...Oh and as a PS....I design glider electrical systems!
I can tell.
A very well reasoned answer, Nimbus, thank you.
And it is more important to maintain a workable supply to the Radio/Logger/GPS at the end of a flying day, than fit additional instrumentation, when there are procedures in place mitigating the need for it (calling on 130.4)
There I disagree. ICAO and the CAA believe that a Mode S transponder is a necessary piece of equipment for aircraft.
If the power requirement of a transponder reduced the typical battery life by a factor of 3, I could see a case for exempting gliders from the forthcoming requirement to carry them. But at 10-20% of the design electrical load, I can't -- while it is undoubtedly
significant, we all make sacrifices to performance to install equipment with a safety benefit.
BTW power consumption data on the TRT600 appears contradictory:
0.2 A on
http://www.filser.de/main.php?dat=e_ger_trt600
0.1 A on
http://www.filser.de/prospekte/TRT600_prosE.pdf
0.4 A on
http://www.filser.de/handbuch/trt600instmane.pdf
I'd imagine a Mode S only environment would significantly decrease the mean power consumption, but that will be a long way off while Mode A/C ground equipment continues to operate.