Skyview output to GTX327

[mmarien]

The garmin GTX327 transponder has an airborne sense to switch from STBY to ALT and back. One method to switch the GTX327 is GPS ground speed. Two questions. Does anybody know if the GTX327 will accept ground speed from NMEA sentences. And two, does Skyview output NMEA.

 

[schristo]

it requires 'aviation' data segments... apparently the gps data is fed to atc which requires that it be provided from certified sources which are not available from garmin portables.

 

[mmarien]

That would exclude connecting my GPS495 to the GTX327 as the GPS495 accepts Aviation format but only outputs NMEA and VHF data.

Appendix D of the Skyview installation manual suggests that the Skyview will output NMEA, Aviation and other formats. I'm going to connect one of the Skyview serial OUT ports to the GTX327 with the belief that it will work.

Failing that I can always use something like the Aircraft Extras airspeed switch as a squat switch and connect it to pin 22 on the GTX327.

 

[schristo]

tried the outputs to no avail... the airborne sensing works fine from standby to altitude with pressure, the only thing you gain from the gps data is turning the unit back to standby when landing since there is no way to determine this from pressure...  i have not tried taking the dynon gps data direct but doubt it will work.  i suspect that the dynon might send 'aviation' data after they complete the update for interfacing with a 430.

 

[mmarien]

The Aircraft Extras airspeed switch ($30) connects to your pitot and can be set to close (normally open) at any where from 70-140mph. Pin 22 of the GTX327 switches to airborne (ALT) when grounded and back to STBY when open. So setting the airspeed switch to close at say 70mph would indicate you are airborne and of course anytime you are less then 70mph (switch open) would indicate that you are on the ground or headed that way.

The airspeed switch is advertised as a safety switch (in conjunction with their FPS system) to deactivate the flaps until you slow to a safe speed (70-140mph) but also makes a handy squat switch for the GTX327.

Perhaps I'll wait to hear from Dynon about the Skyview output formats before I make a decision.

 

[dynonsupport]

We do not output any data except altitude data right now (no NMEA, no aviation). When we have a more functional moving map, we will probably add that, but it will likely be NMEA, not aviation.

I'm confused from below- do you know if the 327 needs NMEA or aviation format? We can consider adding what is needed, but it will likely be quite a few months away.

 

[mmarien]

The GTX327 installation manual says GPS ground speed and shows the connection to a Garmin 400 or 500 series. I don't know what format they output, but Stephen is suggesting it's Aviation format.

Based on the information here, the squat switch is the best way to go for now. It's only one wire so it can always be changed later.

 

[tucsonphil]

Auto switching from STBY to ON may not be a good idea. Several large airports request, via ATIS, that you leave your Transponder on for ground ops. They use their ASDE (surface radar) to track taxing aircraft.

I don't think leaving your transponder ON while taxing is a problem anywhere.

Phil

 

[mmarien]

It is a problem where TWR doesn't want their screen cluttered with aircraft on the ground. In that case, your transponder should be on STBY or OFF. I think that is why Garmin offers the SQUAT option - for us guys that don't always remember to switch the transponder mode. It's also a safety thing. You have better control of your plane when your hands are on the flight controls rather than the transponder.

There is a programable delay time (default 24 sec) before the transponder automatically switches from ALT (or ON) to STBY. That is probably enough time to exit the runway but not enough time to TAXI to the hanger line. So the SQUAT function doesn't accomodate situations as you describe.

Does ATIS specify ON or ALT? I believe the transponder switches to ALT when it senses that it is airborne and STBY when it thinks it's on the ground. If ATIS specifies ON, the solution would be to press the ON button. That action is required regardless of automatic switching as you are STBY at the hanger and ALT in the air.

 

[skysailor]

mmarien,

I fly from these large airports with ASDE in my day job. The FAA puts out on ATIS that the transponder is to be "operated on all taxiways and runways including Mode C". The TCAS in the jet automatically ignores targets at field elevation (derived through FMS routing). I am going to disable the auto airborne feature of my Garmin transponder for this very reason. While I will not fly the Glasair I am building from these airports I think the ASDE system will spread to virtually all tower controlled airports eventually.

 

[mmarien]

Thanks for the heads up. Until that happens, I would think that the SQUAT function is a great option to relieve the pilot of some tedious tasks and let him fly the plane. It doesn't relieve him of checking that the transponder is in the proper mode or stop him from manually changing modes.

Do you have the Future Vision Instrument Panel in your Glasair? Here is a preview of the Skyview retrofit in my Glasair II:

 

[skysailor]

Right now the Glasair is a standard type panel. This kit had the Vision panel before it was abandoned and I bought it but it was sold before me.