GMC 307 vs. GMC 507
 

Both the GMC 307 and the GMC 507 appear to be available for sale currently, and it looks like they're the same price. This prompts two questions:

1. Is there any reason anyone would still choose the 307 over the 507? From what I can tell, the 507 appears to be an upgrade and includes things like audible alerts. In other words, is there something useful that the 307 does that the 507 doesn't do?

2. Is there an upgrade path for 307 owners, short of "buy a new 507"? I would dearly love to have audible alerts of autopilot disconnect, since this has taken me by surprise on a few occasions. The flashing AP visual warning provided by the G5 is not very attention-getting.

http://www.vansairforce.com/communit...d.php?t=167951

Also, one thing they don't mention is the 507 has TRK button, the 307 does not. Also, someone said something about the VNAV button, both 307 and 507 have that I believe.

I had a similar question, and this was the reply from Levi at Garmin:

“From the installers perspective, the GMC 307 primarily interfaces to the system via RS-232. The GMC 507 interfaces primarily on the CAN bus. The GMC 507 was designed to allow us to create our GFC 500 autopilot with the G5 as the primary interface. From the user's perspective, the units are very similar. If you have already purchased the GMC 307, there is really no reason to upgrade.”

Edit: I should add that Levi’s response was specifically for my G3X Touch-based system. Might be different for G5 owners.

G3X and G3X Touch systems provide autopilot tones and voice alerts and a means to connect a TO/GA button, so except for the TRK button, you already have most of the features provided by the GMC 507 with a GMC 307.

If you have a G5 based system, the extra features provided by the GMC 507 are very nice.

I'm getting ready to install a 507 in my RV6A with a dual G5 setup. Am I correct in understanding that the TO/GA button option only works with the GTN series navigators not the GNS series navigators?

Hello LawnDart,

Yes, that is correct.

Keep in mind, however, that the Takeoff (TO) and Go Around (GA) autopilot modes work regardless. You will just have to initiate the missed approach on the GNS in addition to pushing the TO/GA button to execute the missed approach.

With a GTN navigator, it is a single button pressure to execute the missed for both the autopilot and the navigator.

Thanks,
Steve

G5 based systems
 

Also my conclusion! Is there an upgrade path?

The 307's lack of an audible warning of autopilot disconnect is a major disadvantage.

Also, given that they are the same price, is there any reason that anyone in possession of all the relevant info would buy the 307 instead of the 507?

This thread seems to indicate that the GMC 507 is compatible with a G5 based system (no G3X).
This Web page doesn't mention the GMC 507: https://buy.garmin.com/en-US/US/p/514383#overview

Hello FORANE,

The GMC 507 can be used with a G5 only system or a G3X Touch system (with/without G5).

We are working to add GMC 507 support to the G3X system (GDU 370/375 displays).

We don't actually sell the GMC 307 anymore since the GMC 507 is the same price and does more.

Thanks,
Steve

Makes sense
 

Any upgrade path available for us early adopters?