Fuji, the reasons vary, as posted several times before.
The glider I flew most until 2005 (Ka6E, made 1968, bought very second hand, construction mostly wood/fabric) for 20+ years had no more panel space, no more battery space, and was already on the upper limit of max permissible weight. It had no approved scheme. Typical for older gliders of that era.
The glider I now fly (Lak 17A, built 2005, mostly carbon fibre) originally had no approved transponder installation scheme and only one battery barely sufficient for a long flight with normal instruments – I once finished a competition flight switching things off as voltage dropped from 12+ to about 7.
As I am not the tallest pilot (about 5’7”), I fly it with its adjustable seat back one notch forward, and have found a way to carry two more batteries behind it. Not every glider or pilot could accommodate this. I count them as removable portable equipment and so not needing EASA approval. I hope I am right.
The manufacturer has since obtained EASA certification for an approved transponder antenna installation, but included in the approval only 3 specific named transponders, of which at least two would not fit into my panel (which they made, fitting the instruments I asked for, and leaving one small hole for a transponder control unit such as Trig). Unfortunately, Trig is not one of the 3 approved units, so I still can’t fit it. I don’t know what I would have to do, or pay, to have another unit approved, and look to the CAA to make it easier. EASA has not helped in this – in the old days, the BGA could have approved it cheaply and easily..
Many new gliders now being made do have approved schemes. A number of slightly older ones have retrofit approved schemes. If they need a new panel, however, I think it is back to the approved mod issue.
My perception is that most owners are not fitting transponders because of a mixture of reasons – most don’t use CAS, most don’t cloud-fly, most know that glider/glider collisions (one fatality a year on average for the last 20 years, as well as the non-fatal ones) are far more likely than glider with anything else (4 in 40 years), and transponders won’t help those, whereas Flarm will. More are fitting Flarm, few transponders. Flarm is mandatory for continental flying near mountains, and for competitions in some parts of the world. It is cheap (ish - £500 or less) and addresses what people see as an issue. Flarm + transponder + PCAS just won’t fit in most gliders, and without PCAS, TXp is useless for glider/glider alerts. Flarm gives much more useful alerts – level, above, or below, and which direction, and only if on conflicting courses not just nearby (clever algorithm).
In the long term, I think Transponders + ADS-B or something like it might be an interoperable compromise – but I’m not holding my breath. It would probably be less useful in alerts than Flarm, unless a similar algorithm could be incorporated.
Any technical solution will be a long time being widely adopted, unless mandated – gliders last as long as powered aircraft, EASA changes are difficult and disproportionately expensive, and most people simply don’t see anything needing fixing. They spend their money on what are their priorities – doesn’t everybody?
Just saw CGB’s picture. Not EASA approved, I believe.
Chris N