Garmin 430w installation with altimatic IIIb autopilot

I am installing a Garmin 430w replacing a Narco 120, KNS 80 and a garmin 155xl. When I began removing the above avionics, all of the wires went to the right to a blue box filled with relays. I removed all of that, but am not sure how the new 430w provides input to the autopilot. Any suggestions? I have the altimatic III manuals and the manuals for each of the other units, but cannot determine where to make the connection. When I installed a Trutrak it was an easy connection of an rs232 and 429 set of wires. Not sure how it works with the altimatic.

Scott Brooksby, CFII, A&P, IA

Comments

  • Hi, I'll send this to our A&P, Erich Rempert for his comments.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.

    Need help? Let me know!

  • Scott B: I did this same integration exercise a few years ago. When you’re all done and the system is tweaked up, it’s nothing short of humbling how tight of an LPV the plane will fly. Let me see if I can find a schematic to post showing the interconnect.

    Couple of questions:
    Do you already have a radio coupler and a glide slope coupler installed in you A/C?
    Prior to decommissioning, would it fly a competent ILS based upon NAV data from the KNS-80?

    Bob

  • Here are the comments from out A&P, Erich Rempert:

    The Altimatic long predates RS-232 and ARINC429.

    The relays likely switched between the Nav and GPS. the wires coming out of the relay box to the autopilot should be retained and have all the information the autopilot needs. (Common poles of the relays)

    Connect the 430 to these wires via analog connection.

    You can reverse engineer the system by looking at what information was provided by the KNS80 and GPS 155.

    There are schematics in the 430 manual that should help.

    ~Erich Rempert, IA Consultant

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.

    Need help? Let me know!

  • edited May 31
    The radios in the aircraft we're not working very well when I got it that's why I did the upgrade. I did find that the radio coupler has a cable labeled cd34. This is apparently the navigation information. Pins A and B provide left and right deviation information. I will tie into those. I have not found a Glide slope coupler in the aircraft. Although there is a indicator light that does say glideslope coupled I'm just not sure where to look for the coupler for the Glide slope. I wish I could figure out what all of the other wires do on the cd34.

    Scott Brooksby, CFII, A&P, IA

  • Hi Scott B.

    You're absolutely right about the Amphenol CD34. See pdf page 242 (document page 4-37) in:

    https://www.csobeech.com/files/CenturyII&IIIManual.pdf.

    Pin assignments for CD34 are at the right margin of the figure. Signals are all standard ARINC 150 mV levels.

    If you have a glideslope light, you definitely have the box installed. It needs to be mounted within four feet of the artificial horizon for the interface to work properly. On most Pipers it's below the copilot's instruments; on a few it's mounted to the brake channel. It's a metal box with a female DB25. You might be able to follow the wire on the glideslope light back to the box.

    Bob

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