The GTX330 does indeed have an ARINC429 pressure altitude output, but when this was connected (in 2013) to my TAS605, it didn’t work.
Both Garmin and Avidyne washed their hands of it.
So the pressure altitude to the TAS605 had to be wired in gray code (10-11 wires) from the KEA130A encoding altimeter (which also feeds the GTX330).
There was a post here a few years ago, which I can’t find, suggesting that some software revision in one box or the other solves this compatibility issue.
This may not be an issue; something to watch.
The original interface for the GTX330 to GNS430 used ARINC 429 to provide GS to the GTX. GS is used when the aircraft does not have a weight on wheels signal, for example my Bonanza or all of the fixed gear aircraft. This is used to set/reset ground mode on the transponder. This was later changed to RS232 because there were more ports available and Garmin decided to go with the serial interface for ADS-B Out because of the constraints using such a limited number of ARINC ports and protocols. ARINC 429 was also used between the GTX330 and the GNS430 for Mode S TIS. The ARINC data included position information. So for these installations, a wire to the GNS serial port had to be added. Often a serial port was already in use for items such as a moving map, portable device, or a fuel totalizer. The format of this data is typically designated as “Aviation”. The format needed for ADS-B Out of the compliant variety is “ADS-B Out +”. Only one can be selected on a given port. Aviation data format is public information, but “ADS-B Out +” is a proprietary format. So separate serial ports need to be used for ADS-B devices and the other’s such as the MFD/fuel totalizer. Some installers have tried to use a single serial port, but this fails on one or the other.
So if there is a serial port already used in the existing installation between the GPS and the transponder and it is a dedicated port, then all that needs to be done is to configure it properly. If it is not dedicated, a new serial connection needs to be added.
Am likely to swap my 330 for a GTX335 in the next 12 months. I already have a traffic alert system (Mode C and Mode S), so don’t see the need for the more expensive GTX345. Am I missing something?
I do notice that in the USA people seem to default to the GTX345: ADSB-IN, bluetooth connectivity.
Like others I went with the GTX335 (in the the US, where ADS-B IN is a factor) because:
(1) Garmin would sell the GTX335 for installation by me and my A&P, unlike the GTX345 which they will not ship except for dealer installation. I dislike Garmin’s business practices and want to do as little business with they or their dealers as possible.
(2) I didn’t want the obsolescence issue related to installed ADS-B IN needing to interface with potential new portables and apps for decades to come. The OUT part is the product of FAA regulation and is unlikely to change. I don’t want to touch the thing for decades, and would rather update portables if/as required, except where installed hardware is required by regulation.
(3) I prefer a more reliable Wi-Fi connection versus Bluetooth for the in-cockpit connection and my Stratus 2S has a very reliable connection to multiple devices in the cockpit with no action on my part. It just works, shortly after I turn on the avionics master I have two iPads and an iPhone logged on and showing traffic.
(4) The 335 is considerably cheaper with the Internal GPS GTX335 + GPS antenna + GAE12 plug-in encoder bundle and my primary objective was to satisfy the 2020 mandate at my US base with the simplest and most reliable hardware possible, and as few hassles as possible.
RobertL18C wrote:
), so don’t see the need for the more expensive GTX345. Am I missing something?
If you have or plan having any other installed Garmin screens like GTN650, GTN750, G500 etc. etc.the GTX345 will enable you to display weather data on all those displays. If you go for the GTX335 that route is blocked. No portable ADs-B receiver will make this happen.
At least once a week I have call from an aircraft owner realizing this fact and many regret not getting the GTX345. If you have a steam gauge panel it all does not matter but then you might not want any expensive Garmin tarnsponder to start with. Other solutions from smaller vendors might be your choice then anyway.
I would recommend the GTX 345. Weather is not yet available using the UAT receiver in the UK, but in talking to uAvionix at Sun N Fun, they seem to think that there is a 50-50 chance that the UK might spring for ground station coverage. It would probably only take 8 to 10 ground stations to cover the UK. Built in traffic alerting is much better than with a portable and meets the TSO standards. There is ongoing work in the RTCA world that Europe is participating in to bring more weather data to the cockpit. Also, when you decide to sell, the GTX 345 will have greater appeal. I have two BT linked devices in my cockpit (FS210 and FS510) and IMHO, it is more reliable than Wifi.
Sebastian_G wrote:
If you have a steam gauge panel it all does not matter but then you might not want any expensive Garmin transponder to start with. Other solutions from smaller vendors might be your choice then anyway.
Which is the reason Garmin was forced to offer the GTX335 to the open market, not just for installation through their dealers, and discount it heavily. With Garmin forced into that position and with the ability to remove the existing encoder from the plane, the 335 with plug-in encoder and internal GPS became a good technical choice for my purpose. One installed hardware item versus three, plus (unfortunately but unavoidably) a new antenna. Less is more, when it comes to installed equipment in my plane and ties to the manufacturer.
@Silvaire I boast a steam gauge panel, and in fact am going retro as the BK KI825 EHSI has become unreliable, and uneconomic to try and fix – and is being replaced with an old skool overhauled BK KI525.
Another question for the EuroGA brain trust? I am considering upgrading my 530 for a refurbished 530W. I like the knobology of the 530/430 and while I don’t need WAAS/EGNOS (my SOP in a SEP is lite IFR), getting a recently refurbished unit would be nice. There was a window when you could send your 530 to Garmin for overhaul, and it came back as a 530W, but I missed that one.
Other than LPV capability and getting a refurbished unit, is there any other advantage to this swap?
RobertL18C wrote:
Other than LPV capability and getting a refurbished unit, is there any other advantage to this swap?
RobertL18C, I think the main things were:
- Vertical guidance
- Faster screen refresh
- Holds improved
- LNAV is no longer “tram tracks” – due to SBAS it is more like ILS, a cone
- SBAS integrity checks
I think the main question is the cost of the new unit and comparing it with the cost of the likes of IFD 540 (which is just a slide-in replacement) and GTN750.
GTN or IFD will obviously give you visual approaches and Enroute VNAV (which some use to create DIY approach even if the other options fail).
And AFAIK in all cases you need to replace the GNSS antenna and the cable.
