Peter wrote:
The CAA would not be interested in publishing evidence of transponders being turned off – for obvious reasons. It is widely known and openly discussed (face to face) that lots of people are doing it.
Maybe, but the CAA have a duty to do so when assessing the regulatory impact of their asctions and also an overriding responsibility with respect to safety.
I think if they CAA know this is the impact of current regulations they are on very dangerous ground if they fail to act.
It is illegal to turn off your transponder, and also very stupid, but clearly many are tempted, or are actually doing so, as a direct consequence of the CAA’s current policy, and is a fundamental risk to air safety.
A FOI request would be the short answer to see where we are with this.
The CAA would not be interested in publishing evidence of transponders being turned off – for obvious reasons. It is widely known and openly discussed (face to face) that lots of people are doing it.
Two overlapping threads merged
Graham wrote:
The technology clearly exists to derive altitude from primary radar, but civilian ATC radar does not routinely incorporate it.
Yes, I think the technology is there but not worth operational use for ATC regarding traffic & airspace separation standards
Even for military applications radar elevation is not operationally used except for initial vague guess? for interception by aircraft or ground-air defence missiles, radar interception is done without altitude data from the targets, the intercepting aircraft get primary radar reflections on their own receivers and they will calculate an offset to fly versus primary radar illumination, they keep doing that until they get infra-red or visual ident of the target
Peter wrote:
I would very much like to see a pic of a civilian radar which can get altitude…
Indra Lanza PSR 3D is a modern civilian ATC surveillance radar. A phased array for sure.
Somewhat older is the American ARSR (Air Route Surveillance Radar) series, here is the latest one, ARSR-4:
We have two very similar threads, now merged.
The video I posted above shows the “nodding donkey” (I think that was the military slang for it) radar which was used for PAR approaches, and for detecting incoming military aircraft (obviously the enemy won’t be transponding) and missiles.
Nowadays the state of the art is all phased array and they can track hundreds of targets concurrently because the beam can switch direction in microseconds.
I would very much like to see a pic of a civilian radar which can get altitude…
Peter wrote:
Do they have elevation? That would be extremely unusual. With a phase array radar (military) you get that easily but not with a normal rotating dish.
Oops, right, it’s mostly the military ones that have elevation, but it’s not necessarily a phased array. If I remember correctly, TESLA (the Czech electronics company rather than Elon Musk 
) used to make ones with a “nodding” antenna, though it may have been a PAR.
Fuji_Abound wrote:
but presumably only of value if the aircraft is transponding? Without it will not be seen on secondary?
Correct, if the aircraft isn’t transponding, there will be no superposition of altitude information, only a “blob” on the screen at the range and azimuth. If you get a traffic service from a LARS you often get stuff like “traffic in your 2 o’clock, right to left, 2 miles, no altitude information”. That’s all they can do when they get a primary return from a target that is not transponding or transponding in mode A.
This was my understanding also. The technology clearly exists to derive altitude from primary radar, but civilian ATC radar does not routinely incorporate it.
lionel wrote:
This one says its precision of altitude is ±3000ft. That’s useless to “detect airspace infringements”.
Let’s be optimistic and say more tolerances on CAS busts otherwise you will get flagged on GND setting inside LTMA
