EDIT 5-17-2019-- I've excised out some of the portions of the post below. I no longer feel that the exact language of the FARs as they stood during the time when we had "Control Zone extensions" appearing on the chart legend, i.e. late 1992 to September 1993, proves that ultralights were welcome in these areas even without prior authorization. But the modern language does indeed indicate that today's E3 and E4 airspace is not included in the airspace listed in today's FAR 103.17 where ultralights are not to enter without prior permission.
If you want to read more about my take on the pre-1993 history of the "Control Zones" and "Control Zone extensions" before the "alphabet" airspace reclassification, see this link to an entry I wrote for another on-line aviation forum -- https://aviation.stackexchange.com/q...us/64247#64247
----- end edit.
Ron, I assume you are referring to post #20 -- http://eaaforums.org/showthread.php?...ll=1#post75320 - Read it again-- I never said control zones were not depicted prior to 1992. In fact I said they were depicted starting sometime in the mid-1940's. I said the dashed magenta lines first appeared it 1992.
You mean they had rectangular projections sticking out from the circles? I never meant to suggest otherwise. (Ok, I guess I did describe them as round circles. I went back and edited the post so as not to imply they were always round.)
In fact, in FAA advisory circular AC 103-6 from 1983 https://www.faa.gov/documentLibrary/...r/AC_103-6.pdf , we find the word "extension" on the 7th page, in the section on control zones.
But there was no dashed line on the sectional charts separating these areas from the basic inner circles, and these areas were never officially designated as "extensions to control zones" or "control zone extensions" in the "Airspace Designations and Reporting Points" document. So the areas weren't "extensions" in the same sense as we have now.
I don't think that your description of the evolution of the airspace is fundamentally different than mine. The point is that at a certain time (1992), the concept of "Control Zone extensions" suddenly appears as a specific thing on the sectional chart legends, and for the first time we see dashed magenta lines that abut up against the dashed blue circles.
Steve