STEC 30 won't connect to IFD after update

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   I have an STEC-30 autopilot with an ST-901 GPSS module. It has been working great with my IFD-540.
I recently had to send the IFD-540 back to Avidyne to repair a broken USB connector. The unit came back with firmware updated to the current version. The IFD seems to operate well. However, I have a problem with the GPSS mode of the autopilot.

When I went flying with the plane, I had a route to an airport nearby. I first tried the autopilot in HDG mode, and it worked as expected following the DG. When I switch to GPSS mode, the GPSS LED just flashes and the autopilot won't follow the route in the IFD.

I am taking the plane back to the shop for them to debug the issue, but I was wondering if there might be a simple configuration change/issue that can get this fixed quickly. Are there any known issues with the newest firmware?

We did check all the settings before and after the firmware upgrade, and everything seems to be set as expected. I had pictures of every configuration screen saved. I suppose it could just be a loose connection somewhere. Any hints would be appreciated.

Edited by HenryM - 05 Sep 2024 at 5:51pm

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HenryM Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 13 Oct 2017 Location: Texas Status: Offline Points: 502	Post Options Post Reply Quote HenryM Report Post Thanks(0) Quote Reply Topic: STEC 30 won't connect to IFD after update Posted: 05 Sep 2024 at 5:41pm
	I have an STEC-30 autopilot with an ST-901 GPSS module. It has been working great with my IFD-540. I recently had to send the IFD-540 back to Avidyne to repair a broken USB connector. The unit came back with firmware updated to the current version. The IFD seems to operate well. However, I have a problem with the GPSS mode of the autopilot. When I went flying with the plane, I had a route to an airport nearby. I first tried the autopilot in HDG mode, and it worked as expected following the DG. When I switch to GPSS mode, the GPSS LED just flashes and the autopilot won't follow the route in the IFD. I am taking the plane back to the shop for them to debug the issue, but I was wondering if there might be a simple configuration change/issue that can get this fixed quickly. Are there any known issues with the newest firmware? We did check all the settings before and after the firmware upgrade, and everything seems to be set as expected. I had pictures of every configuration screen saved. I suppose it could just be a loose connection somewhere. Any hints would be appreciated. Edited by HenryM - 05 Sep 2024 at 5:51pm

PA23 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 12 Oct 2019 Location: MMU Status: Offline Points: 317	Post Options Post Reply Quote PA23 Report Post Thanks(0) Quote Reply Posted: 05 Sep 2024 at 7:01pm
	You need to fix the programming on the IFD. You will need to know first what type of input the ST-901 is expecting, it can use serial OR ARINC429 and then which interface, the 540 has 6 serial outs and 2 ARINC 429 outputs. Most likely it is going to be ARINC (note serial numbers <5000 are ARINC only) My ST-901 is configured to use ARINC429, format of GAMA 429 speed Low (I think page 2 of the IFD configuration screen). I don't know what the configuration would be if you are using serial. My suggestion for the future would be to take pictures of the configuration screens in the maintenance mode so you have them should you ever need to send your unit back and lose the configuration settings. My guess is you are using ARINC and it is on channel 1, but I have nothing to back that up with, if that interface is currently turned off I would enable it and see if that resolves your issue as you can't hurt anything by turning it on.

HenryM Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 13 Oct 2017 Location: Texas Status: Offline Points: 502	Post Options Post Reply Quote HenryM Report Post Thanks(0) Quote Reply Posted: 05 Sep 2024 at 7:34pm
	Thanks. I have pictures of the configuration screens and as far as I can tell, everything is the same as before the update. I see in the main ARINC 429 Config page that Out 1 is set to Speed = Low, Data = GAMA 429. I think the update didn't change any settings. Perhaps a connection came loose during the time the IFD was out for repair. I am just trying to make sure it isn't some simple setting that changed. It is a pain to go drop off the plane for a few days while the shop works on it. I know the GPSS light would blink if the IFD doesn't have a route set. Chat GPT tells me the following. But I'm not sure how much I can trust it:   The GPSS (GPS Steering) light flashing on an S-TEC ST-901 module typically indicates a problem with GPS steering input or signal. Here are a few common reasons why this might occur: 1. Loss of GPS signal: If the GPS signal is weak, lost, or has significant interruptions, the GPSS light will flash to alert the pilot that the autopilot may not be receiving valid GPS guidance. 2. GPS data error or failure: If the GPS system is providing inaccurate or faulty data, the module may flash the GPSS light to signal that the GPS steering commands are unreliable. 3. Improper GPS mode: The system may not be set to the correct mode for GPSS steering. For instance, if the GPS unit is in VLOC mode (VOR/Localizer) instead of GPS mode, the autopilot might not properly recognize the steering commands. 4. Wiring or connection issues: Loose or faulty wiring between the GPS and the autopilot system could cause the light to flash due to inconsistent signal transmission. 5. Configuration settings: The S-TEC autopilot or GPS system may require specific settings to function in GPSS mode. If these settings are not correctly configured, the GPSS function could fail intermittently. If the issue persists, a review of the aircraft’s manual and consultation with an avionics technician would be recommended to ensure everything is functioning correctly. Edited by HenryM - 05 Sep 2024 at 7:37pm

HenryM Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 13 Oct 2017 Location: Texas Status: Offline Points: 502	Post Options Post Reply Quote HenryM Report Post Thanks(0) Quote Reply Posted: 09 Sep 2024 at 9:32pm
	I didn't get a chance to check the settings on the plane before it went Tóths shop. It was just a configuration issue. Formten avionics shop: "Rechecking the configuration on the IFD, the 429 output was turned off for the autopilot configuration. Turned that back on and the GPSS light stays solid now. Looks like we missed that when we were inputting the configurations." I'll go pick up the plane later this week and test it, but it is likely that was the problem. I need to find out exactly what all was reconfigured after the software upgrade.