Dynon/AFS Oshkosh 2015: SV-GPS-2020 and much more!

[RVDan]

Dynon,
With regards to the SV-GPS-2020, I am wondering what evidence will we have that the GPS, and the SV system including transponder will be accepted by the FAA to meet the requirements of 91.225 and 91.227?

Thanks

 

[Dynon]

In the FAA's own words (see https://www.faa.gov/nextgen/equipadsb/faq/#q4) , we'll need to provide a statement of compliance, installation instructions etc. You'll also need to check that practically speaking that your system ultimately performs to spec. You'll be able to do that by requesting a compliance report from the FAA (see https://www.faa.gov/nextgen/equipadsb/faq/#q10)

 

[RVDan]

I need to capture that web page before they change their minds. Good stuff. Thanks for the response.

 

[dynonsupport]

Dan,
Just an FYI, but that language is from the upcoming AC 90-114 revision which will put in writing how E-AB and LSA can comply with non-TSO'd devices. Dynon has been involved with this AC and drafting language, so you can be pretty sure it won't go away and that Dynon's path is the one the FAA expects experimental operators and manufacturers to follow.

 

[mmarien]

FWIW - I've found the SV-GPS-250 antenna will 'lock on' inside a steel hangar

Getting enough signals for lock and getting correct signals for an accurate position are two different things. I used a handheld GPS receiver to try and navigate to a survey monument under a forest canopy and never got within 50 metres because of multipath and other signal errors caused by the tree cover. I had a 3D lock the whole time plus the receiver was indicating ten metre accuracy. It just wasn't achieving it and worse yet, didn't know that it was getting poor signals. It will be interesting to see if the under the hood GPS antennas will pass the high integrity position report that the FAA requires.

 

[skysailor]

May be possible

I have a certified WAAS navigator (GNS 480) in a Glasair. The antenna is mounted internally and the receiver maintains IFR tolerances. Since the GNS 480 is compliant for ADSB in several STC combinations in the certified world, I think it will pass muster. Won't know until I try it but I will report the results either way.

 

[swatson999]

FWIW - I've found the SV-GPS-250 antenna will 'lock on' inside a steel hangar

Getting enough signals for lock and getting correct signals for an accurate position are two different things. I used a handheld GPS receiver to try and navigate to a survey monument under a forest canopy and never got within 50 metres because of multipath and other signal errors caused by the tree cover. I had a 3D lock the whole time plus the receiver was indicating ten metre accuracy. It just wasn't achieving it and worse yet, didn't know that it was getting poor signals. It will be interesting to see if the under the hood GPS antennas will pass the high integrity position report that the FAA requires.

Why would it not? IIRC, fiberglass is transparent at GPS signal frequencies.

Even if you *had* multipath from some of the airplane structure, wouldn't that simply affect your position by the distance from the antenna to the reflecting point on the aircraft (at *worst*, since GPS fixes are an LSQ solution to a system of x,y,z,t variables)?

You're unlikely to get multipath from trees or buildings while flying...

(Incidentally, canopy cover usually doesn't cause multipath, but it causes signal degradation due to moisture in the canopy blocking the GPS signals intermittently).

 

[swatson999]

I have a certified WAAS navigator (GNS 480) in a Glasair. The antenna is mounted internally and the receiver maintains IFR tolerances. Since the GNS 480 is compliant for ADSB in several STC combinations in the certified world, I think it will pass muster. Won't know until I try it but I will report the results either way.

Same here with a GNS430W. Although, as others have reported, it won't lock on to satellite signals until out of the hangar, while the SV GPS locks on once the hangar door is open (and very accurately, too, as I can see by showing position on an airport diagram), so multipath from all the hangar structures is not a problem, apparently.

 

[dynonsupport]

We have mentioned that the 2020 GPS may not work inside an aircraft because we don't want anyone with that installation in mind to then be frustrated when they get the SV-GPS-2020 and it doesn't work acceptably. This is especially true because our current SV-GPS-250 is extraordinarily sensitive and works in a lot of places that it really shouldn't. I have one inside my car mounted upside down under the dash and it works!

If you have a reasonable installation of the SV-GPS-250, then the SV-GPS-2020 should work fine there. We just don't want anyone to be surprised if they had the SV-GPS-250 mounted under the seat in a lead box and it always worked OK, but now the 2020 doesn't.

The SV-GPS-2020 needs a stronger signal to deliver the integrity needed for ADS-B, and there's nothing we can do about this. The issue is not multipath (read up on circular polarization and how it helps with multipath) or other signal distortions, it's just signal strength and a good view of the sky.

As many people have mentioned, there are lots of materials that should work just fine, like fiberglass. However, this is experimental aviation, and every antenna is basically in a different location, and there may be a few of those that don't work well. For instance, one under the cowl with 180 degrees of the low angle satellites blocked by the firewall may cause issues at times.

 

[jakej]

DS - That's the answer we needed, no complaints from me

Jake J

 

[William_Ince]

DS - That's the answer we needed, no complaints from me 

Me neither.

 

[lolachampcar]

Not only am I not complaining but Dynon has actually worked with the FAA (apparently) to generate a mandate compliant solution that permits the antenna to be tested in different locations. That is a first to my knowledge as all previous compliant position sources have required external mounting and no painting. Thank you for helping to provide some common sense flexibility Dynon.

This one is just for Steve.... TSO'd GPS antennas forbid painting so you may want to consider paint when making comments about fiberglass cowls. Also, most canopies have a tint to them and some use materials which degrade RF; again, something you may want to include in your comments.

 

[swatson999]

I think the restriction against paint is because of metallic paints. Don't know about canopies.

I do know that I have both my SV and by GNS430W antennae under the cowling, and neither has had any problems in 300+ hours. YMMV.

But you are right...fiberglass may be transparent, but metallic paints would almost certainly cause signal degradation.

 

[jakej]

As mentioned before, my GX60 antenna has properly performed since 1998 & 1500hrs under 1/2" of foam sandwich with non metallic paint, I will 'test' the new 2020 antenna in the same position before drilling holes for external mounting.

I'll also report here the results as soon as it's available & mounted.

Jake J

 

[david.perl]

We just don't want anyone to be surprised if they had the SV-GPS-250 mounted under the seat in a lead box and it always worked OK, but now the 2020 doesn't.

why would anyone do that?

 

[n456ts]

4 days until Fall... Any update on a specific release date or ordering info for the 2020 GPS?

 

[lolachampcar]

Aircraft Spruce has them listed so I ordered one. Its direct factory ship so I assumed I'll see it when Dynon ships it.

 

[Dynon]

We don't have a specific release date to share yet. For the record, we didn't say the very first day of fall

 

[jakej]

Many years ago AS&S had new colour version of the VM EMS on their website & listed for purchase,  after some digging I found out these were not manufactured yet & subsequently never were.
I believe Dynon don't operate that way & will have the GPS 2020 available soon, be patient 

Jake J

 

[lolachampcar]

and long before 2020