What is this symbology on a sectional?

Jim_R

Jim_R

Pattern Altitude
Joined
Feb 17, 2010
Messages
1,829
Display Name
Display name:
Jim
What are these gray shaded areas on the sectional chart? They look similar to the magenta shading for Class E around small airports, but the shading fades to the outside, as if the entire world except for these little slivers is...something.

What is it? I went looking in the FAA Aeronautical Chart User's Guide, but couldn't figure it out.

Here are two examples of what I'm talking about:
This severed, unbalanced boomerang shape near the eastern part of the Grand Canyon SFRA:
https://goo.gl/1nJQsp

This straight, narrow rectangle WNW of Las Vegas:
https://goo.gl/VKKxxe

????
 
Its uncontrolled airspace to the ground. Its supposed to be blue but for some reason shows as grey as you mentioned.
 
The space inside those "symbols" is class G airspace from surface all the way up to the class A I believe. Class E latterally abutts from 1200'agl.
 
So...why is the shading on the outside of the box, then, instead of inside like it is for Class E around small airports? (And why, since the slivers are so tiny, bother to demark them at all??)
 
It definitely looks gray, but assuming it's supposed to be a cyan vignette, now rarely seen, where the floor of controlled Class E airspace is 1200 ft or greater on the fuzzy side and 14,500 ft on the hard side (i.e. as nominally defined in FAR 71.71(a)), maybe it operates as a "you should not fly through here" wall to instrument traffic that is below 14,500?

Not sure if it's a clue, but the two "boomerang" shaped ones to the east of the Grand Canyon are right on the border of the KZLA Los Angeles and KZDV Denver "Flight Information Regions" (the regions covered by the ARTCCs or Centers I think), but the one to the northwest of Las Vegas isn't on such a border.
 
Last edited:
Jim_R said:
So...why is the shading on the outside of the box, then, instead of inside like it is for Class E around small airports? (And why, since the slivers are so tiny, bother to demark them at all??)
Click to expand...
The previous responses were wrong, sort of and depending on your point of view. The shading indicates class E airspace with floor 1200AGL that laterally abuts class G airspace. That shaded area is 21637nm across*. The space not enclosed by that shaded line is class G from the surface to 18000 feet and is 0.5nm across.

Also, I believe it is blue. It just looks gray due to optical illusion (all that brown around it). If you use an image processing app with a pixel peeper, I'm guessing that you'll see it's mostly blue.

*edit: if the whole world were under FAA jurisdiction.
 
Last edited:
On closer inspection, I think the shading *is* cyan, but is affected by the terrain color underneath. In the one east of the Grand Canyon, it crosses some white lines, and in those spaces the color is clearly cyan.

Edit: Just saw asicer's response re: color...same conclusion I came to.
 
asicer said:
The previous responses were wrong, sort of and depending on your point of view. The shading indicates class E airspace with floor 1200AGL that laterally abuts class G airspace. That shaded area is 21637nm across. The space not enclosed by that shaded line is class G from the surface to 18000 feet and is 0.5nm across.
Click to expand...
OK, now that the color has been explained I agree that your explanation matches the chart user's guide, so thank you for the help.

But that begs the next question: Why do these areas exist? What practical purpose do they serve? I could understand big chunks of Alaska being Class G from the surface to 18K. I could even understand some irregular chunk of mountainous area. But these are very geometrically well-defined, and very narrow. As eetrojan mentioned, it's like they're walls to east-west IFR traffic. But why?
 
asicer said:
The previous responses were wrong, sort of and depending on your point of view. The shading indicates class E airspace with floor 1200AGL that laterally abuts class G airspace. That shaded area is 21637nm across*. The space not enclosed by that shaded line is class G from the surface to 18000 feet and is 0.5nm across.
Click to expand...

Should be 14,500' MSL which is where Class E starts by default.

The opaque side of the blue vignette indicates Class G up to 14,500', the translucent side indicates Class G only up to 1200'AGL or the altitude shown next to the blue zipper lines (not to be confused with the blue picket fence which indicates restricted areas).
 
Jim_R said:
But that begs the next question: Why do these areas exist? What practical purpose do they serve? I could understand big chunks of Alaska being Class G from the surface to 18K. I could even understand some irregular chunk of mountainous area. But these are very geometrically well-defined, and very narrow. As eetrojan mentioned, it's like they're walls to east-west IFR traffic. But why?
Click to expand...

Why don't we talk about something easier, like how to control the weather?

The FAA is weird about airspace. There's never a periodic review of it to see if something should be changed or streamlined. There are cutouts in class C, D, and E surface areas for airports that no longer exist, closed decades ago in some cases, and other such quirks.

I would imagine that this particular weirdness was caused by something that made sense once upon a time, and then changes were made here and there, finalized and approved and nobody really noticed the sliver of confusion near the gash in the earth... The computer just happily printed it on the chart and everyone went about their day.
 
flyingcheesehead said:
Why don't we talk about something easier, like how to control the weather?
Click to expand...
Hah!
I would imagine that this particular weirdness was caused by something that made sense once upon a time, and then changes were made here and there, finalized and approved and nobody really noticed the sliver of confusion near the gash in the earth... The computer just happily printed it on the chart and everyone went about their day.
Click to expand...
OK, I can buy that. Ultimately, I'm about to go fly someplace I've never been, and want to make sure I'm not missing something significant the chart is trying to tell me. Sounds like in this case, maybe I'm not.
 
A lot of what little Class G airspace above 1200 AGL that was still around, and there wasn’t much, has been going away recently. Look at the Aeronautical Chart Bulletins. The Las Vegas Sectional is on page 393 of the Southwest Chart Supplement. I don’t know if those little ‘slivers’ were a part of that.

EDIT: Those slivers are. As of Nov 8 there is no Class G airspace above 1200 AGL left in Los Angeles Centers airspace. The coordinates in the Chart Bulletin are the boundary of ZLA’s airspace.
 
Last edited:
Jim_R said:
But that begs the next question: Why do these areas exist? What practical purpose do they serve? I could understand big chunks of Alaska being Class G from the surface to 18K. I could even understand some irregular chunk of mountainous area. But these are very geometrically well-defined, and very narrow. As eetrojan mentioned, it's like they're walls to east-west IFR traffic. But why?
Click to expand...
Perhaps at one time these were bigger and not so weird but radar coverage improved to the point that they shrunk to what they are today?
 
asicer said:
Perhaps at one time these were bigger and not so weird but radar coverage improved to the point that they shrunk to what they are today?
Click to expand...
I was trying to find archived sectionals to see what shape those areas have had in the past but I haven't been able to find any. I'm thinking something similar - those areas might be some sort of radar shadow areas due to terrain.
 
Thanks for all the responses. I wonder how long it will take before those little slivers disappear, too...
 
Jim_R said:
Thanks for all the responses. I wonder how long it will take before those little slivers disappear, too...
Click to expand...
The little slivers in North Dakota seem to be gone. They all had curved edges, so my theory was always that they represented the limits of good radar coverage. They definitely weren't the limits of good radio reception based on my experience trying to reach Center below 5,000 feet or so in places nowhere near the former slivers of Class G airspace.

So, indeed...
luvflyin said:
RIP uncontrolled airspace above 1200 in the US.
Click to expand...
 
Jim_R said:
Thanks for all the responses. I wonder how long it will take before those little slivers disappear, too...
Click to expand...

They’re gone. As of November 8. They’ll be off the Las Vegas Sectional on the
next publication, effective March 01
 
iamtheari said:
The little slivers in North Dakota seem to be gone. They all had curved edges, so my theory was always that they represented the limits of good radar coverage. They definitely weren't the limits of good radio reception based on my experience trying to reach Center below 5,000 feet or so in places nowhere near the former slivers of Class G airspace.

So, indeed...
Click to expand...

Radar Coverage has never been a requirement for establishment of Controlled Airspace. Communication is. The ability of communication other than Radio, like satellite methods such as Data Link, is how the Genocide of Class G was accomplished. I think @flyingcheesehead described it perfectly in post #10 how them ‘slivers’ ever got on the Charts in the first place
 
Last edited:
You must log in or register to reply here.
Back
Top