I am posting here to get the opinion of experts in ATC systems on a debate I'm having on a forum with someone that claims to be a pilot.
The debate is regarding 9/11, he seems to be making some extreme claims regarding the ATC systems and I was wondering if any of you guys could set the record straight and explain exactly what he is missing?
He already said he is not an expert in ATC systems, but then talks as if he is and acts like its all so obvious. I however can find nothing supporting how he understands it and no one else seems to talk about the system like he does.
I hope this subject is not offtopic as it is in some forums, but I really don't want to debate 9/11 here, merely deal with the facts of how the system works.
The entire thread is here, but the relevant parts are below.
And earlier in the conversation he says...Originally Posted by K^2
Do you know how a transponder works? It works as an extension of radar detection, not as a separate system. When a radar sends a ping, it's not just a short burst of radio frequency. It's a short code. When transponder picks up that code, it sends a burst of its own, replying to the sent code and also encoding the squak code, and depending on the system some additional information that is difficult for radar to acquire. Mode C specifically, which is what required within 30nm of Class B sends back pressure altitude.
This is very important for the ATC operations in large airports. A squak code is used to identify aircraft, so that the ATC can give specific instruction to a specific blip on the screen. The altitude is important because radar cannot pick it up, and it's another piece of information that the ATC will require.
Now why am I claiming that it's a load of crap that they couldn't find a plane? What happens if I'm flying my crop duster, and I flew into a busy Class B airport area? Am I simply not going to show up on the radar screen which ATC are using to steer the planes? Are you seriously that naive? Do you know what will happen if that crop duster ends up on the path of a 747 going for final? You'll have 300 dead bodies. That's if the 747 doesn't end up dropping on a residential area.
Everything that's big enough to show up on radar shows up on the screen to which all the transponder data is fed. If something does not have transponder, it will be shown without a squak and without an altitude. You see a dot on your radar without a squak in Class B, you report it immediately, because it's a hazard to all aircraft in the area. That's how the system works. That's how people get busted for flying within 30nm of a Class B without a working Mode C Transponder.