Arinc 429 Question..please help

[taverroi]

I have a garmin 420, an sl30... A tru trac vsg ll and a grt sx200 and a s100. I'm being told that I need to have an arinc 429 module for one reason or another. Can somebody school me and tell me just what I'm not gonna be able to do if I don't get one.....or what I am gonna be able to do If I do get one. I don't really even know what the heck it does. Thanks

[rzbill]

I am flying without ARINC 429.

If you want absolute integration of all data sources and ability to use GPSS autopilot steering from each source, you need the ARINC box.

You can comunicate with either RS232 or ARINC 429.
RS232 (as implemented) limits the information passed from equipment to equipment.

For instance:

Without ARINC 429 box, you will not be able to send and show VOR data from 420 to GRT

Without ARINC box, you loose some autopilot functionality ( the "G" in "VSG" ) when driving the autopilot with the GRT.

Here is what you MAY be able to do without buying ARINC box (don't treat as gospel because your equipment is slightly different than mine:

1) Write off the VOR from 420. Use RS232 VOR data from SL30. The 420 can be wired to provide LOC/ILS/GS indication to GRT if you desire (mine is done this way)

2) Connect the autopilot direct to ARINC on the 420. This allows GPSS steering to function.

3) I do not know if it is possible to have both ARINC and RS232 connected to a TruTrac such that you could have the ability to do non-GPSS function through the GRT. This would allow tracking of SL30 signal.

As stated, I am flying non-ARINC. I do not have a GPSS autopilot either. I am only missing VOR from the 430. I don't really miss it that much and not having GPSS is not a bother either. You have a GPSS autopilot. It may be a cluge to get that to work seamlessly with the rest of the boxes unless you buy an ARINC box.

[taverroi]

I can't tell you how much this has helped my understanding.
thanks a million.

[BobTurner]

If you have a 420, as stated, it does not have a VOR.
ARINC is a different digital standard, and needs a pair of wires, compared to RS-232.
The GRT Sport does not come standard with an ARINC interface. It does have RS232 interfaces. Count them, you can use them up fast!
The 420 sends some info out the RS232 line, and some info out the ARINC lines.
The SL30 sends everything out the RS232 line.

I think (??) you can display gps data from the 420 on the GRT EFIS with no arinc, but I think you cannot set the OBS on the 420 from the EFIS without arinc. About the only use of OBS mode is for holding patterns. And I think you can enter it on the 420, although it is awkward.

Does your autopilot have GPSS/GPSV? If so, you should wire a 3 pole double throw switch so you can select the 420, or the EFIS, as the data source for the autopilot. Use the 420 (direct) position to have the autopilot follow a precision LPV GPS approach. IF you have arinc on the EFIS then it will "translate" the SL30 data and allow the autopilot to track a VOR or ILS. This is the main loss if you do not have the arinc module for the GRT.

[taverroi]

Thanks for that info. Yes it does have GPSS, not GPSV. i am having a 3 pole switch wired in as you suggested already. I think maybe I should go ahead and spring for the arinc 429 as i would like to be able to track an ILS.

Only on this forum could I have gotten the answer this quickly. I sincerely apprieciate you guys taking the time to respond to me. TV

[BobTurner]

Okay, with gpss the autopilot will track the left-right gps signals, and it will anticipate turns so it does them smoothly, with no overshoot. If you get an arinc module for the efis then the autopilot will follow heading commands from the efis, and also localizer and vor signals from the SL30 which are processed thru the efis. The autopilot will not follow glide slope signals, neither LPV nor ILS, without GPSV capability in the autopilot.
If you want full ILS capability for the autopilot you will need the arinc module for the efis, AND you will need to get TruTrac to add GPSV to the autopilot.