VAF Forums - New Garmin GNC 355 GPS/COM, July 2019

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Quote:

Originally Posted by g3xpert (Post 1459945)

Hello, apologies I will need to retract the previous statement.

The STC installation manual (REV3) calls out this interface with the RS232 line from the GTX 3XX and to the GNC 355. This interface/communication line has since been removed. It is reflected in the latest TSO installation manual (REV2). The GNC 355 will not receive/require any data from a GTX 3xx.

The STC manual has not been updated due to the STC Rev Cycle not being complete as of yet. So, you can omit this interface and use the latest TSO IM REV2 for guidance.

Apologies for the confusion.

BR,
Brad

Hey Brad, It does seem a bit odd that the 355 TSO Installation Manual Rev. 2, dated January 2020 would supersede information in the newer 355 STC Installation Manual Rev. 3, dated February 2020.

In any case, how exactly is "This interface/communication line has since been removed", accomplished? Hardware change? Software update?

I mean what happens to all the GNC355/GTX3XXs already installed and connected, (many of them by certified guys), as per the GNC355 STC Rev. 3 installation instructions? Will they all suddenly cease to function correctly? Did none of them ever function correctly?

ZT

Quote:

Originally Posted by ZTatZAU (Post 1459957)

The current GNC does not have the software format to receive the GTX 3XX trandponder data over RS232, so it will not read the data even if that hardware communication line remains.

The dates on the certificated installation manuals don't always mean 'newest information' like in the experimental manuals, as the data within them have to follow the appropriate TSO and STC update schedules (per certification requirements). This is why there are two separate installation manuals to follow each certification line....

Nothing happens (no changes made) to fielded units - they operate the same as they were first powered up and the ports would not be configurable to operate, even if the data line was installed.

I have made our certification/product team on the 2" Navigator line aware of the conflicting information in the appropriate manuals.

BR,

Brad

Quote:

Originally Posted by g3xpert (Post 1459968)

Thanks Brad! I appreciate the info.

Can you tell me if the GTX335wGPS&GAE12 could RS-232 its encoder data to the GNC355 by configuring the GTX335 output as ALT FMT 1 as shown in Table 6-1 of the GTX 3X5 TSO Install Manual Rev. 9? If so, how would the GNC355 be configured?

Or is there simply no way to send the GTX335's pressure altitude to the GNC355?

ZT

Quote:

Originally Posted by g3xpert (Post 1459968)

The current GNC does not have the software format to receive the GTX 3XX trandponder data over RS232, so it will not read the data even if that hardware communication line remains. ...

BR,
Brad

I guess the better question Brad, is, do you expect the RS-232 communication line from the GTX3XX to the GNC355 will be restored/created/implemented in future GNC355 SW updates?

And does this shortcoming also affect RS-232 communications from the GTX3XX to the GPS175 and GNX375? Or only the GNC355?

Thanks! ZT