What switching hardware is needed for running two navs on one CDI

Discussion in 'Avionics and Upgrades' started by Morgan3820, Nov 12, 2017.

  1. Morgan3820

    Morgan3820 Cleared for Takeoff

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    I am running short of panel holes and would like to place an E.I. CGR-30P where the Nav 2 CDI currently resides. I seem to recall seeing on some panels where a single CDI was switched to two Navs. Is this possible? Nav 1 is a GNS 430, Nav 2 will be a KX 125 (replacing the 250XL) with a KN 55 g/s receiver. CDI is a Garmin 106A.
    100_4677.JPG
     
    Last edited: Nov 12, 2017
  2. bnt83

    bnt83 Final Approach

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    It looks plausible that a KX125 and GNS can share a CDI through a relay but idk what a KN55 is.
     
  3. Morgan3820

    Morgan3820 Cleared for Takeoff

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    KN 55 is the glideslope receiver. It mounts behind the panel. Unlike the GNS 430, the KX 125 does not have the circuitry to receive the G/S signal
     
  4. Twin_Flyer

    Twin_Flyer Cleared for Takeoff

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    Have you looked into installing a HSI? It would free up the space and there wouldn't be a need to share the CDI.
     
  5. Morgan3820

    Morgan3820 Cleared for Takeoff

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    Eventually, but want the CGR-30P first. Then an A/P. Then A snazzy paint job. Then WAAS, Then, well you get the idea. But you are right it would be a solution.
     
  6. Ravioli

    Ravioli Final Approach

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    I don't think I understand the question. How about a picture cropped to to the pieces of the stack you are replacing? Maybe with some outlining.

    Looks like you got an extra ADF, a DME, a Comm only radio. Plenty of stuff to de-clutter.

    Operationally... (and I don't know) can you do VOR check when both receivers are using a shared CDI?
     
  7. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser!

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    Get rid of the ADF would be my guess
     
  8. Morgan3820

    Morgan3820 Cleared for Takeoff

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    Yes, the ADF is gone.

    Perhaps I should rephrase.

    I want to put a new E.I. CRG-30 where the bottom CDI (#2 ) currently is. Is it possible to run a single CDI switched to two different Navs?
     
  9. Twin_Flyer

    Twin_Flyer Cleared for Takeoff

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    Yeah, I get what you're saying. I just don't like the idea of having one CDI... That one goes tango uniform and you're without nav function... Just sayin'...
     
  10. Ravioli

    Ravioli Final Approach

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    Oh... I totally misunderstood your question.

    You're looking for a place to install your EMS and are considering replacing your #2 CDI with it. Right?

    If so, I'd go all in and put the EGC-30 where your stock MP/FF is. The EGC-30 covers all that and you don't give up any nav capabilities, like using VORs to find an intersection without a crap load of twisting.

    Also, if your dumping the ADF there's space for a larger EMS like a JPI. Just an idea.

    Don't mess with one system at the expense of another unless you really need to.
     
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  11. dmspilot

    dmspilot En-Route

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    You have a round Hobbs meter in a 3" hole you could move. Replace it with a rectangular one?
     
  12. Morgan3820

    Morgan3820 Cleared for Takeoff

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    Yes I hate to give up the redundancy, especially when it is already there. Perhaps pretty the CRG30 where the RPM gauge currently resides is the best compromise. I can always move it later when I get the G5 HSI.

    I want it all.
     
  13. Ravioli

    Ravioli Final Approach

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    Your tachometer (or RPM gauge as you call it) would be an example of removing a redundant primary and completely contrary to your last response.

    Losing the Hobbs is an option, or putting a JPI instead of the ADF is an option. <-- hey he spelled Losing with one o... WTH?
     
  14. GRG55

    GRG55 Final Approach

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    Yes, but "...putting a JPI instead of the ADF..." is grammatically incorrect, so consider that redemption, for the previous foe paw.
     
  15. Ravioli

    Ravioli Final Approach

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    You are correct. Should have been "putting a JPI where the ADF currently is would be an option to consider."
     
  16. GRG55

    GRG55 Final Approach

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    I have to be careful. My wife says the "P.E." after my name actually stands for Poor English. That's my excuse, and I'm sticking with it. :D

    To the OP: I would consider Twin Flyer's (apostrophe in the correct place?) advice and install an HSI before paint. You spend a lot more time looking at the panel than (then??) you do staring at the paint when airborne.
     
  17. bnt83

    bnt83 Final Approach

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    Is the KN55 a new thing? I've never heard of it nor does google find anything about it.

    I honestly cant see wiring all that through a relay, the hours spent doing that won't be cheap when you could dump that horizon tach and stick either the CGR-30P there or move a CDI there.

    There are 18 wires between the 430 and 106. See the example of the switching relay in this, and the 51 wire coming out of it. http://www.aeroelectric.com/Installation_Data/Garmin/GI102-106_IM.pdf

    I would dump that hour meter in a heartbeat.
     
    Last edited: Nov 13, 2017
  18. SbestCFII

    SbestCFII Line Up and Wait

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    Unless you're a rental business, ditch the Hobbs. You don't need it and the engine monitor would sit nicely in it's place. If you still want the 125, you should be able to use that as #2 NAV and you can channel your GS receiver through the 125 to the KI-209. You could off-load the ADF, DME and GNC-250 to subsidize your install.