What's missing when Dynon's receive NMEA vs Arinc?

[DougN]

I'm trying to twist my head around the operational difference between sending an NMEA 0183 stream from a GPS vs sending an Arinc Aviation stream to the Dynon collection.

If I have a GPS capable of supplying its info in either NMEA or Arinc, why would i choose one over the other?

What calculations will be missing? What features won't be present? How about feedback to the GPS for OBS mode? Is that handled in both formats?

Thanks,
Doug

 

[PhantomPholly]

Re: What's missing when Dynon's receive NMEA vs Ar

As I understand it, ARINC contains a superset of the NMEA data including (potentially) vertical steering.

[Edit / correction]

While a TruTrak autopilot accepts both, it will only refer to the ARINC data (if available) and reverts to "ground track" mode if the ARINC signal fails but NMEA is still available.

 

[dynonsupport]

Re: What's missing when Dynon's receive NMEA vs Ar

In GPS land, ARINC gives you a few main changes:

Vertical information. If you have an approach certified GPS, the vertical nav info only comes over ARINC.

OBS feedback. Serial is unidirectional and we cannot send anything to the GPS without ARINC. So no "virtual VOR" without ARINC.

Auto scaling of CDI needles, from Enroute to Terminal, to approach, to varying on the approach. With serial you must switch modes manually, and you only get E/T/A, not the constant vary at the end.

Sending other data to the GPS, such as OAT, IAS, TAS, etc, which lets the GPS do things with the data (like winds).

You will still get winds aloft on the EFIS, HSI needles (the horizontal ones), and other calculations over serial.

If you have a Garmin 430/530, then the only way to get VOR/ILS data out of the unit is via ARINC.

Basically, if you have an HS34 and your GPS has ARINC, you should probably choose ARINC. There is no real reason to use both, and I have no idea why TT would need both connected. All serial navigation data is also on the ARINC stream.

Just as an FYI, the Garmin panel mount GPS units technically output "AVIATION" format on the serial port, not NMEA, which is why I used "serial" above not NMEA.

 

[PhantomPholly]

Re: What's missing when Dynon's receive NMEA vs Ar

Now that is interesting - I wonder if my TruTrak would still function with only the ARINC?  [edit] Yes, it does and only uses NMEA if ARINC becomes unavailable.

 

[DougN]

Re: What's missing when Dynon's receive NMEA vs Ar


i have a TruTrak DII VSG (have had it for about 2 yrs) and I've been running it only on the serial NMEA data from the AvMap GPS.

It won't do the vertical navigation with serial only; and it won't do fly-by lateral nav (the GPSS mode), only fly-over (GPS Nav mode).

As i've mentioned, I'm adding a Garmin GPS-155XL which is approach rated, but not WAAS, so it's not LPV. So... i wonder if i'll get any vertical navigation with the ARINC stream from the GPS-155XL for the non-precision approaches.

 

[dynonsupport]

Re: What's missing when Dynon's receive NMEA vs Ar

I don't have the 155XL manual handy, but the 300XL manual says it only outputs horizontal data over ARINC, no vertical.

 

[Chriseleven]

Re: What's missing when Dynon's receive NMEA vs Ar

I have the following fitted in my aircraft:
D10A EFIS, D10EMS, Garmin 430, Trutrac ADI Pilot II autopilot.

In South Africa we do not have WAAS nor any GPS approaches so I need the VOR/ILS for IF approaches.

As I understand it I need to install a HS34 to get the VOR/ILS data displayed on the EFIS but does this mean that the Trutrac will no longer be able to display the GPS track. Is this correct or am I misunderstanding the posts above.

 

[PhantomPholly]

Re: What's missing when Dynon's receive NMEA vs Ar

I have the following fitted in my aircraft:
D10A EFIS, D10EMS, Garmin 430, Trutrac ADI Pilot II autopilot.

In South Africa we do not have WAAS nor any GPS approaches so I need the VOR/ILS for IF approaches.

As I understand it I need to install a HS34 to get the VOR/ILS data displayed on the EFIS but does this mean that the Trutrac will no longer be able to display the GPS track. Is this correct or am I misunderstanding the posts above.  

Per the features page of TruTrak, the Trutrac ADI Pilot II only supports Ground Track; GPS course track; and altitude hold.  You will be able to use the GPS to track a GPS approach course, but will need to manually change altitude.  It will not couple to a VOR/ILS course at all.

The TT should (if it's like the DigiFlight) accept either NMEA serial or ARINC connection directly from the Garmin, so an HS34 will have no effect on the TT.  If available, hook up the ARINC connection from the Garmin to the TT directly, splitting the wires to also feed the HS34 if you buy one.  You will also need to hook up the HS34 ARINC output lines to the 430 input ARINC lines to be able to set ILS course.

 

[dynonsupport]

Re: What's missing when Dynon's receive NMEA vs Ar

Using the HS34 will not interfere with or change the way the TruTrak operates at all. The connections can be split.

 

[Brantel]

Re: What's missing when Dynon's receive NMEA vs Ar

The TT ADI Pilot II does not have ARINC interfaces only serial...There is no way to get the TT ADI P II to follow VOR/GS/LOC info from the 430.

I have the following fitted in my aircraft:
D10A EFIS, D10EMS, Garmin 430, Trutrac ADI Pilot II autopilot.

In South Africa we do not have WAAS nor any GPS approaches so I need the VOR/ILS for IF approaches.

As I understand it I need to install a HS34 to get the VOR/ILS data displayed on the EFIS but does this mean that the Trutrac will no longer be able to display the GPS track. Is this correct or am I misunderstanding the posts above.  

Per the features page of TruTrak, the Trutrac ADI Pilot II only supports Ground Track; GPS course track; and altitude hold.  You will be able to use the GPS to track a GPS approach course, but will need to manually change altitude.  It will not couple to a VOR/ILS course at all.

The TT should (if it's like the DigiFlight) accept either NMEA serial or ARINC connection directly from the Garmin, so an HS34 will have no effect on the TT.  If available, hook up the ARINC connection from the Garmin to the TT directly, splitting the wires to also feed the HS34 if you buy one.  You will also need to hook up the HS34 ARINC output lines to the 430 input ARINC lines to be able to set ILS course.

 

[ksouthar]

Re: What's missing when Dynon's receive NMEA vs Ar

Is it possible to split the ARINC signal?

I am in the midst of installing an HS34 to a KLN90B. The preferred connection is ARINC but that is connected to a Tru-Trak AP.

Can I feed 2 devices at the same time?

 

[dynonsupport]

Re: What's missing when Dynon's receive NMEA vs Ar

Just like serial, ARINC outputs can be split to multiple inputs, but you can't hook multiple outputs together. This is why the HS34 has one output but two inputs. We can talk to multiple devices with the one output, but we need two inputs to listen to two devices.

 

[ksouthar]

Re: What's missing when Dynon's receive NMEA vs Ar

I finished the installation today and so far, everything seems to be communicating as they should.

KLN-90B GPS drives both HS34 (ARINC) and Tru-Track Digiflight II G (ARINC).

Both are connected to the ARINC A TX and ARINC B TX on the KLN-90B.

Weather permitting, I'll do the flight test tomorrow. Ground tests show normal operations.

ks

 

[ksouthar]

Re: What's missing when Dynon's receive NMEA vs Ar

Finished the installation. Flight tests show normal operations for all the devices.

The KLN-90B GPS drives both the Tru-Trak AP in proper GPSS mode and the HS34 using the ARINC connection split to both devices.

Thanks to everyone for the advice and suggestions. ;D