those same outputs it should work? I looked for the GI 275 installation guide online but no luck.
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blsewardjr
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Re: The New Garmin GI 275 Attitude Indicator (AI/ADI)

Post by blsewardjr »

Unfortunately, autopilots that use turn coordinators (e.g., KAP 140) and those that use attitude indicators (all other BK autopilots) use fundamentally different means for directional control as noted in this article -- https://midwestflyer.com/?p=2954#:~:tex ... d%20system.
An attitude indicator in an autopilot-equipped airplane has two pickup coils, one to sense the bank angle and the other senses the pitch angle. There is also a third pickup coil in the heading indicator or HSI, attached to the heading bug that is used to drive the autopilot’s heading-hold function.... The rate-based system, though not as smooth... as the attitude-based system, obtains its flight information from the turn coordinator and “accelerometers....” Rate- based systems, using turn rate rather than bank angle, form the attitude indicator that will cause the aircraft to turn at the same rate regardless of aircraft speed.
Therefore, the GI275 attitude indicator can't drive the KAP140.
Bernie Seward, IR, AGI
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Rich
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Re: The New Garmin GI 275 Attitude Indicator (AI/ADI)

Post by Rich »

blsewardjr wrote: Wed Jun 10, 2020 8:36 pm Therefore, the GI275 attitude indicator can't drive the KAP140.
So far, I've found this to be universally true for all these new gizmos, including AV-30, G5, ad infinitum. Only a spinning-iron-gyro device will provide the required output.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Tim H
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Re: The New Garmin GI 275 Attitude Indicator (AI/ADI)

Post by Tim H »

This webinar provides a good overview of the GI 275:

https://www.youtube.com/watch?v=zdA9_5ODACY&t=2062s

To skip ahead, at 32:56-35:50 it talks about compatibility with legacy autopilot systems, including the KAP140. That's what got me thinking I could replace my TC.

But, but I think (in the case of the KAP140) only the HSI function is compatible, not the TC. If you have a KAP140 (in any application) you will need to keep your gyroscopic TC.
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Re: The New Garmin GI 275 Attitude Indicator (AI/ADI)

Post by Barry »

Wouldn't it be nice if the WAAS supplied by the 345R through this GI275 could provide a solution for non-WAAS DA40's with the Garmin GFC-700 autopilot?
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Re: The New Garmin GI 275 Attitude Indicator (AI/ADI)

Post by pietromarx »

Barry wrote: Thu Jun 18, 2020 8:15 pm Wouldn't it be nice if the WAAS supplied by the 345R through this GI275 could provide a solution for non-WAAS DA40's with the Garmin GFC-700 autopilot?
That's an interesting thought. You would basically remove the controls from the G1000 and use the GI-275 as the autopilot controller. It would have the (weird?) effect of making the G1000 into the accessory of the GI-275. I'm not sure you'd even have to turn it on except for the minimum equipment list (MEL) for IFR/VFR.
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