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Garmin GTX 32 Remote Transponder Auto Standby

jliltd

Well Known Member
I have a GTX 32 remote-mount transponder controlled by a GTN 650. The transponder automatically switches to "standby" by itself after landing. It also automatically switches to ALT when airborne which can interfere with a lead ship when flying formation. How can I disable the automatic mode switching on the GTX 32? It was a fine idea for this action in the days before ADS-B but now it is a nuisance. The GTX 32 is paired with a GDL 82 for compliant ADS-B out.

In the installation settings for the GTX 32, accessible from the GTN configuration mode for external systems, the only options for auto-standby are a time delay of between 0 and 99 seconds once on the ground. There is no "on" or "off" option. Just the time delay. That's it.

Meanwhile on the Air/Ground Logic menu the options are "Auto Airborne Off", "Squat Switch", "GPS Data" and "Altitude Data". It seems to default to "Altitude Data" and if I select "Auto Airborne Off" it changes for about 5 seconds then reverts back to "Altitude Data". Since that doesn't work perhaps I could select "Squat Switch" and it should never activate airborne since I don't have a squat switch installed.

Has anybody had any luck overriding the automatic mode switching on the GTX 32? Thanks in advance.
 
I suggest you email the Garmin rep who frequents this forum. This cannot be right - except for formation flight, the faa now recommends NOT going to standby on the ground - since that disables your adsb-out.
 
Squat switch

Air/Ground Discrete.
The AIR/GROUND discrete is active-low, and can be configured to interpret if the aircraft is airborne or on the ground based upon whether the input is grounded or open. If it is desired for the air/ground state to be airborne when the squat switch input is grounded, then toggle the AIR/GROUND discrete key to Active for Airborne. If it is desired for the air/ground state to be airborne when the squat switch input is open, then toggle the AIR/GROUND discrete key to Active for Ground. The default configuration is Active for Airborne.

Yes, you can select Squat Switch and force the system in GND mode.
If installing a wire and a switch on the GTX32 connector P3271 pin 22 connected to GND you can manually switch between GND/ Airborne mode.
It is also possible to use pin 16 which is external standby. (GTX 32-OFF).
GTX 32 Installation Manual Page 4-4.
 
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I am talking about the transponder mode control. I don't think the GTX 32 has an air/ground selection. Although digital, it is an old Mode C remote transponder. The GDL 82 has provisions for a squat switch for discrete input but that does not change anything on the transponder.
 
I suggest you email the Garmin rep who frequents this forum. This cannot be right - except for formation flight, the faa now recommends NOT going to standby on the ground - since that disables your adsb-out.

Exactly. This old Mode C transponder was designed by Garmin to do this auto standby stuff long before ADS-B. The GDL 82 was designed to give these older transponders compliant ADS-B out but the transponder determines the standby setting, and the original auto standby in the GTX 32 can cause the aircraft to violate the "always on" ADS-B rule when it switches to standby while the aircraft is still operating on the ground. Also, the auto "on" when airborne can catch a formation flight off guard when a wingman makes sure he is squawking "standby" before takeoff and the transponder takes it on its own to switch to "alt" during climb out.

We need to be able to make these transponders to be completely manually controllable and over-ride the automatic mode switching.
 
GTX 32 Automatic Mode Selection

We are setting this combination of equipment up on our bench to take a look at it, we will respond here with more information after our analysis.

Thanks,

Justin
 
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