On Dec 17, 2:14 am, WingFlaps wrote:
On Dec 17, 2:27 pm, Mxsmanic wrote:

writes:
What is the practical difference between "above, but not
including" (e.g., +12) and "above and including" (e.g., 12)?

I think it serves when you have two airspaces with no margin between them.
For exampple, one is 12/SFC, the other is 70/12+. So at 1200 feet you're in
one airspace, and at 1201 feet, you're in the other. If they were specified
as 11/SFC and 70/12, the space between 1101 feet and 1199 feet inclusive would
be outside either airspace.

You need to understand the vertical relationship between airspaces.
Have a look at a sectional and think about it. Why would you choose to
fly on the vertical limit between to airspsaces anyway?

There are certainly reasons to want to fly at a +X altitude rather
than 100' lower. For example, if you're under a low Class B shelf, you
might want to be as high as possible as a precaution in case there's
an engine failure; 100' higher might give you 1000' further to glide.

But not every +X floor adjoins a designated X ceiling below. For
instance, consider the +05, +08, +11, and +12 Class B segments around
EWR on the NY TAC (see skyvector.com). What's the point of the + for
those segment floors? A +11 lets you fly at 1100', as opposed to 1099'
without the +. But letting you fly one foot higher is of no value,
since that's much less than the accuracy with which you can control or
even measure your altitude. So why do they bother having the + there?