RXP GTN 750 not working with Piper Arrow Turbo iii AP

[pgreenx 1]

Hi all,

I cringe asking about this after reading numerous and similar issues a few yrs ago but here is my problem which I could not figure out from previous posts:

I fly the JF Piper Turbo Arrow iii for about 4 months and the GTN750 has been working great.  All of a sudden the GPS stopped sending signal to the auto pilot.  I happened in mid flight.... As a separate data point, the heading bug actually turns the plane while in GPS mode which it didn't do before (like it was in heading mode).  I know how to use the plane/750 so I know its not a matter of the selecting GPS on the 750 or nav on the AP, etc.  I also do not think its the little nav switch under the AP in the plane which is inactive.

The stock garmin 530 works fine so Im guessing its not the plane, the sim or the auto pilot. The GTN750 also works in my two other planes (Torqism SR22 and stock c172/REP).   I tried to change some setting which I think is the issue but nothing works.

I also reinstalled the plane and the 750 as well as usually suspects like rebooting pc, etc

Any help would be greatly appreciated as after flying with the 750 I just cant go back to the 530.....

Thanks in advance

Paul

[RXP 2,338]

Hi,

I've tried both the PA28 Arrow and the PA28 Arrow Turbo, looking at Dataref Editor what it is doing with the autopilot states and modes when rotating the autopilot mode knob, setting the HDG mode on or off, setting the A/P Master on or off. Suffice to say it is inconsistent and I believe there is a bug in the latest PA28 version(s). For example, rotating the mode to the left fully, then back on HDG (center) doesn't always set the same XP11 autopilot state as turning the knob fully right then back on center. This also depends whether the HDG mode is on or off prior and/or after turning the knob. In other words, the PA28 autopilot panel is not consistently setting the XP11 autopilot modes for the same knob and switches position, it depends on what modes where set prior and even with the same modes set prior, it doesn't always set the same modes afterward?! In all cases, it is never setting the GPSS mode which the GTN/GNS V2 detects and can use,  but instead it is always setting ROLL mode, which prevents changing the autopilot modes to HNAV for example (you can manually try setting the dataref and this won't change the mode). I'll have to make a few more tests but I believe there is something changed in the PA28 code here.

 

[pgreenx 1]

On 12/7/2021 at 4:43 PM, RXP said:

Hi,

I've tried both the PA28 Arrow and the PA28 Arrow Turbo, looking at Dataref Editor what it is doing with the autopilot states and modes when rotating the autopilot mode knob, setting the HDG mode on or off, setting the A/P Master on or off. Suffice to say it is inconsistent and I believe there is a bug in the latest PA28 version(s). For example, rotating the mode to the left fully, then back on HDG (center) doesn't always set the same XP11 autopilot state as turning the knob fully right then back on center. This also depends whether the HDG mode is on or off prior and/or after turning the knob. In other words, the PA28 autopilot panel is not consistently setting the XP11 autopilot modes for the same knob and switches position, it depends on what modes where set prior and even with the same modes set prior, it doesn't always set the same modes afterward?! In all cases, it is never setting the GPSS mode which the GTN/GNS V2 detects and can use,  but instead it is always setting ROLL mode, which prevents changing the autopilot modes to HNAV for example (you can manually try setting the dataref and this won't change the mode). I'll have to make a few more tests but I believe there is something changed in the PA28 code here.

 

Thanks - this is very frustrating and RXP doesn't nessasarily agree there is a problem when I have been emailing with them.

I sent your reply to them. hope it helps.  The plane is fabulous.  I bought the torqusim SR22 to replace the arrow since the gps doesn't work but do not like it nearly as much as the arrow

[RXP 2,338]

I'm able to assist them with this like we did in the past when needed, and I'll be pleased to if they contact me. But what is sure is that there is nothing we can do on our end here, because the aircraft sets the XP11 autopilot in a state which can't work when using "override_gps", and which nonetheless isn't consistent in itself when changing modes back and forth. In this case, I believe both RXP and JF are facing some XP11 limitations, but it is not unsolvable either.

Edited December 23, 2021 by RXP