Issue with Voyager EFIS GPS.

[JimJab]

Well over the last 2 hours of flight time this issue is slowly increasing again with bitching Betty saying "GPS not Available" then "GPS Available" in quick succession and as I said before it's now my Co-pilot EFIS's GPS that has the problem and it's starting to happen more often again.

Now my Co-pilot EFIS satellite page has a few less satellites and satellite signal bars compared to my Pilot EFIS, now this is both on the ground with and without the engine running and in the air. But Six months ago when I did some antenna ground plane testing, I bench tested both EFIS's GPS for satellite signal strength and performance, at that time both my EFIS's satellite pages showed similar GPS signal strength etc.

Brad's post some time back said, try replacing the GPS Antenna, so I have purchased from my local communications company a no brand active GPS antenna, the same specs and size as my current GPS antennas. With great disappointment, swapping and changing around my 3 GPS antennas between my 2 EFIS's, this made little difference in improving my Co-pilot GPS satellite signal performance and all antennas showed similar performance on each EFIS.

A while back, I took the GSP module out of my Pilot EFIS, cleaned the board and re-soldered a couple of possible dry joints, one being the GPS antenna connection, maybe I need to take out the GPS module from the Co-Pilot EFIS and have a good look around that board and it's SMA antenna connection.

Yep, this is all becoming painful again, but sometimes in electronics, it's not one thing causing the problem, but a number of smaller things adding up to make the problem and this is why it can be very hard and painful to find and fix the problem.

Having worked through and tested so many things, I do think Rainer's suggestion way back about EMI or RF interference in my system is playing a part in this GPS issue. But I've had little experience in sniffing out those types of problems and finding where they are coming from is not going to be easy for me.

So I am looking for every other physical issue it could be, but those sniffer probes are coming next, I can see that and needing to lean the tricks in using them is going to be a huge step up, unless I can find someone who can help me, with them.

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DIYSnifferProbes.jpg (6.67 KiB) Viewed 29563 times

Cheers
JimJab

[a.baudry]

hello Jim,
one year ago I gave you the solution:

Hello JimJab,
I had exactly the same problem on my Voyager G2 during about 2 years. I solved it definitively 8 years ago by changing the GPS board. The new one was fitted with a new GPS module U BLOX 5 (or 6, not sure of the figure) much stronger against electromagnetic disturbances than the original U BLOX LEA 4A.
I purchased the new GPS board at MGL. Before the replacement, each flight was polluted by ‘GPS not available’ messages; since the replacement I never had the trouble anymore… I flew more than 600 hours without any problem.
Regards
Alain

... and you never tested it!
Happy new year
Alain

[JimJab]

Hi Alain,

Yep you are right, I have not used your good advice in getting one of those newer GPS modules.

But, I am a bit little a dog with a bone. I would like to find and resolve what is causing the EMI or RF interference in my plane, if I can?
I guess I have not lost all hope in being able to track down and fix the cause of this interference.

It's crazy, but the issue has moved from the Pilot EFIS to the co-pilot EFIS for no other reason than when I moved around the order of the electrical connections to the instrument panel's 2 negative bus bars, they are side by side and directly connected. So now my Pilot EFIS has not had any type of GPS drop out for some months and over quite a few flight hours.

I live in hope, I can track down this EMI or RF interference in my plane so my co-pilot EFIS will stop having these GPS issue as well.

Cheers
JimJab

[a.baudry]

Jim,

I believe that in modern aircrafts with lots of electronic devices, you will never totally get rid of EMI and the EFIS itself is probably one of the main sources of EMI. After all the things you’ve done during that year, you have probably decreased the level of EMI but, in some circumstances hard to define, this level is still above the EMI sensitivity threshold of your GPS modules.

You can work on EMI fighting during several more years without being able for sure to decrease the level below the GPS threshold in any circumstances.

And beside this, the replacement of the GPS board(s) would immediately and drastically increase the EMI sensitivity threshold of your GPSs!

There is hesitation to have: be pragmatic...

Cheers
Alain

[JimJab]

Jim,

I believe that in modern aircrafts with lots of electronic devices, you will never totally get rid of EMI and the EFIS itself is probably one of the main sources of EMI. After all the things you’ve done during that year, you have probably decreased the level of EMI but, in some circumstances hard to define, this level is still above the EMI sensitivity threshold of your GPS modules.

You can work on EMI fighting during several more years without being able for sure to decrease the level below the GPS threshold in any circumstances.

And beside this, the replacement of the GPS board(s) would immediately and drastically increase the EMI sensitivity threshold of your GPSs!

There is hesitation to have: be pragmatic...

Cheers
Alain

Hi Alain,

What a great reply you gave, you have nearly got me to drop this bl--dy EMI bone.

I will contact our MGL dealer and order a replacement GSP module with one of those newer Ubox 4 or 5 modules.

In the meantime, I will get my multimeter, set it to the lowest ohms setting, put a long lead from the negative lead of my multimeter to my battery earth point (disconnecting my battery). Then go around the airframe and engine bay looking for items which are poorly earthed.

Checking things like the earthing to oil cooler, Bing Carby, radiators, fuel tank filler and caps, earthing points, other negative buses points, engine cables to earth etc. where static could build up with air flow.

I have been told this is pretty easy first step and is quite safe without the need for the engine to be running or the planes avionics to be operational.


Cheers
JimJab

[PaulSS]

This is just getting ridiculous, in my opinion. Do you see Garmin and Dynon owners wandering around with EMI diviners, re-soldering parts that have shaken themselves to bits or looking for grounding excuses as to why their kit doesn't do the job it's supposed to?

Meanwhile the silence is still stunning from the top......unless you want to hear about a new radio

[JimJab]

This is just getting ridiculous, in my opinion. Do you see Garmin and Dynon owners wandering around with EMI diviners, re-soldering parts that have shaken themselves to bits or looking for grounding excuses as to why their kit doesn't do the job it's supposed to?

Meanwhile the silence is still stunning from the top......unless you want to hear about a new radio

Hi Paul,

Really not sure where you are coming from with your post, but I am sure you know aviation can be very complicated thing.

There are a number of different Classes of aircraft in the private and sports aviation world.

There are those Factory Manufactured G.A. Certified Aircraft eg. Piper, Cessna etc.... and then you have Factory Manufactured LSA Certified Aircraft eg. Sling 2, Tecnams, Jabiru 230 etc....

The G.A. Certified Class, they require TSO approved avionics, eg. Garmin, Avidyne etc.... Then with LSA Certified Aircraft the manufacturer can use non TSO approved avionics. With both these Classes of aircrafts, the owner/pilots can't change the design of anything on these aircraft without an approval.

These Certified aircraft manufacturers can do lots of R&D and testing to sorted out RF/EMI problems as they bring together different types of avionics. They may find bundling certain wires with other wires and routing other wires the long way around will help stop RF/EMI entering into their aircraft's systems. They may also work closely where required with their Avionics suppliers to finally resolve all EMI issues.

But here is why I need to wander around my aircraft with those EMI sniffers.

My aircraft is not certified, it's in a class called "Experimental", in this class, you can build your own aircraft from your own design or from a kit that has a proven design, eg, RV's, Glassair, Sling 4 and the list goes on.

But here is the clincher and could be my problem. Maybe my aircraft builder knew very little about RF/EMI when he was wring up the plane and did not route some wiring around the plane as in the aircraft build instructions.

Or maybe he did not have any type of wiring schematic, knew nothing about RF/EMI and wiring best practices for a digital systems. Like using twisted pairs and or shielded wire and how to terminate this shield properly to eliminate or reduce RF/EMI inference in the plane's avionics.

So Paul, I understand this could sound ridiculous for some people and your right thinking this is a long and tedious process, this is because I really don't have any real experience with EFIS installations and secondly I can't expected any type of first class support for a product that is getting to be 12 years of age.

So believe I have to step up and take some responsibility for my aircraft's other system that could be causing some type of RF/EMI issues. I am willing to lean and give it my best shot. Other wise it would be stump up the money for a new panel.

Cheers
JimJab

[PaulSS]

I'm not decrying your attempts to solve your problems, Jim, I'm just getting more annoyed at MGL that you have to do things like this, whereas the Garmin and Dynon owners do not. I'm quite conversant with the different classes of aircraft and kit and am probably more au fait with 'Experimental' than I am the certified stuff. What I do see, however, is just how well the likes of uncertified Garmin and Dynon gear functions, when I'm testing aircraft the same as mine, compared to just how poorly mine behaves.

My autopilot is really quite piss-poor and there's been no suggestion from Rainier how things might be improved. No doubt it will blamed by the fact that my EFIS is mounted too well in the panel, or not well enough because it doesn't involve velcro. The AHARS chip must be the cheapest that can be produced in China because it can decide to do its own thing and give false readings on a totally random basis, even when nothing has changed with the aircraft. I would certainly not feel comfortable flying IFR with it, whereas I'd happily do so in the same aircraft with the manufacturers mentioned previously.

I admire your persistence and abilities. I just find it a shame that you find it necessary. An avionics box, made to be fitted in an aircraft, that is susceptible to the tiny amounts of EMI present in that very machine is evidently not fit for purpose, IF that is the cause of the problem. That's like putting a non-waterproof box of kit on a boat.

I really liked the ability to customise the screens on MGL EFIS but I wish I'd just accepted the more fixed layouts of a SkyView.

[JimJab]

That's like putting a non-waterproof box of kit on a boat.

Paul, I get the picture and like the analogy.

Am I getting off subject ?

I can cut Rainer some slack, my only experience with MGL products is limited to my two 12 year old Voyager EFIS systems.

But I really believe, the Voyager EFIS with its current features, is still hanging in there against it's far more modern day rivals, even when being 14 years older and that's a lot in the digital world.

I can still remember the day I took a look at my EFIS's hardware and could see it was based around some standard computer technology of the day and straight way understood why my EFIS could have some issues at its stage in life.

So here is my theory about my Voyager EFIS and RF/EMI issues.

Back at the time when Voyager was being developed, many pilots did not even like the thought of flying with an EFIS. So Rainer needed to use cheaper readily available technologies and designs, so I guess he turned to the computer industry to get his EFIS to a price point where the experimental aviators could go, that's nearly cheaper than buying all those gauges.

But using this consumer computer technologies could have come at a cost. May be the EFIS is not so robust against RF/EMI etc.... but we got an EFIS and the cost savings. In return the installer and maintainer had to be much more diligent in their efforts in reducing RF/EMI in aircraft systems so the EFIS and GPS could remain rock solid.

Also, I have to keep reminding myself, this is 14 year old EFIS technology we are talking about here and I know it easy to class it against todays technology, but is that fair.

So, here's hoping I am able to develop my knowledge to sniff out this RF/EMI. But then how do I fix it ?, what, more ferrite beads the masses say, but hopefully this time I will know where to place them.


Cheers
JimJab

[mikeh]

Keep it up Jim,
Your persistence increases the knowledge base.
Cheers
Mike