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  #1  
Old 05-05-2022, 05:12 PM
Dandlac58's Avatar
Dandlac58 Dandlac58 is offline
 
Join Date: Oct 2021
Location: Sierra Vista
Posts: 44
Default Why is my TruTrak knocking my GNS430 GPS Signal Offline?

I have a GNS430W in my panel, it is connected to a TruTrak DigiFlight Autopilot with Course or GPSS tracking and Altitude Hold.

The GNS430W works perfectly until I turn on my TT autopilot. Shortly after turning it on, I get a warning on my GNS430W that it has lost GPS signal and to begin Dead Reckoning navigation. I also lose GPS signal on my IPAD at the same time and it is getting GPS data and ADSB in from the Uavionix Echo in the panel!

If I turn off the A/P, the GPS signal returns and begins working correctly again. So it seems clear the A/P is causing the problem...

Anyone have any idea(s) about what is going on and how I can fix. I dont mind dead reckoning but I'd much rather let my autopilot fly the airplane while I maintain much better piloting and situational awareness over every aspect of the airplane, the airspace, etc.

Thanks in Advance.
Dan
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Dan L
N327CD
2004 RV7 and RV7A (birthed as a 7A, then 7 from 2006 until this past October and now RV7A again - has all mounts, gear, brake plumbing for both configurations)
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  #2  
Old 05-06-2022, 07:15 AM
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TruTrakAndrew TruTrakAndrew is offline
 
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Location: Fayetteville, AR
Posts: 212
Default

I haven't ever heard of this before. Is the servo mounted very near the GPS antenna or is the GPS antenna coax routed very near the servo? From what it sounds like this isn't upon applying power to the autopilot, but upon engaging the servos. Is that correct?
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Andrew Barker
Andrew.Barker(at)Honeywell.com
Honeywell
TruTrak

RV-4 214NY "Carrie Ann"
RV-10 989TS - undergoing complete overhaul!!!
Rans S21 - 6219B
EAA - 309420
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  #3  
Old 05-06-2022, 02:44 PM
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Dandlac58 Dandlac58 is offline
 
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Location: Sierra Vista
Posts: 44
Default Additional Information on Problem

Quote:
Originally Posted by TruTrakAndrew View Post
I haven't ever heard of this before. Is the servo mounted very near the GPS antenna or is the GPS antenna coax routed very near the servo? From what it sounds like this isn't upon applying power to the autopilot, but upon engaging the servos. Is that correct?
Hi Andrew,
Thanks for working on this with me.
When I power on the Auto Pilot no problem. The problem occurs when:

I push the left button to select GPS course following,
and/or
Activate "Altitude Hold" function.

The reason I say and/or is because I didn't realize the auto pilot was causing the problem until near the end of the flight...(I was busy aviating, navigating, and communicating - I know you know...lol) so I'm not sure if the problem would have occurred if I only activated the a/p to follow the GPS course or if the problem only began when I activated Altitude Hold, or if the problem only occurred because I activated both functions. I hope that makes sense.

The GPS antenna is mounted on the top of the fuselage right behind the canopy at its farthest rearward location. I do NOT know if the GPS coax is near the servo... I did not build the airplane, I bought it from the gentleman who bought it from the gentleman who built it (I am not a builder, just a flyer but I do have some mechanical and electrical experience and knowledge!) Which servo are you talking about? Im assuming the altitude hold servo - where is the servo likely to be located?

Next thing I will do is fly the airplane again next week and fly the airplane with the autopilot following a compass course only (i.e. 150 degrees), then following a GPSS course and see if we get the failure. Then turn on Altitude Hold and see what happens. See if I can troubleshoot it down to a specific function.

Thanks
Dan
__________________
Dan L
N327CD
2004 RV7 and RV7A (birthed as a 7A, then 7 from 2006 until this past October and now RV7A again - has all mounts, gear, brake plumbing for both configurations)
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  #4  
Old 05-06-2022, 04:33 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 8,226
Default Ground check

Put your 430W on the ‘satillite signal strength’ page (top, far right on the page matrix). Observe the bar heights. Turn on the various autopilot functions, watch for the bars to go down. If/when they do, it means that autopilot function is radiating a signal that interferes with the gps signal. Do you have any other gps units that come on only with the autopilot?
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  #5  
Old 05-06-2022, 05:20 PM
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TruTrakAndrew TruTrakAndrew is offline
 
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Location: Fayetteville, AR
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Default

Bob offers very sound advice above.

The pitch servo is mounted just aft of the baggage compartment near the pitch reversing bellcrank. Let me know when the issue occurs and we can dig into what might be causing it.
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Andrew Barker
Andrew.Barker(at)Honeywell.com
Honeywell
TruTrak

RV-4 214NY "Carrie Ann"
RV-10 989TS - undergoing complete overhaul!!!
Rans S21 - 6219B
EAA - 309420
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  #6  
Old 05-06-2022, 05:47 PM
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Dandlac58 Dandlac58 is offline
 
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Location: Sierra Vista
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Default

Quote:
Originally Posted by BobTurner View Post
Put your 430W on the ‘satillite signal strength’ page (top, far right on the page matrix). Observe the bar heights. Turn on the various autopilot functions, watch for the bars to go down. If/when they do, it means that autopilot function is radiating a signal that interferes with the gps signal. Do you have any other gps units that come on only with the autopilot?
Great Idea Bob. I should be able to try that on the ground too, after the 430W has established a 3d position.

My GRT EFIS I believe has its own GPS and I know my Uavionix Echo has its own GPS which also feeds position info to my EFB on my IPAD and as I said it fails (the GPS data on the IPAD) at the same time as the GPS in the 430W. In fact I initially thought it might be the WIFI between them which was knocking out the GPS since I thought it might be causing too much interference for the low power GPS signals.
The power for the EFIS and the Echo comes on when I turn on main power breaker for the airplane. The fellow who owned it before me didnt put the Echo on its own circuit breaker... I am going to change that so I can turn it on and off independently.
__________________
Dan L
N327CD
2004 RV7 and RV7A (birthed as a 7A, then 7 from 2006 until this past October and now RV7A again - has all mounts, gear, brake plumbing for both configurations)

Last edited by Dandlac58 : 05-06-2022 at 05:59 PM. Reason: Clarity and additional information.
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  #7  
Old 05-06-2022, 05:53 PM
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Dandlac58 Dandlac58 is offline
 
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Default

Quote:
Originally Posted by TruTrakAndrew View Post
Bob offers very sound advice above.

The pitch servo is mounted just aft of the baggage compartment near the pitch reversing bellcrank. Let me know when the issue occurs and we can dig into what might be causing it.
I will do that after I have tried Bob's idea and my own, although will I be able to set Altitude Hold to "ON" in the TT without it being airborne and moving? I have a two mile taxiway I could use at KFHU if I just need to be moving...
I will also inspect the pitch servo for proximity to the coax for the GNS430W antenna.
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Dan L
N327CD
2004 RV7 and RV7A (birthed as a 7A, then 7 from 2006 until this past October and now RV7A again - has all mounts, gear, brake plumbing for both configurations)
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  #8  
Old 05-09-2022, 09:32 AM
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TruTrakAndrew TruTrakAndrew is offline
 
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Yes, you can engage the entire system on the ground and do not need to be moving.
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Andrew Barker
Andrew.Barker(at)Honeywell.com
Honeywell
TruTrak

RV-4 214NY "Carrie Ann"
RV-10 989TS - undergoing complete overhaul!!!
Rans S21 - 6219B
EAA - 309420
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  #9  
Old 05-17-2022, 12:32 PM
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Dandlac58 Dandlac58 is offline
 
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Location: Sierra Vista
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Default Update

Quote:
Originally Posted by TruTrakAndrew View Post
Yes, you can engage the entire system on the ground and do not need to be moving.
Hi Andrew,

I pulled my a/c out of the hangar so the GPS antenna had a clear view of the sky.

I powered on the 430W and let it boot and waited for it to get a 3D position. I then watched the satellite receive page where it showed that all Sats it was receiving were green with a "D" designation (showing it was getting correction information).

I then turned on each (and every) other system one at a time, to determine if it might cause a reduction in GPS signal strength. I turned each system off before turning another on. This included my GTX327, SL40, Uavionix Echo, IPAD and TruTrak autopilot, dual emags. The GRT Sport EFIS was always on.

No reduction in GPS signal strength.

I then turned all systems on and taxied the airplane around the airport, no reduction in GPS receive signal strength.

Next test is to go up for a flight to see if the problem re-occurs while in-flight.

More to follow.

Dan
__________________
Dan L
N327CD
2004 RV7 and RV7A (birthed as a 7A, then 7 from 2006 until this past October and now RV7A again - has all mounts, gear, brake plumbing for both configurations)
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  #10  
Old 05-17-2022, 12:35 PM
Dandlac58's Avatar
Dandlac58 Dandlac58 is offline
 
Join Date: Oct 2021
Location: Sierra Vista
Posts: 44
Default Update

Quote:
Originally Posted by BobTurner View Post
Put your 430W on the ‘satillite signal strength’ page (top, far right on the page matrix). Observe the bar heights. Turn on the various autopilot functions, watch for the bars to go down. If/when they do, it means that autopilot function is radiating a signal that interferes with the gps signal. Do you have any other gps units that come on only with the autopilot?
Hi Bob,
This is my follow-up post to Andrew:

Hi Andrew,

I pulled my a/c out of the hangar so the GPS antenna had a clear view of the sky.

I powered on the 430W and let it boot and waited for it to get a 3D position. I then watched the satellite receive page where it showed that all Sats it was receiving were green with a "D" designation (showing it was getting correction information).

I then turned on each (and every) other system one at a time, to determine if it might cause a reduction in GPS signal strength. I turned each system off before turning another on. This included my GTX327, SL40, Uavionix Echo, IPAD and TruTrak autopilot, dual emags. The GRT Sport EFIS was always on.

No reduction in GPS signal strength.

I then turned all systems on and taxied the airplane around the airport, no reduction in GPS receive signal strength.

Next test is to go up for a flight to see if the problem re-occurs while in-flight.

More to follow.

Dan
__________________
Dan L
N327CD
2004 RV7 and RV7A (birthed as a 7A, then 7 from 2006 until this past October and now RV7A again - has all mounts, gear, brake plumbing for both configurations)
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