wrote:
.. . . snip . . .
If you put a transponder in your glider - either with or without an
encoder - it needs to be calibrated and so noted in your aircraft log
book. You are then required to have checked every twenty-four months.
If you are going to put a transponder in the glider, then spring for an
encoder - In for a penny, in for a pound and all that. Without the
encoder ATC as well as TCAS only gets azimuth and range. With the
encoder you get the third demension, altitude.
Sure beats ending up in Denver as a pitot cover on a B-767!

Billy Hill, Zulu

Zulu,

Having owned a few junky older airplanes (like old Bonanzas) with only
Mode A transponders, I can't recall any requirement for calibration or
any recurrent inspection of these. If you're flying IFR, you have to
have a pitot/static check every two years, and if you have Mode C, you
have to have the encoder calibrated, but I wasn't aware of anything
other than that.

Ed