Is GNS430W GPS antenna good for SV?

[Camillo]

Hallo.
First question is: will one GPS antenna, coming from my GNS430W, will be good for 430, SkyView and Trutrak ADI or do I need a second one?
Thanks
Camillo

 

[PhantomPholly]

A GPS antenna provides information to the GPS receiver (in this case the 430). That unit in turn can send digital data (ARINC or Serial) to many other units.

1 GPS receiver = 1 antenna.

 

[Camillo]

Thank-you.
But...is it not possible to use a tri-plexer as for VOR signal?
That way, I will only have to install one antenna and then to buy the SkyView receiver or connecting it directly from 430.

Is this right?

 

[dynonsupport]

The Dynon SkyView doesn't use a GPS antenna. We only accept serial input streams. The GPS "puck" we sell is actually a full GPS receiver in the "antenna" and all that comes out is serial data. This is totally different than the way the 430 works.

Even if we could use an external antenna, using one is not a good idea for redundancy since GPS antennas are powered. They aren't just simple metal structures like a VOR or Comm antenna. They have amplifiers in them and are powered by the GPS. So if you had three GPS units hooked to one antenna, the antenna could fail or any GPS could fail and you would lose all your data.

If you don't need redundancy, just use the serial out from the 430. If you do, you need another antenna.

 

[Camillo]

Thank-you very much. It is now clear to me that Dynon GPS receiver will give me redundancy.

I read in installation manual (7-1) that "A valid GPS signal is required for time, magnetic heading calibration and moving map functionality". GPS informations are also required at page 5-3 (Magnetic heading  Calibration §) for the same purpose (calibration). So, no real problem for redundancy.

On the other hand, another task for the GPS signal is backup attitude calculations in case of a pitot or static blockage (5-2). This may be a valid reason for having a separate GPS receiver.

I will think which solution best fits my missions.
For the moment, may you confirm please that - apart form attitude backup - during the flight a GPS input is not needed in order to obtain heading? I guess magnetic heading only comes from magnetometer, which is included in ADAHRS module.

Thanks.

 

[dynonsupport]

Correct, you do not need GPS in flight for anything relating to heading, attitude, speed, etc.

Without GPS you will not have synthetic vision (since we don't know where you are), the moving map, or some fuel computer functions.

 

[dynonsupport]

One other technical detail is that we use GPS time to set the clock in the system if it's there. The Aviation format that comes out of the 430 series doesn't have time, but NMEA data that comes out of most portables and our puck does. That means that if you want time automatically set, you want a NMEA serial GPS somewhere in the system.

 

[PhantomPholly]

And to confirm for the above poster:

Connecting the Dynon puck/GPS receiver in addition to connecting your GNS 430W should provide backup GPS data to the Skyview unit. If your pitot gets blocked AND your 430 fails, this backup will provide GPS stabilization to your Skyview in IFR conditions.

 

[Camillo]

Thank-you very much to both.
I will tolerate less redundancy from GPS input for the SkyView system because I will also have a TruTrak ADI with its own GPS receiver and maybe I will also install my Garmin 296 on the right part of the panel.

So, I will have two GPSs in addition to the 430W itself and a backup "attitude" instrument (the ADI) with its own battery. I think that way only a nuclear explosion below the airplane will cause total attitude and direction loss ;-)

As I understood, linking the 430 to the SV, the only matter will be, in my case, not having updated time. A little trade-off.

Thanks

 

[PhantomPholly]

As I understood, linking the 430 to the SV, the only matter will be, in  my case, not having updated time. A little trade-off.

Thanks

Initially yes, but later they will have an ARINC decoder unit. If you add that, then SkyView will have access to all of the enhanced GPS data including updated time.

 

[glasair]

The GPS antenna for the GNS430 and GNS430W is an integral part of the IFR certified system. In fact, the antenna was changed from the one for the 430 to the one for the 430W. It had its coverage pattern enhanced to be more sensitive to satellites low in the sky near the horizon. If you use the GNS430(W) for IFR enroute, terminal, or approach regimes of flight, you are not supposed to mess with the certified configuration consisting of the panel mounted GPS, the antenna, and the indicator. I have wondered about the indicator. If you do not use an approved indicator with the GNS430 and instead display the CDI information on something unapproved like the Skyview when ARINC to the Skyview becomes available, I don't think you are operating in a "certified" mode anymore since the certification of the GNS430 includes an approved indicator. Archaic but true.

 

[PhantomPholly]

I have wondered about the indicator.  If you do not use an approved indicator with the GNS430 and instead display the CDI information on something unapproved like the Skyview when ARINC to the Skyview becomes available, I don't think you are operating in a "certified" mode anymore since the certification of the GNS430 includes an approved indicator.  Archaic but true.

There has been a great deal of discussion about this, as well as "what is certified." The general consensus is that for a home built plane, the "indicator" need only reliably report the data output by the certified GPS.

Here is a good article on the subject.

 

[glasair]

I read the article but found nothing that supported the view that for a "homebuilt" aircraft the rules for the indicator displaying the course information from the IFR certified GPS are any different than for an aircraft with a standard airworthiness certificate. Where can I find the discussion that formed that concensus opinion? Now I am curious since the Garmin-sold CDI indicator I am using is taking up valuable panel real estate in my Glasair and if I don't legally need it, I would probably remove it if I could display the info on a Dynon EFIS and be IFR legal.

 

[Camillo]

Yes, I had the same question some time ago.

But, here in Italy, it will not be a real issue, because an experimental airplane, when using a certified engine (which I had to buy), can be approved for IFR use, but ONLY in VMC conditions. It is forbidden to have an experimental airplane flying into IMC conditions.

So, as far I understood, there is a bit of non-written tolerance from ENAC engineers (equivalent to FAA) about mixing together certified and non certified stuff and about strict compliance to rules which apply to the actual general aviation airplanes (for instance, I was not asked to install an ADF, which I installed, however).

 

[PhantomPholly]

I read the article but found nothing that supported the view that for a "homebuilt" aircraft the rules for the indicator displaying the course information from the IFR certified GPS are any different than for an aircraft with a standard airworthiness certificate.  Where can I find the discussion that formed that concensus opinion?  Now I am curious since the Garmin-sold CDI indicator I am using is taking up valuable panel real estate in my Glasair and if I don't legally need it, I would probably remove it if I could display the info on a Dynon EFIS and be IFR legal.

I will recommend the Vans Airforce RV forum for your search. It probably has the world's largest active community of homebuilders - partly because RVs are the most popular kit, and partly because just by being the biggest it attracts every other sort of home builder.

There have been many discussions on this subject - search on "legal" and "ifr."