430 / STEC / EFIS problem

[jroser]

Recently installed new GRT HX efis system to supplement my gns430 and stec20 autopilot. 430 use to provide gps steering to stec 20. After installing HX , the 430 is not providing steering to the stec20 any more. When I turn on the autopilot I notice that the FPM(flight path marker) turns red indicating loss of information. I believe the problem is with the port assignment on the 430. I was wondering if anyone might recommend how to set up the 430 for this problem ?Grt is out until Monday due to Oshkosh. Just trying to do some trouble shooting this weekend. I am very pleased with the HX. Very nice addition.

Thanks.

[MauleDriver]

I have a similar setup (G430 GRT/HX and Trutrak) but can't talk to Stec specific issues. Not familiar with your installation either.

The optimal way to fly this setup is have the GRT control the autopilot using the G430 data (or GRT data for backup). In my installation I have a switch that allows me to operate that way, or to switch back to having the G430 drive the AP directly.

So a first questions are, "are you wired up so that the GRT can use the G430 data to drive the AP?" and "do you have a switch allowing you to switch back and forth?" Figuring out what mode you are in or what modes are available would be a first step.

Said another way, if you are not wired up in a way to allow the GRT to drive the AP, you would be missing some of the advantage of having added the GRT.

I think the red FPM means nothing. I noticed it during flight and couldn't figure out what it meant. As I recall the factory explained that when flying in a strong crosswind, the FPM may move off the left or right edge of the screen and when it does, it turns red to let you know that it's actual location on the synthetic vision backdrop is not to scale. I assume you are bench testing but I would suggest ignoring that.

Is your G430 a WAAS box? Do you or did you have GPSS steering? That is, did your old setup anticipate turns or did it over fly waypoints before turning?

The optimal way to connect the G430W and the GRT is with an ARINC connection. If you have that, the G430 ARINC config should be ARINC IN1 and IN2 are OFF and the ARINC Out should be LOW and GAMA429.

If you only or also have an RS232 connection, the G430 channel linking the 2 should be set to RX=SHADIN-FADC and TX=AVIATION. I don't know why but that's how I'm setup.

Hope some of that may be of help.

[MauleDriver]

I should add that if everything is setup 'right' and you have what I think is the optimal setup, controlling the AP is now done thru the GRT.

So operationally you would dial in a heading on the GRT and the AP would turn to that heading. Or you would tell the GRT to navigate to a waypoint using either 430/GPS data or NAV data or even GRT/GPS data and the AP would follow that instruction.

[jroser]

Thanks MauleDriver.
I have a nonwass 430 and it is providing all info as it should to the HX thru the 429 arinc and rs232 data. Works great. Initially , in talking with Ben at grt , he advised the HX could not work with the stec20. Did not inquire at that point as to why. I figured the 430 would provide as it has for gpss steering to the stec. I am thinking that during the gns 429 arinc set up phase to the HX that something was changed that affected my old set up to the stec. Not even sure if it is even possible now to provide steering to the stec from the 430 due to limited 429 outputs. I do plan on installing the grt servos this winter. Heading to Alaska next weekend and was hoping to have the autopilot working. No biggy, just have to hand fly. That's what it's suppose be about, I think..... I appreciate the help as I was just troubleshooting this weekend until someone is available next week at grt.

[MauleDriver]

I think you got it - not enough ARINC outputs on the G430.

Just brainstorming here but I'm thinking that maybe you'll want to give up the ARINC link to the GRT and instead use the one output for the Stec. I think the RS232 link to the GRT will give you what you need for display purposes.

In my case, I had the ARINC port on the G430 misconfigured and flew it that way for quite awhile before getting it fixed. Didn't notice the problem until trying to fly coupled approaches with the AP.

[jroser]

Thanks again. The flight director makes it really easy to fly approaches by hand. Yes, I plan on confirming my suspicions with GRT. I will check with grt on using the 232 only for the HX also.
Thanks
John

[BobTurner]

S-Tec is a good, certified autopilot but lacks modern digital interfaces. The Hx will not drive it.
You should try to restore the wiring you had before, then use what 430 ports are left to connect to the Hx.
If the STec takes Gama429 on its arinc line it is permissible to do a one to two splice and connect the 430 out to both the HX and STec, as long as both want Gama429.
If you do not also connect an arinc out from the Hx into the 430 it won't transfer OBS data from the Hx to the 430.
You can get ILS data from the 430 to the Hx without the arinc lines by using the analog connections. It's in the manuals and diagrams on the grt web site.

[jroser]

Thanks Bob.
Yes everything is wired and working properly on HX and receiving info from the 430. No wires were disturbed from the stec. Your info on the gama 429 may be the link. I am not sure on the stec20 what info it requires from the 430. Hoping grt will have some ideas.
Vor/loc/gs all work great. Nice system.

[BobTurner]

Just to clarify: your system 20 also has a GPSS box installed (it may be remote)? Only the GPSS box needs an ARINC input. The rest of the autopilot works off the analog signals that drive the cdi needle.
I presume you used to have a DG which is now gone? If so, the STec will not work in heading mode (the Hx cannot send this info in analog form) but the other modes should work as before.

[h&jeuropa]

As Bob has mentioned, I'm assuming you have the GPSS module (ST901). It allows your Stec 20 to accept ARINC steering commands.

More than likely your original setup had ARINC from the 430 going to the ST901 and also analog signals from your DG or HSI going to the ST901. I assume you removed the DG or HSI when you installed the HX.

Your GRT HX will output ARINC commands that your ST901 can use. I'm pretty certain the HX will output them regardless what mode the Hx is in - it will output ARINC commands whether in HDG mode or Flt Pln mode.

So if you wire your system like diagram WD-1008 with a toggle switch to select the steering source and leave the ST901 in GPSS position, when in Hx source, the HX will command the ST901 using ARINC and provide steering when in HDG or Flt Pln modes. When in 430 source, the 430 will command the ST901 using ARINC. In 430 source, HDG will not be available because there is no analog signal from a DG or HSI (assuming you removed the old DG or HSI).

You should not need the RS232 serial GPS signal from the 430 to the Stec shown in the diagram.

Hope this helps. Here is a link to the wiring diagram:

http://www.grtavionics.com/Horizon-430W-ADSB.pdf

Jim Butcher