GTN750xi and stec55x

[Joe_B1]

It all worked fine until my avionics shop did a software update. Now when I press the NAV button twice on the autopilot, I can't get gpss to show up. My guess is the 55 isn't getting GPS coordinates from Garmin anymore. Any ideas if there is a source select menu or how to determine if the GTN is the source.

Thanks,

Joe

 

[midlifeflyer]

Best guess: your avionics shop or the update process disabled the STEC GPSS functionality while doing the update. Why not ask them?

 

[Joe_B1]

Best guess: your avionics shop or the update process disabled the STEC GPSS functionality while doing the update. Why not ask them?

I sent them an email earlier today but have yet to receive a reply. I assume they will be back to me shortly. I just figured someone here could help.

Is this STEC GPSS something in the config menu (which is not something I want to mess with) or is it something in the pilots side?

 

[midlifeflyer]

I sent them an email earlier today but have yet to receive a reply. I assume they will be back to me shortly. I just figured someone here could help.

Is this STEC GPSS something in the config menu (which is not something I want to mess with) or is it something in the pilots side?

I don't know the inner configuration stuff. I am working with a pilot with an STEC 55X-G5 combo. His avionics guy explained that he configured the setup to enable GPSS only in the STEC rather than the G5 (or in both). That suggests to me there are switches or configuration items somewhere to turn stuff on or off, but I could be off-base.

 

[Joe_B1]

I don't know the inner configuration stuff. I am working with a pilot with an STEC 55X-G5 combo. His avionics guy explained that he configured the setup to enable GPSS only in the STEC rather than the G5 (or in both). That suggests to me there are switches or configuration items somewhere to turn stuff on or off, but I could be off-base.

Hopefully I will hear back today. Thanks.

 

[Ryan Klems]

For GPSS to function there is an ARINC 429 connection from the GTN to the 55X in addition to the standard analog deviation connections. Most likely somehow in the software update on the GTN the ARINC port got turned off or its configuration reset. In the documentation for the GTN install there should have been an Appendix A filled out which would list all the configuration settings and ports. If you have that you could compare to you current settings and see what might have gotten changed/erased.

 

[Joe_B1]

For GPSS to function there is an ARINC 429 connection from the GTN to the 55X in addition to the standard analog deviation connections. Most likely somehow in the software update on the GTN the ARINC port got turned off or its configuration reset. In the documentation for the GTN install there should have been an Appendix A filled out which would list all the configuration settings and ports. If you have that you could compare to you current settings and see what might have gotten changed/erased.

It worked the day before the upgrade and now, no. So it's a definite software / port issue. The avionics shop is closed until Tuesday so I have to wait but I don't anticipate a problem getting it fixed. The wx is getting crappy for the next few days so can't fly anyway.

I guess, just to satisfy my curiosity, if the 55x was not receiving ARINC data from the 750 and I pressed the NAV button twice would the gpss icon show up or is it smart enough to ignore the mode and stay in NAV?

 

[Ryan Klems]

I guess, just to satisfy my curiosity, if the 55x was not receiving ARINC data from the 750 and I pressed the NAV button twice would the gpss icon show up or is it smart enough to ignore the mode and stay in NAV?

From the 55x POH:

"If the GPS Navigator has a valid flight plan active and the autopilot is in the GPSS Mode, the autopilot will follow that flight plan. If no flight plan is active, the autopilot will annunciate a flashing GPSS and FAIL will be steady. The aircraft will continue straight, wings level"

so I would presume that if it wasn't getting the ARINC 429 data it should behave similarly.

 

[Joe_B1]

I read that but mine doesn't behave that way. It doesn't flash fail, it just ignores the second button push and stays in NAV mode. Strange.