Darryl Ramm wrote on 11/30/2019 10:13 PM:
On Saturday, November 30, 2019 at 7:30:25 PM UTC-8, Mike Schumann wrote:
On Saturday, November 30, 2019 at 8:26:42 AM UTC-6, Eric Greenwell wrote:
Darryl Ramm wrote on 11/29/2019 10:36 PM:
Again if you are installing TABS just set the transponder squat switch to
"None" and use manual ON/ALT switching on the transponder.

I might forget to switch it correctly. Would using the "gear is down"
switch to change between ground/airborne be a sensible choice? The pattern
(and the first 500'-1000' after the takeoff) would be flown showing the
glider was on the ground, of course, but that might be better than having
the whole flight showing as on the ground.



If you use a squat switch with a Trig transponder, I believe that also puts
the Transponder into GRND mode, so it wouldn't be responding to
interrogations. The one place you do want ADS-B OUT and your transponder
operating is in the pattern. That's where half of the midairs occur.
Turning off ADS-S B OUT or your transponder as soon as you lower the gear is
a really bad idea.

Mike has an important point. Please do not dick around and end up disabling a
safety system. If you are in the air the transponder needs to be in ALT mode.

What is actually going on is a bit more messy, but "not responding to
interrogations" is a useful summary. In GND mode Mode-S transponders will
actually reply to direct addressed Mode-S interrogations, and do some other
things, but that a far from a necessary set for the transponder to operate
normally (e.g. it can't be acquired as a target by SSR). It will keep
transmitting ADS-B Out, but messages encode the glider is on the ground, and
some message content changes slightly. How all different ADS-B receivers all
respond to that is uh anybody's guess. I just have an image in my mind of
somebody seeing a transponder reply LCD thingy blink when in GND mode at some
time and say "ha see it's replying OK". Ah nope, it's replying to a small
subset of stuff. Flying in GND mode is a bad idea.

I thought it might be a bad idea, but it was easy to do, so worth asking. When I
do a TABS install, I will use an airspeed sensor - easy and cheap enough.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1