I agree, but you have to wait for perhaps 99% of jets (basically everything with mandatory TCAS) to install RA-capable gear not based on Mode C before you can relax the law on Mode C TXP carriage.
It’s going to take time.
Fair enough
PS I forgot to compliment NCYankee on his very useful write up!
NCYankee’s contributions are state of the art stuff 
NB Silvaire, what is your grudge against transponders? OK, they make us visible to all and sundry, but ADS-B does too, even putting us on FR24 and the like. What then do you dislike about them?
It is important to realise the differences between USA and Europe. I do think UAT adds direct benefits for users in the USA as discriped by NCYankee.
As UAT is not used in Europe, while it seems that the percentage of aircraft that carry mode S in Europe is higher then in USA. Solutions like the Trig TT-31 seem to be a good solution. If upgrading to ADS-B I would ALWAYS recommend to choose an ADS-B out ready device, even if there is no desire for ADS-B OUT. Your unit is ready for this should the situation change.
There are signs, which NCYankee also mentioned that their are going to be transponder manufacturers coming with an internal or add on WAAS GPS to meet the ADS-B out requirements as full compliant.
It is also important that there a test carried out (in the UK with NATS) which allow to connect a non certified GPS source, and to see if that would be of any help to ATC. This is an interesting feature. It is also important to notice that their are quite some installations flying with these uncertified GPS (including the appriopriate settings). This would be still usefull for traffic aviodance (just like the usefull buth uncertified Flarm devices)
Jan, mostly I don’t like the prospect of carrying around and maintaining two pieces of equipment to do the same job. I’m also quite aware of how extra equipment and weight degrades aircraft performance. My 65 HP aircraft, which BTW will never carry an electrical system or position reporting equipment, performs about as well as others with 85 HP and a lot of electrical stuff. The biggest electrical load on some of those planes is the transponder – which I don’t think would be case with a pure ADS-B system.
Also, as an entirely separate issue associated with Mode S and ADS-B (and not transponders in general) I have grave reservations about continuously broadcasting my identity to government when flying VFR, because it opens up the door for them to bill my aircraft by the mile for every movement. I have every expectation that some government entities would do that in a heartbeat after the technology has been installed to allow it. Whether they get away with it remains to be seen. Some would characterize this as a civil liberties issue, but I’m more concerned that liberty and money are inextricably related.
What is the ADS-B situation in EU/EASA-land right now?
Is there for instance an approved ADS-B specification that equipment can be compliant with?
Maybe that has been the case for many years, but I get the impression that the ADS-B requirements have changes quite a lot the US I guessed that the EU would do no better.
Can I for example get a Trig TT31 and a Garmin GTN to be ADS-B OUT approved/certified in an EASA aircraft? How costly would the paper work be?
With that combination you are fine for compliance European ADS-B out, however it is considered a major change, which makes it quite expensive. The most senseable way is to wire this such that it can be enabled in software. EASA has made some proposals to relax rules for general aviation. If these rules make it as they are now, you could enable the ADS-B out in software and be compliant. Without wasting money on a major change.
Are there any published timescales on mandatory ADS-B in Europe?
In April I spoke to a fairly senior guy from a European transponder manufacturer who thought it would be
and something between 2020 and never for all the traffic in between the two
IOW, a bit like Mode S, except that southern Europe has more or less ignored Mode S, but we now have EASA mandating stuff.
Even the 2020 deadline is likely to slip, in his view, to maybe 2022 for an actual installation deadline.
And this was a TXP mfg who would normally dish out the “it will be mandatory next year, and the penalty will be death” industry line.
Are there any published timescales on mandatory ADS-B in Europe?
Yes, but these are for large aircraft only, starting with January 2015 for all NEW large aircraft, and December 2017 for ALL large aircraft (retrofit).
None for general aviation.
For sure ADS-B will be mandated first for IFR General Aviation. I don’t think ADS-B will become mandatory for VFR General Aviation. However this is all speculation.
I think it will be like the 8,33 kHz, currently mandatory for IFR aircraft, not for VFR aircraft. However if you want to fly into certain controlled airspace or some airports you will need 8,33 kHz to fly in that airspace. So no mandatory for VFR, instead you must have it when flying to some controlled fields.
Is 8,33 kHz mandatory for VFR? No. Do you need 8,33 kHz for VFR? It depends if you want to fly that airspace, if you want, you need 8,33 kHz, else you don’t.
You don’t need a VHF COM or a transponder in most countries. The possibilities you have flying which such aircraft become more and more limited. I think the same thing would happen in the long run with ADS-B, where you would need ADS-B to get into the CTR of a controlled airfield, as ADS-B has huge advantages for ATC at approach, tower and ground.
Often these new technologies become mandatory first for newly manufactured aircraft. After a while retrofit installation will become mandatory. This was true with mode S and 8,33 kHz for example.
