STEC ST-901 GPSS troubleshooting, need pinout

[philiplane]

I am troubleshooting wiring with an STEC ST901 GPS steering unit and I need either the installation manual or just the pinout pages. Does anyone have a copy handy?

Thanks!

[Andy95W]

This is what I have. If you get something better, please send me a PM. If this picture isn't good enough, I can email the actual PDF.

[bradp]

Not to divert the thread too much, but does the 901-model work with non-STEC autopilots (i.e. Century autopilots)?

[jetdriven]

I dont think so. There are others that do, such as the DAC GDC31.  The max gain setting for that unit for a Century autopilot is .33 and their math in the install manual requires .37.  so it only banks 20 degrees and goes .10 miles outside the 90 degree turns, but its alright.

[OR75]

1 hour ago, jetdriven said:

I dont think so. There are others that do, such as the DAC GDC31.  The max gain setting for that unit for a Century autopilot is .33 and their math in the install manual requires .37.  so it only banks 20 degrees and goes .10 miles outside the 90 degree turns, but its alright.

you can adjust the gain. I recently installed the DAC 31 , adjusted the gain, flies the magenta line perfectly with no overshoot

 

[jetdriven]

.0302 is the highest gain for REF 1.  Has anyone used REF 2 input on a Century II/ III autopilot?

Edited July 11, 2017 by jetdriven

[OR75]

17 hours ago, jetdriven said:

.0302 is the highest gain for REF 1.  Has anyone used REF 2 input on a Century II/ III autopilot?

is it a Century IIB you have ? you should only have to disconect J1-22 to up the gain

 

[jetdriven]

It already is.  It's set to the highest gain for REF 1

[OR75]

how is the rate of turn when you use the console knob ? (on the 1C385)

[jetdriven]

great.  So is heading mode. Its just sluggish in GPSS mode and its t the highest gain for REF1.

[OR75]

not sure what to say .... i am on the lowest but one gain . Going from the lowest to the next gain made a big difference.

I suggest checking that there is no loose wire or call DAC 

[MoonFlyer68]

I hate to start a new topic only to have someone say I should have used the search function. Well I did the search and this thread seems the most applicable.

 

My situation is that I purchased 2 AV-30's last week just before the $300 per unit increase.  I had been holding out until the adapter box to allow the heading bug to drive my S-tec autopilot was approved but who knows how much longer for that. Also I recently bought an S-tec GPSS steering system off ebay.

 

My question is this, is it possible to install the GPSS and the AV-30 during my next annual and have the GPSS functionality even though there is nothing connected to a heading bug?  Is my best bet to just try and be patient and get the whole installation done once the AV-30 can interface to the autopilot so that everything is done in one big shot and not have to go back later to add it?

 

Thoughts???

[LANCECASPER]

10 hours ago, MoonFlyer68 said:

I hate to start a new topic only to have someone say I should have used the search function. Well I did the search and this thread seems the most applicable.

 

My situation is that I purchased 2 AV-30's last week just before the $300 per unit increase.  I had been holding out until the adapter box to allow the heading bug to drive my S-tec autopilot was approved but who knows how much longer for that. Also I recently bought an S-tec GPSS steering system off ebay.

 

My question is this, is it possible to install the GPSS and the AV-30 during my next annual and have the GPSS functionality even though there is nothing connected to a heading bug?  Is my best bet to just try and be patient and get the whole installation done once the AV-30 can interface to the autopilot so that everything is done in one big shot and not have to go back later to add it?

 

Thoughts???

the AV-30 on the STC list for the STEC GPSS. I doubt it. Even if it was and you bought the GPSS unit used you'll need to buy the STC from STEC (Genesys), which usually negates any discount you paid by buying it used. 

Whether the AV-30 interface ever materializes is up for debate. It's hard to compete with the Garmin GI-275 which is already approved.

[MoonFlyer68]

Thanks for your input. Certainly buying products that already have all functions approved by the FAA is the best way to go. Buying an item without that requires a little faith.

Regarding the STC from S-tec, from my research which includes other threads from Mooneyspace, there is no STC for the GPSS. It is considered and option for the autopilot which I already have the STC for. Hence it can be installed with just a logbook entry and of course adding the users manual to my flight pubs.

[LANCECASPER]

1 hour ago, MoonFlyer68 said:

Thanks for your input. Certainly buying products that already have all functions approved by the FAA is the best way to go. Buying an item without that requires a little faith.

Regarding the STC from S-tec, from my research which includes other threads from Mooneyspace, there is no STC for the GPSS. It is considered and option for the autopilot which I already have the STC for. Hence it can be installed with just a logbook entry and of course adding the users manual to my flight pubs.

This GPSS should be a stamped as a separate part number for 12v or 24v and maybe a different stamp for a King HSI or a Century HSI, etc. I have my doubts this will work with the AV-30. Maybe though. It would be interesting to see how an IA would write up the Form 337 on this.

[MoonFlyer68]

That is the issue, right now it will not work.  Uavionix is still certifying the box that will allow them to work together. So my question is, can the GPSS system be installed and functional even if it is not hooked up to a DG for heading mode. Can the GPSS mode operate without heading from a DG.

[LANCECASPER]

Take it to an avionics shop and get a professional opinion by someone that would sign off on it.

[MoonFlyer68]

4 hours ago, LANCECASPER said:

Take it to an avionics shop and get a professional opinion by someone that would sign off on it.

I absolutely plan to. For now I was just trying to get an idea if this was even a possibility before I start talking to the shop. Right now I am overseas for work and won't be back in the states for a couple months.

[LANCECASPER]

@Jake@BevanAviation would be the one who would know

[MoonFlyer68]

The more I think on it, I believe I have the plan for now. Not the greatest plan by any means, but one that will guarantee everything works.  I will have them remove the #2 NAV CDI but leave all wiring in place. Move my current vacuum DG to that slot so I will still have heading functions for my autopilot. Then I will install the AV-30'S as primary ADI and DG. Using this plan, I can absolutely add the GPSS to the autopilot because the original DG is still in the panel. The only big drawback to this plan is that I will still need the vacuum system so I can't remove it.

Still, I feel this plan will allow all the new equipment I want installed during this annual and a minimum amount of effort to make the final changes once the AV-30 is certified to drive the autopilot.

[Jake@BevanAviation]

@MoonFlyer68The S-Tec flight computer would have to be converted to the ST-901, and the ST-901 would have to be set to what ever compass system you are trying to use.  In theory if the ST-901 had the appropriate connections to the GPS navigator, it should be able to provide the simulated heading error to the flight computer.

[MoonFlyer68]

1 hour ago, Jake@BevanAviation said:

@MoonFlyer68The S-Tec flight computer would have to be converted to the ST-901, and the ST-901 would have to be set to what ever compass system you are trying to use.  In theory if the ST-901 had the appropriate connections to the GPS navigator, it should be able to provide the simulated heading error to the flight computer.

Thanks for the info Jake. As I said before, I think leaving my current DG in the plane (just moved to another hole) will allow me to get everything set up with the least amount of problems. Of course the absolute miracle would be if the Uavionix autopilot adapter box gets approved before my annual.  Just not seeming very likely right now.