Using the magenta circles

It is on the IFR charts because -- at least in theory -- the information
helps VFR pilots determine where they can legally scud run and at what
airports they can legally fly a standard 1000-foot pattern on a marginal VFR
day. Whether that is safe or whether VFR pilots actually are aware of or
follow these rules is another matter.

The distinction between a 700-foot transition zone or a 1200-foot transition
zone basically helps VFR pilots to determine if they can fly a standard
800-foot or 1000-foot pattern on a day when there is a 1000-foot ceiling.
The answer is yes for airports with 1200-foot transition zones and no for
airports with 700-foot transition zones.

A related issue has to do with Class E Surface Areas -- generally commuter
or regional airlines are permitted only to fly at airports which have Class
E Surface Areas and thus -- at least in theory -- where it should not be
possible for an IFR airplane to break out of a cloud and find a VFR airplane
1 foot below. This means that on marginal VFR days it is at least
theoretically safer for an IFR pilot to land at an airport with a Class E
Surface Area than with Class G airspace on the surface.

--
Richard Kaplan, CFII

www.flyimc.com