The complete listing for all Class A, Class B, Class C, Class D, and Class E airspace areas and for all reporting points can be found in FAA Order 7400.9J, Airspace Designations and Reporting Points, dated August 31, 2001. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. "
But I'll be d***ed if I can find FAA Order 7400.9J anywhere! I found the above info at
Class G (U.S. Airspace) by definition (FAR 71 and AIM) is considered everything not otherwise labeled Class a,b,c,d, or e. Generally speaking in continental U.S. Class E base is at 1200 agl or 700 agl (transition area for IAP at an airport - magenta on VFR sectional) unless designated otherwise (some mountainous areas that are >1200' agl). Class G is below this.
"Generally speaking in continental U.S. Class E base is at 1200 agl or 700 agl (transition area for IAP at an airport - magenta on VFR sectional) unless designated otherwise (some mountainous areas that are >1200' agl). Class G is below this."
cvsfly,
Are you telling us that there is generally no Class G airspace between 1200' AGL and 14,500 MSL? Take a look at a Los Angeles sectional and tell me where Class E airspace begins when not designated on the chart. That's right...14, 500 MSL.
If the Class E base was generally at 1200' AGL, why does the chart legend have that funny blue shading that brings Class E to 1200' AGL?
This is a misconception many of my students have as well. None have flown in the western half of our country where the chart doesn't have that note on it bringing all Class E to 1200' AGL. Many pilots think Class E airspace always starts at 1200' unless otherwise designated. They wouldn't know what to think if they saw blue shading around an airport.
I think the misconception is because John King or some other aviation lame-o uses G=ground as a nmemonic for where class G exists.
The best definition for the veritcal limit of class G is the floor of the overlying airspace, which is 14,500 in the absence of any other marked airspace.
Thats why I said --- "unless designated otherwise (some mountainous areas that are >1200' agl)". and offshore, etc. Read your charts. They usually have all the answers concerning airspace dimensions.
OK...how is the Class E "designated" on the L.A. chart? Yes, mountainous areas are sometimes zipper lined to provide a Class E floor but this is not the case in my example. There is no designation on the chart or in the legend of where Class E starts so...it starts at 14, 500' MSL. It is actually the lack of a designation which tells us this.
"CLASS E AIRSPACE EXISTS AT 1200' AGL UNLESS OTHERWISE DESIGNATED AS SHOWN ABOVE"
What becomes a bit confusing is that the Jeppesen cross-sectional view of the airspace system shows E begining at 1500' AGL - but that's only above 14500' MSL, isn't it? The words for this can be found in FAR 71.71(a2). It doesn't seem like there would be much real estate within the USA that would be affected by this provision. Just my .02
Referencing a "VFR" Sectional chart. I don't have one infront of me and maybe I haven't looked at one closely lately. The base of class E is designated at 700agl around airports that typically have only unicom services and an IAP (i.e. no TWR, CZ) this allows Instrument approaches to be contained in "controlled" airspace a little longer - think VFR weather minimums. These typically look like a key hole with magenta shading. The blue shading on the outside of this area designates class E at 1200 agl. Offshore areas have a symbol like _--_-- _ in blue with [25] designating the altitude = 2500'msl (the symbol is kind of hard to replicate here) and mountanious areas typically >14,500 msl & >1500' agl have segments of airspace outlining airways (what is it 4 or 5 nm clearance from centerline?) Oh, by the way is LA Lower Alabama?
While I don't have a western US chart here, the floor of class E, where G ends out west, does not have a chart designation symbol, other than when it is less than 14,500, using the blue vignette, as stated above.
I am told that the 14,500 level was chosen because of the highest point in the continental US, and to allow for uncontrolled airspace over the US when controlled airspace is not necessary.
I make a point (ahem, MADE a point..) of teaching all of my students about the difference between eastern and western US airspace and chart symbology. I found it helps them to "see" a victor airway, for example. A close study of the two page Jepp diagram should make the subject clear, along with the description in the FAR/AIM.
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