Another good tip is to focus your attention on the inbound half-circle side. You can be both at x500 ft and converging.
Don’t ask me how I learnt that lesson.
They don’t do that by transponder they do it by recording radio calls.
This might be the real reason, the guy of the tower meant. The crew even did not give any radio calls, although there was much traffic in the circuit.
I have never had an instructor telling me to turn the transponder off for any reason. Most French aircraft are fitted with Mode C. There are a few airfields where you would pay for T&Gs even with no ATS present. They don’t do that by transponder they do it by recording radio calls.
Also even at places like Cannes Mandelieu most clubs who are based there would have a block, annual landing fee, so there is no necessity to hide your touch and goes or full stop landings.
So I’m not sure why the controller you spoke to would say what he said.
In the eight years I’ve had TAS in my plane, I don’t think I’ve spotted a single traffic outside the circuit that wasn’t beforehand flagged by either TAS or ATC.
Not true for me. Being equipped with TAS as well I saw several plane in short distance which where announced neither by ATC nor the TAS. I‘m talking only about the engine driven ones, not gliders. And it’s true as lower your altitude and the closer to an airfield, the more planes you will spot.
Especially on the smaller airfields I find often aircrafts in traffic circuits on training purposes with switched off transponders. I do not know why the instructors do not put the transponders on. I only got an answer once, when I was asking on the radio, that it is was a vintage aircraft not equipped with transponder. But normally they keep silent on the radio.
In France once a controller told me, after a near miss in the traffic circuit, that during the time where no one is on the tower, the instructor switch off the transponders by purpose to avoid flight track recordings and to pay for the touch and goes. But I don’t know if this is really the truth because if no one is on the field you normally pay nothing in France.
I find more or less the same
In the eight years I’ve had TAS in my plane, I don’t think I’ve spotted a single traffic outside the circuit that wasn’t beforehand flagged by either TAS or ATC. I doesn’t mean I don’t spend much of my time looking out, but I have a pretty low opinion of my capacity to eyeball unknown traffic (*). So TAS and if possible a Traffic Service, any time.
Snoopy wrote:
but a lot of people fly non-TXPMaybe in the UK? In Austria TXP Mode-S is mandatory in airspace E which is almost everywhere.
Same in the UK – you must turn on the TXP if fitted.
Allegedly, some say “TXP fails intermittently”, others switch it to mode A (no altitude).
Although that discussion is for the other thread…
but a lot of people fly non-TXP
Maybe in the UK? In Austria TXP Mode-S is mandatory in airspace E which is almost everywhere.
Dual TAS (Air Traffic AT-1 and ADSB GNX375) on my ship, and I still spend as much time scanning the outside world as possible. Glass cockpits and gadgets having the side effect of pilots playing with those instead of looking out…
Birds are another threat to watch for, as well as hang gliders and such, though they are getting equipped with Flarm… not the birds though 
dutch_flyer I think these things “just happen” randomly, and apart from taking some measures there is little one can do.
I has an active TAS (not cheap – about 13k GBP) which is great but a lot of people fly non-TXP, especially given today’s UK CAA policy on 100% busting. So the other measures are e.g. not flying below 2000ft, flying above cloud, etc. Flying in cloud is probably the safest 
