Checked the AIP. Mode S is not required anywhere here, and the CAA has no plans to introduce any requirement either.
So you read the wrong German AIP. I guess we passed 2008.
§4 of GEN 1.5
(5) For the following VFR flights, aircraft shall be equipped with an SSR transponder:
1. flights in Class C Airspace or Class D Airspace (not control zone);
2. flights in transponder mandatory zones (TMZ);
3. flights at night in controlled airspace;
4. flights with power-driven aircraft, except for gliders, above 5000
ft MSL or above a height of 3500 ft GND, whichever is higher.
The transponder shall have Mode A 4096 code capability and Mode C automatic altitude reporting. Mode S technology for trans- ponders in compliance with applicable international standards (at least level 2 with SI Code and Elementary Surveillance ELS func- tionality) will be required for new aircraft with effect from 31 March 2005 at the latest, and for all aircraft with effect from 31 March 2008. The air navigation services organisation shall publish excep- tions to items 1 and 2 in “Nachrichten für Luftfahrer”.
“Here” = Norway. I thought maybe there were requirements coming for 20k+ or something (which I thought was the alt in Germany/UK). Only to find that there are no plans for any mode S requirements whatsoever.
I’ve got a couple more data points in last 2 days, two PA28 types at 8000-9000ft in Switzerland. Neither was 7000, so this means even “common” types do appear if they are high enough.
What is amazing is the very low density of this traffic. It incidentally shows that IFR GA activity in Europe in the “common” (rental scene) types is extremely low, which does suggest that an easier to get IR isn’t going to increase IFR traffic much.
Edit: just looking at a PA28-161, squawking 7000, at 4000ft, again in Switzerland. So for sure FR24 is not filtering 7000 squawks but must be filtering ones at lower levels.
Here’s another data point for you. Me in a PA28 last Sunday (trying out new nav kit) http://www.flightradar24.com/data/airplanes/g-kemi/#79b11e0
Started out squawking 7000, then got a dedicated squawk from Cambridge radar (unusual on a Sunday) and then back to 7000 west abeam Wisbech. 4,000 ft initially and then 5,000 from Leicester.
Not sure whether it is coincidental but FR24 picked me up climbing through 3,000 ft, which is when Cambridge gave me a dedicated squawk, and the trace ends at 1400 ft.
Aircraft has mode S.
I saw several common types <2000ft with a 7000 squawk here in Germany. My understanding was, that only FLARM or ADSB-out-targets are displayed on FR 24.
I get the feeling, that we need another filter to get representative results…..
Yes – I am now looking at a G-reg PA28-181, 7000 squawk, at 1600 feet, near Shoreham/Lydd!
So there is more to this FR24 “filtering”.
only FLARM or ADSB-out-targets are displayed on FR 24.
Definitely not so. Almost no GA is radiating ADS-B (maybe 0.1% or 0.01%). Mine shows up OK (Mode S, GTX330, firmware from 2005). FLARM… possible?
Tomorrow I might do the planned EGKA-LFAT as VFR, 7000, 5400ft, then FL064, and we can see if it shows up in the above URL.
Back to homebuilts, earlier I saw an RV12, Swiss again, 7000 squawk, 7200 feet (I have a 7000ft min filter on the RVs). The only homebuilt seen today in Europe > 7000ft.
ADS-B out is getting more common, but most GA-types still do not use it. I guess it´s most common in the glider community. Regarding the filtering: keep in mind that you need coverage to be able to display an ADS-B target. If the antenna is behind the next mountain (Switzerland) it´s well possible to think FR24 is filtering below FL70 when in fact they just don´t receive a thing! I´ve seen glider and microlights at much lower altitudes on FR24 regularly, especially in the Dutch/German border region.
Traffic density below FL150 is extremely low, except for TMA traffic. I will try to get numbers for this, but my guess is that in Germany less than 2% of all traffic has cruising levels of FL150 or below.
Traffic density below FL150 is extremely low
I guess you mean Eurocontrol IFR traffic, @Caba?
I guess it´s most common in the glider community
That would be FLARM, however, not ADS-B. Does FR24 pick up FLARM? I would think not since the apparent purpose of FR24 is tracking airline traffic. They are not really interested in GA and seem to filter out most of it. I am certain it is deliberate filtering (in most cases) and not being below terrain because for example I have seen PA28-type traffic showing up in the very flat south east UK, 7000, at low altitudes. An observed exception always disproves a proposed theory 
So far everything I see does suggest that there is very little high altitude traffic in most types, away from places where such altitude is necessary e.g. Switzerland.
Peter wrote:
They are not really interested in GA and seem to filter out most of it.
No filtering from what I have seen. It’s just that you need a dedicated FLARM device and hook it up to FR24. At least that’s my understanding, and is what I have seen them do.
And this is me two days ago.
(As Peter noted, the GS is completely bogus.)
