Using the magenta circles

Thanks, Richard. That's somewhat along the lines I was wondering
about. However, both of the cases you listed are for IFR flights.
Makes me wonder why, if this information is more useful to the IFR
pilot than the VFR pilot, is it on sectional charts when it sounds
like it would be more useful on low level enroute charts (although,
I'll be the first to admit that I have a sectional or WAC available
when flying IFR).

"Richard Kaplan" wrote in message ws.com...
"Ace Pilot" wrote in message
om...

common use is doing T&Gs in the pattern below 700 feet AGL when the
weather is marginal. Other uses?

1. The altitude where controlled airspace begins can be a factor for an IFR
pilot selecting an airport at which to fly an instrument approach if he is
concerned about airplanes legally flying a traffic pattern 1 foot below him
when he breaks out of a cloud.

2. In areas with unusual and predictable weather patterns, i.e. a very thin
marine fog layer, some pilots depart IMC in Class G airspace in anticipation
of breakout out on top into VMC conditions before entering controlled
airspace -- not necessarily wise but legal nonetheless.

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