TRSA and /X

"Guy Elden Jr" wrote in message
oups.com...
Something I've always wondered... why do TRSAs even exist? Seems like a
dangerous proposition to choose some airports as having the concept of
a voluntary controlled airspace? Why not a Class C (their closest
cousin as far as I can tell)?

They are left-over from when Class C airspace was called an ARSA. The main
difference between an ARSA and a TRSA was that the former required
participation, while the latter did not. Then, and now, the TRSA is sort of
"in-between" Class C (mandatory radar services) and Class D (no radar
services).

As for why participation is optional, well that's sort of like asking why
participation in radar services is optional in Class E airspace. Do you ask
that question? I suppose you (or someone else) might, but I don't.

The bottom line here is that TRSAs exist where there's a terminal radar
facility (approach/departure control), but where there's not enough traffic
to justify mandatory participation (as is the case for Class C, or Class B
for that matter). It's really just Class E airspace, where radar services
are being provided by a terminal controller rather than a center (enroute)
controller (that's a bit of an oversimplification too, but it's the basic
idea).

The boundaries show you where the terminal controller provides the radar
services rather than the center controller. The only difference in radar
services is who is providing them; it's still just your run-of-the-mill
Class E services, which are optional wherever you are.

I suppose you might ask why, if there's not that much traffic, there's a
terminal radar facility. Usually the answer to that question has to do with
the type of aircraft using the airspace (and usually an airport within that
airspace). But I wouldn't be surprised if the answer to that question does
vary with facility (and no, I don't know the answer for every situation).

Pete