While aero-towing a Mode-C transponder equipped glider, and using
PowerFlarm and transponder in the tow plane, most of the time the
glider will show up on the PF as a threat aircraft. Since the PF
prioritizes threats, this precludes another more distant "intruder"
aircraft as being displayed as a threat. I'm not entirely sure how PF
really deals with this, but it did prompt the idea of turning the
glider's transponder to standby during the tow. And how best to
accomplish this while minimizing the risk of the glider pilot
forgetting to switch the transponder back to ALT after release?

It’s accepted practice to turn off all but one transponder when
formation flying with power aircraft. This to prevent each transponder
from replying to ATC or TCAS at the same time and each stepping on the
other so the receive end gets interference. This probably has not been
much of a problem with a tow plane and glider because traditionally
few tow planes have had transponders.

At Minden, NV, near a busy terminal area and near approach paths into
Reno, all of the tow planes have transponders, and most of the gliders
do as well. Yet we have not adopted a policy of leaving the glider
transponder in standby mode until tow release so as to prevent the
multiple transponder proximity conflict.

Perhaps a change in our normal tug to glider “radio check” prior to
launch: Tug says “transponder on standby” to glider prior to launch,
glider responds, “on standby”. At tow release, glider uses the term,
“transponder on” instead of the “off tow” or “thanks for the tow” used
currently. If glider does not use that phraseology, tow plane
responds, “check transponder on”.

Comments and suggestions . . .

bumper
zz
Minden, NV