Anyone else notice that most of Class G above 1,200 no longer exists?

[flyingron]

You are wrong. TCAS has nothing to do with radar. It is on board equipment that actively interrogates transponders in nearby aircraft and displays their position relative to the airplane equipped with TCAS. It cannot see airplanes without transponders, or planes that have the transponder turned off.

We call devices that determine range and direction by interrogating other aircraft's transponders secondary radar. It's perhaps not the best term but it is RADAR.

It only works if the guy is presenting mode C by the way. A transponder itself isn't sufficient.

 

[Dav8or]

We call devices that determine range and direction by interrogating other aircraft's transponders secondary radar. It's perhaps not the best term but it is RADAR.

It only works if the guy is presenting mode C by the way. A transponder itself isn't sufficient.

Really?? It can't see Mode A? I am assuming it does see Mode S since that is newer though. Fortunately, I don't think there are too many people flying around with just Mode A anymore. From what I can tell, it has pretty much faded away.

 

[flyingron]

It doesn't know what to do with a mode A return. All that provides is the squawk code with no altitude. TCAS resolutions are all about altitude. It might give an advisory target with -- as an altitude but it's not really doing the TCAS thing with only a mode A.

Mode S includes mode C so yes Mode S works. In fact if you have two TCAS equipped planes converging, they will negotiate a resolution over mode S.

 

[Everskyward]

Really?? It can't see Mode A? I am assuming it does see Mode S since that is newer though. Fortunately, I don't think there are too many people flying around with just Mode A anymore. From what I can tell, it has pretty much faded away.

I've seen targets without altitudes on TCAS which I assumed to be airplanes without mode C or S. It obviously won't do an RA but the traffic is visible.