Serial Connection on VSGV

[PhantomPholly]

Hey guys,

A question came up on another forum about the role of the serial connection and the VSGV autopilot.

I know that without the ARINC lines connected you will not get vertical steering.

The question is, since ARINC is essentially a superset of the data in the serial stream does the autopilot REQUIRE the serial connection?

Sorry if this has been asked before - even sorrier if it was me asking!

Cheers,

Bill

[TrutrakTech]

Never be sorry about a question!

The answer to your question is yes and no. With the ARINC connected to the VSGV, you will get both lateral and vertical steering commands (assuming your source can output both). At that time, the serial connection only provides the GPS ground track. Without the serial connection, you will get no DG in the upper left of the display (on the newest models of the DII), it will say NO GPS. On the older models (2.25 and older software), you will see HDG instead of TRK, indicating that the AP is reading from it's internal magnetometer instead of the GPS ground track.

So, while it's not required, it's best to go ahead and have it connected. This also gives you a back up in the rare case that your ARINC source would become corrupted. The VSGV can then use the GPS NAV mode to still follow a flightplan.

[PhantomPholly]

Interesting. So, what would happen if I used the ARINC lines from my GNS480 but used the serial line from my 496?

Are you saying that steering commands from the 496 would be ignored if the unit is receiving ARINC steering from the 480?

Would that not provide true backup in the event my 480 failed?

[TrutrakTech]

Interesting. So, what would happen if I used the ARINC lines from my GNS480 but used the serial line from my 496?

Are you saying that steering commands from the 496 would be ignored if the unit is receiving ARINC steering from the 480?

Would that not provide true backup in the event my 480 failed?

Nothing adverse would happen. It would work perfectly. When an ARINC steering command is present, it gets priority as we assume you'd like to use GPSS if it's available over GPS Nav.

That would be a great way to have a back up rigged. It would also eliminate the need for switched input. Thanks!

[PhantomPholly]

That's what happens when you have a software background...

:D

You might want to make this an announcement, make a post that is a sticky, and update your manuals to let all your customers understand this interesting default behavior. This is VERY valuable info!!!

[PhantomPholly]

Per the TruTrak post on the RV Forum -

If the following conditions are ALL true:

- You did indeed connect different GPS units to the TruTrak (one via ARINC, the other via Serial);
- Both GPS units have an active flight plan;
- The TruTrak is set to mode GPSS (following the ARINC GPS flight Plan)
- The ARINC GPS fails, or the wires fail

THEN:

The unit will NOT default to the flight plan from the Serial source. It will instead default to GPS ground track.

You could then press the MODE button to follow the secondary GPS flight plan.

This still provides SOME backup capability.